Development of a Hydrologic Model to Assess the Feasibility of Water Leasing in the Middle Rio Grande Basin

The demand for water in the southwestern United States has increased in tandem with a rapid growth of population over the past 50 years. With ever increasing demands being placed on available water supplies, improving water management becomes crucial to the sustainability of the region's water resources. The National Science Foundation (NSF) Science and Technology Center (STC) for the Sustainability of semi-Arid Hydrology and Riparian Areas (SAHRA) is interested in the feasibility of water leasing as a method for more efficiently distributing water among competing users. Economists working on the project will run water leasing simulations in an auction-type environment to understand the pros and cons of water leasing in a free market system. To include hydrologic processes in the water leasing simulations, an MMS-PRMS hydrologic model was developed for a portion of the Middle Rio Grande Basin (MRGB) near Albuquerque, New Mexico. This portion of the MRGB contains a detailed network of diversions, canals, and drains that transport water through the system. In order to capture the complexity of the system, the model was developed using the highest resolution information available. In the model, each Hydrologic Response Unit (HRU) is represented as a trader. To achieve the 15 trader limit desired by economists, the model structure was simplified using two basic constraints; 1) HRUs having a common source and point of return to the river were lumped; and 2) HRUs with less than 20% agricultural land use were omitted from the auction simulations. A new Evapotranspiration (ET) module was implemented in the model to better estimate ET associated with different crops. Modules were also developed so that the end user has the flexibility to manipulate water deliveries based on crop type and land use. The MMS- PRMS model for the MRGB should help economists determine if the incentive to profit by selling or buying water can make more efficient use of the available water supply.