Investigation of sustainable national water resources management of India in a changing climate

Freshwater scarcity and unsustainable water use is a growing concern in many developing countries including India. Increasing water demand coupled with rainfall variability associated with climate change exacerbates water scarcity. The increase in water demand is attributed to population and economic growth as well as technological change, and the gap between the actual water available and the demand continues to widen. This study aims to develop a large-scale assessment model of sustainable water use in India during the period 1970 – 2010 at a spatial resolution of 50 km x 50 km and a temporal resolution of monthly timescale. A Community Land Model CLM 4.0, developed by the National Centre for Atmospheric Research (NCAR) of the US, and census-based statistical database are used in this study to quantify and assess the sustainable water use in India. We define the measure of sustainable water use as the difference between the total water available and the total water demand. For each grid cell, the total water available is modelled as the sum of surface runoff and groundwater. The total water demand is estimated as the sum of irrigation, industrial, domestic and environmental water demand in each grid cell. Among the demands, the irrigation water demand is modelled based on census data sets of irrigated areas and irrigation water withdrawal while the domestic and industrial water demand is modelled as a function of population, economic and technological indicators such as gross domestic product, electricity, fuel consumption and industrial outputs. However, the environmental water demand is modelled as a function of total water available, following hydrology based approach, with seasonal variation of water demand to meet the various ecosystem services considered. Based on preliminary analysis, the rate of increase in industrial water demand (~2% increase per annum) and domestic water demand (~1.2% increase per annum) is higher than the rate of increase in irrigation water demand, thus increasing contribution to the water scarcity in the country (~54% of total population)._This rapid growth in industrial and domestic water demand highlights the importance of accurate projection of the future demand. Modelled results of industrial and domestic water demand closely match the observations obtained from the National Commission on Integrated Water Resources Development (NCIWRD) of India. The modelled results are shown to be superior to FAO (Food and Agriculture Organization) estimates of industrial water demand. The difference may be associated with the fact that the FAO estimates do not consider the water requirement for power production in the quantification of industrial water demand.