MODSIM versus RiverWare: A comparative analysis of two surface water modeling tools.
In the Pacific Northwest (PN) region, MODSIM has traditionally been the tool used to develop and simulate river and reservoir operations for planning, biological assessments, and operational forecasting because MODSIM had the unique capability of distributing water based on priority water rights. RiverWare has recently added that capability and new models are being developed for basins in the PN region, including the Deschutes, Rogue, Upper Snake, and Boise river basins. However, a set of criteria does not exist that could be used to determine when it would be more appropriate to use one model over the other. Is there a set of criteria that could be developed to evaluate which model ,MODSIM or RiverWare, is the more appropriate tool for a given application?
Need and Benefit
Reclamation hydrologists use river-reservoir distribution models to plan for future water supply conditions and to understand the impact of potential changes to distribution and storage systems. In many western states, prior appropriation governs the way that water is distributed, and therefore, it is imperative that models can distribute water based on priority water rights. For many years, MODSIM was one of the few distribution models that could simulate distribution based on priority water rights, and therefore many thousands of dollars have been invested in the development of MODSIM models. MODSIM models use a network solver that can make it difficult to determine how water is moving through the system, and to some, can seem like a "black box". RiverWare, on the other hand, is viewed to be more transparent in the way water is distributed. Given RiverWare's transparent nature and new capability of being able to distribute water based on priority water rights, new RiverWare models are being developed where MODSIM models already exist. In addition, many of the new RiverWare models are being developed using a daily timestep, whereas the MODSIM models use monthly timestep.
The PN region has struggled with the decision to continue to use MODSIM or move to RiverWare for its planning models based on these new features. After some investigation, it has been determined that it is not clear that one model is better than the other, and that each have value depending on the project objectives. The proposed research will develop the set of criteria to compare, evaluate, and decide which model is most appropriate for a given set of objectives and conditions. This will also provide the reasoning and background for discussions with stakeholders since new MODSIM models are being developed for stakeholders that cannot afford the RiverWare license fee (MODSIM is a free software).
In summary, there are many basins that have both RiverWare and MODSIM models. It would be beneficial to develop a set of criteria to evaluate the models in each basin to determine when it is appropriate to use one over the other so that the past investments in model development are not lost and so that the most efficient tool is used for each application.
Although this project is specific to the PN region given the number of MODSIM models that currently exist, the findings from this study could provide information to other regions and stakeholders as to whether a particular model may be more beneficial for their project objectives.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
MODSIM versus RiverWare: A comparative analysis of two river reservoir modeling tools (final, PDF,
By Jennifer Johnson
Report completed on November 19, 2014