Impacts of Climate Change and Land-use Change on the Water Resources of the Upper Kharun Catchment, Chhattisgarh, India

Abstract

The Upper Kharun Catchment (UKC) is one of the most important, economically sound and highly populated watersheds of Chhattisgarh state in India. It covers diverse land use types: urban, rural, agricultural, forest and industrial areas. The study area is a part of the newly formed state, which was established in 2000 and is characterized by considerable population growth and expansion of urban areas, industrialization, and irrigation areas and facilities for meeting the increasing food demand. Furthermore, the government has planned the formation of the new capital city. The planning unit is partly in the study area, and hence there is an urgent need to estimate the impact of future land use change on the water resources of UKC, and to consider whether and to which degree the intensification of irrigated agriculture is putting the groundwater resources of the UKC at risk of over-exploitation that might lead to a major water crisis in near future. <br /> Climate change is likely to severely affect the surface and groundwater resources due to changes in precipitation and evapotranspiration and their spatio-temporal distribution. The impact of future climate change may be felt more severely in the study area, which is already under stress due to the current population increase and associated demands for energy, freshwater and food. In spite of the uncertainties about the precise magnitude of climate change and its possible impacts, particularly on regional scales, measures must be taken to anticipate, mitigate and/or adapt to its adverse effects on surface and ground-water availability.<br /> There is no research documented in literature related to climate change and land use change impacts on water resources of the UKC. Hence, an attempt is made to overcome these shortcomings and to run the model SWAT with high resolution input data taking irrigation issues relevant in the UKC explicitly into account. For this purpose, the climate scenarios of the PRECIS regional climate model were bias corrected to station level, and land use maps of 1991, 2001, 2011 and 2021 were prepared with details of surface and groundwater-irrigated areas. The results of the study provide the base for framing strategies for water resource management in the study area.<br /> The main findings show that the overall rainfall trend for the UKC increased at a rate of 1.94 mm per annum at p=0.033 level of significance from 1961-2011. No statistically significant change in rainfall in the month of peak rainfall was observed. Mid July remains the period of peak rainfall over the years (1961-2011). There was no significant trend for mean annual temperature. However, slight increase in temperature was detected in specific months.<br /> The bias-corrected PRECIS RCM scenarios show an increasing trend for both mean annual rainfall and temperature (except for the q0 and q1 scenarios for the 2020s, where there is a decrease in annual rainfall compared to the baseline). The mean monthly rainfall increases for all scenarios, except for the month of June, where a significant decrease in rainfall is predicted.<br /> The main land use change pattern between 1991 and 2011 shows a significant increase in urban areas by 4.67%, decrease in wasteland by 3.76%, increase in area under two-season crops by 5.43 %, while 5.67% of the area is under more than two-season crops with paddy as a summer crop. The two and more than two-season crops are irrigated by groundwater sources. The land use scenario of 2021 shows a further increase in built-up area by 2.6% compared to 2011. Also, the groundwater-irrigated area with two-season crops is expected to increase by 24.25% and the area with more than two-season crops with summer paddy by 12.57%, which indicates an excessive increase in groundwater irrigation for some villages in the UKC and unsustainable use of the precious groundwater resources.<br /> On the UKC scale, the impact of land use change on different water balance components is small. There is a decreasing trend of annual discharge, water yield and groundwater contribution to streamflow, and an increasing trend of annual surface runoff and actual evapotranspiration over the decades. The impact on water resources is significant and clearly visible at sub-catchment level, where an increasing trend for urban areas can be observed. Based on the bias-corrected climate scenarios q0, q1 and q14, changes in the main water balance components were simulated with the SWAT model.<br /> The simulated annual discharge for the 2020s ranged between 25.9% decrease to 23.6% increase depending on the PRECIS scenario. For the 2050s, discharged ranges between 17.6% decrease to 39.4% increase, and for the 2080s an increase in the range of 16.3% to 63.7% is simulated. <br /> The annual surface runoff for the 2020s ranges between 28.8% decrease to 26.8% increase. For the 2050s, predictions vary between 17.9% decrease to 44.1% increase, whereas for the 2080s an increase in the range of 19.5% to 69.6% is expected.<br /> The annual percolation for the 2020s is estimated to range between 12.8% decrease to 8.7% increase. Predictions for the 2050s range between 10.3% decrease to 15.4% increase, and for the 2080s between 0.3% decrease and 13.7% increase. <br /> The annual groundwater contribution to streamflow for the 2020s is expected in the range of 7.0% decrease to 14.7% increase. Predictions for the 2050s range from 13.3% decrease to 64.7% increase, and for the 2080s between 10.4% decrease and 59.1% increase. Scenario Q1 shows a decrease in annual groundwater quantity in all time steps.