abstract: Rapid urbanization and population growth occurring in the cities of South Western United States have led to significant modifications in its environment at local and regional scales. Both local and regional climate changes are expected to have massive impacts on the hydrology of Colorado River Basin (CRB), thereby accentuating the need of study of hydro-climatic impacts on water resource management in this region. This thesis is devoted to understanding the impact of land use and land cover (LULC) changes on the local and regional hydroclimate, with the goal to address urban planning issues and provide guidance for sustainable development. In this study, three densely populated urban areas, viz. Phoenix, Las Vegas and Denver in the CRB are selected to capture the various dimensions of the impacts of land use changes on the regional hydroclimate in the entire CRB. Weather Research and Forecast (WRF) model, incorporating the latest urban modeling system, is adopted for regional climate modeling. Two major types of urban LULC changes are studied in this Thesis: (1) incorporation of urban trees with their radiative cooling effect, tested in Phoenix metropolitan, and (2) projected urban expansion in 2100 obtained from Integrated Climate and Land Use Scenarios (ICLUS) developed by the US Environmental Protection Agency for all three cities. The results demonstrated prominent nocturnal cooling effect of due to radiative shading effect of the urban trees for Phoenix reducing urban surface and air temperature by about 2~9 °C and 1~5 °C respectively and increasing relative humidity by 10~20% during an mean diurnal cycle. The simulations of urban growth in CRB demonstratedii nocturnal warming of about 0.36 °C, 1.07 °C, and 0.94 °C 2m-air temperature and comparatively insignificant change in daytime temperature, with the thermal environment of Denver being the most sensitive the urban growth. The urban hydroclimatic study carried out in the thesis assists in identifying both context specific and generalizable relationships, patterns among the cities, and is expected to facilitate urban planning and management in local (cities) and regional scales. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2017