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Study on the utilization efficiency of land and water resources in the Aral Sea Basin, Central Asia
Accepted Manuscript Title: Study on the utilization efficiency of land and water resources in the Aral Sea Basin, Central Asia Authors: Zhang Jiaoyou, Chen Yaning, Li Zhi, Song Jinxi, Fang Gonghuan, Li Yupeng, Zhang Qifei PII: DOI: Article Number:
S2210-6707(19)30181-7 https://doi.org/10.1016/j.scs.2019.101693 101693
Reference:
SCS 101693
To appear in: Received date: Revised date: Accepted date:
21 January 2019 17 June 2019 30 June 2019
Please cite this article as: Zhang J, Chen Y, Li Z, Song J, Fang G, Li Y, Zhang Q, Study on the utilization efficiency of land and water resources in the Aral Sea Basin, Central Asia, Sustainable Cities and Society (2019), https://doi.org/10.1016/j.scs.2019.101693 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Study on the utilization efficiency of land and water
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resources in the Aral Sea Basin, Central Asia
Study on the utilization efficiency of land and water resources in the Aral Sea Basin, Central Asia
ZHANG Jiaoyou1,2, CHEN Yaning1*, LI Zhi1, SONG Jinxi3, FANG Gonghuan1, LI Yupeng1,2,
State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;
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1
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ZHANG Qifei1,2
University of Chinese Academy of Sciences, Beijing 100049, China;
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College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China
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1、Author: ZHANG Jiaoyou
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Email: [email protected]
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2、*Corresponding author: CHEN Yaning Email: [email protected]
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3、Name: LI Zhi Email: [email protected]
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4、Name: SONG Jinxi
Email: [email protected]
5、Name: FANG Gonghuan
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Email: [email protected]
6、Name: LI Yupeng Email: [email protected]
7、Name: ZHANG Qifei Email: [email protected]
Highlights
The security of land and water resources is one of the strategic and forward-looking issues that China should attach great importance to in the process of promoting the construction of the Silk Road Economic Belt. Using MODIS remote sensing data and the Water Use Efficiency Monitor in Central
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Asia (WUEMoCA) database.
Crop and water productivity in irrigated areas along the Syr Darya River is greater than
that of the Amu Darya River, and that of the upper irrigation areas is larger than the lower ones.
The Fergana Valley and Tashkent areas have the relatively highest land and water resources utilization efficiency.
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Abstract
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This paper analyzes and calculates the utilization and efficiency of land and water
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resources in the Aral Sea Basin (ASB) from 2000 to 2014, using MODIS remote sensing data and the Water Use Efficiency Monitor in Central Asia (WUEMoCA)
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database. The results show that: (1) Over the past 15 years, the water area in ASB has
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decreased at a rate of 1,048 km2 per year, from a proportion of 2.5% in 2000 to 1.5% in 2014. The Aral Sea in particular has witnessed a significant reduction of 60.28% of
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its area, dropping from 28,119 km2 in 2000 to 11,169 km2 in 2014. (2)The annual
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yield per unit area of wheat was the highest (4.16 tons/ha), followed by rice (2.27 tons/ha) and cotton (2.22 tons/ha). Water productivity of wheat in the ASB was the
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highest (0.881 kg/m3), followed by rice (0.689 kg/m3) and wheat (0.451 kg/m3). (3) Generally, crop and water productivity in irrigated areas along the Syr Darya River is greater than that of the Amu Darya River, and that of the upper irrigation areas is larger than the lower ones. The Fergana Valley and Tashkent areas have the relatively highest land and water resources utilization efficiency.
Keywords: utilization efficiency; land and water resources; Aral Sea Basin 1
Introduction
Every country in the world is affected by geographical conditions, which are mainly
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reflected in the interconnection between water, land and inhabitants (FAO, 2013). The
rise in water scarcity along with increased competition for water and land from both agricultural and non-agricultural sectors are driving the need to improve crop water
productivity in order to guarantee adequate food for future generations with the same
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or less water and land than are currently available (Platonov et al., 2008). In Aral Sea
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Basin (ASB) countries, production activity is generally determined by the diversity of
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the geographical environment and the imbalance of land and water resources
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distribution (Spoor, 2010; Granit et al., 2012). Upstream mountain areas, which comprise about 90% of the basin region, have very little cultivated land for food
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production, but these areas are rich in water resources. In contrast, countries located
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in the middle and lower reaches of the basin have relatively rich cultivated land resources but rely on the upstream water supply to develop irrigation agriculture (Yao
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and Zhou, 2013；Jalilov et al., 2018). This imbalance in the distribution of water and
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land resources has become the source of various conflicts among countries in Central Asia (Micklin, 2002; Severskiy, 2004; Bernauer, 2012; Karthe et al., 2015). In
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addition, the impact of climate change (Li et al., 2015; Li et al., 2017; Chen et al., 2018) and human activities caused by population growth, the mass development of regional irrigated agriculture irrigation and mismanagement of water resources has led to the degradation of land and water ecosystems in Central Asia and jeopardized the socio-economic development of the region (Ji et al., 2009; Karthe et al., 2017). Over the past 100 years, intensive land development and water use have led to
serious environmental degradation, such as the drying up of the Aral Sea, soil salinization and desertification (Mannig et al., 2018). Since the 1960s, the problem in the ASB has attracted the attention of researchers around the world (Micklin, 1988;
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Granit et al., 2012; Bekchanov et al., 2016; Lee and Jung, 2018). Martius et al. (2004) argued that sustainable and efficient land and water use must be developed on the
basis of sound scientific research, and that the complexity of the problems requires an interdisciplinary approach which integrates natural resource management as well as economic and institutional changes. The model combines a variety of interrelated
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disciplines (groundwater, soil salinity, land use, economic evaluation, etc.) into a
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unified concept to test different farming scenarios.
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Due to the lack of available data pertaining to Central Asia, renewable data such as
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remote sensing data are now being increasingly used to analyze land and water resources in the ASB (Dimov et al., 2017; Löw et al., 2018; Alka et al., 2018).
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Platonov et al. (2008) used high spatial resolution satellite images (Land Sat ETM+),
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based on the classification of crops, crop yield and actual evapotranspiration, to
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calculate and evaluate water productivity and crop productivity in the Syr Darya Basin. Conrad et al. (2016) studied the agricultural land and water resources in the
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region by employing remote sensing data. Specifically, he applied advanced remote sensing technology to establish a database of land use and water resources utilization,
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developing an index system to estimate the productivity of irrigated agriculture and to compare irrigation systems and monitor their performance. Meanwhile, Kulmatov (2014) discussed the problems of rational use and protection and management of water and irrigated land resources in Uzbekistan and analyzed the utilization of water resources on the main branches the economy (irrigation, industry
and drinking water supply) from 2000 to 2009. Uzbekistan is a major agricultural production area in the ASB and uses more than 50% of the region's water resources. And he also evaluated land degradation in the irrigated areas of Uzbekistan and
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proposed several possibilities for sustainable use of irrigated land. Other researchers investigating the same region and working in the same general field include Ji et al.
(2009) and Yao and Zhou (2013). Based on the concept of “pressure-state-response”, Ji et al. (2009) established the safety state index of land and water resources in Central Asia, and analyzed and compared the development of land and water
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resources and its safety state index. A few years later, Yao and Zhou (2013) analyzed
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water resources allocation problems in the ASB by using game theory, arguing that
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the “Coordination Game” could make each country obtain optimal rewards and help
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them escape the “Prisoners Dilemma”.
Against this backdrop of regionalized water and arable land shortages, the greatest
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challenge for the coming decades will be to increase food production to ensure food
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security for a steadily growing world population, particularly in countries with
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limited water and land resources (Smith, 2000). Most countries in the world use 60%-80% of their water resources for agricultural production, and that figure rises to
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more than 80% in arid and semi-arid countries (Smith, 2000). With increasing pressure on land use and water, some of the arid and semi-arid regions in the world
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have become the focus of agricultural production development. Indeed, maximizing agricultural productivity in these areas has become a major concern not only of local governments but of regional and national authorities, as local agricultural issues can have a broad impact on surrounding jurisdictions. The exploitation of water and land resources in the ASB – known as the Aral Sea
crisis – is the most prominent environmental problem encountered in the construction of the Silk Road Economic Belt in Central Asia, as the project is centered on promoting a green ecological environment and a stable social environment to support
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sustainable development (Yang and Wang, 2010; Guo et al., 2015; Howard , 2016; Xu, 2017). This vision, however, stands in stark contrast to the current status quo of water
and land resources utilization in the basin region. Therefore, the present article
analyzes the water and land resources utilization and efficiency in the ASB with the
aim of providing a scientific basis for a Central Asian sustainable water resources
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management strategy. As well, this paper aims to provide a reference for the
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construction of the Silk Road towards realizing sustainable and efficient utilization of
2.1
Overview of the Aral Sea Basin
56°E-78°E/33°N-52°N
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The ASB located at
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Study area and data sources
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2
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land and water resources in the affected area.
in central Eurasia (Fig.
1).
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Percentage-wise, it includes most of Tajikistan (TJK, 99%), Turkmenistan (TKM, 95%) and Uzbekistan (UZB, 95%), over half of Kyrgyzstan (KGZ, 59%), over
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one-third of northern Afghanistan (AFG, 38%), nearly one-eighth of the Kyzylorda and South Kazakhstan provinces of Kazakhstan (KAZ, 13%), and a small portion of
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the Islamic Republic of Iran in the Tedzhen/Murghab Basin, which covers a total area of 176×104 km2 (FAO, 2013). Topographically, the ASB can roughly be divided into two main regions: the Turan Plain and the mountains. Within these divisions is the Karakum Desert, which is located in the western portion of the basin in Turkmenistan; the Kyzykum Desert,
which is located in the northwest portion of the basin (i.e., southwest of Kazakhstan and Uzbekistan and northwest of Turkmenistan); and the Tianshan and Pamir mountains, which are situated in the east and southeast part of the basin region. The
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rest of the ASB consists of various types of alluvial plains, intermountain valleys, and arid and semi-arid grasslands.
The basin has a distinct continental climate that features high solar radiation and relatively low humidity, little rainfall, uneven distribution of precipitation, and large
differences between daily and seasonal temperatures. At low altitudes, from north to
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south, average temperatures in July are 26°C and 30°C while high temperatures are
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45°C and 50°C, respectively; Average temperatures in January are -8°C and -0°C,
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respectively, with the lowest temperature hovering around -38°C (CAWATERinfo,
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2018).
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In terms of the region’s social economy, the main economic activity in the ASB is
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the development of irrigation agriculture. And the Fergana Valley irrigation zone is a prime example of large-scale irrigation systems in Central Asia. According to Conrad
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et al. (2013; 2016) and as shown in Figure 1, the ASB is divided into eight major irrigated areas. Agricultural production activities in this region are concentrated in
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these eight areas, which are mainly distributed along and fed by the Amu Darya and
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Syr Darya rivers and the Kara Kum canal. Because of the fragility of the ecological environment in arid regions, the ASB has become extremely vulnerable to climate change and human activities. Starting in the 1960s, water diversion projects, which were mainly intended for the massive expansion of cotton cultivation, transformed the agricultural landscape of the region (Bekchanov et al., 2016). However, at the same time, the irrigation projects detrimentally affected the ASB water system and caused
serious ecological environment problems across the region as well as in other parts of Central Asia (Karthe et al., 2015). 2.2
Data collection and processing
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The MODIS remote sensing data from NASA (National Aeronautics and Space Administration) used in this study is from 2000-2014. The data products employed are global land water mask data MOD44W (spatial resolution of 250 meters) and land
cover data MCD12Q1 (spatial resolution of 500 meters). The Sinusoidal map
projection transformation shows as a WGS84 ellipsoid of the Albers Equal Area
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projection, which can then be applied to complete the image stitching. Next, the water
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land mask data and land use data images for each year are cut by using the vector
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boundary of the Aral Sea watershed. The data of land use land classification comes
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from the University of Maryland (UMD) and includes eleven sets of land cover types.
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In this paper, the land use types were reclassified into water area, forest land, shrub,
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grassland, cultivated land, urban construction land and bare land. The land and water resource utilization efficiency data (2000-2014) come from the
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monitoring database of water resources utilization efficiency in Central Asia
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(WUEMoCA). The statistics cover the following three main aspects: irrigable area (ha); irrigated crop acreage (ha); and farm gross output (tons). The water and land
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resources utilization efficiency indicators include crop yield (tons/ha), economic water productivity ($/m3) and unit price of crops ($/tons). The physical crop water productivity (kg/m3) was calculated by the ratio of economic water productivity ($/m3) to the crops price ($/tons).
3 Results and Analysis 3.1 Current level of utilization efficiency of land resources in the Aral Sea Basin 3.1.1 Development and utilization status of land resources
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In general, land cover reflects the natural condition of the earth's surface layer, and
land use is the external driving force of land cover change. Land use in Central Asia
is also highly vulnerable to political and economic factors (Han et al., 2012). The four
main types of land use in the ASB are grassland, bare land, shrub and cultivated land
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(Fig. 2). Among these types, grassland dominates, accounting for the largest
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proportion of all land use composition. Grassland covers a total area of about
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73.64×104 km2 and accounts for 42.87% of the total land area in the ASB. Shrubs and
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bare land account for 24.32% and 23.82%, respectively, while cultivated land area covers only around 10.78×104 km2, accounting for 6.28% of the basin. Despite being
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significantly smaller than the other three land use types, cultivated land, naturally
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drained with fertile soils, is the main support for the social and economic development in the region.
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Table 1 provides details on cultivated land resources in the ASB. As shown in the
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table, Uzbekistan has the largest arable land (43%), as well as the biggest cultivated land area (52%) and the largest area of irrigated land (54%). In contrast, Kyrgyzstan
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and Tajikistan have the least share of arable land and the smallest irrigation area. This is because 90% of Kyrgyzstan and Tajikistan is mountainous. However, despite their lack of cultivated land, the two countries provide most of the water resources for countries downstream and thus have control over the amount of water released to them. In Kazakhstan, Turkmenistan and Uzbekistan, deserts and mountains comprise less than 10% of the land, which means that these three countries have enormous
potential to develop irrigated agriculture, if more water were available (FAO, 2013). A peculiarity of land conditions of Central Asia is the salt effect caused by natural Conditions and human activity. Excessive use of irrigation water coupled with
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inadequate drainage systems has caused large-scale land degradation and water quality deterioration in downstream parts of the basin (Qadir, 2010).
3.1.2 Spatial and temporal variations of land resource utilization efficiency
The total irrigable area of the ASB is 508.675×104 hectares, of which the irrigable area of Uzbekistan is 318.50×104 hectares, accounting for 62.6% of the total irrigated
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area of the basin (Fig. 3). The main crops grown there are cotton, wheat, rice, corn,
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fruit trees and vegetables. In 2000-2014, cotton, wheat, rice and corn accounted for
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76.55% of the total irrigated farmland area. The annual cotton area is about
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185.26×104 hectares (41.15%), followed by wheat 105.85×10 4 hectares (23.51%),
to
world
food
production
statistics
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According
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corn 29.55×104 hectares (6.56%), and rice 23.98×104 hectares (5.33%) (Fig. 4).
(https://www.statista.com/register/premiumaccount/), Uzbekistan and Turkmenistan's
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cotton production in 2017 ranked eighth and ninth in the world, respectively. It can also be seen from Figure 4 that the irrigated area of crops in the ASB is constantly
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increasing, which means it is approaching or even exceeding the irrigable area. In
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other words, the development degree of irrigated farmland is close to saturation. Figure 5 shows time-varying trends for wheat, cotton and rice yields in the ASB
from 2000 to 2014. The total crop production change indicates a stable trend, peaking in 2009 at 1257.12×104 tons, with the average annual output for 2000-2014 leveling out at 903.08×104 tons. The average annual output of wheat is 443.26×10 4 tons and accounts for about 50% of the annual output of crops across the entire basin region.
Cotton (396.98×104 tons) and rice (62.84×104 tons) are the second and third main crops, respectively. During the Soviet period, from 1925 to 1985, cotton acreage increased from 2 million hectares to 7.2 million hectares (Martius et al., 2004).
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However, with the collapse of the Soviet Union and a subsequent spike in population, wheat production began to expand to ensure food security. In Uzbekistan, for example, cotton once accounted for more than 50% of agricultural output under the Soviet
regime. After independence, Uzbekistan adjusted the proportion of cotton and wheat
planted, reducing cotton cultivation and transforming the country from a wheat
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importer to a wheat exporter.
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In this paper, grain yield per hectare (t/ha) is used to indicate the utilization
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efficiency of land resources (Platonov et al., 2008). In looking at the time variation
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trend of main crop yields per unit area in the ASB in Figure 6, we can see that cotton,
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wheat and rice yield per unit area are basically stable and show no obvious time
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changes. Wheat yield per hectare is the highest from 2000 to 2014, averaging 4.16 tons, followed by rice yield (2.27 t/ha) and cotton yield (2.22 t/ha).
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From the perspective of spatial distribution (Fig. 7), the spatial distribution of yield per unit area in the ASB shows obvious differences. On the whole, the high average
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yield of wheat, rice and cotton is mainly concentrated in the Fergana Valley and
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Tashkent irrigated areas (Fig. 7d). The highest cotton yield was found in Tajikistan and Afghanistan in the southeast, followed by Uzbekistan and Turkmenistan (Fig. 7a), while Tajikistan and Afghanistan have higher wheat yields (Fig. 7b). Two states in Kazakhstan (Kyzylorda and South Kazakhstan) and one in Tajikistan (Sogd) have the highest per unit area ice yields (Fig. 7c). 3.2
Current utilization efficiency of water resources in the Aral Sea Basin
3.2.1 Development and utilization status of water resources The ASB includes the Syr Darya Basin to the north and the Amu Darya Basin to the south. Across this region, the three main types of water resources are surface
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renewable water, groundwater, and reclaimed water (sewage and irrigation water), with surface water being the most plentiful. However, surface water is unevenly
distributed due to the region’s diverse topography causing significant differences in local climate. The spatial distribution of precipitation resources varies according to
location (CAWATERinfo, 2018). Most of the water vapor forms precipitation in the
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eastern mountains, leaving little precipitation in the rest of the basin. In the south and
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southeast mountains, the annual average precipitation ranges between 600 mm and
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800 mm, whereas in the foothill zone, it ranges between 300 mm and 400 mm, and in
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low-altitude areas, between 80 mm and 200 mm (CAWATERinfo, 2018). This
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discrepancy in precipitation effectively divides the ASB into three main runoff areas:
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the upstream river source area, the middle water consumption area, and the downstream delta area.
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Average annual surface water in the ASB measures approximately 105.21 km3/year. In the Amu Darya and Syr Darya basins, average annual surface water measures
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68.58 km3/year and 36.63 km3/year, respectively. Tajikistan and Kyrgyzstan each
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account for 56.78% and 27.75% of the surface water resources, respectively, while only 15% of the annual average runoff in the ASB occurs in Kazakhstan, Uzbekistan and Turkmenistan. Hence, the spatial distribution of water resources in the basin is severely unbalanced (Table 2). The global land water data (MOD44W) from MODIS provides spatial distribution difference and time variation trends for water resources in the ASB from 2000 to
2014. As can be seen from Figure 8, the water area of the ASB decreased at a rate of 1,048 km2 per year, meaning that 1,048 km2 of water area was converted into non-water area annually. Water area accounted for only about 2% of the entire basin
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area. Hence, the proportion of non-water area increased from 97.5% in 2000 to 98.5% in 2014, while the proportion of water area decreased from 2.5% in 2000 to 1.5% in 2014.
As can be seen in Figure 9a, there was a significant change in the Aral Sea water area. Specifically, the water area in the southern Aral Sea underwent more changes,
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while the water area in the northern Aral Sea changed less. This is mainly due to the
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construction of the Dike Kokaral dam between the northern and southern portions of
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the Aral Sea, which led to the Syr Darya streamflow stabilizing the northern part
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(Alka et al., 2018). As of 2000, the eastern and western parts of the southern Aral Sea were still integrated, but by 2005, they were completely separated and the coastline as
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a whole was shrinking westward. The Aral Sea area decreased from 28,119 km 2 in
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2000 to 11,169 km2 in 2014, which represents a decrease of 60.28%. Prior to 1960,
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the Aral Sea was listed as the world's fourth largest lake. After 1960, however, the sea began to shrink due to increased cotton production, reclamation of barren land, and
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increased extraction of irrigation water from the Amu Darya and Syr Darya rivers. Overall, the volume of the Aral Sea decreased from 1,085.4 km3 in 1960 to 23.3 km3
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in 2014 (Fig. 9b).
Studies show that massive exploitation of land and water resources over a long period of time causes continuous deterioration of the ecological environment. One of the immediate results of the exploitation of water resources in the ASB was that the amount of water entering the lake dropped sharply and the lake shrank significantly
(Deng et al., 2010). Using remote sensing data, Jin et al. (2017) studied the environmental changes caused by irrigation activities in the Amu Darya Basin. Their results show that although the surface water generated in the upstream areas have
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increased over the past decade (13 km3/ year), the water reserves in the downstream areas are decreasing (-27 km3/ year) at double the rate.
Massive water withdrawals from the Amu Darya and Syr Darya Rivers used for
irrigation have led to the progressive desiccation of the Aral Sea (Karthe et al., 2015). As illustrated in Figure 10, the Amu Darya and Syr Darya rivers have steadily
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reduced their runoffs into the Aral Sea (SIC ICWC, 2018; CAWATER, 2018). The
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amount of water from the Amu Darya River decreased from 288.67×10 8 m3 in 1992 to
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37.72×108 m3 in 2014, and the amount entering the Aral Sea decreased by an
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astounding 87%. In contrast, the change in the Aral Sea caused by the Syr Darya
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River is relatively small. In 1992, the amount of water from the Syr Darya entering
51.27×108 m3.
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the sea was 45.79×108 m3, and in 2014, the amount of water entering it was
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3.2.2 Spatial and temporal variation of water resource utilization efficiency
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Over the past 60 years, Central Asia has experienced a warming trend of approximately 0.36-0.42°C/10 years (Chen et al., 2016). Climate warming directly
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affects the stability of regional water circulation and water systems and leads to changes in runoff supply mode and water resource quantity (Chen et al., 2017). Therefore, under the influence of climate change and human activities, the water resources in the ASB are rapidly depleting. Moreover, seasonal variation and total variation of river runoff in the future could exacerbate existing conflicts between upstream and downstream countries regarding irrigation water and hydropower
(Mannig et al., 2018). It is therefore very important to make rational use of irrigation water resources and improve the utilization efficiency of agricultural water resources (Zhang, 2018).
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Water productivity analysis combines physical accounting of water with yield or economic output to give an indication of how much value is being obtained from the
use of water (Abdullaev, 2004). Physical water productivity (kg/m3) refers to crop yield per cubic meter of water consumed, and economic water productivity ($/m3) represents the agricultural economic value created by unilateral water (Platonov et al.,
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2008; IWMI, 2003). As depicted in Figure 11, the yield of wheat per cubic meter of
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water consumed is the largest, followed by rice and cotton (Fig.11a). However, the
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economic value of cotton per cubic meter of water consumed is the largest, followed
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by rice and wheat (Fig. 11b). In 2000-2014, wheat created 0.881 kg and USD 0.191 by consuming an average of one cubic meter of water. The annual water productivity
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of rice are 0.689 kg/m3 and USD 0.268 $/m3, and cotton's annual water productivity
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are 0.451 kg/m3 and USD 0.727 $/m3. From 2000 to 2014, the physical water
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productivity of crops in the whole ASB showed a relatively stable trend, with an annual average of 0.674 kg/m3. Because of the impact of crop prices, economic water
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productivity showed an uptrend, with an annual average of 0.467 $/m3.
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In terms of spatial distribution (Fig. 12), the high physical water productivity of the three main crops is mainly concentrated in the Fergana Valley and Tashkent irrigation areas in the northwest (Fig. 12d). Kyrgyzstan and Tajikistan, upstream of the Syr Darya (Fergana Valley irrigation area), have the most productive wheat and cotton water resources (Fig. 12a; 12b), while the highest productivity of rice water resources is mainly located in Kyrgyzstan and South Kazakhstan (Fig. 12c).
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Discussion
(1) Central Asia faces significant water-related challenges, including water scarcity, deterioration of water quality and inefficient use of water. These challenges can only
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be met if all Central Asian countries work together. Sound water management decisions require a reliable hydrological and meteorological data base. Unfortunately,
after the collapse of the Soviet Union in 1991, the existing hydro-meteorological monitoring network has also deteriorated. Many monitoring stations were abandoned
due to lacking financial support by the new independent republics (CAWa, 2018). The
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remaining stations are often equipped with out dated sensors which provide only
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non-digital data of low temporal resolution. Given this situation, the CAWa project
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aims to provide a sound scientific and reliable regional data base for sustainable water
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management strategies in Central Asia. This article makes full use of the data
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provided by the WUEMoCA project in the CAWa subproject. As WUEMoCA is still
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in development (Conrad, 2016) it only provides key indicators to better understand land use and its intensity, as well as the productivity of irrigated farmland, in order to
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compare irrigation systems at least regionally in the future. (2) At present, there are few works on the utilization efficiency of water and land
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resources in the ASB. Comparing to previous studies, in this study, the changes of water and land resources utilization efficiency of different crops in time and space
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were analyzed more carefully. Fergana Valley is an ancient irrigated oasis, with relatively high farming standards, long and good traditions of irrigation and water management (Horst et al., 2005). This paper showed that, spatially, the utilization efficiency of land and water resources in the Fergana Valley irrigated area is higher. However, the whole Central Asia region, especially the ASB, adopting the traditional
irrigation method on the whole, and the utilization efficiency of water resources is still lower, and the Fergana Valley irrigated area is no exception (Pereira et al., 2009; Reddy et al., 2013). Irrigation water management in Central Asia is notorious for its
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inefficiency (Awan, 2011). According to research of Lee and Jung (2018), the water resource utilization efficiency of crops in the ASB is lower than that in other parts of Asia. Therefore, the ASB needs to improve the utilization efficiency of land and water
resources on the whole, and in particular, it should pay attention to the regions, which mainly lied at lower basin with low utilization efficiency of land and water resources
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obtained in this paper.
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(3) The arid and semi-arid climate in the ASB determined the development of its
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irrigated agriculture. Because of low cost and the energy demand, furrow irrigation
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and basin irrigation are still the main irrigation methods here, and 99% of the irrigated area in central Asian countries uses these methods (Micklin, 2007;
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Bekchanov et al., 2010; Woznicki and Nejadhashemi, 2013). Therefore, it is
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necessary to improve irrigation methods and crop planting structure. Drip irrigation
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technology is one of the best methods to reduce water consumption, reducing ineffective water evaporation and improving water resource utilization efficiency.
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And there is also a need to improve irrigation channels, reducing leakage and improve water delivery efficiency (Ward and Pulidovelazquez 2008; Bekchanov et al., 2016).
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Cotton cultivation has always been dominant in crop planting structure in pursuit of higher economic benefits. The water consumption of cotton is relatively large. Therefore, while guaranteeing economic benefits, the proportion of cotton should be reasonably adjusted to reduce the high water consumption crops. Furthermore, the economic conditions of countries, food and energy security, technology, education,
employment, geographical conditions, population and legal systems must be considered to improve water efficiency (Lee and Jung 2018). 5
Conclusions
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(1) Of the various types of land use in the ASB, grassland accounted for the largest
proportion, covering a total area of about 73.64×10 4 m2 or 42.87% of the land in the region. Shrub and bare land accounted for 24.32% and 23.82% respectively, while
cultivated land area covered 10.78×104 m2. The basin had a total irrigable area of
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508.675×104 hectares, with Uzbekistan having the largest total irrigable area
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(318.50×104 hectares) or 62% of the region, followed by Kazakhstan. Kyrgyzstan's
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available irrigation area was the lowest. The total area of cotton, wheat, rice and
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maize, which were the main crops in the ASB in 2000-2014, used 76.55% of the total irrigated farmland area. The cotton area covered 185.265×10 4 ha (41.15%), followed
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by wheat at 105.855×104 ha (23.51%) and rice at 23.985×104 ha (5.33%). In terms of
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crop yield productivity, the annual yield per hectare of wheat was the highest (4.16 tons/ha), followed by rice (2.27 tons/ha) and cotton (2.22 tons/ha). Regarding spatial
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distribution, the irrigation area along the Syr Darya River was larger than that along
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the Amu Darya River, and the irrigation area upstream was larger than the area downstream.
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(2) The average annual surface water resources of the ASB in 2000-2014
measured 166.021 km3. The surface water resources of the Amu Darya Basin measured 79.396 km3, and those of the Syr Darya Basin measured 36.626 km3. Tajikistan and Kyrgyzstan accounted for 51% and 25.2% of the resources, respectively, whereas Kazakhstan, Uzbekistan and Turkmenistan accounted for only 10% of the ASB water resources. Hence, the water resources spatial distribution in
the region was severely unbalanced. From 2000 to 2014, the water area of the entire ASB decreased at an annual rate of 1,048 km2. The area of the Aral Sea also decreased, dropping from 28,119 km2 in
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2000 to 11,169 km2 in 2014, a decrease of 60.28%. The amount of water entering the sea from the Amu and Syr Darya rivers likewise saw a sizeable drop of 26.6% in
1992. In 2014, the size of the Aral Sea had decreased to 2% of what it had been in 1960, making it one of the planet’s worst environmental disasters. Regarding the
water productivity of crops, wheat had the highest water productivity, producing
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0.881 kg by consuming an average of one cubic meter of water, followed by rice at
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0.689 kg/m³ and cotton at 0.451 kg/m³, while the economic benefit of water resource
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utilization of cotton (0.727 $/m3) is the largest, followed by rice (0.268 $/m3) and
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wheat (0.191 $/m3). In terms of spatial distribution, the high water productivity of the three main crops was concentrated in the Fergana and Tashkent irrigation areas in the
Acknowledgements
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northwest.
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The research is supported by the Strategic Priority Research Program of the Chinese
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Academy of Sciences (XDA19030204; XDA2004030201-2). References
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U
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10.1007/s11442-018-1528-3
Study Area (eight major irrigated areas: I-the Fergana Valley; II- Tashkent and Syr Darya;
A
Fig. 1
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III-Chardara and Aris; IV-Kyzyl Orda; V-Upper Amu Darya; VI-Zerafshan and Amu Darya; VII-Kara
A
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D
Kum Canal ; VIII-Amu Darya Delta)
Fig. 2
Land use map of the ASB
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Irrigable area of countries in the ASB
Fig. 4
Trend of crop planting structure and planting area in the ASB from 2000 to 2014
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CC
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TE
D
M
A
N
U
Fig. 3
Fig. 5
Main crop yield of the ASB from 2000 to 2014
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Change trends in main crop yields per unit area in the ASB from 2000 to 2014
A
CC
EP
TE
D
M
A
N
Fig. 6
Fig. 7 2014
Annual yield spatial distribution of main crops among administrative in the ASB from 2000 to
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Variations of water and land area in the ASB from 2000 to 2014
Fig. 9
Spatial and temporal variation characteristics of water area and volume in the Aral Sea
A
CC
EP
TE
D
M
A
N
U
Fig. 8
Fig. 10
Change trend in the amount of water injected into the Aral Sea from 1992 to 2014
(Measured by two gauging stations, samanbay and karateren, located on Amu Darya
Water productivity of main crops in the ASB from 2000 to 2014
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Fig. 11
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Syr Darya respectively )
Fig. 12
Administrative differences of water productivity of main crops in ASB from 2000 to 2014
Table 1
Land Resources in the ASB (CAWATERinfo, 2018)
Area
of Cultivable Area
Cultivated Area
Irrigated Area
ha
ha
%
ha
%
ha
%
Kazakhstan*
34,440,000
23,872,400
40
1,658,800
17
786,200
10
Kyrgyzstan*
12,490,000
1,257,400
2
595,000
6
422,000
5
Tajikistan
14,310,000
1,571,000
3
769,900
8
719,000
9
Turkmenistan
48,810,000
7,013,000
12
1,805,300
18
1,735,000
22
Uzbekistan
44,884,000
25,447,700
43
5,207,800
52
4,233,400
54
154,934,000
59,161,500
100
10,036,800
100
7,895,600
100
Aral
Sea
Basin
Table 2
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* Only provinces in the Aral Sea Basin are included
Surface Water Resources in the Aral Sea Basin (Mean Annual Runoff, km 3/year)
N
(CAWATERinfo, 2018)
Kyrgyzstan
27.54
Tajikistan
1.01
Turkmenistan
-
Uzbekistan
5.56
Total Aral Sea Basin
36.63
EP CC
D
2.52
TE
Kazakhstan
Amudarya
3
Total Aral Sea Basin
km /year
%
-
2.52
2.39
1.65
29.20
27.75
58.73
59.74
56.78
1.41
1.41
1.34
6.79
12.35
11.74
68.58
105.21
100.00
M
Syrdarya
A
River Basin
Country
A
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country
Country
S2210-6707(19)30181-7 https://doi.org/10.1016/j.scs.2019.101693 101693
Reference:
SCS 101693
To appear in: Received date: Revised date: Accepted date:
21 January 2019 17 June 2019 30 June 2019
Please cite this article as: Zhang J, Chen Y, Li Z, Song J, Fang G, Li Y, Zhang Q, Study on the utilization efficiency of land and water resources in the Aral Sea Basin, Central Asia, Sustainable Cities and Society (2019), https://doi.org/10.1016/j.scs.2019.101693 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Study on the utilization efficiency of land and water
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resources in the Aral Sea Basin, Central Asia
Study on the utilization efficiency of land and water resources in the Aral Sea Basin, Central Asia
ZHANG Jiaoyou1,2, CHEN Yaning1*, LI Zhi1, SONG Jinxi3, FANG Gonghuan1, LI Yupeng1,2,
State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;
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1
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ZHANG Qifei1,2
University of Chinese Academy of Sciences, Beijing 100049, China;
3
College of Urban and Environmental Sciences, Northwest University, Xi’an 710127, China
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2
1、Author: ZHANG Jiaoyou
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Email: [email protected]
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2、*Corresponding author: CHEN Yaning Email: [email protected]
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3、Name: LI Zhi Email: [email protected]
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4、Name: SONG Jinxi
Email: [email protected]
5、Name: FANG Gonghuan
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Email: [email protected]
6、Name: LI Yupeng Email: [email protected]
7、Name: ZHANG Qifei Email: [email protected]
Highlights
The security of land and water resources is one of the strategic and forward-looking issues that China should attach great importance to in the process of promoting the construction of the Silk Road Economic Belt. Using MODIS remote sensing data and the Water Use Efficiency Monitor in Central
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Asia (WUEMoCA) database.
Crop and water productivity in irrigated areas along the Syr Darya River is greater than
that of the Amu Darya River, and that of the upper irrigation areas is larger than the lower ones.
The Fergana Valley and Tashkent areas have the relatively highest land and water resources utilization efficiency.
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Abstract
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This paper analyzes and calculates the utilization and efficiency of land and water
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resources in the Aral Sea Basin (ASB) from 2000 to 2014, using MODIS remote sensing data and the Water Use Efficiency Monitor in Central Asia (WUEMoCA)
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database. The results show that: (1) Over the past 15 years, the water area in ASB has
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decreased at a rate of 1,048 km2 per year, from a proportion of 2.5% in 2000 to 1.5% in 2014. The Aral Sea in particular has witnessed a significant reduction of 60.28% of
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its area, dropping from 28,119 km2 in 2000 to 11,169 km2 in 2014. (2)The annual
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yield per unit area of wheat was the highest (4.16 tons/ha), followed by rice (2.27 tons/ha) and cotton (2.22 tons/ha). Water productivity of wheat in the ASB was the
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highest (0.881 kg/m3), followed by rice (0.689 kg/m3) and wheat (0.451 kg/m3). (3) Generally, crop and water productivity in irrigated areas along the Syr Darya River is greater than that of the Amu Darya River, and that of the upper irrigation areas is larger than the lower ones. The Fergana Valley and Tashkent areas have the relatively highest land and water resources utilization efficiency.
Keywords: utilization efficiency; land and water resources; Aral Sea Basin 1
Introduction
Every country in the world is affected by geographical conditions, which are mainly
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reflected in the interconnection between water, land and inhabitants (FAO, 2013). The
rise in water scarcity along with increased competition for water and land from both agricultural and non-agricultural sectors are driving the need to improve crop water
productivity in order to guarantee adequate food for future generations with the same
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or less water and land than are currently available (Platonov et al., 2008). In Aral Sea
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Basin (ASB) countries, production activity is generally determined by the diversity of
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the geographical environment and the imbalance of land and water resources
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distribution (Spoor, 2010; Granit et al., 2012). Upstream mountain areas, which comprise about 90% of the basin region, have very little cultivated land for food
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production, but these areas are rich in water resources. In contrast, countries located
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in the middle and lower reaches of the basin have relatively rich cultivated land resources but rely on the upstream water supply to develop irrigation agriculture (Yao
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and Zhou, 2013；Jalilov et al., 2018). This imbalance in the distribution of water and
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land resources has become the source of various conflicts among countries in Central Asia (Micklin, 2002; Severskiy, 2004; Bernauer, 2012; Karthe et al., 2015). In
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addition, the impact of climate change (Li et al., 2015; Li et al., 2017; Chen et al., 2018) and human activities caused by population growth, the mass development of regional irrigated agriculture irrigation and mismanagement of water resources has led to the degradation of land and water ecosystems in Central Asia and jeopardized the socio-economic development of the region (Ji et al., 2009; Karthe et al., 2017). Over the past 100 years, intensive land development and water use have led to
serious environmental degradation, such as the drying up of the Aral Sea, soil salinization and desertification (Mannig et al., 2018). Since the 1960s, the problem in the ASB has attracted the attention of researchers around the world (Micklin, 1988;
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Granit et al., 2012; Bekchanov et al., 2016; Lee and Jung, 2018). Martius et al. (2004) argued that sustainable and efficient land and water use must be developed on the
basis of sound scientific research, and that the complexity of the problems requires an interdisciplinary approach which integrates natural resource management as well as economic and institutional changes. The model combines a variety of interrelated
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disciplines (groundwater, soil salinity, land use, economic evaluation, etc.) into a
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unified concept to test different farming scenarios.
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Due to the lack of available data pertaining to Central Asia, renewable data such as
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remote sensing data are now being increasingly used to analyze land and water resources in the ASB (Dimov et al., 2017; Löw et al., 2018; Alka et al., 2018).
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Platonov et al. (2008) used high spatial resolution satellite images (Land Sat ETM+),
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based on the classification of crops, crop yield and actual evapotranspiration, to
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calculate and evaluate water productivity and crop productivity in the Syr Darya Basin. Conrad et al. (2016) studied the agricultural land and water resources in the
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region by employing remote sensing data. Specifically, he applied advanced remote sensing technology to establish a database of land use and water resources utilization,
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developing an index system to estimate the productivity of irrigated agriculture and to compare irrigation systems and monitor their performance. Meanwhile, Kulmatov (2014) discussed the problems of rational use and protection and management of water and irrigated land resources in Uzbekistan and analyzed the utilization of water resources on the main branches the economy (irrigation, industry
and drinking water supply) from 2000 to 2009. Uzbekistan is a major agricultural production area in the ASB and uses more than 50% of the region's water resources. And he also evaluated land degradation in the irrigated areas of Uzbekistan and
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proposed several possibilities for sustainable use of irrigated land. Other researchers investigating the same region and working in the same general field include Ji et al.
(2009) and Yao and Zhou (2013). Based on the concept of “pressure-state-response”, Ji et al. (2009) established the safety state index of land and water resources in Central Asia, and analyzed and compared the development of land and water
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resources and its safety state index. A few years later, Yao and Zhou (2013) analyzed
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water resources allocation problems in the ASB by using game theory, arguing that
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the “Coordination Game” could make each country obtain optimal rewards and help
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them escape the “Prisoners Dilemma”.
Against this backdrop of regionalized water and arable land shortages, the greatest
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challenge for the coming decades will be to increase food production to ensure food
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security for a steadily growing world population, particularly in countries with
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limited water and land resources (Smith, 2000). Most countries in the world use 60%-80% of their water resources for agricultural production, and that figure rises to
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more than 80% in arid and semi-arid countries (Smith, 2000). With increasing pressure on land use and water, some of the arid and semi-arid regions in the world
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have become the focus of agricultural production development. Indeed, maximizing agricultural productivity in these areas has become a major concern not only of local governments but of regional and national authorities, as local agricultural issues can have a broad impact on surrounding jurisdictions. The exploitation of water and land resources in the ASB – known as the Aral Sea
crisis – is the most prominent environmental problem encountered in the construction of the Silk Road Economic Belt in Central Asia, as the project is centered on promoting a green ecological environment and a stable social environment to support
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sustainable development (Yang and Wang, 2010; Guo et al., 2015; Howard , 2016; Xu, 2017). This vision, however, stands in stark contrast to the current status quo of water
and land resources utilization in the basin region. Therefore, the present article
analyzes the water and land resources utilization and efficiency in the ASB with the
aim of providing a scientific basis for a Central Asian sustainable water resources
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management strategy. As well, this paper aims to provide a reference for the
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construction of the Silk Road towards realizing sustainable and efficient utilization of
2.1
Overview of the Aral Sea Basin
56°E-78°E/33°N-52°N
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The ASB located at
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Study area and data sources
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2
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land and water resources in the affected area.
in central Eurasia (Fig.
1).
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Percentage-wise, it includes most of Tajikistan (TJK, 99%), Turkmenistan (TKM, 95%) and Uzbekistan (UZB, 95%), over half of Kyrgyzstan (KGZ, 59%), over
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one-third of northern Afghanistan (AFG, 38%), nearly one-eighth of the Kyzylorda and South Kazakhstan provinces of Kazakhstan (KAZ, 13%), and a small portion of
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the Islamic Republic of Iran in the Tedzhen/Murghab Basin, which covers a total area of 176×104 km2 (FAO, 2013). Topographically, the ASB can roughly be divided into two main regions: the Turan Plain and the mountains. Within these divisions is the Karakum Desert, which is located in the western portion of the basin in Turkmenistan; the Kyzykum Desert,
which is located in the northwest portion of the basin (i.e., southwest of Kazakhstan and Uzbekistan and northwest of Turkmenistan); and the Tianshan and Pamir mountains, which are situated in the east and southeast part of the basin region. The
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rest of the ASB consists of various types of alluvial plains, intermountain valleys, and arid and semi-arid grasslands.
The basin has a distinct continental climate that features high solar radiation and relatively low humidity, little rainfall, uneven distribution of precipitation, and large
differences between daily and seasonal temperatures. At low altitudes, from north to
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south, average temperatures in July are 26°C and 30°C while high temperatures are
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45°C and 50°C, respectively; Average temperatures in January are -8°C and -0°C,
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respectively, with the lowest temperature hovering around -38°C (CAWATERinfo,
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2018).
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In terms of the region’s social economy, the main economic activity in the ASB is
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the development of irrigation agriculture. And the Fergana Valley irrigation zone is a prime example of large-scale irrigation systems in Central Asia. According to Conrad
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et al. (2013; 2016) and as shown in Figure 1, the ASB is divided into eight major irrigated areas. Agricultural production activities in this region are concentrated in
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these eight areas, which are mainly distributed along and fed by the Amu Darya and
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Syr Darya rivers and the Kara Kum canal. Because of the fragility of the ecological environment in arid regions, the ASB has become extremely vulnerable to climate change and human activities. Starting in the 1960s, water diversion projects, which were mainly intended for the massive expansion of cotton cultivation, transformed the agricultural landscape of the region (Bekchanov et al., 2016). However, at the same time, the irrigation projects detrimentally affected the ASB water system and caused
serious ecological environment problems across the region as well as in other parts of Central Asia (Karthe et al., 2015). 2.2
Data collection and processing
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The MODIS remote sensing data from NASA (National Aeronautics and Space Administration) used in this study is from 2000-2014. The data products employed are global land water mask data MOD44W (spatial resolution of 250 meters) and land
cover data MCD12Q1 (spatial resolution of 500 meters). The Sinusoidal map
projection transformation shows as a WGS84 ellipsoid of the Albers Equal Area
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projection, which can then be applied to complete the image stitching. Next, the water
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land mask data and land use data images for each year are cut by using the vector
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boundary of the Aral Sea watershed. The data of land use land classification comes
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from the University of Maryland (UMD) and includes eleven sets of land cover types.
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In this paper, the land use types were reclassified into water area, forest land, shrub,
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grassland, cultivated land, urban construction land and bare land. The land and water resource utilization efficiency data (2000-2014) come from the
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monitoring database of water resources utilization efficiency in Central Asia
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(WUEMoCA). The statistics cover the following three main aspects: irrigable area (ha); irrigated crop acreage (ha); and farm gross output (tons). The water and land
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resources utilization efficiency indicators include crop yield (tons/ha), economic water productivity ($/m3) and unit price of crops ($/tons). The physical crop water productivity (kg/m3) was calculated by the ratio of economic water productivity ($/m3) to the crops price ($/tons).
3 Results and Analysis 3.1 Current level of utilization efficiency of land resources in the Aral Sea Basin 3.1.1 Development and utilization status of land resources
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In general, land cover reflects the natural condition of the earth's surface layer, and
land use is the external driving force of land cover change. Land use in Central Asia
is also highly vulnerable to political and economic factors (Han et al., 2012). The four
main types of land use in the ASB are grassland, bare land, shrub and cultivated land
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(Fig. 2). Among these types, grassland dominates, accounting for the largest
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proportion of all land use composition. Grassland covers a total area of about
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73.64×104 km2 and accounts for 42.87% of the total land area in the ASB. Shrubs and
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bare land account for 24.32% and 23.82%, respectively, while cultivated land area covers only around 10.78×104 km2, accounting for 6.28% of the basin. Despite being
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significantly smaller than the other three land use types, cultivated land, naturally
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drained with fertile soils, is the main support for the social and economic development in the region.
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Table 1 provides details on cultivated land resources in the ASB. As shown in the
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table, Uzbekistan has the largest arable land (43%), as well as the biggest cultivated land area (52%) and the largest area of irrigated land (54%). In contrast, Kyrgyzstan
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and Tajikistan have the least share of arable land and the smallest irrigation area. This is because 90% of Kyrgyzstan and Tajikistan is mountainous. However, despite their lack of cultivated land, the two countries provide most of the water resources for countries downstream and thus have control over the amount of water released to them. In Kazakhstan, Turkmenistan and Uzbekistan, deserts and mountains comprise less than 10% of the land, which means that these three countries have enormous
potential to develop irrigated agriculture, if more water were available (FAO, 2013). A peculiarity of land conditions of Central Asia is the salt effect caused by natural Conditions and human activity. Excessive use of irrigation water coupled with
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inadequate drainage systems has caused large-scale land degradation and water quality deterioration in downstream parts of the basin (Qadir, 2010).
3.1.2 Spatial and temporal variations of land resource utilization efficiency
The total irrigable area of the ASB is 508.675×104 hectares, of which the irrigable area of Uzbekistan is 318.50×104 hectares, accounting for 62.6% of the total irrigated
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area of the basin (Fig. 3). The main crops grown there are cotton, wheat, rice, corn,
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fruit trees and vegetables. In 2000-2014, cotton, wheat, rice and corn accounted for
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76.55% of the total irrigated farmland area. The annual cotton area is about
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185.26×104 hectares (41.15%), followed by wheat 105.85×10 4 hectares (23.51%),
to
world
food
production
statistics
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According
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corn 29.55×104 hectares (6.56%), and rice 23.98×104 hectares (5.33%) (Fig. 4).
(https://www.statista.com/register/premiumaccount/), Uzbekistan and Turkmenistan's
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cotton production in 2017 ranked eighth and ninth in the world, respectively. It can also be seen from Figure 4 that the irrigated area of crops in the ASB is constantly
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increasing, which means it is approaching or even exceeding the irrigable area. In
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other words, the development degree of irrigated farmland is close to saturation. Figure 5 shows time-varying trends for wheat, cotton and rice yields in the ASB
from 2000 to 2014. The total crop production change indicates a stable trend, peaking in 2009 at 1257.12×104 tons, with the average annual output for 2000-2014 leveling out at 903.08×104 tons. The average annual output of wheat is 443.26×10 4 tons and accounts for about 50% of the annual output of crops across the entire basin region.
Cotton (396.98×104 tons) and rice (62.84×104 tons) are the second and third main crops, respectively. During the Soviet period, from 1925 to 1985, cotton acreage increased from 2 million hectares to 7.2 million hectares (Martius et al., 2004).
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However, with the collapse of the Soviet Union and a subsequent spike in population, wheat production began to expand to ensure food security. In Uzbekistan, for example, cotton once accounted for more than 50% of agricultural output under the Soviet
regime. After independence, Uzbekistan adjusted the proportion of cotton and wheat
planted, reducing cotton cultivation and transforming the country from a wheat
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importer to a wheat exporter.
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In this paper, grain yield per hectare (t/ha) is used to indicate the utilization
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efficiency of land resources (Platonov et al., 2008). In looking at the time variation
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trend of main crop yields per unit area in the ASB in Figure 6, we can see that cotton,
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wheat and rice yield per unit area are basically stable and show no obvious time
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changes. Wheat yield per hectare is the highest from 2000 to 2014, averaging 4.16 tons, followed by rice yield (2.27 t/ha) and cotton yield (2.22 t/ha).
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From the perspective of spatial distribution (Fig. 7), the spatial distribution of yield per unit area in the ASB shows obvious differences. On the whole, the high average
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yield of wheat, rice and cotton is mainly concentrated in the Fergana Valley and
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Tashkent irrigated areas (Fig. 7d). The highest cotton yield was found in Tajikistan and Afghanistan in the southeast, followed by Uzbekistan and Turkmenistan (Fig. 7a), while Tajikistan and Afghanistan have higher wheat yields (Fig. 7b). Two states in Kazakhstan (Kyzylorda and South Kazakhstan) and one in Tajikistan (Sogd) have the highest per unit area ice yields (Fig. 7c). 3.2
Current utilization efficiency of water resources in the Aral Sea Basin
3.2.1 Development and utilization status of water resources The ASB includes the Syr Darya Basin to the north and the Amu Darya Basin to the south. Across this region, the three main types of water resources are surface
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renewable water, groundwater, and reclaimed water (sewage and irrigation water), with surface water being the most plentiful. However, surface water is unevenly
distributed due to the region’s diverse topography causing significant differences in local climate. The spatial distribution of precipitation resources varies according to
location (CAWATERinfo, 2018). Most of the water vapor forms precipitation in the
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eastern mountains, leaving little precipitation in the rest of the basin. In the south and
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southeast mountains, the annual average precipitation ranges between 600 mm and
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800 mm, whereas in the foothill zone, it ranges between 300 mm and 400 mm, and in
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low-altitude areas, between 80 mm and 200 mm (CAWATERinfo, 2018). This
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discrepancy in precipitation effectively divides the ASB into three main runoff areas:
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the upstream river source area, the middle water consumption area, and the downstream delta area.
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Average annual surface water in the ASB measures approximately 105.21 km3/year. In the Amu Darya and Syr Darya basins, average annual surface water measures
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68.58 km3/year and 36.63 km3/year, respectively. Tajikistan and Kyrgyzstan each
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account for 56.78% and 27.75% of the surface water resources, respectively, while only 15% of the annual average runoff in the ASB occurs in Kazakhstan, Uzbekistan and Turkmenistan. Hence, the spatial distribution of water resources in the basin is severely unbalanced (Table 2). The global land water data (MOD44W) from MODIS provides spatial distribution difference and time variation trends for water resources in the ASB from 2000 to
2014. As can be seen from Figure 8, the water area of the ASB decreased at a rate of 1,048 km2 per year, meaning that 1,048 km2 of water area was converted into non-water area annually. Water area accounted for only about 2% of the entire basin
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area. Hence, the proportion of non-water area increased from 97.5% in 2000 to 98.5% in 2014, while the proportion of water area decreased from 2.5% in 2000 to 1.5% in 2014.
As can be seen in Figure 9a, there was a significant change in the Aral Sea water area. Specifically, the water area in the southern Aral Sea underwent more changes,
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while the water area in the northern Aral Sea changed less. This is mainly due to the
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construction of the Dike Kokaral dam between the northern and southern portions of
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the Aral Sea, which led to the Syr Darya streamflow stabilizing the northern part
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(Alka et al., 2018). As of 2000, the eastern and western parts of the southern Aral Sea were still integrated, but by 2005, they were completely separated and the coastline as
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a whole was shrinking westward. The Aral Sea area decreased from 28,119 km 2 in
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2000 to 11,169 km2 in 2014, which represents a decrease of 60.28%. Prior to 1960,
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the Aral Sea was listed as the world's fourth largest lake. After 1960, however, the sea began to shrink due to increased cotton production, reclamation of barren land, and
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increased extraction of irrigation water from the Amu Darya and Syr Darya rivers. Overall, the volume of the Aral Sea decreased from 1,085.4 km3 in 1960 to 23.3 km3
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in 2014 (Fig. 9b).
Studies show that massive exploitation of land and water resources over a long period of time causes continuous deterioration of the ecological environment. One of the immediate results of the exploitation of water resources in the ASB was that the amount of water entering the lake dropped sharply and the lake shrank significantly
(Deng et al., 2010). Using remote sensing data, Jin et al. (2017) studied the environmental changes caused by irrigation activities in the Amu Darya Basin. Their results show that although the surface water generated in the upstream areas have
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increased over the past decade (13 km3/ year), the water reserves in the downstream areas are decreasing (-27 km3/ year) at double the rate.
Massive water withdrawals from the Amu Darya and Syr Darya Rivers used for
irrigation have led to the progressive desiccation of the Aral Sea (Karthe et al., 2015). As illustrated in Figure 10, the Amu Darya and Syr Darya rivers have steadily
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reduced their runoffs into the Aral Sea (SIC ICWC, 2018; CAWATER, 2018). The
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amount of water from the Amu Darya River decreased from 288.67×10 8 m3 in 1992 to
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37.72×108 m3 in 2014, and the amount entering the Aral Sea decreased by an
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astounding 87%. In contrast, the change in the Aral Sea caused by the Syr Darya
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River is relatively small. In 1992, the amount of water from the Syr Darya entering
51.27×108 m3.
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the sea was 45.79×108 m3, and in 2014, the amount of water entering it was
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3.2.2 Spatial and temporal variation of water resource utilization efficiency
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Over the past 60 years, Central Asia has experienced a warming trend of approximately 0.36-0.42°C/10 years (Chen et al., 2016). Climate warming directly
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affects the stability of regional water circulation and water systems and leads to changes in runoff supply mode and water resource quantity (Chen et al., 2017). Therefore, under the influence of climate change and human activities, the water resources in the ASB are rapidly depleting. Moreover, seasonal variation and total variation of river runoff in the future could exacerbate existing conflicts between upstream and downstream countries regarding irrigation water and hydropower
(Mannig et al., 2018). It is therefore very important to make rational use of irrigation water resources and improve the utilization efficiency of agricultural water resources (Zhang, 2018).
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Water productivity analysis combines physical accounting of water with yield or economic output to give an indication of how much value is being obtained from the
use of water (Abdullaev, 2004). Physical water productivity (kg/m3) refers to crop yield per cubic meter of water consumed, and economic water productivity ($/m3) represents the agricultural economic value created by unilateral water (Platonov et al.,
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2008; IWMI, 2003). As depicted in Figure 11, the yield of wheat per cubic meter of
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water consumed is the largest, followed by rice and cotton (Fig.11a). However, the
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economic value of cotton per cubic meter of water consumed is the largest, followed
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by rice and wheat (Fig. 11b). In 2000-2014, wheat created 0.881 kg and USD 0.191 by consuming an average of one cubic meter of water. The annual water productivity
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of rice are 0.689 kg/m3 and USD 0.268 $/m3, and cotton's annual water productivity
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are 0.451 kg/m3 and USD 0.727 $/m3. From 2000 to 2014, the physical water
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productivity of crops in the whole ASB showed a relatively stable trend, with an annual average of 0.674 kg/m3. Because of the impact of crop prices, economic water
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productivity showed an uptrend, with an annual average of 0.467 $/m3.
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In terms of spatial distribution (Fig. 12), the high physical water productivity of the three main crops is mainly concentrated in the Fergana Valley and Tashkent irrigation areas in the northwest (Fig. 12d). Kyrgyzstan and Tajikistan, upstream of the Syr Darya (Fergana Valley irrigation area), have the most productive wheat and cotton water resources (Fig. 12a; 12b), while the highest productivity of rice water resources is mainly located in Kyrgyzstan and South Kazakhstan (Fig. 12c).
4
Discussion
(1) Central Asia faces significant water-related challenges, including water scarcity, deterioration of water quality and inefficient use of water. These challenges can only
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be met if all Central Asian countries work together. Sound water management decisions require a reliable hydrological and meteorological data base. Unfortunately,
after the collapse of the Soviet Union in 1991, the existing hydro-meteorological monitoring network has also deteriorated. Many monitoring stations were abandoned
due to lacking financial support by the new independent republics (CAWa, 2018). The
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remaining stations are often equipped with out dated sensors which provide only
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non-digital data of low temporal resolution. Given this situation, the CAWa project
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aims to provide a sound scientific and reliable regional data base for sustainable water
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management strategies in Central Asia. This article makes full use of the data
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provided by the WUEMoCA project in the CAWa subproject. As WUEMoCA is still
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in development (Conrad, 2016) it only provides key indicators to better understand land use and its intensity, as well as the productivity of irrigated farmland, in order to
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compare irrigation systems at least regionally in the future. (2) At present, there are few works on the utilization efficiency of water and land
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resources in the ASB. Comparing to previous studies, in this study, the changes of water and land resources utilization efficiency of different crops in time and space
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were analyzed more carefully. Fergana Valley is an ancient irrigated oasis, with relatively high farming standards, long and good traditions of irrigation and water management (Horst et al., 2005). This paper showed that, spatially, the utilization efficiency of land and water resources in the Fergana Valley irrigated area is higher. However, the whole Central Asia region, especially the ASB, adopting the traditional
irrigation method on the whole, and the utilization efficiency of water resources is still lower, and the Fergana Valley irrigated area is no exception (Pereira et al., 2009; Reddy et al., 2013). Irrigation water management in Central Asia is notorious for its
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inefficiency (Awan, 2011). According to research of Lee and Jung (2018), the water resource utilization efficiency of crops in the ASB is lower than that in other parts of Asia. Therefore, the ASB needs to improve the utilization efficiency of land and water
resources on the whole, and in particular, it should pay attention to the regions, which mainly lied at lower basin with low utilization efficiency of land and water resources
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obtained in this paper.
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(3) The arid and semi-arid climate in the ASB determined the development of its
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irrigated agriculture. Because of low cost and the energy demand, furrow irrigation
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and basin irrigation are still the main irrigation methods here, and 99% of the irrigated area in central Asian countries uses these methods (Micklin, 2007;
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Bekchanov et al., 2010; Woznicki and Nejadhashemi, 2013). Therefore, it is
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necessary to improve irrigation methods and crop planting structure. Drip irrigation
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technology is one of the best methods to reduce water consumption, reducing ineffective water evaporation and improving water resource utilization efficiency.
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And there is also a need to improve irrigation channels, reducing leakage and improve water delivery efficiency (Ward and Pulidovelazquez 2008; Bekchanov et al., 2016).
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Cotton cultivation has always been dominant in crop planting structure in pursuit of higher economic benefits. The water consumption of cotton is relatively large. Therefore, while guaranteeing economic benefits, the proportion of cotton should be reasonably adjusted to reduce the high water consumption crops. Furthermore, the economic conditions of countries, food and energy security, technology, education,
employment, geographical conditions, population and legal systems must be considered to improve water efficiency (Lee and Jung 2018). 5
Conclusions
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(1) Of the various types of land use in the ASB, grassland accounted for the largest
proportion, covering a total area of about 73.64×10 4 m2 or 42.87% of the land in the region. Shrub and bare land accounted for 24.32% and 23.82% respectively, while
cultivated land area covered 10.78×104 m2. The basin had a total irrigable area of
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508.675×104 hectares, with Uzbekistan having the largest total irrigable area
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(318.50×104 hectares) or 62% of the region, followed by Kazakhstan. Kyrgyzstan's
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available irrigation area was the lowest. The total area of cotton, wheat, rice and
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maize, which were the main crops in the ASB in 2000-2014, used 76.55% of the total irrigated farmland area. The cotton area covered 185.265×10 4 ha (41.15%), followed
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by wheat at 105.855×104 ha (23.51%) and rice at 23.985×104 ha (5.33%). In terms of
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crop yield productivity, the annual yield per hectare of wheat was the highest (4.16 tons/ha), followed by rice (2.27 tons/ha) and cotton (2.22 tons/ha). Regarding spatial
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distribution, the irrigation area along the Syr Darya River was larger than that along
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the Amu Darya River, and the irrigation area upstream was larger than the area downstream.
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(2) The average annual surface water resources of the ASB in 2000-2014
measured 166.021 km3. The surface water resources of the Amu Darya Basin measured 79.396 km3, and those of the Syr Darya Basin measured 36.626 km3. Tajikistan and Kyrgyzstan accounted for 51% and 25.2% of the resources, respectively, whereas Kazakhstan, Uzbekistan and Turkmenistan accounted for only 10% of the ASB water resources. Hence, the water resources spatial distribution in
the region was severely unbalanced. From 2000 to 2014, the water area of the entire ASB decreased at an annual rate of 1,048 km2. The area of the Aral Sea also decreased, dropping from 28,119 km2 in
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2000 to 11,169 km2 in 2014, a decrease of 60.28%. The amount of water entering the sea from the Amu and Syr Darya rivers likewise saw a sizeable drop of 26.6% in
1992. In 2014, the size of the Aral Sea had decreased to 2% of what it had been in 1960, making it one of the planet’s worst environmental disasters. Regarding the
water productivity of crops, wheat had the highest water productivity, producing
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0.881 kg by consuming an average of one cubic meter of water, followed by rice at
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0.689 kg/m³ and cotton at 0.451 kg/m³, while the economic benefit of water resource
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utilization of cotton (0.727 $/m3) is the largest, followed by rice (0.268 $/m3) and
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wheat (0.191 $/m3). In terms of spatial distribution, the high water productivity of the three main crops was concentrated in the Fergana and Tashkent irrigation areas in the
Acknowledgements
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northwest.
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The research is supported by the Strategic Priority Research Program of the Chinese
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Martius C, Lamers J, Wehrheim P, et al. (2004). Developing sustainable land and water
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N
U
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10.1007/s11442-018-1528-3
Study Area (eight major irrigated areas: I-the Fergana Valley; II- Tashkent and Syr Darya;
A
Fig. 1
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III-Chardara and Aris; IV-Kyzyl Orda; V-Upper Amu Darya; VI-Zerafshan and Amu Darya; VII-Kara
A
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D
Kum Canal ; VIII-Amu Darya Delta)
Fig. 2
Land use map of the ASB
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Irrigable area of countries in the ASB
Fig. 4
Trend of crop planting structure and planting area in the ASB from 2000 to 2014
A
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D
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A
N
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Fig. 3
Fig. 5
Main crop yield of the ASB from 2000 to 2014
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Change trends in main crop yields per unit area in the ASB from 2000 to 2014
A
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D
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A
N
Fig. 6
Fig. 7 2014
Annual yield spatial distribution of main crops among administrative in the ASB from 2000 to
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Variations of water and land area in the ASB from 2000 to 2014
Fig. 9
Spatial and temporal variation characteristics of water area and volume in the Aral Sea
A
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M
A
N
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Fig. 8
Fig. 10
Change trend in the amount of water injected into the Aral Sea from 1992 to 2014
(Measured by two gauging stations, samanbay and karateren, located on Amu Darya
Water productivity of main crops in the ASB from 2000 to 2014
A
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Fig. 11
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Syr Darya respectively )
Fig. 12
Administrative differences of water productivity of main crops in ASB from 2000 to 2014
Table 1
Land Resources in the ASB (CAWATERinfo, 2018)
Area
of Cultivable Area
Cultivated Area
Irrigated Area
ha
ha
%
ha
%
ha
%
Kazakhstan*
34,440,000
23,872,400
40
1,658,800
17
786,200
10
Kyrgyzstan*
12,490,000
1,257,400
2
595,000
6
422,000
5
Tajikistan
14,310,000
1,571,000
3
769,900
8
719,000
9
Turkmenistan
48,810,000
7,013,000
12
1,805,300
18
1,735,000
22
Uzbekistan
44,884,000
25,447,700
43
5,207,800
52
4,233,400
54
154,934,000
59,161,500
100
10,036,800
100
7,895,600
100
Aral
Sea
Basin
Table 2
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* Only provinces in the Aral Sea Basin are included
Surface Water Resources in the Aral Sea Basin (Mean Annual Runoff, km 3/year)
N
(CAWATERinfo, 2018)
Kyrgyzstan
27.54
Tajikistan
1.01
Turkmenistan
-
Uzbekistan
5.56
Total Aral Sea Basin
36.63
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D
2.52
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Kazakhstan
Amudarya
3
Total Aral Sea Basin
km /year
%
-
2.52
2.39
1.65
29.20
27.75
58.73
59.74
56.78
1.41
1.41
1.34
6.79
12.35
11.74
68.58
105.21
100.00
M
Syrdarya
A
River Basin
Country
A
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country
Country