A modeling framework to evaluate climate change and watershed development impacts on water security

Abstract

The long-term impacts of climate change on water resources are expected to be considerable in many parts of the globe. Resulting hydrologic changes can have a high impact on river basins like Krishna, India and Murray Darling, Australia where severe competition of water between stakeholders and states exists. Australia is already experiencing significant impacts of climate change: the average surface air temperatures have increased by 0.9°C since 1950 and precipitation has declined along the east and west coasts of the country. Analysis of emission scenarios suggests that warming of between 1°C and 2.5°C is likely by 2070 if emissions are low and between 2°C and 5°C under a high emission scenario. In India climate change possess challenges due to its vast geographic diversity. The projections for the country suggests that some regions will experience more intense rainfall and flood risks while other areas are going to get sparse rainfall and prolonged droughts. Accordingly, runoff is predicted to vary both spatially and temporally. Watershed Development (WSD) programs in rain-fed dry land agriculture in India have been introduced to ensure the sustainability of the surface and groundwater resources by harvesting rainwater, and to improve the livelihoods of farmers. A number of artificial water storage and diversion structures were established in the last few decades under this program. This will further intensify the problem by reducing the inflow into the reservoirs. This paper presents an integrated conceptual framework to assess impacts of climate change and WSD impacts on water security and to assess response strategies to cope with the combined impacts. The framework used in this study involves the integration of biophysical and hydrological modelling coupled with socio-economic modelling to provide a quantitative hydro-economic evaluation of the performance associated with each scenario-response combination. In this research, results from a general circulation model (GCM) are downscaled to the sub-basin level to generate input forcing information adapted to run a regional hydrological model on the future climate scenarios. In order to assess the climate change impacts on hydrological cycle, a fully distributed surface and groundwater modelling is proposed. The impact of watershed development on hydrology will also be analysed using this modelling framework. An integrated water allocation-economic modelling will be carried out to assess the water security and its economic value. Finally, the modelling framework will be used to evaluate a range of scientifically defensible social and economic policies driven by stakeholders, rather than seeking a single preferred (optimal) alternative. The conceptual framework presented in this paper is designed to respond to future climate change within a whole of river basin approach. The framework will be applied in the Musi catchment in Andhra Pradesh, India, designed to examine water security strategies under climate change.