Water Resources Assessment of Basins of India Using Space Inputs
In the context of Indian economy, continuously growing demands on freshwater due to over-abstraction, water pollution and climate change, without opportunities arising from improved water management, are not thinkable. In this context, it becomes essential for assessment of water resources in all the basins of India. Changes in the land use, enhanced urbanization, river modification and other human activities modify the storage capacity of watersheds and impact high flows, groundwater recharge and low flows. This study is a reassessment of country’s water availability and mean state considering the recent three decades (1985–2015) and would help in evaluating the country’s existing and planned water system future demands over the years under a range of hydrologic conditions. The present paper emphasizes on quantifying basin-scale water resources on water balancing exercise through hydrological modelling approach by transforming basin/subbasin terminal gauge site discharges, aggregating meteorological data.
Daily rainfall data of 0.25 × 0.25° grids and daily temperature data of 1 × 1° grids were got from India Meteorological Department (IMD) and converted into spatial format. Land use and land cover map from the year 2004–2005 to 2014–2015 prepared under Natural Resources Census (NRC) project of NRSC using IRS AWiFS satellite data (56 m resolution) were used in the study. Command area boundaries for irrigation support estimation and waterbody maps for estimating standing water evaporation losses were used. SRTM digital elevation model (90 m resolution) was used for basin/subbasin boundary delineation. Soil textural map, land use and land cover (LULC), daily rainfall, daily temperature, waterbody and command area maps were integrated in modified Thornthwaite-Mather modelling framework to compute the monthly soil moisture, evapotranspiration and surface runoff. In this study, Thornthwaite-Mather method of potential evapotranspiration (PET) was modified by incorporating land cover coefficients for taking into account the variations in vegetation types and crop season.
A software tool, namely, water resources assessment tool (WRAT), was developed by the National Remote Sensing Service Centre, ISRO, Hyderabad, for computation of water balance components in modified Thornthwaite-Mather modelling framework using geospatial datasets. The tool integrates all input images such as basin boundary, LULC map, soil, rainfall, temperature, command area and reservoir mask and generates the outputs in the form of image layers and text files. The abstractions such as domestic, industrial and livestock consumptive demand were estimated for the 30-year period for each subbasin. The groundwater fluxes were computed for each year using the information provided by Central Ground Water Board (CGWB). The surface storage fluxes were also estimated during the study period for major and medium reservoirs located in the basins. The model-computed surface discharge was calibrated and validated with observed discharge at G&D sites within the basin/subbasin. The calibration and validation were done by trial-and-error method by varying the model parameters to match model- estimated discharge and observed discharge after accounting upstream abstractions. The validated model outputs were then used to assess water resources availability in the basin. The average annual water resource of the basins for the study period of 30 years (1985–2015) has been assessed as 1999.20 BCM. The mean annual rainfall of all the basins for the study period of 30 years is found to be 3880 BCM.
KeywordsWater resources availability Runoff Hydrological Response Unit Water resource management
The authors extend sincere thanks to the chairman of the Central Water Commission and head of the National Remote Sensing Centre for their kind support. The support extended by the colleagues through their valuable suggestions and comments are gratefully acknowledged. The views expressed in the paper are personal of the authors.
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