Ecology, Environment and Conservation Paper

MODELLING FUTURE WATER SUPPLY AND DEMAND IN JHARKHAND REGION OF SUBARNAREKHA RIVER BASIN BY USING WEAP MODEL WITH RCP 4.5

Randhir Kumar, Pratibha Kumari, Ajai Singh, P.K. Parhi and V.K. Tripathi

Abstract

The allocation of scarce available water resources requires careful planning and implementation. This can be accomplished only when complete information about water availability and demand for water of all the stakeholders is known. The present study applies the Water Evaluation and Planning System (WEAP) Model to evaluate water resources vulnerability under future climatic conditions inthe middle reach of the Subarnarekha river basin, Jharkhand, India. The Subarnekha river basin covers the area in the states of Jharkhand, Odisha and a comparatively smaller parts in West Bengal. The WEAP model was developed by the Stockholm Environment Institute (SEI) for evaluating the planning and management of water resource systems. Demand sites were classified as an industry, water demands of institutional, agriculture, and human and livestock population. Each demand site was connected to its source and where applicable a return link mas made to a river. Annual water use rate/person, per hectare for agriculture and per head of livestock were determined and changed into cubic meter per annum and used as input to the WEAP model. For the WEAP modeling framework, the year 2017 was chosen as a current year for which all available required information and input data were given to the model and future water demand situation was analyzed for the period 2018 – 2030. The projected annual rainfall (mm) over the middle reach of Subarnarekha river basin, for GFDL-ESM2M with RCP4.5, during 2017-30 (14 years) was determined. Dry conditions with an annual rainfall of nearly 716 mm for the year 2022 was predicted. Whereas, the year 2026 would experience high rainfall (1945 mm) indicating a wet condition. The remaining years would experience the normal rainfall condition. The years expected to encounter heavy rains also show high runoff value and vice versa. The model calculated water demands were always on a higher side than actual water use rates of population and livestock. These higher demand calculations are reflected in unmet demands. Demands are higher in non-monsoon months than in monsoon months as expected. Annual (2017-2030) domestic/ population and livestock unmet demand for the Subarnarekha river basin was also estimated and it was observed that the unmet demands would experience a decrease in the years 2019, 2021, 2024, 2026, 2028.