The effect of increasing green house gases (GHGs) is already changing the worlds climate, increasing atmospheric temperatures and affecting the land-surface, for example, by changing water availability and the viability of crops. These direct and indirect climate change impacts interact with each other, thereby increasing or decreasing the overall impact of a changing climate. South Asia (SA) is a region with complex orography, ranging from high glaciated mountains, the headwaters for large rivers that flow through several countries to feed vast lowland deltas. The region has extensive irrigation systems that support an intensive agricultural industry. These features, together with a highly variable climate, make SA vulnerable to climate change and important for developing understanding of interactions between land-surface climate impacts.
This thesis develops simulations to study the interactions between water resources and crop production for SA using a land surface model. Analysis of SA river flows from regional climate model (RCM) simulations indicate an increasing water resource toward 2100. However this RCM does not include abstraction or irrigation. The Joint UK Land Environment Simulator (JULES) represents rivers but irrigation and crops require development to represent key features of the SA crop calendar; these include: the correct growing season inputs for crops, the capability to simulate several crops in rotation during a single growing period (sequential cropping) and crop specific irrigation.
This thesis addresses the main development needs for representing the SA region. A method is presented for estimating sowing and harvest dates for SA based on the dominating climatological phenomena, the Asian Summer Monsoon (ASM). This method provides a more accurate alternative to the global datasets of cropping calendars than is currently available and generates more representative inputs for climate impact assessments. In order to model the SA cropping system more accurately, the development and implementation of sequential cropping in JULES with crop specific irrigation is presented to develop simulations to understand how changes in the SA climate could affect water resources and crops. Finally I present simulations in which all of the individual developments from this thesis are brought together; these show the progress that has been made towards simulations that enable analysis of the impacts of climate on rivers, irrigation and crops for SA in a fully integrated way.
