The Water Supply Stress Index Model (WaSSI) is a web-based tool that predicts changes in water supply and demand, carbon dynamics, and biodiversity under multiple stresses. WaSSI was developed to fill a critical need for planning tools to evaluate tradeoffs between ecosystem services so that sound management decisions may be made in the face of climate, economic, and demographic change.

 

How does WaSSI Work - The core of WaSSI is a water balance model that is sensitive to land cover and climate, and operates on a monthly time step at the 8-digit Hydrologic Unit Code (HUC) watershed scale across the conterminous U.S and at the 0.5 degree grid resolution in Mexico. Gross ecosystem productivity, ecosystem respiration, and net ecosystem carbon exchange are estimated using actual evapotranspiration. Similarly, potential biodiversity of reptiles, birds, amphibians, mammals, vertebrates, and trees are estimated as a function of evapotranspiration. For the U.S., annual US Geological Survey (USGS) water demand estimates are adjusted for population, disaggregated to the monthly scale, and compared to groundwater and surface water supply to assess water supply stress.

 

Who should Use WaSSI - Resource managers for making informed management decisions in light of changing environmental conditions; educators, researchers, NGOs, and the general public for gaining insight on the effects of global change on water, carbon, and biodiversity at both local and continental scales.

 

Who is behind WaSSI - USDA Forest Service scientists from the Eastern Forest Environmental Threat Assessment Center developed the model algorithms. This web application was developed with programming support from Praecipio Consulting through a partnership between the Eastern Forest Environmental Threat Assessment Center and the USDA Forest Service International Programs to facilitate transfer of the science to all users.

 

Getting Started with WaSSI - After reading the background information, select the Options tab to define a region for simulation (U.S. or Mexico). Once a region is selected, explore the model inputs by clicking on the Input Viewer tab. A simulation scenario can be created and executed from the Simulation Tool tab. Please be patient!!! The model is simulating the water balance, water supply and demand, ecosystem productivity, and biodiversity for the entire region (U.S. or Mexico) over as many as 100 years and may take several minutes to complete. After a simulation, explore model outputs in the Output Viewer. Try making changes to the simulation scenario to assess the impact of climate, land use, and population change on water supply stress, ecosystem productivity, and biodiversity.

 

Appropriate Use - There is considerable uncertainty in prediction of future climate and ecosystem response to climate change. Users are encouraged to use WaSSI results with caution in light of this uncertainty. The WaSSI model assumes a static land cover distribution and phenology except where users develop scenarios to assess the impact of forest cover reduction and leaf area index change.

 

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