Effect of Global Temperature Changes on Rainfall Fluctuations over River Basins Across Eastern Indo-GangeticPlains

Available online at www.sciencedirect.com

ScienceDirect Aquatic Procedia 4 (2015) 721 – 729

INTERNATIONAL CONFERENCE ON WATER RESOURCES, COASTAL AND OCEAN ENGINEERING (ICWRCOE 2015)

Effect of Global Temperature Changes on Rainfall Fluctuations Over River Basins across Eastern Indo-GangeticPlains Aradhana Yaduvanshia and Ashwini Ranadea a

Center of Excellence in Climatology, Department of Physics,Birla Institute of technology, Mesra, Ranchi, 835215, India

Abstract Annual weather cycle of India comprises mainly wet and dry periods with monsoonal rains as one of the significant wet periods. All India monsoon rainfall shows strong spatio-temporal variations and large departures from its normal values. It is proposed in this study to document climatological characteristics, fluctuation features and periodic cycles in annual, seasonal and monthly rainfall series of seven river basins across eastern Indo-Gangetic plains (EIGP) using longest possible instrumental area-averaged monthly rainfall series (sometimes goes back up to 1829) up to 2007. Understanding its relationships with the global tropospheric temperature changes and El Nino-La-Nina events are also attempted. Climatologically mean annual rainfall vary from 1070.5mm (±216.8 mm) over Tons to 1508.6mm (±205.2 mm) over Subarnarekha river basin. The highest rainfall over EIGP occurs during monsoon (1188±115.4mm) and that is during month of July (372.6±56.3mm). The annual and monsoonal rainfall of all river basins is normally distributed, except post-monsoon and winter. Over the period of available records, rainfall fluctuations showed 2-to-3 tendencies in the combination of increase, decrease and normal. Annual rainfall of none of the river basins show significant long term trend however, monsoonal rainfall of Brahmani, Sons, Mahanadi and EIGP does show significant decreasing long-term trend. In recent 20 years all river basins show declining tendency in monsoonal rainfall. Power spectra of all rainfall series are characterized by consistent significant peaks at 3-5 years, 10-20 years, 40 years and >80 years of wavelength. Short-term fluctuations of period <10 years is the major contributor of total variance of annual/monsoon rainfall (77.6%), followed by decadal variations of period 10-30 years (13.1%) and long-term trend of period >30 years (9.3%). The short term variations can be attributed to the variability in intensity and duration of rain producing weather systems, decadal variability is seems to be in relation with the different climatic signal and long-term changes are the manifestation of asymmetry in whole tropospheric warming across globe. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2015 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015. Peer-review under responsibility of organizing committee of ICWRCOE 2015

Keywords: rainfall fluctuations; classical harmonic analysis; global temperature change; river basins, water availability

* Corresponding author. E-mail address: [email protected]

2214-241X © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015 doi:10.1016/j.aqpro.2015.02.093

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1.

Introduction

Heterogeneous changes in global tropospheric temperatures from last few decades are observed to make spatio-temporal changes in global rainfall distribution. Potential climate change and its impacts on rainfall distribution pose a threat to water resources throughout the world.The Intergovernmental panel on climate change (IPCC; Kundzewicz 2007) concluded the major impacts of climate change on fresh water resources as, the droughtaffected areas will likely increase in extent; and heavy precipitation events are very likely to increase in frequency and intensity. For the country like India,development and management of water resources is of great importance as rainfall is a seasonal phenomenon (four months duration) over the country. As accounted by the IPCC, the Indian sub-continent will adversely be affected by enhanced variation in climate, rise in temperature and substantial reduction of summer rainfall in some parts and water stress by 2020 (Cruz et al. 2007). All annual, seasonal and monthly rainfall across India shows strong spatio-temporal variations and large departures from its normal values. Many of the studies shows overall declining trend in the monsoonal rainfall over major part of the country (Mooley and Parthasarathy, 1984; Kulkarni, 2012, and many more). Rupakumar et.al (1992) employed significant decreasing trend over Madhya Pradesh and near eastern India. Guhathakurta (2011) and Rajeevan, (2008) showed decreasing trend in winter rainfall in all sub division except Jharkhand. During recent global warming, the monsoon activity has been found to be somewhat subdued – monsoon rainfall was less by 2.4% during 1979-2009 compared to the period 1949-1978 (Ranade et al., 2008; Sontakke et al., 2008). (Annamalai et al.2013). Dash et al. (2009) have shown the increase in the number of monsoon break days over India, while decline in the number of monsoon depressions are given by Ajayamohan, (2010). Increasing trend of heavy rainevents (IPCC, 2007) also attracts the attention of many researchers. Many of them (Goswami et al., 2006; Rajeevan et al., 2008; and many more) have found it across the Indian subcontinent. Ranade and Singh (2014) have found increasing trend in 1-to 5-day isolated extreme rain events (EREs) and no change in 1- to 25-day EREs since 1951. Indo-Gangetic Plains (IGP) of India (geographical area ‫ ׽‬6,00,000 km2) is one of the largest fertile plains in the world formed by the river systems (dominated by three main rivers, the Indus, Ganges, and Brahmaputra, encompassing most of northern and eastern India. It is one of the most sensitive parts of the country regarding monsoon performance. Historical records show that, whenever there was a drought condition over country, the most affected part of the country was IGPs. Good rainfall activities over this region are mainly due to active summer monsoon circulation, frequent formation of rain producing weather systems in nearby seas and secondary disturbances formed in active monsoon trough region. During boreal summer, a planetary scale atmospheric circulation develops over Afro Asia-Indo-Pacific region with heating and rising motion (heat lows) over Middle East and China-Mongolia sector,outflows from upper troposphere anticyclone over Tibetan-Himalaya-KarakoramHindukush Highlands (THIKHIHILS), subsides over eight deep highs across the globe and return flow from lower troposphere of the different highs through a variety of meander courses converging into the heat lows.Ranade et.al.(2010) have found out seventeen convergences developed across Asia- Pacific region during boreal summer. Line-cum-eddy convergence formed across IGP is the major source of frequent rain spells across EIGP. It is formed between the monsoon flow from Arabian Sea and north westerlies from Azores High. Small-scale eddies are formed in this combined flow, which is popularly known as the monsoon trough. Synoptic-scale weather systems formed in Bay of Bengal also align with this convergence zone and produce heavy rains across IGP, especially EIGP due to its proximity of Bay of Bengal. Recently Singh and Singh(2012) have shown large heterogeneity in tropospheric (1000200hPa) temperature changes across the globe. They have observed faster warming of southern hemisphere than northern hemisphere and decrease in the gradient of tropospheric temperature from THIKHIHILS to other parts of the globe causing weakening of monsoon circulation and monsoonal rainfall across India. In the background of recent global tropospheric warming and projected climate change scenarios,study of longterm basin-scale rainfall variability is of great concern for water resources management of basin area. Very little attempt has been made earlier in order to understand such long-term basin-scale rainfall variations. Ranade et.al.(2008) have studied climatological and fluctuation features of parameters of hydrological wet season over 11 major and 36 minor river basins of India. They have not found any significant long-term trend in wet season parameters of any basin, but declining tendency in wet season rainfall/rainwater is noticed over some of the major

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basins of eastern Indo-Gnagetic Plains (EIGP).Singh and Sontakke (2002) have documented the longest instrumental-period fluctuations of rainfall amounts during 1829–1999 across IGPs. They have found increasing tendency (170 mm/100-yr, significant) over western IGPs, decreasing tendency (5 mm/100-yr) over central IGPs and eastern IGPs (50 mm/100-yr), which are not significant. In the present study we documented the climatological characteristics, fluctuation features and periodic cycles of longest instrumental rainfall series of EIGP river basins and its relationship with global temperature changes especially over THIKHIHILS. The three main objectives of the study are as follows: x To document climatological characteristics and fluctuation features of annual, seasonal and monthly rainfall series across EIGP using longest possible instrumental area-averaged monthly rainfall series. x To find out the relative strengths in periodic cycles in all rainfall sequences. x To understand the relationship of short-term, decadal and long-term variability with the global tropospheric temperature changes, and different climatic signals across globe. In the backdrop of asymmetric global warming scenario and diminuendo phase of rainfall over India, the results of the present study can be utilized for the extrapolation of monsoonal rainfall in order to plan and management of water resources under global warming scenario. 2.

Physical description of river basins and its data availability

Longest instrumental area-averaged monthly rainfall sequence (Sontakke and Singh (1996) and Sontakke et al. (2008) for the seven river basins (Subarnarekha, Brahmani, Kasai, Damodar, Son, Tons and Mahanadi) are used in the study. Monthly rainfall sequence for EIGP region has been prepared by area averaging of rainfall in seven basin rainfall across EIGP. A well spread network of 316 rain gauge station data acquired from the India Meteorological Department (IMD) were used to develop longest instrumental monthly basin rainfall data from 1901 to 2006. For the earliest years (prior to 1901) data has been reconstructed back with lesser number of observations using established objective method. Description of physical features of river basins and the rainfall data availability are given in Table 1. Over all 46 rain gauge stations were available during 1829-2006 for the development of data in EIGP area. The EIGP basin encompassed within geographical co-ordinates of 79030'-89002'E and 19020'- 25035' N. Data series length of each basin is different from another based upon the availability of station data. Annual, seasonal (Pre monsoon-March to May, Monsoon-June through September, Post monsoon-October to December and WinterJanuary and February) and monthly (May to October) rainfall sequences were developed for each river basins and EIGP. All these were subjected to test for their homogeneity, randomness, trend and periodicity. Monthly temperature and geopotential height of standard isobaric levels (1,000–150 hPa) across the globe available on 2.5°resolution from the NCEP-NCAR reanalysis (Kalnayet al.1996) and SST anomalies in the Niño 3.4 region (5oN-5oS, 120o-170oW) are also used in the study 3.

Results and Discussion

3.1 Climatological and fluctuation features of annual, seasonal and monthly rainfall The basic statistics e.gmean, standard deviation (SD) etc. for annual and seasonal rainfall series of seven river basins and EIGP are given in Table 1. Climatological features shows that mean annual rainfall vary from 1070.5mm (±216.8 mm) over Tons to 1508.6mm (±205.2 mm) over Subarnarekha river basin. Monsoonal rainfall is appearing to be major contributor to annual rainfall. The mean rainfall during monsoon season varies from 946.5mm (±198.6) over Tons to 1188.6 mm (±186mm) over Mahanadi river basin. The highest pre-monsoon rainfall occurs over Damoder (180.5±71.5mm) while that of post-monsoon occurs over Subarnarekha basin (150.3±96.5). The highest monthly rainfall in EIGP area occurs in the month of July (338.45mm). The coefficient of variation is about 13-21% for annual and monsoonal rains. It indicates that the probability of getting zero rainfall in seasonal series is very negligible. Nature of frequency distribution for each time series has also been studies by employing chi sq test and fisher’s g-statistics test (Rao, 1952). The distribution of annual and monsoonal rainfall is Gaussian (normal) at 1 % level of significance (l.o.s) for all river basins as well EIGP. Post-monsoon and winter rainfall is significantly different from normal. July rainfall is normally distributed for most of the river basins (except Subarnarekha, Brahmani and Kasai), while other monthly rainfall series are significantly different from normal. In order to understand the long-term trend in rainfall sequences, actual and 9 point Gaussian low pass filtered values are plotted

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for the entire available record. Critical visual examination reveals that, in general over the period of available records, rainfall fluctuations showed 2-to-3 tendencies in the combination of increase, decrease and normal. Figure 1 shows the actual and 9 point filtered values of monsoonal rainfall for seven river basins and EIGP. To understand the significance of long-term trend, two statistical tests (least-square linear trend test and Mann-Kendall Rank test for randomness against trend (hereafter MK test) (WMO, 1966) are performed on the time-series. These tests does not suggest significant long-term trend in annual rainfall of river basins across EIGP. However, monsoonal rainfall does show significant decreasing long-term trend (at 5% l.o.s) for Brahmani, Sons, Mahanadi and EIGP, but winter rainfall of Subarnarekha, EIGP and post monsoon rainfall of Kasai does show significant (5% l.o.s) rise on long-term basis. Table 1. Physiographic features of river basins across EIGP. No. of rain Longest Drainage Length gauges period of Area of river Basin Name Since rainfall (sq.km) (km) 1901 data Subarnarekha

32,647

395

4

1859-2006

Brahmani

50,581

800

3

1871-2006

Kasai

21,625

465

3

1859-2006

Damodar

64,753

541

11

1829-2006

Son

1,11,300

784

9

1842-2006

Tons

39,425

264

5

1860-2006

Mahanadi

1,45,040

587

11

1848-2006

EIGP

4,65,371

-

46

1871-2006

Mean annual rainfall (±SD) 1508.6 (±205.28) 1440.6 (±203.21) 1444.7 (±230.44) 1468.8 (±207.60) 1210.8 (±176.19) 1070.5 (±216.84) 1415.2 (±207.23) 1368 (±111.35)

Mean (±SD) 1142.33 (±165 ) 1141.4 (±180.57) 1115.2 (±187.64) 1116.9 (±165.56) 1043.3 (±155.93) 946.5 (±198.65) 1188.6 (±186) 1100.2 (±115.4)

Monsoon rainfall (mm) Maximum Minimum (year of (year of occurrence) occurrence)

%age contribution to annual

1578(1956)

725.8(1865)

76.0

1597.1(1943)

646.3(1970)

79.2

1584.4(1984)

758(1945)

77.2

1596.3(1995)

724.2(1982)

76.0

1413.9(1936)

676(1903)

86.2

1488.3(1948)

465.6(1979)

88.4

1686(1861)

754.1(1974)

84.0

1355.8(1922)

802.8(1979)

79.0

Tendencyin rainfall fluctuations in recent years of global warming are studied by following three ways, (i) Change in the mean of the recent 30-yr period (1977–2006) compared to the previous years (prior to 1977); (ii) recent 20-yr period (1987–2006) compared to previous years (prior to 1987); and (iii) recent 10-yr period (1997– 2006) compared to previous years (prior to 1997); Each of 88 time series are undergone by Student’s t test for the difference between the means of two subperiods and Wilcoxon–Mann–Whitney rank-sum test for two independent samples at 5% l.o.s.(Wilks 2006).

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Fig. 1.Inter-annual series for monsoon rainfall over seven river basins and EIGP. Dark lineindicates 9-point filtered value.

In recent 30 years, annual and monsoonal rainfall does not show any significant trend, however significant decrease is seen in pre-monsoon and winter rainfall of Subarnarekha river basin and significant increase in Postmonsoon rainfall of Son basin. In recent 20 years, all rainfall series shows significant decrease (Figure 2). Most of the rainfall series does not show any significant trend in recent 10 year period. Broadly speaking, a spatially coherent significant long-term trend for recent 30 years is not seen across EIGP. However, persistent positive and negative tendencies are spread across the seven river basins. These tendencies can be attributed to changes in physical parameters of weather systems formed in Bay of Bengal and Monsoon trough region. Significant negative tendencies in most of the rainfall series in recent years may be related to the overall declining tendency of mean annual rainfall across IGP. Sontakke et al. (2008) have reported that mean annual rainfall over the country during 1965–2006 was less by 4.23% compared to the period of 1931–64.

Figure 2. Recent 20-year change (significant at 95% confidence limit) in the monsoon rainfall of seven river basins across EIGP (dark shading indicates significant decrese).

3.2 Periodic cycles in rainfall series Inter-annual variations of various rainfalls are seen to be highly dominated by natural variability. This variability is a mixture of various regular and irregular oscillations. Some of the variations are periodic in nature; some are random while some are due to nonlinear feedback processes between different climatic elements. Harmonic analysis has been attempted in order to understand the relative strengths of periodic cycles in the interannual rainfall series.In harmonic analysis, time series is transformed in to finite number of sine and cosine waveforms after removing annual cycle. The amplitudes (Fourier coefficients) of sine and cosine waves are calculated depending upon the record length N is even or odd. The variance contained or power of each harmonic (linear combination of sine and cosine wave) is determined from the Fourier coefficients. The detailed mathematical expressions for the calculation of Fourier coefficients and respective variances (power) are given in Singh et.al. (2002).The power spectrum displaying the normalized spectral density (percentage of variance) against wavelength for monsoon inter-annual rainfall series is shown in Figure 3. Similar spectrums have been generated for remaining rainfall series also. Significance limits are drawn at 5%, 1% and 0.1% l.o.s. (Schickedanz and Bowen, 1977). Power spectra of all rainfall sequences show strong regularity. There are significant peaks (5% l.o.s.) in the spectrum at 3-5 years, 10-20 years, 40 years and >80 years can be seen generally in all the rainfall series. Peaks at wavelength 3-5 years and 10-20 years are considered as the dominant short term fluctuations or seasonal variations which are occurring periodically in the inter-annual variability. Peaks at 40-year are observed only in annual and monsoonal rainfall of Brahmani, winter rainfall of Tons and post monsoon rainfall in EIGP. 80-year cycles are observed in annual, monsoonal and post monsoonal rainfall of Kasai, annual rainfall of Damodar and post monsoonal rainfall of Subarnarekha and Brahmani. These are the measure of persistence and can be attributed to the secular long-term trends. More than 80 years cycles are also observed in selected rainfall series (e.g. annual and monsoonal rainfall of Son, Mahanadi and EIGP, and pre-monsoon of Subarnarekha, Kasai, Damodar and EIGP).

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Significant peaks at wavelengths >80 years are difficult to attributed to long-term trend or very-long cycle because wavelengths >80 years consist of only one cycle. Major significant peaks in the range of 3-5years, 10-20years and >40 years are quite consistent in seven river basins across EIGP. In order to get robust picture of the distribution of variance in these wavelength ranges, waves are combined in three band based upon their periods- (i) Combination of waves with periodicity < 10 years; (ii) 10-30 years; and (iii) > 30 years. Combined variance explained by the waves of wavelength <10 years is the manifestation of the contribution by short term fluctuations, that of 10-30 years is of decadal variability and > 30 years is of long-term trend. On an average for monsoon rains, short term fluctuations carry major variance which varies from 70.6% (over Brahmani) to 82.5% (Subarnarekha). The decadal variability is between 9.5% (Brahmani) to 16.4% (Mahanadi) and the long-term trend carries variances ranges from 3.9% (Subarnarekha) to 19.9% (Brahmani). The distribution of variances from annual rains is similar to that of seasonal and monthly rains. Harmonic analysis clearly indicates that, the rainfall variability of seven river basins in EIGP is mostly dominated by short-term fluctuations. These fluctuations can be attributed to the variations in the date of occurrence, intensity and duration of rain producing weather systems formed in Bay of Bengal and eastern part of the monsoon trough. Jadhav and Munot (2008) have shown that, since 1961, number and duration of deep depressions are decreasing at the rate 1.5-6 days per 10year and that of low pressure areas increasing at the rate of 1.4-8 days per 10 year. Decadal variability is seems to be in relation with the different climatic signal across the globe. Detailed investigations revels that, there is rising tendency in global tropospheric temperature throughout the globe. Longterm changes are the manifestation of asymmetry in whole tropospheric warming across globe.

Figure 3. The monsoonrainfall spectrum for seven river basins and EIGP. Dotted lines indicate significance level at 95%, 90% and 99.9% confidence limit.

3.3 Effect of global tropospheric temperatures changes and ENSO phenomenon on rainfall variability It has been understood that the Indian summer monsoon is a regular occurring, tropical, thermally driven phenomenon. Its spatio-temporal variability depending upon intensity, location and depth of general, monsoonal and regional circulation features, tele-connections with different climatic signals and interactions between tropical, subtropical and extra-tropical atmospheric weather phenomenon. In this study we have examined the effect of global

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tropospheric temperature changes on rainfall of EIGP. We have performed correlation and composite analysis of EIGP rainfall with the tropospheric (150-1000hPa) temperature/thickness averaged over different areas of Globe: the Northern hemisphere (NH), the Southern hemisphere (SH), the Extra-tropical NH (ExNH), the Extra-tropical SH (ExSH), the North Pole (NP), the South Pole (SP), the Sothern Indian Ocean high (SIOH), the Australian high (AUSH), the North Pacific high (NPH), the South Pacific high (SPH), the Azores high (AZH), the Mascarina high (MAH) and the THIKHIHILs. It has been observed that, the temperature of the troposphere over the THIKHIHILs is ~10°C higher than that over the entire globe. It is in the middle of the eastern hemisphere act as elevated heat source during borealsummer. Due to deep troposphericheating, large-scale low level convergence occur over two heat lows (over Middle-east and China-Mangolia sector) at lower levels and upper level divergence develops in and around the THIKHIHILsfacilitating unusual combination. Gradients in temperature/geopotential from THIKHIHILS to different highs play an important role in intensification and weakening of Asia-Pacific monsoon circulation and associated rainfall. The correlation coefficients (CC) between EIGP rainfall and tropospheric temperatureand thickness of THIKHIHILS are shown in Table 2. The CC in all months in monsoon season except August is highly significant at 1% level of significance (l.o.s.). It has been observed that, in the month of August, the upper level anticyclonic circulation is shifted towards westward, and the rainfall conditions across EIGP are mostlyin relation with the low pressure area developed over IGP. Small-scale eddies formed in the monsoon trough region is one of the main cause of rainfall during August in EIGP. Table 2: Correlation coefficients between Tropospheric temperature/thickness of YHIKHIHILS and EIGP rainfall Months June July

Correlation coefficient Tropospheric temperature Tropospheric thickness 0.57** 0.59** 0.33**

0.30**

August

-0.03

0.02

September

0.46**

0.47**

JJAS

0.32**

0.35**

The CC of tropospheric temperature over different parts of the globe is not found significant. So, composite analysis has been done in order to understand the effect of extreme temperature condition on rainfall variability. Extreme warm years (temperature > mean+1SD) and extreme cold years (temperature < mean-1SD) are selected during 1951-2006 period. The difference between mean rainfall amounts of warm and cold years is tested for its significance by student t-test. Similar analysis has been done for geopotential thicknesses, tropospheric temperature gradients and thickness gradients from THIKHIHILs to other parts of globe. The results show that tropospheric temperature and thickness of ExNH is showing significant (5% l.o.s.) difference in JJAS rainfall amount of EIGP. Warmest and thickest is the ExNH, wettest is the EIGP area. It has been seen that, presence of hot troposphere over the Middle East compare to other parts of the globe is essential condition for the occurrence of the summer monsoon circulation. Temperature gradient from THIKHIHILS to SIOH and that to AZH are showing significant changes in JJAS rainfall in their extreme years. It has been well known that, the El Nino La-Nina, one of the climatic indicex of tropical Pacific Oceanis the most effective climatic signal for Indian summer monsoon (Parthsarthy and Pant, 1985; Webster and Yang 1992 and many more).In this study we have examined the effect of it on rainfall of EIGP river basins. Niño 3.4 SST during DJF is significantly (5%l.o.s.) negatively correlated with Subarnarekha and Damoder river basin monsoon rainfall, while concurrent significant (1% l.o.s) negative relationship also existed for Tons basin. Composite analysis shows that during extreme El Nino years, EIGP rainfall is significantly decreases by 8.3% than that of extreme La Nina years. 4.

Conclusion

Climatological characteristics, fluctuation features and periodic cycles of annual, seasonal and monthly rainfall series of seven river basins across EIGP are studied, using longest possible instrumental area-averaged monthly rainfall series. The mean annual rainfall across EIGP found to be varies from 1070.5mm (±216.8 mm) over Tons to 1508.6mm (±205.2 mm) over Subarnarekha river basin and that of monsoon rainfall varies from 946.5mm (±198.6)

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over Tons to 1188.6 mm (±186mm) over Mahanadi river basin.The annual and monsoonal rainfall of all river basins is normally distributed, while post-monsoon and winter rainfalls are significantly different from normal.Significant long-term trend is not seen in annual rainfall across EIGP, however, significant decrease is seen in monsoon rainfall of Brahmani, Sons, Mahanadi and EIGP.In recent 30 years, annual and monsoon rainfall does not show any spatially coherent significant long-term trend, however significant decrease is noticed in recent 20 years. Power spectra of rainfall across EIGP are characterized by consistent, significant peaks at 3-5 years, 10-20 years, 40 years and >80 years wavelength.Short-term fluctuations of period <10 years is the major contributor of total variance of annual rainfall (77.6%), followed by decadal variations of period 10-30 years (13.1%) and longterm trend of period >30 years (9.3%). Similar results are obtained for monsoon rainfall. Temperature (thickness) of THIKHIHILS and the gradients of that to SIOH and AZH and extreme El Nino and La-NiNa phases significantly affected EIGP monsoon rainfall. Acknowledgements The authors are extremely grateful to India Meteorological Department, Pune and Indian Institute of Tropical Meteorology, Pune for providing valuable station and river basin rainfall data. References Ajayamohan, R.S., Merryfield, W.J., Kharin, V.V., 2010. Increasing trend of synoptic activity and its relationship with extreme rain events over Central India.Jrournalof Climate 23:1004–1013 Annamalai, H., Hafner, J., Sooraj, K.P., and Pillai, P., 2013. Global warming shifts monsoon circulation, drying South Asia. Journal of Climate.,26, 2701–2718. Cruz, R.V., Harasawa, H., Lal, M., Wu, S., Anokhin, Y., Punsalmaa, B., Honda, Y., Jafari, M., Li, C., Huu, Ninh, N., 2007. Asia. 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