Elsevier

Global and Planetary Change

Volume 139, April 2016, Pages 78-96
Global and Planetary Change

Hydrologic sensitivity of Indian sub-continental river basins to climate change

https://doi.org/10.1016/j.gloplacha.2016.01.003Get rights and content

Highlights

  • Indian sub-continental river basins are projected to shift in warmer and wetter climate.

  • Surface runoff is more sensitive to changes in precipitation and air temperature.

  • Larger uncertainty in precipitation projections.

Abstract

Climate change may pose profound implications for hydrologic processes in Indian sub-continental river basins. Using downscaled and bias corrected future climate projections and the Soil Water Assessment Tool (SWAT), we show that a majority of the Indian sub-continental river basins are projected to shift towards warmer and wetter climate in the future. During the monsoon (June to September) season, under the representative concentration pathways (RCP) 4.5 (8.5), the ensemble mean air temperature is projected to increase by more than 0.5 (0.8), 1.0 (2.0), and 1.5 (3.5) °C in the Near (2010–2039), Mid (2040–2069), and End (2070–2099) term climate, respectively. Moreover, the sub-continental river basins may face an increase of 3–5 °C in the post-monsoon season under the projected future climate. While there is a large intermodel uncertainty, robust increases in precipitation are projected in many sub-continental river basins under the projected future climate especially in the Mid and End term climate. A sensitivity analysis for the Ganges and Godavari river basins shows that surface runoff is more sensitive to change in precipitation and temperature than that of evapotranspiration (ET). An intensification of the hydrologic cycle in the Indian sub-continental basins is evident in the projected future climate. For instance, for Mid and End term climate, ET is projected to increase up to 10% for the majority of the river basins under both RCP 4.5 and 8.5 scenarios. During the monsoon season, ensemble mean surface runoff is projected to increase more than 40% in 11 (15) basins under the RCP 4.5 (8.5) scenarios by the end of the 21st century. Moreover, streamflow is projected to increase more than 40% in 8 (9) basins during the monsoon season under the RCP 4.5 (8.5) scenarios. Results show that water availability in the sub-continental river basins is more sensitive towards changes in the monsoon season precipitation rather than air temperature. While in the majority of the sub-continental river basins, water availability is projected to increase, spatial and temporal (interannual) variability in the monsoon season precipitation under the projected future climate may play a significant role. Changes in the hydrologic processes under the projected future climate indicate that substantial efforts may be required to develop water management strategies in the Indian sub-continental river basins in the future.

Introduction

Future projections of hydrologic processes provide useful information for water resources management and agricultural practices under climate change, which play a vital role in socioeconomic development (Fung, F., et al., 2013, Ruth, M., et al., 2007). Climate change impacts assessment of the hydrologic cycle is generally conducted using physically based hydrologic and statistical models (Dibike, Y.B. and Coulibaly, P., 2005, Mishra, V., et al., 2014, Mishra, V., et al., 2010b, Nijssen, B., et al., 2001, Okkonen, J. and Kløve, B., 2010, Vano, J.A., et al., 2012). Under the projected future climate, hydrologic cycle is expected to intensify (Huntington, 2006), which may affect water balance components leading to changes in streamflow and water availability (Arnell, N.W., 1999, Chang, H., et al., 2002, Middelkoop, H., et al., 2001, Mimikou, M.A., et al., 1999). Changing climate conditions also affects surface runoff, soil erosion, and sediment yield of a river basin (Lilhare, R., et al., 2014, Nearing, M.A., et al., 2005, Phan, D.B., et al., 2011). In addition to climate change, land use/land cover changes in river basins can be sensitive to changes in the water cycle (Frans, C., et al., 2013, Guo, H., et al., 2008, Hu, Q., et al., 2005, Mander, Ü., et al., 1998, Mishra, V., et al., 2010a, Praskievicz, S. and Chang, H., 2011, Tomer, M.D. and Schilling, K.E., 2009, Tong, S.T., et al., 2012).

Evidence of intensification in the hydrologic cycle has been documented worldwide (Dai, A., 2011, Hayhoe, K., et al., 2007, Jung, M., et al., 2010, Sheffield, J. and Wood, E.F., 2008, Trenberth, K.E., 2011). For instance, Jung et al. (2010) reported a decline in global land evapotranspiration during the recent decades due to limited moisture supply. Other than the observed impacts of climate change on evapotranspiration (McVicar et al., 2008), soil moisture (Mishra et al., 2014), and streamflow, climate extremes have increased during the recent decades (Mishra et al., 2015) and are likely to become more prominent under the projected climate change (Easterling et al., 2000). Observations (Allen, M.R. and Ingram, W.J., 2002, Lenderink, G. and Van Meijgaard, E., 2008, Min, S.-K., et al., 2011, Mishra, V., et al., 2012) and climate model projections (GutowskiJr, W.J., et al., 2007, Kharin, V.V., et al., 2007, Meehl, G.A., et al., 2000) show that precipitation extremes increase in response to warming climate. Moreover, Min et al. (2011) show that human-induced increases in greenhouse gases contribute to an intensification of extreme precipitation events over the Northern Hemisphere's land areas. Changes in hydrologic extremes have been noted at a global scale with substantial variability in occurrences of droughts and floods (Dai, A., et al., 1998, Higgins, S.I., et al., 2000). For instance, Sheffield and Wood (2008) reported a large variability in drought occurrences, their durations, and areal extent in many regions. Among the natural disasters, the economic and environmental implications of droughts are higher due to the wide areal extent and persistence (Wilhite et al., 2000), which may further increase under the changing climate conditions. Floods are also likely to increase under the projected climate. Milly et al. (2002) report that the frequency of great floods has increased substantially in the 20th century and significant positive trends in great floods are consistent with the climate model projections.

Climate variability and climate change substantially affect water resources and agricultural production in India. Gosain et al. (2006) found that under the climate warming scenario, severity of droughts and intensity of floods may increase in many parts of the region. Most of the studies based on general circulation model (GCMs) suggest that India will face warmer and wetter conditions under the projected future climate (Kumar, K.K., et al., 2005, Mishra, V., et al., 2014). Kumar et al. (2011) reported that air temperatures in India during the late 21st century will very likely exceed the highest values experienced in the 130-year instrumental record. They further found that changes in the monsoon climate could increase human and the crop mortality, posing a socioeconomic threat in India.

Despite the profound implications of changes in the monsoon season precipitation (Bollasina, M.A., et al., 2011, Goswami, B.N., et al., 2006, Mishra, V., et al., 2012) as well as air temperature (Auffhammer, M., et al., 2006, Barnett, T.P., et al., 2005a, Mall, R.K., et al., 2006a, Mall, R.K., et al., 2006b, Mishra, V., et al., 2014, Xu, J., et al., 2009) that have been already observed, impacts of the projected future climate on hydrologic processes in the Indian sub-continental river basins are not well studied (Gosain, A.K., et al., 2011, Gosain, A.K., et al., 2006). For instance, there are only a few studies documenting watershed scale changes under the projected future climate for the Indian sub-continental river basins. One possible reason for the lack of our understanding of climate change impacts on water resources in India has been the availability of observed streamflow data for the Indian sub-continental river basins. Observed streamflow data for many gauge stations have recently been made available by the Central Water Commission (CWC). However, for the basins that have international boundaries (e.g. Ganges, Brahmaputra, and Indus), the data remain classified and are not publically available for climate change impact assessment. For these river basins, streamflow data were obtained from the Global Runoff Data Center (GRDC) for a limited period (~ 15–20 years). The other potential limitation in understanding the hydrologic impacts of climate change relates to anthropogenic alterations (water storage and diversion related data) in the sub-continent river basins. In this study, we examine the sensitivity of the hydrologic processes to climate change in the Indian sub-continental river basins. We aim to address the following scientific questions: 1) To what extent changes in air temperature and precipitation are projected under the future climate in the Indian sub-continental river basins? And 2) How sensitive are the key water cycle components in the sub-continental river basins to the projected future climate?

Section snippets

Overview of the study area

The basic hydrological unit for planning and development of water resources is a river basin. In the present study, 18 major Indian sub-continental basins were selected for climate change impact assessment and sensitivity analysis (Fig. 1). The entire country has been divided into 22 basins as per the Central Water Commission (CWC), there are 12 major river basins (catchment area > = 20,000 km2) the biggest being the Ganga-Brahmaputra-Meghna, with a catchment area of about 1100,000km2 (Source: //indiawris.nrsc.gov.in/wrpinfo/index.php?title=Basins#CWC_Basin

Model calibration and evaluation

The SWAT model was calibrated for all the 18 river basins using the observed streamflow data (Table 1). The calibration and evaluation periods varied for the sub-continental river basins based on the availability and quality of the observed streamflow data (Table 1, Table 2). Fig. 3 shows the calibration and evaluation of the SWAT model for five major river basins from different locations in India; results for the rest of the basins are presented in supplemental Figure S1. For the Ganges River

Conclusions

We evaluated the hydrologic sensitivity (precipitation, air temperature, surface runoff, evapotranspiration, and streamflow) to climate change for the 18 Indian sub-continental river basins. We calibrated and evaluated the sub-continental basins using the SWAT model against the observed streamflow at the gauge stations that have minimal anthropogenic influence. The SWAT model showed a satisfactory performance in simulating monthly streamflow for most of the selected basins in the Indian

Acknowledgment

The authors acknowledge the financial support from the ITRA-Water project and Varahamihir Ministry of Earth Science Fellowship from. The work was partially supported by the Ganga River Basin Management (GRBM) project. The authors also appreciate constructive comments from the Editor.

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