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Increasing temperatures and changes in precipitation patterns and amounts are expected to increase pressures on water resources and result in decreasing water quality and quantity. Water utilities face the challenge to anticipate and plan for deteriorations in the water quality of untreated abstraction sources (so-called raw water quality) and to manage consequent risks, a challenge exacerbated through deep uncertainty associated with climate change. This research proposes a framework how to integrate effects of climate change on raw water quality into risk assessment and to build capacity to anticipate and respond to change. A national assessment of public water supply catchments in Scotland was used as a demonstration case for applying the framework. The analysis was conducted with data from 154 drinking water supply catchments from a period of 2011-2016. Empirical relationships between catchment characteristics and water quality were examined to understand overarching drivers, pressures, and underlying catchment sensitivities leading to impacts on raw water quality. Risk screenings were developed for two water quality indicators, colour and E. coli, and UKCP18-based climate and land use projections were used to identify and map catchments and areas with potential increases in risk. The screenings identified crucial controls on water quality, high risk areas, areas of uncertainty, and allowed first suggestions for possible response options based on catchment vulnerabilities. They also provided a basis for a strategic review of and planning for the complete supply system, by providing a starting point for transferring results and insights from individual sites, and by allowing for a first appraisal of long-term sustainability of supply. By focusing on catchment integrity and resilience as a crucial part of climate change mitigation and adaptive management, this research emphasises an ecosystem-based approach as a frame for water service providers to achieve multiple objectives.

One of the biggest global challenges is to achieve sustainable water, energy and food security simultaneously while enhancing ecosystems integrity and climate change resilience. This challenge is more critical in semi-arid regions of developing countries where water resources are subject to increasing demands and unplanned urban associated with fragmented sectoral policies require complex trade-offs between resources and degrading environment. In India, due to lack of accountability of resources stocks and flows, for example, water losses for hydropower production, there is an unclear picture of inter-dependencies between water, energy and agriculture at the production level. In the context of climate change and inevitable growth in resource demands, changes in one sector may have direct or indirect impact on another sector inter-connected in a nexus. Therefore, it is important to develop an understanding on the inter-links between water, energy and agriculture sectors, identify drivers that influences these links and predict impact of climate change and socio-economic growth on the natural resource base to inform integrated policies aimed at introducing synergies and achieving sustainable systems with minimal natural resource demand, reduced emissions and resource efficient growth. The place-based approach is adopted for this research. Cauvery River basin, an agriculturally dominant, semi-arid region with rapidly growing cities and industries is chosen. It is a politically sensitive, and geographically challenging region in Peninsular India mostly spanning the twin states of Karnataka and Tamil Nadu. Amongst many resources related issues, the most pressing are physical and social water scarcity, rapid urban expansion, contested trans-boundary water governance and allocation, groundwater mining, energy-intensive irrigation, large and small water resource interventions (from millions of field bunds at the farm-scale to a small number of highly significant multipurpose dams). These all operate in a regulatory vacuum for environmental flows and provides the focus for this thesis on water resources sustainability under changing climate and land use futures. This thesis examines the cross-sectoral use of resources and impact of sectoral policies, climate change and management practices on the riverine ecosystem. The assessment of the water-energy-agriculture nexus is done under three sub-aims focused on nexus in agriculture production, energy production and water resources. Using irrigation census data, the spatial variability of energy consumption for pumping irrigation water is analysed and various factors such as climate, water allocation, investment, culture and policies influencing irrigation regime are discussed. In addition, we provide an estimate of net energy consumption for irrigation and associated carbon emissions. The results reveal over consumption of electricity for irrigation which can be managed with increasing irrigation water efficiency and enhancing rainwater irrigation. In the business-as-usual future scenario, growth in agricultural production would require more water and energy consumption and if energy is generated at hydro or thermal power plants, this would mean that more water must be mobilised for food security and energy security. In order to estimate consumptive water use in energy production sector, Landsat and Sentinel satellite data are used. Analysis algorithms ran in GEE over satellite images between 2000-2019 provided estimates of reservoir water area which combined with climate data provided evaporative water losses for hydropower generation. Moreover, positive correlation between hydropower generated and water in reservoirs suggests that at present energy sector is highly vulnerable to hydrological changes and increasing water demand. For assessing the changes in hydrological regime associated with climate change, land use change, population growth and increasing demand for resources, hydrological model GWAVA is implemented by considering a selection of IPCC defined climate change scenarios and shared socio-economic pathways. Six distinct combinations of scenarios with green socio-economic growth (SSP1), worst case scenario (SSP3), minimum emissions (RCP 2.6) and worst-case climate scenario (RCP 8.5) were simulated. The simulation results demonstrate that socio-economic factors dominate the cause for plausible hydrological alterations and ecosystem degradation. Simulations with better water demand management, increased water use efficiency and ecosystems-based river water allocations shows minimal changes in hydrological regime and minimal risks to river ecosystem even under worst case climate change scenario. Overall, this thesis provides a framework for using theoretical and empirical data in a data scare region to address water-energy-agriculture nexus challenges by answering where and why pressures exists and what are their key drivers. The study recommends that there is need for greater collaborative engagement between the respective State Governments working together for implementing integrated policies for reducing exploitation of resources in the pursuit of growth and development.