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Water footprint assessment of main cereals in Iran
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Water footprint assessment of main cereals in Iran Behnam Ababaei a,b , Hadi Ramezani Etedali c,∗ a
INRA-SupAgro, UMR759, Laboratoire d’Ecophysiologie des Plantes sous Stress Environnementaux (LEPSE), F-34060 Montpellier, France Limagrain Europe, Native Traits Group, F-63720 Chappes, France c Department of Water Engineering, Imam Khomeini International University, Qazvin, Iran b
a r t i c l e
i n f o
Article history: Received 11 February 2016 Received in revised form 10 July 2016 Accepted 12 July 2016 Available online xxx Keywords: Virtual water Water footprint Wheat Barley Maize Iran
a b s t r a c t Iran is mostly located in arid and semiarid regions which makes agricultural water management considerably important in this country. In this research the concept of ‘water footprint’ (WF) is applied at the regional scale for the first time in the country. The calculation framework of Ababaei and Ramezani Etedali (2014) was adopted and modified to better account for the gray and white WFs. The weighted average of each WF component (green, blue, gray and white) and the national total water footprint (NTWF) of the production of main cereals (wheat, barley and maize) were calculated. The NTWF of wheat, barley and maize production were estimated 36,777, 7975 and 3744 million cubic meters (MCM) per year for the period 2006–2012. The ratio of total green WF of three crops to the aggregated NTWF (i.e. all crops) was 43%, and the ratios of the green WF to the NTWF were 47%, 42% and 2% for wheat, barley and maize, respectively. These results show that wheat and barley production are significantly large consumers of the green water resources (i.e. effective precipitation). This implied that there are great opportunities to improve the green water productivity through increasing yield, especially in wheat and barley rainfed lands. The average national green+blue WFs were estimated 24,628, 5,123 and 1,604 MCM per year for wheat, barley and maize, respectively, and 31,356 MCM per year altogether. The ratios of national gray + white WF to the NTWF were also estimated 33%, 36% and 57% for wheat, barley and maize, respectively. These values show the importance of better irrigation management strategies to reduce the share of gray and white WF which is important in both terms of water resources management and environment conservation. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Increasing populations, socioeconomic developments, global freshwater withdrawal, dying rivers and high pollution levels are all signs of growing water scarcity (Gleick, 1993 Postel, 2000; WWAP, 2009; Mekonnen and Hoekstra, 2010). Agriculture is the main user of fresh water with 85% of global surface and ground water consumption (Shiklomanov, 2000; Molden, 2007) and reducing the consumptive water use in this important sector of economy is part of all major strategies related to relieving water scarcity (Chukalla et al., 2015). To this end, major efforts have been dedicated to reducing the non-beneficial consumptive water use and the non-recoverable water losses (e.g. Hoekstra, 2003; Falkenmark
∗ Corresponding author. E-mail addresses: [email protected], [email protected] (B. Ababaei), [email protected], [email protected] (H. Ramezani Etedali).
and Rockström, 2006) which at the same time can result in increasing water productivity (Molden, 2007). The water footprint concept, first introduced by Hoekstra (2003) and later elaborated by Hoekstra and Chapagain (2008), is recently being used for fresh water resources management (Wackernagel and Rees, 1996; Wackernagel et al., 1997; Wackernagel and Jonathan, 2001; Ababaei and Ramezani Etedali, 2014). The water footprint (WF) of a product (usually known as virtual water content) is defined as the volume of water consumed or polluted for producing the product, measured over its full production chain and is an indicator of the allocation of freshwater resources to different part of the production process. Knowledge of how allocated water resources are consumed over the production process is highly valuable for water resources managers and policy makers. Many studies have focused on virtual water and virtual water transfer (Hoekstra and Hung, 2002, 2005; Hoekstra and Chapagain, 2007, 2008; Liu et al., 2007) and some distinguished green (i.e. effective precipitation) and blue (i.e. irrigation) water components (Liu et al., 2009; Liu and Yang, 2010; Siebert and Doll, 2008, 2010; Liu et al., 2007, 2009; Gerbens-Leenes et al.,
http://dx.doi.org/10.1016/j.agwat.2016.07.016 0378-3774/© 2016 Elsevier B.V. All rights reserved.
Please cite this article in press as: Ababaei, B., Ramezani Etedali, H., Water footprint assessment of main cereals in Iran. Agric. Water Manage. (2016), http://dx.doi.org/10.1016/j.agwat.2016.07.016
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2009; Aldaya et al., 2010; Ababaei and Ramezani Etedali, 2014). The gray WF, which was introduced in order to express water pollution in terms of a volume polluted (Hoekstra et al., 2011), was first used for the analysis of the WF of wheat in different regions of Italy by Aldaya and Hoekstra (2010). Water footprint can be decreased through increasing yields, using more efficient irrigation systems (like drip irrigation), reducing non-beneficial evapotranspiration (e.g. by using mulches), reducing fertilizer loss, enhancing effective use of precipitation, optimizing crop planting dates and choosing crops and varieties with higher yield (Zhuo et al., 2016; Chukalla et al., 2015). Zhuo et al. (2016) estimated green, blue and gray WF in Yellow river basin for the period 1961–2009 and showed the sum of green and blue WFs has reduced due to improved crop yields and the gray WF increased because of the growing use of fertilizers. Also they concluded that the ratio of blue to green WF has increased due to expansion of irrigated lands. Ababaei and Ramezani Etedali (2014) used the framework proposed by Hoekstra et al. (2009) and introduced a new term, the white WF, for wheat irrigated lands as an indicator of irrigation water losses and showed that the national total WF (NTWF) of Iran’s wheat production for the period 2006–2012 is around 42,143 million cubic meters (MCM) per year (including 16% gray and 25% white WF). Their results suggest that the investigations of the gray and white WF are essential in production of main cereals. Most of the studies on virtual water and water footprint in Iran have been limited to one specific crop or small study areas (e.g. Dehghanpur and Bakhshoodeh, 2008; Babazadeh and Sarai Tabrizi, 2012; Pourjafarinejad et al., 2013; Arabi Yazdi et al., 2015; Omidi and Homaee, 2015) which cannot provide policy-makers with accurate information on how water resources are used. There are only a few comprehensive studies which consider more than one crop and spatial variations of climate, soil and management (e.g. Montazar et al., 2009; Ababaei and Ramezani Etedali, 2014). Hence, the purpose of this study is to estimate the green, blue, gray and white WFs of the main cereals (wheat, barley and maize) in the main cereal producing provinces of Iran at the provincial and national levels. We quantify different WF components of crop production using a regional water balance model, AGWAT, which calculates the crop water requirements and actual water use taking into account local climate, soil conditions and irrigation management strategies.
2. Materials and methods The national green, blue, gray and whitewater footprints of wheat, barley and maize production were estimated following the calculation frameworks of Hoekstra and Chapagain (2008) and Hoekstra et al. (2009), and modifications proposed by Ababaei and Ramezani Etedali (2014). Within this framework, the WF is considered as an indicator of the allocation of water by humanity and hence the consumption by ecosystems is not considered a WF (Hoekstra et al., 2011). Irrigation requirements and effective precipitation were estimated using the AGWAT model (IRIMO, 2001) which calculates crop evapotranspiration (ET, in mm) and irrigation requirements using FAO-Penman-Monteith method under standard and non-standard conditions (Allen et al., 1998). The model was applied at the regional scale (for the first time in the country) using the input data available in the model database. Irrigation was triggered when 50% of the total available water was depleted and filled the root zone moisture content back to the field capacity. As effective precipitation (Peff , in mm) is not provided in the database, the net irrigation requirements (IR, in mm) were first calculated by considering gross irrigation requirement (GI, in mm) and average irrigation efficiency (IE, dimensionless) in each region. Average irrigation efficiencies were provided in the model database as the
values used by local authorities for regional water resources planning. Total effective precipitation was calculated as the difference between the actual crop evapotranspiration (ETc , in mm) and the net irrigation requirements (IR), which were both extracted from the model database. The green and blue water uses (CWU, in m3 /ha) were considered equal to the net irrigation requirement and effective precipitation (Eqs. (1)–(4)). Obviously, no blue water use was considered under rainfed conditions: CWUBlue,Irr = IR = 10 × IE × GI
(1)
CWUGreen,Irr = 10 × Peff = 10 × (ETc − IR)
(2)
CWUBlue,RF = 0
(3)
CWUGreen,RF = 10 × Peff
(4)
Where the RF and Irr subscripts show rainfed and irrigation conditions, respectively. Next, the green (WFGreen ) and blue (WFBlue ) water footprints (in m3 /ton) were calculated by dividing the green and blue CWU (in m3 /ha) by actual crop yield (in ton/ha) separately under rainfed and irrigated conditions. Irrigated and rainfed yields of wheat, barley and maize were obtained from the Ministry of Agricultural-Jihad for the period 2006–2012 at a provincial scale. Volume of water required to assimilate the fertilizers leached in run off is called the gray WF (Hoekstra, 2003). In this study, the gray water footprint (WFGray ) related to nitrogen application was only estimated as the main source of pollution in agricultural area in Iran (Eqs. (5)–(6)). The nitrogen application rates (NAR, in kg/ha) were obtained from the Ministry of Agricultural-Jihad. The WFgray (m3 /ton) was calculated following Chapagain et al. (2006) and Hoekstra et al. (2011). The USEPA standard was considered (Chapagain et al., 2006) for the maximum allowable concentration (CMax , in mg/L) of nitrate in surface and groundwater which recommends a maximum concentration of 10 mg/L. This standard was adopted since most of the agricultural water is extracted from and returned to the same resources used for domestic purposes and pollution needs to be kept below an acceptable threshold. The natural nitrogen concentrations (CNat , in mg/L) were conservatively assumed to be zero as no data or model simulations was available at this spatial scale. WFGray,Irr =
˛Irr × NARIrr 1 × CMax − CNat YieldIrr
(5)
WFGray,RF =
˛RF × NARRF 1 × CMax − CNat YieldRF
(6)
The ␣ values were assumed to be equal to the values applied by Chapagain et al. (2006) and Hoekstra et al. (2011), i.e. 10% and 5% of the total nitrogen fertilizer applied under irrigated and rainfed conditions, respectively. Moreover, the irrigation loss (only that part which is not considered as the gray WF, m3 /ton) was considered as part of the total WF and referred to by the term “white water footprint” (WFWhite , in m3 /ton). The equations used here to calculate the white WF are different with those first proposed by Ababaei and Ramezani Etedali (2014) in order to consider the contribution of the white WF to the gray WF. This modification was deemed necessary as deep percolation assimilates fertilizers in the soil. A part of irrigation water (called leaching requirement) is usually applied by farmers to control soil salinity and keep yield reduction below an acceptable level. This part is considered as the gray WF. The remaining part of the white WF is assumed lost since in most regions of the country water table is now deeper than 50 m (and is going deeper at the average rate of ∼1 m/year) and it takes years for this water to return to the source. W F White,Irr = max(0, WFWhite,RF = 0
10 × (GI − IR) − WFGray,Irr ) YieldIrr
(7) (8)
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Fifteen (for wheat and barley) and twelve (for maize) provinces were considered as the main producing provinces according to the data provided by the Ministry of Agricultural-Jihad at a provincial scale (Fig. 1). The green, blue, gray and white WFs of wheat, barley and maize productions for each selected province (the term WF in Eq. (9)) were estimated by taking the average WF (in m3 /ton) over all the regions in that province. The national WF components were estimated by taking the average of each component over all the provinces considering the share of each province in the total production of wheat, barley and maize in all the selected provinces as weighting factors (Eqs. (9)–(10)). Finally, the volume of each WF component at the provincial and national levels were calculated as the weighted averages of the WF components under irrigated and rainfed conditions considering the share of each production system (irrigated or rainfed) in the total production of the selected provinces or the total national production (Eqs. (11)–(12)). Details of the calculations are provided by Ababaei and Ramezani Etedali (2014). The same equations were used for wheat, barley and maize. WFVi,x,y = Prodi,x,y × WFi,x,y
AWFx,y =
(9)
WFVi,x,y
i
(10) Prodi,x,y
i
WAWFx = ˇ.AWFx,Irr + (1 − ˇ)AWFx,RF
(11)
NWFx = TotProd × WAWFx
(12)
where i: province index (1–15 for wheat and barley, 1–12 for maize); x: green, blue, gray or white; y: Irr (irrigated) or RF (rainfed); Prod: production in each province under irrigated or rainfed conditions (Mton); WFV: the total volume of each WF component (MCM); AWF: the national weighted average of each WF component (m3 /ton) under irrigated or rainfed conditions; : the share of total irrigated production in the selected provinces (0.66, 0.69 and 1.0 for wheat, barley and maize, respectively) or the whole country (0.68, 0.67 and 0.99 for wheat, barley and maize, respectively); WAWF: the national weighted average of each WF component (m3 /ton) for all production systems (irrigated and rainfed); TotProd: total production of the selected provinces or the total national production (Mton); and NWF: the total volume of each WF component in the selected provinces or the total national volume of each WF component (MCM). 3. Results The data on wheat, barley and maize production in the main cereal producing provinces is presented in Tables 1–3, respectively. The selected provinces accounted for 86.5%, 84.7% and 95.8% of the national wheat, barley and maize productions. For wheat,
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the proportions of irrigated and rainfed productions across the whole country’s cultivated lands were 67.7% and 32.3%, respectively. These proportions were 67.1% and 32.9% for barley, and 99.9% and 0.1% for maize, respectively. As maize is rarely cultivated under rainfed conditions in Iran, we did not include rainfed-cultivated maize in this analysis. According to the data obtained, the national average of wheat yield in irrigated and rainfed lands were about 3.4 and 1.0 ton/ha, respectively. These values were 3.1 and 1.0 ton/ha for barley, and 7.6 and 3.8 ton/ha for maize, showing large gaps between irrigated and rainfed sectors as was expected for a dry country. Nitrogen application rates (NARs) in the main producing provinces are presented in Table 4.
3.1. Wheat The WF components of wheat production are summarized in Table 5. For irrigated wheat, the green WF ranged from 499 to 1023 m3 /ton, the blue WF from 521 to 1402 m3 /ton, the gray WF from 337 to 822 m3 /ton, and the white WF from 222 to 1637 m3 /ton. The average total WF of irrigated wheat overall the selected provinces was around 2657 m3 /ton. For rainfed wheat, the green WF varied between 1282 and 4166 m3 /ton, and the gray WF between 100 and 740 m3 /ton. The average total WF of rainfed wheat production was estimated 3071 m3 /ton. Table 6 shows the national average of the WF components of wheat production. The NTWF of wheat over the period 2006–2012 was 36,777 MCM/year (47% green, 20% blue, 19% gray and 15% white; Fig. 2) of which about 86.6% was consumed in the main wheat producing provinces. Ardebil (13.6%), Fars (12.8%) and East Azerbaijan (11.1%) constituted 37.6% of the wheat NTWF. In irrigated lands, these three provinces accounted for 14.5%, 50.3%, 43.0% and 52.3% of the total green, blue, gray and white WFs related to wheat production, respectively. In rainfed lands, the largest green WFs were found in Kurdistan (9.2%), Kermanshah (6.6%) and Zanjan (5.7%) while the largest gray WFs were related to Zanjan (2.3%), Kermanshah (2.0%) and Golestan (1.9%).
3.2. Barley Table 7 shows the WF components of barley in the selected provinces. For irrigated barley, the green WF ranged from 302 to 798 m3 /ton, the blue WF from 435 to 1305 m3 /ton, the gray WF from 393 to 740 m3 /ton, and the white WF from 212 to 1402 m3 /ton. The average total WF of irrigated barley among all the selected provinces was 2640 m3 /ton. For rainfed lands, the green WF ranged from 1433 to 3528 m3 /ton and the gray WF from 160 to 341 m3 /ton across the selected provinces. The average total WF of rainfed barley was 2594 m3 /ton.
Fig. 1. Major wheat (left), barley (center) and maize (right) producing provinces in Iran.
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Table 1 Wheat production data for the main wheat producing provinces. Province
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azerbaijan Ardebil East Azerbaijan Lorestan Markazi Tehran Zanjan Qazvin Total (Main Provinces) Total (National)
Production (ton)
Share (%)
National Share (%)
Yield (kg/ha)
Irrigated
Rainfed
Total
Irrigated
Rainfed
Irrigated
Rainfed
Total
Irrigated
Rainfed
1,578,195 1,254,269 994,297 475,667 384,030 352,909 149,478 332,104 329,954 283,104 215,306 286,251 424,140 85,351 255,899 7,400,951 8,778,996
103,768 93,022 206,968 442,123 417,436 333,758 492,957 283,664 270,715 287,902 291,500 169,691 2694 341,459 77,380 3,815,035 4,192,808
1,681,962 1,347,291 1,201,265 917,790 801,466 686,666 642,435 615,769 600,668 571,006 506,806 455,941 426,834 426,810 333,278 11,215,987 12,971,804
93.8 93.1 82.8 51.8 47.9 51.4 23.3 53.9 54.9 49.6 42.5 62.8 99.4 20.0 76.8 66.0 67.7
6.2 6.9 17.2 48.2 52.1 48.6 76.7 46.1 45.1 50.4 57.5 37.2 0.6 80.0 23.2 34.0 32.3
18.0 14.3 11.3 5.4 4.4 4.0 1.7 3.8 3.8 3.2 2.5 3.3 4.8 1.0 2.9 84.3 –
2.5 2.2 4.9 10.5 10.0 8.0 11.8 6.8 6.5 6.9 7.0 4.0 0.1 8.1 1.8 91.0 –
13.0 10.4 9.3 7.1 6.2 5.3 5.0 4.7 4.6 4.4 3.9 3.5 3.3 3.3 2.6 86.5 –
4,058 2,994 2,900 3,067 4,638 3,864 4,149 3,122 4,240 3,014 3,102 3,800 4,764 3,700 4,045 3,508 3,438
817 498 624 2,021 1,192 1,033 993 1,037 1,145 861 1,179 943 1,010 965 894 1,049 1,010
Table 2 Barley production data for the main barley producing provinces. Province
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azerbaijan Qazvin Qom Khuzestan West Azerbaijan Total (Main Provinces) Total (National)
Production (ton)
Share (%)
National Share (%)
Yield (kg/ha)
Irrigated
Rainfed
Total
Irrigated
Rainfed
Irrigated
Rainfed
Total
Irrigated
Rainfed
474,211 165,520 43,715 181,318 132,269 16,410 149,978 67,977 129,952 28,176 62,234 93,632 81,170 47,526 35,035 1,709,124 1,954,694
45,494 56,318 155,818 3765 47,787 155,264 173 74,295 2940 101,095 45,158 8252 17 32,186 31,532 760,093 959,771
519,705 221,838 199,533 185,084 180,057 171,673 150,151 142,272 132,892 129,270 107,392 101,885 81,186 79,712 66,567 2,469,217 2,914,465
91.2 74.6 21.9 98.0 73.5 9.6 99.9 47.8 97.8 21.8 58.0 91.9 100.0 59.6 52.6 69.2 67.1
8.8 25.4 78.1 2.0 26.5 90.4 0.1 52.2 2.2 78.2 42.0 8.1 0.0 40.4 47.4 30.8 32.9
24.3 8.5 2.2 9.3 6.8 0.8 7.7 3.5 6.6 1.4 3.2 4.8 4.2 2.4 1.8 87.4 –
4.7 5.9 16.2 0.4 5.0 16.2 0.0 7.7 0.3 10.5 4.7 0.9 0.0 3.4 3.3 79.2 –
17.8 7.6 6.8 6.4 6.2 5.9 5.2 4.9 4.6 4.4 3.7 3.5 2.8 2.7 2.3 84.7 –
2,631 3,905 4,483 4,037 2,808 2,414 3,817 3,015 3,619 2,958 2,681 3,488 3,139 1,739 2,460 3,172 3,075
595 1,363 1,273 757 781 1,193 1,502 1,056 1,091 1,597 883 767 167 418 1,003 1,101 1,034
Table 3 Maize production data for the main maize producing provinces. Province
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan Total (Main Provinces) Total (National)
Production (ton)
Share (%)
National Share (%)
Yield (kg/ha)
Irrigated
Rainfed
Total
Irrigated
Rainfed
Irrigated
Rainfed
Total
Irrigated
Rainfed
515,718 468,814 293,018 232,660 98,144 76,292 49,483 45,061 43,862 34,757 32,702 25,139 1,915,649 1,998,107
0 0 0 0 0 0 0 0 0 0 0 0 0 1840
515,718 468,814 293,018 232,660 98,144 76,292 49,483 45,061 43,862 34,757 32,702 25,139 1,915,649 1,999,947
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.9
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
25.8 23.5 14.7 11.6 4.9 3.8 2.5 2.3 2.2 1.7 1.6 1.3 95.9 –
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 –
25.8 23.4 14.7 11.6 4.9 3.8 2.5 2.3 2.2 1.7 1.6 1.3 95.8 –
8,572 6,294 9,019 7,427 11,123 8,978 5,414 8,255 6,740 5,843 8,666 6,907 7,698 7,645
0 0 0 0 0 0 0 0 0 0 0 0 0 3,761
Table 8 shows the national average of the WF components of barley production. The NTWF of barley production was estimated 7975 MCM/year (42% green, 22% blue, 19% gray and 17% white; Fig. 3) of which 85% was related to the main barley producing provinces. Khorasan contributed 27.3% to the barley NTWF. In irrigated lands, this province constituted 11.3%, 35.1%, 23.1% and 49.8% of the total green, blue, gray and white WFs related to barley production, respectively. In rainfed lands, the largest green WFs were
found in Lorestan (11.0%) and Kermanshah (10.6%). Also the largest gray WFs were related to these two provinces with 2.5% and 2.4%, respectively. 3.3. Maize Table 9 shows the WF components of maize for the selected provinces. In irrigated lands, the green WF of maize production
Please cite this article in press as: Ababaei, B., Ramezani Etedali, H., Water footprint assessment of main cereals in Iran. Agric. Water Manage. (2016), http://dx.doi.org/10.1016/j.agwat.2016.07.016
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Table 4 Nitrogen application rates (kg/ha) for selected provinces in irrigated and rainfed lands (2006–2012)a . Wheat
Barley
Maize
Province
Irrigated
Rainfed
Province
Irrigated
Rainfed
Province
Irrigated
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azarbaijan Ardebil East Azarbaijan Lorestan Markazi Tehran Zanjan Qazvin
333.7 230.8 192.5 160.1 261.4 161.6 156.4 105.1 267.9 111.3 154.7 235.4 228.3 193.4 202.7
65.3 73.7 17.0 126.8 83.6 55.2 54.4 31.1 23.0 43.7 81.6 83.4 25.0 94.2 26.0
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azerbaijan Qazvin Qom Khuzestan West Azerbaijan
194.6 153.3 223.4 271.0 190.8 114.8 216.5 135.8 169.5 100.0 120.1 209.7 269.7 123.9 565.2
19.0 87.2 66.8 51.6 31.1 66.5 54.1 28.5 73.1 81.2 35.1 46.3 0 63.6 32.2
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan
448.3 400.1 371.8 558.5 454.7 348.3 171.7 325.4 450.9 276.0 473.3 233.9
a
Source: Ministry of Agricultural-Jihad.
Table 5 Water footprint components of wheat production for the main wheat producing provinces. Province
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azarbaijan Ardebil East Azarbaijan Lorestan Markazi Tehran Zanjan Qazvin Average CV Min Max
WFIrr (m3 /ton)
Water Use (mm)
WFRF (m3 /ton)
ETc
IR
Peff
Green
Blue
Gray
White
Total
Green
Gray
Total
607 426 606 419 592 574 697 493 494 536 631 555 510 554 570 551 13% 419 697
365 218 407 159 267 313 377 219 232 290 314 302 272 275 300 287 22% 159 407
242 207 200 259 324 261 321 275 262 246 317 254 238 279 269 264 13% 200 324
597 693 690 845 699 676 773 880 618 817 1023 668 499 753 666 726 17% 499 1,023
899 729 1402 521 576 811 908 700 547 963 1011 794 571 744 742 794 28% 521 1,402
822 771 664 522 564 418 377 337 632 369 499 619 479 523 501 540 25% 337 822
452 359 1637 271 255 598 969 620 222 873 1133 419 223 544 376 597 65% 222 1,637
2,770 2,553 4,393 2,159 2,094 2,502 3,027 2,536 2,020 3,022 3,667 2,501 1,771 2,563 2,285 2,657 24% 1,771 4,393
2,967 4,166 3,205 1,282 2,721 2,527 3,231 2,648 2,289 2,860 2,693 2,692 2,352 2,887 3,012 2,769 21% 1,282 4,166
400 740 137 314 351 267 274 150 100 254 346 442 123 488 145 302 55% 100 740
3,367 4,906 3,341 1,596 3,072 2,794 3,505 2,798 2,390 3,113 3,039 3,134 2,475 3,375 3,158 3,071 22% 1,596 4,906
Table 6 The total volume (WFV) of each WF component for the main wheat producing provinces. Province
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azarbaijan Ardebil East Azarbaijan Lorestan Markazi Tehran Zanjan Qazvin Sum AWF (m3 /ton) WAWF (m3 /ton): Main Provinces WAWF (m3 /ton): National NWF (MCM): Main Provinces NWF (MCM): National
WFVIrr (MCM)
WFVRF (MCM)
Green
Blue
Gray
White
Total
Green
Gray
Total
942 869 686 402 269 238 116 292 204 231 220 191 212 64 170 5107 690 1361 1328 15,265 17,222
1418 915 1394 248 221 286 136 232 181 272 218 227 242 64 190 6244 844 557 571 6244 7406
1298 967 660 248 216 148 56 112 208 105 107 177 203 45 128 4679 632 519 525 5824 6809
713 451 1628 129 98 211 145 206 73 247 244 120 94 46 96 4502 608 401 412 4502 5340
4371 3202 4368 1027 804 883 453 842 666 855 789 716 751 219 585 20,531 2774 2838 2835 31,835 36,777
308 388 663 567 1136 843 1593 751 620 823 785 457 6 986 233 10,158 2663
41 69 28 139 146 89 135 43 27 73 101 75 0 167 11 1145 300
349 456 692 705 1282 933 1728 794 647 896 886 532 7 1152 244 11,303 2963
Irr: irrigated, RF: rainfed, WFV: total volume of each WF component, AWF: national weighted average of each WF component for all production systems (m3 /ton) under irrigated or rainfed conditions, WAWF: national weighted average of each WF component for all production systems (irrigated and rainfed) (m3 /ton), NWF: total volume of each WF component in the selected provinces or total national volume of each WF component (MCM).
Please cite this article in press as: Ababaei, B., Ramezani Etedali, H., Water footprint assessment of main cereals in Iran. Agric. Water Manage. (2016), http://dx.doi.org/10.1016/j.agwat.2016.07.016
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Fig. 2. Shares of wheat WF components in irrigated (Irr) and rainfed (RF) lands of the main wheat producing provinces.
Table 7 Water footprint components of barley production for the main barley producing provinces. Province
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azerbaijan Qazvin Qom Khuzestan West Azerbaijan Average CV Min Max
WFIrr (m3 /ton)
Water Use (mm)
WFRF (m3 /ton)
ETc
IR
Peff
Green
Blue
Gray
White
Total
Green
Gray
Total
553 446 485 455 493 507 391 402 481 374 418 440 399 351 399 486.5 12% 446.0 553.2
342 253 195 332 272 224 199 200 282 149 234 225 222 174 186 278.6 20% 195.0 342.1
210 195 290 122 221 283 191 202 199 225 109 215 177 176 213 207.6 23% 121.8 290.3
798 500 648 302 786 1,173 501 670 549 759 406 616 562 1,014 864 607 38% 302 798
1,305 642 435 824 970 928 522 664 780 504 1,152 646 708 1,003 757 835 29% 435 1,305
740 393 393 671 679 476 567 450 468 338 448 601 859 713 2,298 575 82% 393 740
1,402 430 212 393 674 1,018 119 587 559 413 673 160 87 807 0 622 61% 212 1,402
1,723 576 320 583 989 1,200 228 794 738 549 2,042 268 131 1,334 0 838 71% 320 1,723
3,528 1,433 2,280 1,610 2,827 2,374 1,275 1,913 1,821 1,406 1,232 2,800 10,594 4,218 2,119 2,336 100% 1433 3,528
160 320 271 341 199 279 180 135 335 254 199 302 0 761 160 258 64% 160 341
3,688 1,753 2,551 1,952 3,026 2,652 1,455 2,048 2,156 1,661 1,431 3,102 10,594 4,979 2,280 2,594 89% 1,753 3,688
Fig. 3. Shares of barlet WF components in irrigated (Irr) and rainfed (RF) lands of the main barley producing provinces.
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Table 8 The total volume (WFV) of each WF component for the main barley producing provinces. Province
WFVIrr (MCM)
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azarbaijan Qazvin Qom Khuzestan West Azarbaijan Sum AWF (m3 /ton) WAWF (m3 /ton): Main Provinces WAWF (m3 /ton): National NWF (MCM): Main Provinces NWF (MCM): National
WFVRF (MCM)
Green
Blue
Gray
White
Total
Green
Gray
Total
378 83 28 55 104 19 75 46 71 21 25 58 46 48 30 1088 637 1120 1154 2766 3363
619 106 19 149 128 15 78 45 101 14 72 60 57 48 27 1540 901 624 604 1540 1761
351 65 17 122 90 8 85 31 61 10 28 56 70 34 81 1107 648 529 521 1306 1518
665 71 9 71 89 17 18 40 73 12 42 15 7 38 0 1166 683 472 458 1166 1334
2013 325 74 397 411 59 256 161 306 57 167 189 180 168 137 4901 2868 2745 2736 6778 7975
160 81 355 6 135 369 0 142 5 142 56 23 0 136 67 1678 2207
7 18 42 1 10 43 0 10 1 26 9 2 0 24 5 199 262
168 99 398 7 145 412 0 152 6 168 65 26 0 160 72 1877 2469
Irr: irrigated, RF: rainfed, WFV: total volume of each WF component, AWF: national weighted average of each WF component for all production systems (m3 /ton) under irrigated or rainfed conditions, WAWF: national weighted average of each WF component for all production systems (irrigated and rainfed) (m3 /ton), NWF: total volume of each WF component in the selected provinces or total national volume of each WF component (MCM).
Table 9 Water footprint components of maize production for the main maize producing provinces. Province
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan Average CV Min Max
WFIrr (m3 /ton)
Water Use (mm) ETc
IR
Peff
Green
Blue
Gray
White
Total
590 546 662 731 680 667 566 680 623 731 529 534 628 11% 529 731
566 528 618 729 630 629 495 628 592 685 525 475 592 12% 475 729
28 29 43 10 50 38 70 52 31 46 4 59 38 48% 4 70
33 45 48 13 45 42 130 63 46 79 5 85 53 61% 5 130
656 822 686 983 567 701 915 761 879 1172 605 688 786 21% 567 1172
523 636 619 501 409 388 317 394 669 472 505 339 481 23% 317 669
338 624 348 842 181 502 1234 722 577 1302 371 611 638 52% 181 1302
1550 2127 1700 2339 1201 1633 2596 1940 2171 3026 1486 1723 1958 25% 1201 3026
ranged from 5 to 130 m3 /ton, the blue WF from 567 to 1172 m3 /ton, the gray WF from 317 to 669 m3 /ton, and the white WF from 181 to 1302 m3 /ton. The average total WF for irrigated maize among all the selected provinces was 1958 m3 /ton, i.e. the highest water productivity among all the three studied crops. Table 10 shows the national average of the WF components of maize production. The NTWF of maize production was estimated around 3744 MCM/year (2% green, 41% blue, 29% gray and 28% white; Fig. 4) of which 95.9% of the maize NTWF was related to the main maize producing provinces. Khuzestan (26.6%) and Fars (21.4%) together accounted for 48.0% of the NTWF related to maize production. For irrigated maize, these two provinces constituted 46.4%, 47.6%, 52.4% and 44.2% of the total green, blue, gray and white WFs related to maize production, respectively. 3.4. Discussion Over the period 2006–2012, the NTWFs of wheat, barley and maize production were estimated 36,777, 7975 and 3744 MCM per year, i.e. totally 48,496 MCM per year which is around half of the
total water withdrawal in the country (currently around 100,000 MCM per year; Keshavarz 2015). Of this amount, the shares of wheat, barley and maize were 76%, 16% and 8%, respectively. The green, blue, gray and white WFs accounted for 43%, 22%, 19% and 16% of the NTWF related to the production of all crops, respectively, indicating the importance of the green WF in the production of the main cereals in the country. The average national green + blue WFs were estimated 24,628, 5123 and 1604 MCM per year for wheat, barley and maize, respectively, and 31,356 MCM per year altogether. It shows that of the NTWF of the production of wheat, barley and maize, 67%, 64% and 43% was attributed to the green + blue WF. The contribution of the green + blue WF components to the NTWF of the production of all crops were 51%, 11% and 3% with wheat being the largest contributor. Wheat has been a strategic crop for the country being cultivated in 4.7 and 23 times larger areas and producing 4.6 and 5.9 times more than barley and maize, respectively. For that, water resources allocation in wheat production has a deep impact on national freshwater consumption and must be treated with more precision and conservatism.
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Table 10 The total volume (WFV) of each WF components for the main maize producing provinces. Province
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan Sum AWF (m3 /ton)a WAWF (m3 /ton): Main Provinces WAWF (m3 /ton): National NWF (MCM): Main Provinces NWF (MCM): National
WFVIrr (MCM) Green
Blue
Gray
White
Total
17 21 14 3 4 3 6 3 2 3 0 2 79 41 41 41 79 83
338 385 201 229 56 53 45 34 39 41 20 17 1458 761 761 761 1458 1521
270 298 181 116 40 30 16 18 29 16 17 9 1040 543 543 542 1040 1084
174 292 102 196 18 38 61 33 25 45 12 15 1012 528 528 528 1012 1056
800 997 498 544 118 125 128 87 95 105 49 43 3590 1874 1874 1872 3590 3744
Cultivated under rainfed conditions in Iran. Irr: irrigated, RF: rainfed, WFV: total volume of each WF component, AWF: national weighted average of each WF component for all production systems (m3 /ton) under irrigated or rainfed conditions, WAWF: national weighted average of each WF component for all production systems (irrigated and rainfed) (m3 /ton), NWF: total volume of each WF component in the selected provinces or total national volume of each WF component (MCM). a AWF is very close to WAWF as the share of rainfed-cultivated maize is negligible.
Fig. 4. Shares of maize WF components in irrigated (Irr) lands of the main maize producing provinces. Maize is rarely cultivated under rainfed conditions in Iran.
On the other hand and over the same period, the gray + white WF accounted for 33%, 36% and 57% of the NTWF of wheat, barley and maize production, respectively. These WF components constituted 25%, 6% and 4% of the aggregated NTWF of the production of these cereals with the share of the white WF being 15%, 17% and 28% of the NTWF of wheat, barley and maize production, respectively. These values imply that a great share of water consumed for cereal production is lost during irrigation and perhaps never reaches the water table. Considering the fact that Iran is located in an arid region of the world, these values imply the importance of a better irrigation management strategies to reduce the share of white WF which is important in both terms of water resources management and environment conservation. At the provincial level, wheat productions in Ardebil (10.3%), Fars (9.7%) and East Azerbaijan (8.5%) were the largest contributors to the NTWF related to the production of the main cereals. These provinces consumed 13,834 MCM per year for wheat production, i.e. more than 28.5% of the NTWF for the cereals. From the same
point of view, Khorasan (4.5%), Fars (1.1%) and Isfahan (1.0%) were the largest water consumers in barley production, while Khuzestan (2.1%) and Fars (1.6%) were the largest users for maize production. Figs. 5–7 show the segregation of the NTWF of wheat, barley and maize, respectively, at the provincial level. These figures brings an important question up about the government’s strategy for improving water use efficiency. While the government is more concerned with increasing water use efficiency by using more efficient irrigation methods (like pressurized irrigation systems), and decreasing the share of the white WF, these results show an alternative option (for wheat and barley). In most of the selected provinces, the share of the green WF is significantly higher than the white and blue WFs, especially in provinces with more rainfed wheat-cultivated lands. In the case of wheat, the white WF is relatively important in only three major wheat producing provinces, i.e. Ardebil, Fars and East Azerbaijan. The same pattern can be detected for barley with the white WF in Khorasan, Hamadan, Isfahan, Markazi and Fars having large contribution (>0.9%) to the barley NTWF. This shows
Please cite this article in press as: Ababaei, B., Ramezani Etedali, H., Water footprint assessment of main cereals in Iran. Agric. Water Manage. (2016), http://dx.doi.org/10.1016/j.agwat.2016.07.016
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Fig. 5. Contribution of WF components to the wheat NTWF in irrigated (Irr) and rainfed (RF) lands of the main wheat producing provinces.
Fig. 6. Contribution of WF components to the barley NTWF in irrigated (Irr) and rainfed (RF) lands of the main barley producing provinces.
Fig. 7. Contribution of WF components to the maize NTWF in irrigated (Irr) lands of the main maize producing provinces. Maize is rarely cultivated under rainfed conditions in Iran.
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that there are great opportunities to increase water productivity and decrease water use in irrigated lands through increasing yield in rainfed production systems. With the national average yield of rainfed wheat and barley being less than one third of that in irrigated lands and at the same time the total WF of irrigated and rainfed lands being close (for wheat 2657 vs 3071 m3 /ton; for barley 2640 vs 2594 m3 /ton; see Tables 5 and 7), shifting strategies from decreasing the share of white WF to increasing the green WF productivity (by increasing yield per unit of the green water use) or applying supplementary irrigation in rainfed wheat and barley production systems (to increase yield without considerably increasing the share of the blue WF) seem promising alternatives worthy of further investigation.
specific region. Any other options leading to increased yield and higher green water productivity (like applying supplementary irrigation) is equally important. The data and estimated values presented in this study help policy-makers make more educated decisions on to the allocation of limited agricultural water resources. They can also be used by other researchers as they are collected and provided at the regional level at which it is very hard to get detailed data on crop production and water consumption. This data can also be used by researchers involved in global-scale studies that usually do not have access to this type of data at the regional level and may improve large-scale estimates of water footprint components which will otherwise deviate from values estimated at smaller spatial scales.
4. Conclusions References The approach proposed by Ababaei and Ramezani Etedali (2014) was applied to estimate the water footprint components of wheat, barley and maize production as the main cereals produced in Iran. A modification was made to the original calculation procedure to account for the interaction of the gray and white WFs. As more sophisticated and accurate model simulations were not available, conservative value of maximum acceptable concentration of nitrogen in the receiving water bodies were used to estimate the volume of water required for dilution (i.e. the gray WF). Estimation of WF components at the regional scale was proposed to enable determining where each WF component is originally located. At the same time, this approach takes into account the spatial variability of factors affecting crop water consumption much better than the approaches usually taken at the global scale studies (Ababaei and Ramezani Etedali, 2014). It was found that the green WF related to the country’s national production is about 2.3 and 1.9 times the blue WF for wheat and barley, confirming the importance of green water in cereal production in arid regions. In Iran, wheat and barley are mostly planted and harvested in autumn and springer and their growing periods are closely matched with the wet season, which is the main reason for the green WF being considerable in wheat and barley productions. On the other hand, irrigation is the largest source of water for maize production (18.4 times the green water) due to negligible precipitation during maize growing season. Relatively lower yields in rainfed lands and a lower opportunity cost of green water compared to the blue water (Mekonnen and Hoekstra, 2010) lead to the idea that taking opportunities to increase the use of green WF (by shifting crop sowing date) or to increase the green WF productivity (by increasing yield in rainfed lands, for example, by applying supplementary irrigation) can be of great importance to farmers who are already suffering from insufficient (blue) water resources. Increasing production from rainfed lands will reduce the need for higher level of production from irrigated lands in water-scarce areas like Iran and will thus result in reduced blue water requirement. Moreover, precision farming can substantially reduce the share of the white (due to reduction in irrigation water loss) and gray (due to reduction in fertilizer leaching to groundwater or to surface water through runoff) water footprints, which were shown to be large parts of total water footprint in cereal production (Jenkinson, 2001; Norse, 2005). The results show that the government’s strategy of tackling scarce agricultural water resources by solely focusing on improving irrigation efficiency should be reconsidered. While pressurized irrigation systems are costly and hard to maintain and operate for most farmers, improving water productivity (specially for green water) in cereal production can be more easily achieved with enhanced farm management strategies like changing sowing date or using cultivars with more adapted growing season to wet spells in each
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Water footprint assessment of main cereals in Iran Behnam Ababaei a,b , Hadi Ramezani Etedali c,∗ a
INRA-SupAgro, UMR759, Laboratoire d’Ecophysiologie des Plantes sous Stress Environnementaux (LEPSE), F-34060 Montpellier, France Limagrain Europe, Native Traits Group, F-63720 Chappes, France c Department of Water Engineering, Imam Khomeini International University, Qazvin, Iran b
a r t i c l e
i n f o
Article history: Received 11 February 2016 Received in revised form 10 July 2016 Accepted 12 July 2016 Available online xxx Keywords: Virtual water Water footprint Wheat Barley Maize Iran
a b s t r a c t Iran is mostly located in arid and semiarid regions which makes agricultural water management considerably important in this country. In this research the concept of ‘water footprint’ (WF) is applied at the regional scale for the first time in the country. The calculation framework of Ababaei and Ramezani Etedali (2014) was adopted and modified to better account for the gray and white WFs. The weighted average of each WF component (green, blue, gray and white) and the national total water footprint (NTWF) of the production of main cereals (wheat, barley and maize) were calculated. The NTWF of wheat, barley and maize production were estimated 36,777, 7975 and 3744 million cubic meters (MCM) per year for the period 2006–2012. The ratio of total green WF of three crops to the aggregated NTWF (i.e. all crops) was 43%, and the ratios of the green WF to the NTWF were 47%, 42% and 2% for wheat, barley and maize, respectively. These results show that wheat and barley production are significantly large consumers of the green water resources (i.e. effective precipitation). This implied that there are great opportunities to improve the green water productivity through increasing yield, especially in wheat and barley rainfed lands. The average national green+blue WFs were estimated 24,628, 5,123 and 1,604 MCM per year for wheat, barley and maize, respectively, and 31,356 MCM per year altogether. The ratios of national gray + white WF to the NTWF were also estimated 33%, 36% and 57% for wheat, barley and maize, respectively. These values show the importance of better irrigation management strategies to reduce the share of gray and white WF which is important in both terms of water resources management and environment conservation. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Increasing populations, socioeconomic developments, global freshwater withdrawal, dying rivers and high pollution levels are all signs of growing water scarcity (Gleick, 1993 Postel, 2000; WWAP, 2009; Mekonnen and Hoekstra, 2010). Agriculture is the main user of fresh water with 85% of global surface and ground water consumption (Shiklomanov, 2000; Molden, 2007) and reducing the consumptive water use in this important sector of economy is part of all major strategies related to relieving water scarcity (Chukalla et al., 2015). To this end, major efforts have been dedicated to reducing the non-beneficial consumptive water use and the non-recoverable water losses (e.g. Hoekstra, 2003; Falkenmark
∗ Corresponding author. E-mail addresses: [email protected], [email protected] (B. Ababaei), [email protected], [email protected] (H. Ramezani Etedali).
and Rockström, 2006) which at the same time can result in increasing water productivity (Molden, 2007). The water footprint concept, first introduced by Hoekstra (2003) and later elaborated by Hoekstra and Chapagain (2008), is recently being used for fresh water resources management (Wackernagel and Rees, 1996; Wackernagel et al., 1997; Wackernagel and Jonathan, 2001; Ababaei and Ramezani Etedali, 2014). The water footprint (WF) of a product (usually known as virtual water content) is defined as the volume of water consumed or polluted for producing the product, measured over its full production chain and is an indicator of the allocation of freshwater resources to different part of the production process. Knowledge of how allocated water resources are consumed over the production process is highly valuable for water resources managers and policy makers. Many studies have focused on virtual water and virtual water transfer (Hoekstra and Hung, 2002, 2005; Hoekstra and Chapagain, 2007, 2008; Liu et al., 2007) and some distinguished green (i.e. effective precipitation) and blue (i.e. irrigation) water components (Liu et al., 2009; Liu and Yang, 2010; Siebert and Doll, 2008, 2010; Liu et al., 2007, 2009; Gerbens-Leenes et al.,
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2009; Aldaya et al., 2010; Ababaei and Ramezani Etedali, 2014). The gray WF, which was introduced in order to express water pollution in terms of a volume polluted (Hoekstra et al., 2011), was first used for the analysis of the WF of wheat in different regions of Italy by Aldaya and Hoekstra (2010). Water footprint can be decreased through increasing yields, using more efficient irrigation systems (like drip irrigation), reducing non-beneficial evapotranspiration (e.g. by using mulches), reducing fertilizer loss, enhancing effective use of precipitation, optimizing crop planting dates and choosing crops and varieties with higher yield (Zhuo et al., 2016; Chukalla et al., 2015). Zhuo et al. (2016) estimated green, blue and gray WF in Yellow river basin for the period 1961–2009 and showed the sum of green and blue WFs has reduced due to improved crop yields and the gray WF increased because of the growing use of fertilizers. Also they concluded that the ratio of blue to green WF has increased due to expansion of irrigated lands. Ababaei and Ramezani Etedali (2014) used the framework proposed by Hoekstra et al. (2009) and introduced a new term, the white WF, for wheat irrigated lands as an indicator of irrigation water losses and showed that the national total WF (NTWF) of Iran’s wheat production for the period 2006–2012 is around 42,143 million cubic meters (MCM) per year (including 16% gray and 25% white WF). Their results suggest that the investigations of the gray and white WF are essential in production of main cereals. Most of the studies on virtual water and water footprint in Iran have been limited to one specific crop or small study areas (e.g. Dehghanpur and Bakhshoodeh, 2008; Babazadeh and Sarai Tabrizi, 2012; Pourjafarinejad et al., 2013; Arabi Yazdi et al., 2015; Omidi and Homaee, 2015) which cannot provide policy-makers with accurate information on how water resources are used. There are only a few comprehensive studies which consider more than one crop and spatial variations of climate, soil and management (e.g. Montazar et al., 2009; Ababaei and Ramezani Etedali, 2014). Hence, the purpose of this study is to estimate the green, blue, gray and white WFs of the main cereals (wheat, barley and maize) in the main cereal producing provinces of Iran at the provincial and national levels. We quantify different WF components of crop production using a regional water balance model, AGWAT, which calculates the crop water requirements and actual water use taking into account local climate, soil conditions and irrigation management strategies.
2. Materials and methods The national green, blue, gray and whitewater footprints of wheat, barley and maize production were estimated following the calculation frameworks of Hoekstra and Chapagain (2008) and Hoekstra et al. (2009), and modifications proposed by Ababaei and Ramezani Etedali (2014). Within this framework, the WF is considered as an indicator of the allocation of water by humanity and hence the consumption by ecosystems is not considered a WF (Hoekstra et al., 2011). Irrigation requirements and effective precipitation were estimated using the AGWAT model (IRIMO, 2001) which calculates crop evapotranspiration (ET, in mm) and irrigation requirements using FAO-Penman-Monteith method under standard and non-standard conditions (Allen et al., 1998). The model was applied at the regional scale (for the first time in the country) using the input data available in the model database. Irrigation was triggered when 50% of the total available water was depleted and filled the root zone moisture content back to the field capacity. As effective precipitation (Peff , in mm) is not provided in the database, the net irrigation requirements (IR, in mm) were first calculated by considering gross irrigation requirement (GI, in mm) and average irrigation efficiency (IE, dimensionless) in each region. Average irrigation efficiencies were provided in the model database as the
values used by local authorities for regional water resources planning. Total effective precipitation was calculated as the difference between the actual crop evapotranspiration (ETc , in mm) and the net irrigation requirements (IR), which were both extracted from the model database. The green and blue water uses (CWU, in m3 /ha) were considered equal to the net irrigation requirement and effective precipitation (Eqs. (1)–(4)). Obviously, no blue water use was considered under rainfed conditions: CWUBlue,Irr = IR = 10 × IE × GI
(1)
CWUGreen,Irr = 10 × Peff = 10 × (ETc − IR)
(2)
CWUBlue,RF = 0
(3)
CWUGreen,RF = 10 × Peff
(4)
Where the RF and Irr subscripts show rainfed and irrigation conditions, respectively. Next, the green (WFGreen ) and blue (WFBlue ) water footprints (in m3 /ton) were calculated by dividing the green and blue CWU (in m3 /ha) by actual crop yield (in ton/ha) separately under rainfed and irrigated conditions. Irrigated and rainfed yields of wheat, barley and maize were obtained from the Ministry of Agricultural-Jihad for the period 2006–2012 at a provincial scale. Volume of water required to assimilate the fertilizers leached in run off is called the gray WF (Hoekstra, 2003). In this study, the gray water footprint (WFGray ) related to nitrogen application was only estimated as the main source of pollution in agricultural area in Iran (Eqs. (5)–(6)). The nitrogen application rates (NAR, in kg/ha) were obtained from the Ministry of Agricultural-Jihad. The WFgray (m3 /ton) was calculated following Chapagain et al. (2006) and Hoekstra et al. (2011). The USEPA standard was considered (Chapagain et al., 2006) for the maximum allowable concentration (CMax , in mg/L) of nitrate in surface and groundwater which recommends a maximum concentration of 10 mg/L. This standard was adopted since most of the agricultural water is extracted from and returned to the same resources used for domestic purposes and pollution needs to be kept below an acceptable threshold. The natural nitrogen concentrations (CNat , in mg/L) were conservatively assumed to be zero as no data or model simulations was available at this spatial scale. WFGray,Irr =
˛Irr × NARIrr 1 × CMax − CNat YieldIrr
(5)
WFGray,RF =
˛RF × NARRF 1 × CMax − CNat YieldRF
(6)
The ␣ values were assumed to be equal to the values applied by Chapagain et al. (2006) and Hoekstra et al. (2011), i.e. 10% and 5% of the total nitrogen fertilizer applied under irrigated and rainfed conditions, respectively. Moreover, the irrigation loss (only that part which is not considered as the gray WF, m3 /ton) was considered as part of the total WF and referred to by the term “white water footprint” (WFWhite , in m3 /ton). The equations used here to calculate the white WF are different with those first proposed by Ababaei and Ramezani Etedali (2014) in order to consider the contribution of the white WF to the gray WF. This modification was deemed necessary as deep percolation assimilates fertilizers in the soil. A part of irrigation water (called leaching requirement) is usually applied by farmers to control soil salinity and keep yield reduction below an acceptable level. This part is considered as the gray WF. The remaining part of the white WF is assumed lost since in most regions of the country water table is now deeper than 50 m (and is going deeper at the average rate of ∼1 m/year) and it takes years for this water to return to the source. W F White,Irr = max(0, WFWhite,RF = 0
10 × (GI − IR) − WFGray,Irr ) YieldIrr
(7) (8)
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Fifteen (for wheat and barley) and twelve (for maize) provinces were considered as the main producing provinces according to the data provided by the Ministry of Agricultural-Jihad at a provincial scale (Fig. 1). The green, blue, gray and white WFs of wheat, barley and maize productions for each selected province (the term WF in Eq. (9)) were estimated by taking the average WF (in m3 /ton) over all the regions in that province. The national WF components were estimated by taking the average of each component over all the provinces considering the share of each province in the total production of wheat, barley and maize in all the selected provinces as weighting factors (Eqs. (9)–(10)). Finally, the volume of each WF component at the provincial and national levels were calculated as the weighted averages of the WF components under irrigated and rainfed conditions considering the share of each production system (irrigated or rainfed) in the total production of the selected provinces or the total national production (Eqs. (11)–(12)). Details of the calculations are provided by Ababaei and Ramezani Etedali (2014). The same equations were used for wheat, barley and maize. WFVi,x,y = Prodi,x,y × WFi,x,y
AWFx,y =
(9)
WFVi,x,y
i
(10) Prodi,x,y
i
WAWFx = ˇ.AWFx,Irr + (1 − ˇ)AWFx,RF
(11)
NWFx = TotProd × WAWFx
(12)
where i: province index (1–15 for wheat and barley, 1–12 for maize); x: green, blue, gray or white; y: Irr (irrigated) or RF (rainfed); Prod: production in each province under irrigated or rainfed conditions (Mton); WFV: the total volume of each WF component (MCM); AWF: the national weighted average of each WF component (m3 /ton) under irrigated or rainfed conditions; : the share of total irrigated production in the selected provinces (0.66, 0.69 and 1.0 for wheat, barley and maize, respectively) or the whole country (0.68, 0.67 and 0.99 for wheat, barley and maize, respectively); WAWF: the national weighted average of each WF component (m3 /ton) for all production systems (irrigated and rainfed); TotProd: total production of the selected provinces or the total national production (Mton); and NWF: the total volume of each WF component in the selected provinces or the total national volume of each WF component (MCM). 3. Results The data on wheat, barley and maize production in the main cereal producing provinces is presented in Tables 1–3, respectively. The selected provinces accounted for 86.5%, 84.7% and 95.8% of the national wheat, barley and maize productions. For wheat,
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the proportions of irrigated and rainfed productions across the whole country’s cultivated lands were 67.7% and 32.3%, respectively. These proportions were 67.1% and 32.9% for barley, and 99.9% and 0.1% for maize, respectively. As maize is rarely cultivated under rainfed conditions in Iran, we did not include rainfed-cultivated maize in this analysis. According to the data obtained, the national average of wheat yield in irrigated and rainfed lands were about 3.4 and 1.0 ton/ha, respectively. These values were 3.1 and 1.0 ton/ha for barley, and 7.6 and 3.8 ton/ha for maize, showing large gaps between irrigated and rainfed sectors as was expected for a dry country. Nitrogen application rates (NARs) in the main producing provinces are presented in Table 4.
3.1. Wheat The WF components of wheat production are summarized in Table 5. For irrigated wheat, the green WF ranged from 499 to 1023 m3 /ton, the blue WF from 521 to 1402 m3 /ton, the gray WF from 337 to 822 m3 /ton, and the white WF from 222 to 1637 m3 /ton. The average total WF of irrigated wheat overall the selected provinces was around 2657 m3 /ton. For rainfed wheat, the green WF varied between 1282 and 4166 m3 /ton, and the gray WF between 100 and 740 m3 /ton. The average total WF of rainfed wheat production was estimated 3071 m3 /ton. Table 6 shows the national average of the WF components of wheat production. The NTWF of wheat over the period 2006–2012 was 36,777 MCM/year (47% green, 20% blue, 19% gray and 15% white; Fig. 2) of which about 86.6% was consumed in the main wheat producing provinces. Ardebil (13.6%), Fars (12.8%) and East Azerbaijan (11.1%) constituted 37.6% of the wheat NTWF. In irrigated lands, these three provinces accounted for 14.5%, 50.3%, 43.0% and 52.3% of the total green, blue, gray and white WFs related to wheat production, respectively. In rainfed lands, the largest green WFs were found in Kurdistan (9.2%), Kermanshah (6.6%) and Zanjan (5.7%) while the largest gray WFs were related to Zanjan (2.3%), Kermanshah (2.0%) and Golestan (1.9%).
3.2. Barley Table 7 shows the WF components of barley in the selected provinces. For irrigated barley, the green WF ranged from 302 to 798 m3 /ton, the blue WF from 435 to 1305 m3 /ton, the gray WF from 393 to 740 m3 /ton, and the white WF from 212 to 1402 m3 /ton. The average total WF of irrigated barley among all the selected provinces was 2640 m3 /ton. For rainfed lands, the green WF ranged from 1433 to 3528 m3 /ton and the gray WF from 160 to 341 m3 /ton across the selected provinces. The average total WF of rainfed barley was 2594 m3 /ton.
Fig. 1. Major wheat (left), barley (center) and maize (right) producing provinces in Iran.
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Table 1 Wheat production data for the main wheat producing provinces. Province
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azerbaijan Ardebil East Azerbaijan Lorestan Markazi Tehran Zanjan Qazvin Total (Main Provinces) Total (National)
Production (ton)
Share (%)
National Share (%)
Yield (kg/ha)
Irrigated
Rainfed
Total
Irrigated
Rainfed
Irrigated
Rainfed
Total
Irrigated
Rainfed
1,578,195 1,254,269 994,297 475,667 384,030 352,909 149,478 332,104 329,954 283,104 215,306 286,251 424,140 85,351 255,899 7,400,951 8,778,996
103,768 93,022 206,968 442,123 417,436 333,758 492,957 283,664 270,715 287,902 291,500 169,691 2694 341,459 77,380 3,815,035 4,192,808
1,681,962 1,347,291 1,201,265 917,790 801,466 686,666 642,435 615,769 600,668 571,006 506,806 455,941 426,834 426,810 333,278 11,215,987 12,971,804
93.8 93.1 82.8 51.8 47.9 51.4 23.3 53.9 54.9 49.6 42.5 62.8 99.4 20.0 76.8 66.0 67.7
6.2 6.9 17.2 48.2 52.1 48.6 76.7 46.1 45.1 50.4 57.5 37.2 0.6 80.0 23.2 34.0 32.3
18.0 14.3 11.3 5.4 4.4 4.0 1.7 3.8 3.8 3.2 2.5 3.3 4.8 1.0 2.9 84.3 –
2.5 2.2 4.9 10.5 10.0 8.0 11.8 6.8 6.5 6.9 7.0 4.0 0.1 8.1 1.8 91.0 –
13.0 10.4 9.3 7.1 6.2 5.3 5.0 4.7 4.6 4.4 3.9 3.5 3.3 3.3 2.6 86.5 –
4,058 2,994 2,900 3,067 4,638 3,864 4,149 3,122 4,240 3,014 3,102 3,800 4,764 3,700 4,045 3,508 3,438
817 498 624 2,021 1,192 1,033 993 1,037 1,145 861 1,179 943 1,010 965 894 1,049 1,010
Table 2 Barley production data for the main barley producing provinces. Province
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azerbaijan Qazvin Qom Khuzestan West Azerbaijan Total (Main Provinces) Total (National)
Production (ton)
Share (%)
National Share (%)
Yield (kg/ha)
Irrigated
Rainfed
Total
Irrigated
Rainfed
Irrigated
Rainfed
Total
Irrigated
Rainfed
474,211 165,520 43,715 181,318 132,269 16,410 149,978 67,977 129,952 28,176 62,234 93,632 81,170 47,526 35,035 1,709,124 1,954,694
45,494 56,318 155,818 3765 47,787 155,264 173 74,295 2940 101,095 45,158 8252 17 32,186 31,532 760,093 959,771
519,705 221,838 199,533 185,084 180,057 171,673 150,151 142,272 132,892 129,270 107,392 101,885 81,186 79,712 66,567 2,469,217 2,914,465
91.2 74.6 21.9 98.0 73.5 9.6 99.9 47.8 97.8 21.8 58.0 91.9 100.0 59.6 52.6 69.2 67.1
8.8 25.4 78.1 2.0 26.5 90.4 0.1 52.2 2.2 78.2 42.0 8.1 0.0 40.4 47.4 30.8 32.9
24.3 8.5 2.2 9.3 6.8 0.8 7.7 3.5 6.6 1.4 3.2 4.8 4.2 2.4 1.8 87.4 –
4.7 5.9 16.2 0.4 5.0 16.2 0.0 7.7 0.3 10.5 4.7 0.9 0.0 3.4 3.3 79.2 –
17.8 7.6 6.8 6.4 6.2 5.9 5.2 4.9 4.6 4.4 3.7 3.5 2.8 2.7 2.3 84.7 –
2,631 3,905 4,483 4,037 2,808 2,414 3,817 3,015 3,619 2,958 2,681 3,488 3,139 1,739 2,460 3,172 3,075
595 1,363 1,273 757 781 1,193 1,502 1,056 1,091 1,597 883 767 167 418 1,003 1,101 1,034
Table 3 Maize production data for the main maize producing provinces. Province
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan Total (Main Provinces) Total (National)
Production (ton)
Share (%)
National Share (%)
Yield (kg/ha)
Irrigated
Rainfed
Total
Irrigated
Rainfed
Irrigated
Rainfed
Total
Irrigated
Rainfed
515,718 468,814 293,018 232,660 98,144 76,292 49,483 45,061 43,862 34,757 32,702 25,139 1,915,649 1,998,107
0 0 0 0 0 0 0 0 0 0 0 0 0 1840
515,718 468,814 293,018 232,660 98,144 76,292 49,483 45,061 43,862 34,757 32,702 25,139 1,915,649 1,999,947
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.9
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
25.8 23.5 14.7 11.6 4.9 3.8 2.5 2.3 2.2 1.7 1.6 1.3 95.9 –
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 –
25.8 23.4 14.7 11.6 4.9 3.8 2.5 2.3 2.2 1.7 1.6 1.3 95.8 –
8,572 6,294 9,019 7,427 11,123 8,978 5,414 8,255 6,740 5,843 8,666 6,907 7,698 7,645
0 0 0 0 0 0 0 0 0 0 0 0 0 3,761
Table 8 shows the national average of the WF components of barley production. The NTWF of barley production was estimated 7975 MCM/year (42% green, 22% blue, 19% gray and 17% white; Fig. 3) of which 85% was related to the main barley producing provinces. Khorasan contributed 27.3% to the barley NTWF. In irrigated lands, this province constituted 11.3%, 35.1%, 23.1% and 49.8% of the total green, blue, gray and white WFs related to barley production, respectively. In rainfed lands, the largest green WFs were
found in Lorestan (11.0%) and Kermanshah (10.6%). Also the largest gray WFs were related to these two provinces with 2.5% and 2.4%, respectively. 3.3. Maize Table 9 shows the WF components of maize for the selected provinces. In irrigated lands, the green WF of maize production
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Table 4 Nitrogen application rates (kg/ha) for selected provinces in irrigated and rainfed lands (2006–2012)a . Wheat
Barley
Maize
Province
Irrigated
Rainfed
Province
Irrigated
Rainfed
Province
Irrigated
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azarbaijan Ardebil East Azarbaijan Lorestan Markazi Tehran Zanjan Qazvin
333.7 230.8 192.5 160.1 261.4 161.6 156.4 105.1 267.9 111.3 154.7 235.4 228.3 193.4 202.7
65.3 73.7 17.0 126.8 83.6 55.2 54.4 31.1 23.0 43.7 81.6 83.4 25.0 94.2 26.0
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azerbaijan Qazvin Qom Khuzestan West Azerbaijan
194.6 153.3 223.4 271.0 190.8 114.8 216.5 135.8 169.5 100.0 120.1 209.7 269.7 123.9 565.2
19.0 87.2 66.8 51.6 31.1 66.5 54.1 28.5 73.1 81.2 35.1 46.3 0 63.6 32.2
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan
448.3 400.1 371.8 558.5 454.7 348.3 171.7 325.4 450.9 276.0 473.3 233.9
a
Source: Ministry of Agricultural-Jihad.
Table 5 Water footprint components of wheat production for the main wheat producing provinces. Province
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azarbaijan Ardebil East Azarbaijan Lorestan Markazi Tehran Zanjan Qazvin Average CV Min Max
WFIrr (m3 /ton)
Water Use (mm)
WFRF (m3 /ton)
ETc
IR
Peff
Green
Blue
Gray
White
Total
Green
Gray
Total
607 426 606 419 592 574 697 493 494 536 631 555 510 554 570 551 13% 419 697
365 218 407 159 267 313 377 219 232 290 314 302 272 275 300 287 22% 159 407
242 207 200 259 324 261 321 275 262 246 317 254 238 279 269 264 13% 200 324
597 693 690 845 699 676 773 880 618 817 1023 668 499 753 666 726 17% 499 1,023
899 729 1402 521 576 811 908 700 547 963 1011 794 571 744 742 794 28% 521 1,402
822 771 664 522 564 418 377 337 632 369 499 619 479 523 501 540 25% 337 822
452 359 1637 271 255 598 969 620 222 873 1133 419 223 544 376 597 65% 222 1,637
2,770 2,553 4,393 2,159 2,094 2,502 3,027 2,536 2,020 3,022 3,667 2,501 1,771 2,563 2,285 2,657 24% 1,771 4,393
2,967 4,166 3,205 1,282 2,721 2,527 3,231 2,648 2,289 2,860 2,693 2,692 2,352 2,887 3,012 2,769 21% 1,282 4,166
400 740 137 314 351 267 274 150 100 254 346 442 123 488 145 302 55% 100 740
3,367 4,906 3,341 1,596 3,072 2,794 3,505 2,798 2,390 3,113 3,039 3,134 2,475 3,375 3,158 3,071 22% 1,596 4,906
Table 6 The total volume (WFV) of each WF component for the main wheat producing provinces. Province
Fars Khuzestan Khorasan Golestan Kermanshah Hamadan Kurdestan West Azarbaijan Ardebil East Azarbaijan Lorestan Markazi Tehran Zanjan Qazvin Sum AWF (m3 /ton) WAWF (m3 /ton): Main Provinces WAWF (m3 /ton): National NWF (MCM): Main Provinces NWF (MCM): National
WFVIrr (MCM)
WFVRF (MCM)
Green
Blue
Gray
White
Total
Green
Gray
Total
942 869 686 402 269 238 116 292 204 231 220 191 212 64 170 5107 690 1361 1328 15,265 17,222
1418 915 1394 248 221 286 136 232 181 272 218 227 242 64 190 6244 844 557 571 6244 7406
1298 967 660 248 216 148 56 112 208 105 107 177 203 45 128 4679 632 519 525 5824 6809
713 451 1628 129 98 211 145 206 73 247 244 120 94 46 96 4502 608 401 412 4502 5340
4371 3202 4368 1027 804 883 453 842 666 855 789 716 751 219 585 20,531 2774 2838 2835 31,835 36,777
308 388 663 567 1136 843 1593 751 620 823 785 457 6 986 233 10,158 2663
41 69 28 139 146 89 135 43 27 73 101 75 0 167 11 1145 300
349 456 692 705 1282 933 1728 794 647 896 886 532 7 1152 244 11,303 2963
Irr: irrigated, RF: rainfed, WFV: total volume of each WF component, AWF: national weighted average of each WF component for all production systems (m3 /ton) under irrigated or rainfed conditions, WAWF: national weighted average of each WF component for all production systems (irrigated and rainfed) (m3 /ton), NWF: total volume of each WF component in the selected provinces or total national volume of each WF component (MCM).
Please cite this article in press as: Ababaei, B., Ramezani Etedali, H., Water footprint assessment of main cereals in Iran. Agric. Water Manage. (2016), http://dx.doi.org/10.1016/j.agwat.2016.07.016
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Fig. 2. Shares of wheat WF components in irrigated (Irr) and rainfed (RF) lands of the main wheat producing provinces.
Table 7 Water footprint components of barley production for the main barley producing provinces. Province
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azerbaijan Qazvin Qom Khuzestan West Azerbaijan Average CV Min Max
WFIrr (m3 /ton)
Water Use (mm)
WFRF (m3 /ton)
ETc
IR
Peff
Green
Blue
Gray
White
Total
Green
Gray
Total
553 446 485 455 493 507 391 402 481 374 418 440 399 351 399 486.5 12% 446.0 553.2
342 253 195 332 272 224 199 200 282 149 234 225 222 174 186 278.6 20% 195.0 342.1
210 195 290 122 221 283 191 202 199 225 109 215 177 176 213 207.6 23% 121.8 290.3
798 500 648 302 786 1,173 501 670 549 759 406 616 562 1,014 864 607 38% 302 798
1,305 642 435 824 970 928 522 664 780 504 1,152 646 708 1,003 757 835 29% 435 1,305
740 393 393 671 679 476 567 450 468 338 448 601 859 713 2,298 575 82% 393 740
1,402 430 212 393 674 1,018 119 587 559 413 673 160 87 807 0 622 61% 212 1,402
1,723 576 320 583 989 1,200 228 794 738 549 2,042 268 131 1,334 0 838 71% 320 1,723
3,528 1,433 2,280 1,610 2,827 2,374 1,275 1,913 1,821 1,406 1,232 2,800 10,594 4,218 2,119 2,336 100% 1433 3,528
160 320 271 341 199 279 180 135 335 254 199 302 0 761 160 258 64% 160 341
3,688 1,753 2,551 1,952 3,026 2,652 1,455 2,048 2,156 1,661 1,431 3,102 10,594 4,979 2,280 2,594 89% 1,753 3,688
Fig. 3. Shares of barlet WF components in irrigated (Irr) and rainfed (RF) lands of the main barley producing provinces.
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Table 8 The total volume (WFV) of each WF component for the main barley producing provinces. Province
WFVIrr (MCM)
Khorasan Hamadan Kermanshah Isfahan Fars Lorestan Tehran Ardebil Markazi Golestan East Azarbaijan Qazvin Qom Khuzestan West Azarbaijan Sum AWF (m3 /ton) WAWF (m3 /ton): Main Provinces WAWF (m3 /ton): National NWF (MCM): Main Provinces NWF (MCM): National
WFVRF (MCM)
Green
Blue
Gray
White
Total
Green
Gray
Total
378 83 28 55 104 19 75 46 71 21 25 58 46 48 30 1088 637 1120 1154 2766 3363
619 106 19 149 128 15 78 45 101 14 72 60 57 48 27 1540 901 624 604 1540 1761
351 65 17 122 90 8 85 31 61 10 28 56 70 34 81 1107 648 529 521 1306 1518
665 71 9 71 89 17 18 40 73 12 42 15 7 38 0 1166 683 472 458 1166 1334
2013 325 74 397 411 59 256 161 306 57 167 189 180 168 137 4901 2868 2745 2736 6778 7975
160 81 355 6 135 369 0 142 5 142 56 23 0 136 67 1678 2207
7 18 42 1 10 43 0 10 1 26 9 2 0 24 5 199 262
168 99 398 7 145 412 0 152 6 168 65 26 0 160 72 1877 2469
Irr: irrigated, RF: rainfed, WFV: total volume of each WF component, AWF: national weighted average of each WF component for all production systems (m3 /ton) under irrigated or rainfed conditions, WAWF: national weighted average of each WF component for all production systems (irrigated and rainfed) (m3 /ton), NWF: total volume of each WF component in the selected provinces or total national volume of each WF component (MCM).
Table 9 Water footprint components of maize production for the main maize producing provinces. Province
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan Average CV Min Max
WFIrr (m3 /ton)
Water Use (mm) ETc
IR
Peff
Green
Blue
Gray
White
Total
590 546 662 731 680 667 566 680 623 731 529 534 628 11% 529 731
566 528 618 729 630 629 495 628 592 685 525 475 592 12% 475 729
28 29 43 10 50 38 70 52 31 46 4 59 38 48% 4 70
33 45 48 13 45 42 130 63 46 79 5 85 53 61% 5 130
656 822 686 983 567 701 915 761 879 1172 605 688 786 21% 567 1172
523 636 619 501 409 388 317 394 669 472 505 339 481 23% 317 669
338 624 348 842 181 502 1234 722 577 1302 371 611 638 52% 181 1302
1550 2127 1700 2339 1201 1633 2596 1940 2171 3026 1486 1723 1958 25% 1201 3026
ranged from 5 to 130 m3 /ton, the blue WF from 567 to 1172 m3 /ton, the gray WF from 317 to 669 m3 /ton, and the white WF from 181 to 1302 m3 /ton. The average total WF for irrigated maize among all the selected provinces was 1958 m3 /ton, i.e. the highest water productivity among all the three studied crops. Table 10 shows the national average of the WF components of maize production. The NTWF of maize production was estimated around 3744 MCM/year (2% green, 41% blue, 29% gray and 28% white; Fig. 4) of which 95.9% of the maize NTWF was related to the main maize producing provinces. Khuzestan (26.6%) and Fars (21.4%) together accounted for 48.0% of the NTWF related to maize production. For irrigated maize, these two provinces constituted 46.4%, 47.6%, 52.4% and 44.2% of the total green, blue, gray and white WFs related to maize production, respectively. 3.4. Discussion Over the period 2006–2012, the NTWFs of wheat, barley and maize production were estimated 36,777, 7975 and 3744 MCM per year, i.e. totally 48,496 MCM per year which is around half of the
total water withdrawal in the country (currently around 100,000 MCM per year; Keshavarz 2015). Of this amount, the shares of wheat, barley and maize were 76%, 16% and 8%, respectively. The green, blue, gray and white WFs accounted for 43%, 22%, 19% and 16% of the NTWF related to the production of all crops, respectively, indicating the importance of the green WF in the production of the main cereals in the country. The average national green + blue WFs were estimated 24,628, 5123 and 1604 MCM per year for wheat, barley and maize, respectively, and 31,356 MCM per year altogether. It shows that of the NTWF of the production of wheat, barley and maize, 67%, 64% and 43% was attributed to the green + blue WF. The contribution of the green + blue WF components to the NTWF of the production of all crops were 51%, 11% and 3% with wheat being the largest contributor. Wheat has been a strategic crop for the country being cultivated in 4.7 and 23 times larger areas and producing 4.6 and 5.9 times more than barley and maize, respectively. For that, water resources allocation in wheat production has a deep impact on national freshwater consumption and must be treated with more precision and conservatism.
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Table 10 The total volume (WFV) of each WF components for the main maize producing provinces. Province
Fars Khuzestan Kermanshah Kerman Qazvin Hamadan Ardebil Lorestan Hormozgan Ilam Yazd West Azerbaijan Sum AWF (m3 /ton)a WAWF (m3 /ton): Main Provinces WAWF (m3 /ton): National NWF (MCM): Main Provinces NWF (MCM): National
WFVIrr (MCM) Green
Blue
Gray
White
Total
17 21 14 3 4 3 6 3 2 3 0 2 79 41 41 41 79 83
338 385 201 229 56 53 45 34 39 41 20 17 1458 761 761 761 1458 1521
270 298 181 116 40 30 16 18 29 16 17 9 1040 543 543 542 1040 1084
174 292 102 196 18 38 61 33 25 45 12 15 1012 528 528 528 1012 1056
800 997 498 544 118 125 128 87 95 105 49 43 3590 1874 1874 1872 3590 3744
Cultivated under rainfed conditions in Iran. Irr: irrigated, RF: rainfed, WFV: total volume of each WF component, AWF: national weighted average of each WF component for all production systems (m3 /ton) under irrigated or rainfed conditions, WAWF: national weighted average of each WF component for all production systems (irrigated and rainfed) (m3 /ton), NWF: total volume of each WF component in the selected provinces or total national volume of each WF component (MCM). a AWF is very close to WAWF as the share of rainfed-cultivated maize is negligible.
Fig. 4. Shares of maize WF components in irrigated (Irr) lands of the main maize producing provinces. Maize is rarely cultivated under rainfed conditions in Iran.
On the other hand and over the same period, the gray + white WF accounted for 33%, 36% and 57% of the NTWF of wheat, barley and maize production, respectively. These WF components constituted 25%, 6% and 4% of the aggregated NTWF of the production of these cereals with the share of the white WF being 15%, 17% and 28% of the NTWF of wheat, barley and maize production, respectively. These values imply that a great share of water consumed for cereal production is lost during irrigation and perhaps never reaches the water table. Considering the fact that Iran is located in an arid region of the world, these values imply the importance of a better irrigation management strategies to reduce the share of white WF which is important in both terms of water resources management and environment conservation. At the provincial level, wheat productions in Ardebil (10.3%), Fars (9.7%) and East Azerbaijan (8.5%) were the largest contributors to the NTWF related to the production of the main cereals. These provinces consumed 13,834 MCM per year for wheat production, i.e. more than 28.5% of the NTWF for the cereals. From the same
point of view, Khorasan (4.5%), Fars (1.1%) and Isfahan (1.0%) were the largest water consumers in barley production, while Khuzestan (2.1%) and Fars (1.6%) were the largest users for maize production. Figs. 5–7 show the segregation of the NTWF of wheat, barley and maize, respectively, at the provincial level. These figures brings an important question up about the government’s strategy for improving water use efficiency. While the government is more concerned with increasing water use efficiency by using more efficient irrigation methods (like pressurized irrigation systems), and decreasing the share of the white WF, these results show an alternative option (for wheat and barley). In most of the selected provinces, the share of the green WF is significantly higher than the white and blue WFs, especially in provinces with more rainfed wheat-cultivated lands. In the case of wheat, the white WF is relatively important in only three major wheat producing provinces, i.e. Ardebil, Fars and East Azerbaijan. The same pattern can be detected for barley with the white WF in Khorasan, Hamadan, Isfahan, Markazi and Fars having large contribution (>0.9%) to the barley NTWF. This shows
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Fig. 5. Contribution of WF components to the wheat NTWF in irrigated (Irr) and rainfed (RF) lands of the main wheat producing provinces.
Fig. 6. Contribution of WF components to the barley NTWF in irrigated (Irr) and rainfed (RF) lands of the main barley producing provinces.
Fig. 7. Contribution of WF components to the maize NTWF in irrigated (Irr) lands of the main maize producing provinces. Maize is rarely cultivated under rainfed conditions in Iran.
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that there are great opportunities to increase water productivity and decrease water use in irrigated lands through increasing yield in rainfed production systems. With the national average yield of rainfed wheat and barley being less than one third of that in irrigated lands and at the same time the total WF of irrigated and rainfed lands being close (for wheat 2657 vs 3071 m3 /ton; for barley 2640 vs 2594 m3 /ton; see Tables 5 and 7), shifting strategies from decreasing the share of white WF to increasing the green WF productivity (by increasing yield per unit of the green water use) or applying supplementary irrigation in rainfed wheat and barley production systems (to increase yield without considerably increasing the share of the blue WF) seem promising alternatives worthy of further investigation.
specific region. Any other options leading to increased yield and higher green water productivity (like applying supplementary irrigation) is equally important. The data and estimated values presented in this study help policy-makers make more educated decisions on to the allocation of limited agricultural water resources. They can also be used by other researchers as they are collected and provided at the regional level at which it is very hard to get detailed data on crop production and water consumption. This data can also be used by researchers involved in global-scale studies that usually do not have access to this type of data at the regional level and may improve large-scale estimates of water footprint components which will otherwise deviate from values estimated at smaller spatial scales.
4. Conclusions References The approach proposed by Ababaei and Ramezani Etedali (2014) was applied to estimate the water footprint components of wheat, barley and maize production as the main cereals produced in Iran. A modification was made to the original calculation procedure to account for the interaction of the gray and white WFs. As more sophisticated and accurate model simulations were not available, conservative value of maximum acceptable concentration of nitrogen in the receiving water bodies were used to estimate the volume of water required for dilution (i.e. the gray WF). Estimation of WF components at the regional scale was proposed to enable determining where each WF component is originally located. At the same time, this approach takes into account the spatial variability of factors affecting crop water consumption much better than the approaches usually taken at the global scale studies (Ababaei and Ramezani Etedali, 2014). It was found that the green WF related to the country’s national production is about 2.3 and 1.9 times the blue WF for wheat and barley, confirming the importance of green water in cereal production in arid regions. In Iran, wheat and barley are mostly planted and harvested in autumn and springer and their growing periods are closely matched with the wet season, which is the main reason for the green WF being considerable in wheat and barley productions. On the other hand, irrigation is the largest source of water for maize production (18.4 times the green water) due to negligible precipitation during maize growing season. Relatively lower yields in rainfed lands and a lower opportunity cost of green water compared to the blue water (Mekonnen and Hoekstra, 2010) lead to the idea that taking opportunities to increase the use of green WF (by shifting crop sowing date) or to increase the green WF productivity (by increasing yield in rainfed lands, for example, by applying supplementary irrigation) can be of great importance to farmers who are already suffering from insufficient (blue) water resources. Increasing production from rainfed lands will reduce the need for higher level of production from irrigated lands in water-scarce areas like Iran and will thus result in reduced blue water requirement. Moreover, precision farming can substantially reduce the share of the white (due to reduction in irrigation water loss) and gray (due to reduction in fertilizer leaching to groundwater or to surface water through runoff) water footprints, which were shown to be large parts of total water footprint in cereal production (Jenkinson, 2001; Norse, 2005). The results show that the government’s strategy of tackling scarce agricultural water resources by solely focusing on improving irrigation efficiency should be reconsidered. While pressurized irrigation systems are costly and hard to maintain and operate for most farmers, improving water productivity (specially for green water) in cereal production can be more easily achieved with enhanced farm management strategies like changing sowing date or using cultivars with more adapted growing season to wet spells in each
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