Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Civil and Environmental Engineering


Jagath J. Kaluarachchi


Water scarcity is the major challenge that water managers face in semi-arid areas, especially in regions that depend on agriculture for rural livelihood. Climate change is one of the major stresses that is expected to exacerbate water scarcity problems in semi-arid regions. In this study, a risk-based approach was used to assess the climate change impacts on the risk of agricultural water scarcity in semi-arid and snowmelt-dominated river basins that are dependent on agriculture. The Sevier River Basin, located in south central Utah, was used as the case study for this work. An agricultural water deficit index was proposed to represent the basin performance in terms of water supply and agricultural water demand. The basin's natural water supply was estimated using a semi-distributed tank model. FAO AquaCrop model was used to estimate the crop water requirements for major crops in the basin. The risk-based methodology begins using a vulnerability analysis to identify the system sensitivity to climate change. Sensitivity of system response to climatic variability was identified by establishing the climate response function, which is the relationship between basin agricultural water shortage and climate variables (i.e., precipitation and temperatures). The climate response function was then used to predict the basin agricultural water shortage in this century across four time slices using the projections of precipitation and temperature from downscaled and bias corrected GCMs outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for RCP4.5 and RCP8.5 scenarios.

The results of this study suggested that more natural water supply is expected in the Sevier River Basin due to the expected increase in precipitation during the future off seasons. However, projected temperature increases in the future may increase crop water requirements. It is also found that there is a high risk of unacceptable climate change impacts on agricultural water scarcity in the basin in the period 2025-2049 under RCP4.5 and for 2075-2099 under the RCP8.5 scenario, indicating climate change adaptation actions may be needed.