Global water resources are under growing threat due to increased demand by society and potential limitations in resource availability due to global climate change. These threats can be mitigated through improved resource management; however, such mitigation cannot be effective unless the driving forces due to global climate change are sufficiently understood and conceptualized to allow for meaningful analysis. The watershed is the fundamental unit of evaluation for natural water resources and precipitation is the critical input to the watershed water balance. Analysis of dynamic watershed water balances provides for the quantity and timing of streamflow and of recharge to subsurface groundwater reservoirs. The evolution of the quantity and timing of streamflow and recharge will determine the future viability and sustainability of the natural water cycle and water resources. The watershed water balance will evolve as a consequence of climate change and associated trends in precipitation and temperature, regardless if change occurs as a result of natural or anthropogenic factors.
This project will create a modular, risk-assessment framework to evaluate the potential impact of global climate change on the watershed water balance, in general, and on streamflow generation and recharge to groundwater reservoirs, in particular. Existing global climate simulation model results will be used to probabilistically describe the possible range of change to precipitation and temperature trends that will be applied to watershed water balance analyses as part of the climate change, or an alternative hypothesis, branch of the framework. Historical precipitation and temperature trends will be described probabilistically and applied to watershed water balance analyses as part of the null hypothesis, or historical statistics, branch of the framework. Comparison of results between the two framework branches, null and alternative hypotheses, provides for relative change in volume and timing of streamflow generation and aquifer recharge as well as corresponding probabilities for these changes. The watershed water balance risk-assessment framework will be applied to a specific watershed using existing watershed water balance models to provide estimates of the risk to streamflow and groundwater from climate change for a semi-arid landscape.
Project efforts to date include (i) selection of the Dolan Creek watershed in Val Verde County, Texas, as the semi-arid study area, (ii) acquisition and processing of historical weather observations for the study area to produce the probabilistic description of weather data and incorporation of this probabilistic description in a weather generator, probabilistic simulation framework, (iii) acquisition and processing of global climate model simulations for the study area to produce the probabilistic description of climate trends and incorporation of this probabilistic description in a weather generator, probabilistic simulation framework, (iv) validation and testing of the data-based weather generator which will provide for the null hypothesis branch of the framework, (v) validation and testing of the climate projection-based weather generator which will provide for the alternative hypothesis branch of the framework, and (iv) preliminary description and parameterization of the study area for representation in water balance models.