Global climate models (GCMs) have proven to be a valuable tool for investigating the impact of man-made green house gases on Earth’s climate. The immediate impact of global warming is increased temperatures. In early 1990s, the Intergovernmental Panel on Climate Change (IPCC) estimated a rise in global mean temperatures of 1.5oC to 4.5oC. The indirect impacts of the climate change include: normal summers but warmer winters; normal daily high temperatures, but warmer nighttime lows; increases in extreme precipitation events (Karl, 1997); and changes in the hydrologic cycle including increased cloudiness. The rapid progress in computer technologies has allowed for horizontal resolution of the order of several hundred kilometers and advanced treatment of physics in GCMs. Although global effects are important, the more immediate impacts on humans will be on the regional and local scales. Therefore it is not practical to predict demands for water, electricity, or agricultural aid based on a global perspective. The description of the Hydrologic Cycle improves with increasing resolution due to the better topographical representation. Therefore it is imperative to study regional scale climatic changes. In this project, the study is concentrated on the Upper Brazos River region in the South Western United States.

In response to increased fresh water use by humans, water resources planners have developed new approaches for optimizing use of existing water supplies. For the semi-arid High Plains and Low Rolling Plains areas of Texas, optimal use of water supplies is critical. The water resources of this region are limited by the combination of low rainfall rates of 20 inches or less per year and potential evapotranspiration rates of up to 100 inches per year. Water resources planners have a challenging task in allocating scarce water resources. However, current planning methods rely on historic meteorologic data to determine expected water yields. The possibility that climate change could dramatically alter current hydrologic systems and invalidate projections of firm yield should be examined.

The main objective of the project is to develop a method of transferring climate change as predicted by a Regional Climate Model to assess the Brazos River Basin water resources system. The study involves developing a Regional Climate Model for 1XCO2 and 2XCO2 scenarios using the Modular Modeling System (MMS) developed by USGS. The results obtained by a GCM are used as the boundary conditions for the Regional Climate Model. The CSIRO Mark 2 GCM model was used to generate a GCM for the study area. The other objective of the project is to compare the dynamic regional model generated by the MMS with the downscaled statistical model already generated for this region by Troy Dorman (2003). The climate change data obtained by the Regional Climate Model will be used to assess the likely impact of changes on the Hydrologic Cycle in the Brazos River Basin. The changes in the Evapotranspiration levels and the recharge due to the Climate Change will also be analyzed.

KEYWORDS

Regional climate modeling, GCMs, Brazos river basin water resources, weather prediction, climate modeling, MMS.

Last Updated: 2006-03-07