In DCDC II, we have continued to implement and refine our signature computer-simulation model, WaterSim, to investigate how alternative climate conditions, rates of population growth, and policy choices interact to affect future water supply and demand conditions in Phoenix. We designed WaterSim not only as a decision-support tool but as a hybrid boundary object designed to link science and policy to improve environmental decision making under conditions of uncertainty. As such, the modeling effort incorporates structured ongoing feedback from stakeholders and researchers.
WaterSim is a hierarchical model that uses supply from surface and groundwater sources and demand from residential, commercial, and agricultural sectors, incorporating the rules that govern reservoirs, aquifer use, and land-use change. Gober et al. (2011) in Environment and Planning B and Sampson et al. (2011) in Journal of Environmental Management described the development of WaterSim.
The current version of the model, WaterSim 5.0, is comprised of (1) a Microsoft C# interface; (2) a C# library module; and (3) a simulation model (FORTRAN) that houses the rules and algorithms to model water supply and demand, all at the water provider-level. WaterSim 5.0 runs on an annual time-step, but monthly estimates can be generated for many of the output variables. WaterSim 5.0 produces water supply and use patterns for 33 Phoenix Metropolitan Area water providers.
Research using WaterSim has explored the impact that reduced surface water supplies due to drought and climate change may have on different scenarios of growth and water policy. Policies explored have included mandatory reductions in groundwater pumping needed to achieve safe yield and voluntary sharing of water resources among various water suppliers under stressed supply conditions.
- Gober, P., E.A. Wentz, T. Lant, M.K. Tschudi, and C.W. Kirkwood. 2011. WaterSim: A simulation model for urban water planning in Phoenix, Arizona, USA. Environment and Planning B 38(2):197-215. DOI: 10.1068/b36075.
- Sampson, D.A., V. Escobar, M.K. Tschudi, T. Lant, and P. Gober. 2011. A provider-based water planning and management model—WaterSim 4.0—for the Phoenix Metropolitan Area. Journal of Environmental Management 92(10):2596-2610. DOI:10.1016/j.jenvman.2011.05.032.
- Gober, P., and C.W. Kirkwood. 2010. Vulnerability assessment of climate-induced water shortage in Phoenix. Proceedings of the National Academy of Sciences USA 107(50):21295-21299.
- White, D. D., A. Y. Wutich, K. L. Larson, P. Gober, T. Lant, and C. Senneville. 2010. Credibility, salience, and legitimacy of boundary objects: water managers’ assessment of a simulation model in an immersive decision theater. Science & Public Policy 37(3):219-232.