Investigation of sustainable water use and blue water scarcity at state and monthly scales
Document TypePhD thesis
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© 2018 Dr. Naveen Joseph
India is the second most populous country and the largest freshwater consumer in the world. The country faces severe freshwater scarcity primarily driven by increasing water demand and declining freshwater availability. Large-scale assessments using distributed hydrological models have become an important tool to quantify the impacts of global climate change and water use changes on water resources sustainability. The current large-scale assessments, however, need improvement in accounting for industrial and environmental water demand as most of these assessments may not include sufficiently accurate estimates of these water demands. This thesis aims to develop a large-scale assessment framework to estimate sustainable water use and water footprint in India via the combined use of a global earth system model and a census-based statistical database. The core part of this research focuses on developing a modelling framework and applying it for estimating the blue water scarcity in India. The modelling is carried out for the period 1991–1999 at a spatial resolution of 50 km x 50 km and a monthly timescale. As a measure of deficiency in water supply relative to water demand, Water Stress Index (WSI) and Per-capita Available Water (PAW) are used in this study, consistent with Sustainable Development Goal 6.4.2 of the United Nations. WSI is defined as the ratio of total water withdrawal to total available water, and PAW is defined as the ratio of total available water to the total population. The total available water is modelled as the sum of surface and sub-surface runoff using the Community Land Model, CLM 4.0, developed by the National Centre for Atmospheric Research (NCAR) of the US. The total water withdrawal is defined as the sum of the irrigation, industrial, domestic and environmental water uses. These water withdrawals are modelled using census-based statistical data collected from various national and state governmental organisations in India. This thesis provides a detailed review of large-scale water resources assessments and the methods by which blue water scarcity is quantified. The review identified that the selection of appropriate spatial and temporal scales of assessment is critical. By refining the spatial scale from country to state and the temporal scale from annual to monthly time steps, water scarcity is better captured due to the distinctive seasonality of water availability and demand. Moreover, the analysis suggests alternative methods to better quantify the available water and various water uses in large-scale modelling frameworks. Further, it highlights the importance of using satellite observations of soil water, snow water and groundwater to improve the overall water budget. Following the methods discussed in the review, this thesis estimates the industrial water use in India by incorporating datasets on industrial production, industrial consumables, economic and technological development indicators. The study generates time-series of state-wise monthly industrial water demand in India for the period 1991 to 2010. The state of Maharashtra and Tamil Nadu lead the volume of industrial water use in India, and most of the states show a consistent increasing temporal pattern. The research also shows that industrial water use exhibits seasonality with higher water use during March and less seasonal fluctuations from April to September. Domestic water use in India from 1971 to 2010, at state-scale and monthly time-steps, is estimated by incorporating indicators of population and economic development. The analysis identifies an exponential increase in per-capita domestic water use across the country consistent with the rise in per-capita Gross Domestic Product (GDP). The state of Uttar Pradesh leads the domestic water use followed by Maharashtra and Andhra Pradesh. The seasonal variation in domestic water use is modelled using air temperature as an indicator. The significance of this thesis lies in quantifying blue water scarcity by compiling each of the components of total available water and total water demand. The analysis also incorporates the excess water component, which is the amount of water remaining after meeting the demands at each time step. It is found that around 0.62 billion people in India face severe water stress (WSI > 0.4) at least one month every year during the period from 1991 to 1999. Moreover, the research identified severe groundwater depletion in the states of Gujarat, Rajasthan and Tamil Nadu. Water scarcity is more severe in Gujarat, Rajasthan, Maharashtra and Uttar Pradesh with Rajasthan facing severe water stress for more than 90% of the analysis period. The thesis also highlights the significance of incorporating environmental flows and reservoir-storage component into the water scarcity framework. When the environmental flow is neglected, it results in an underestimation of water stress by 10 – 15% and reservoir component reduces severe water stress for 0.1 – 0.2 billion people in the country.
Keywordsblue water scarcity; sustainable water use; water footprint; large-scale water resources assessment
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