We continue to develop and refine our signature computer-simulation model, WaterSim, under an open source community framework. This year, we completed and released a new version of WaterSim (5.0) as an open source model that can be downloaded from DCDC’s web site. The model development process is guided by the DCDC WaterSim Steering Committee, as well as structured dialogue with regional water providers.
WaterSim 5.0 is a demand-driven model with water deliveries from the various sources based on provider-specific rights for each water source. WaterSim 5.0 includes additional sources of water that were not incorporated in earlier versions, including water supplied from reclaimed and reverse osmosis (RO) reclaimed water sources; water banking as a policy option, where water banked outside the regional aquifer during times of abundance can be used to meet demand when surface water supplies are curtailed (e.g., during drought); and various options for recharging of regional groundwater. The WaterSim 5.0 Application Programming Interface (API) includes C# access to the FORTRAN model’s parameters and functions with robust error checking, a mechanism to include an annual feedback loop, and database support for loading model parameters and saving model output. Version 5.0 also includes extensive documentation, including source code for the C# application interface (API) and FORTRAN model, documentation for the API and FORTRAN model parameters, and a sample user interface to the model (including an install program) that can be installed remotely on most personal computers (see /watersim/).
Based on continued engagement with researchers and regional water managers, we continue to work on refinements to WaterSim 5.0. A provider-specific ground water credit based sub-model has been added to reflect the current system of regulating groundwater and requirements for an assured water supply designation. Several indicators of sustainability at the regional and provider level, such as percent and length of deficits, groundwater yield trends, and use of effluent, have been added to the API to make it easier to compare the sustainability of various scenarios. In late 2010, several of the regional water providers received new assured water supply designations, and the water rights for these providers were updated based on these new designations. An extensive process of validation and verification was initiated. Stream flows and water allocations for the CAP and SRP supplies as well as groundwater withdrawal rights and rates were verified. Planning for a fall workshop is underway to introduce the new version of WaterSim to regional water providers, solicit their review and verification of the data input for their community, and review how the model performs for their area under different conditions of supply and demand.
This new version of the model is being used this summer to continue exploring the application of advanced scenario analysis to examine the uncertainty of climate change on regional water management. We developed a scenario generator that can create a large number of scenarios based on varying levels of factors such as climate change or water banking. Tools to analyze these scenario ensembles are being developed and it is anticipated that this summer a paper examining the spatial impacts of water shortages on growth will be developed. Also in the planning stages for this fall is a workshop to explore how the new versions of WaterSim can be used as a tool in sustainability education at the K-12, Community College, and University levels, as well as workshops to explore adding an agriculture and natural environment supply/demand model to WaterSim.
WaterSim is not only a simulation model for decision support for water sustainability and urban climate adaptation but also a research tool. This past year, geographers Alan Murray, Patricia Gober, Luc Anselin, Sergio Rey and others published research using WaterSim 4.0 for decision analysis (Murray et al. 2012, Water Resources Management). Their research applies spatial optimization models to support water supply allocation between service provider districts, where some districts experience deficits and others experience surpluses in certain years. The approach seeks to reconcile and integrate projections derived from WaterSim while taking into account current and future climate conditions. The formulated and applied models are designed to help better understand the expected increasingly complex interactions of providers under conditions of climate change.
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 4.0, 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 4.0 runs on an annual time-step, but monthly estimates can be generated for many of the output variables. WaterSim 4.0 produces water supply and use patterns for 33 Phoenix Metropolitan Area water providers.
DCDC II’s WaterSim Steering Committee developed recommendations for model improvements based on feedback from the research community and community partners. The new version of WaterSim, which will include a Microsoft.Net-based standalone model (which does not require Powersim) with a documented application interface (API), is being developed in FORTRAN and C#.