Simulating the Rio Grande Surface Water Flow System in the Upper Rio Grande Basin

The Rio Grande originates in the San Juan Mountains of southern Colorado and travels through Colorado, New Mexico and along the United States border in Texas to the Gulf of Mexico, a distance of about 1,900 miles.  Its watershed covers about 182,000 square miles and its major tributaries are Conejos River, Rio Chama, Rio Jemez, Rio Puerco, Rio Salado, Pecos River and Rio Conchos.  Spring snow melt runoff and monsoon flow are the primary sources of water to the river. Another source of water, known as San Juan Chama Project water, is diverted from the San Juan basin in Colorado through tunnels to the Rio Grande Basin and the Rio Chama in New Mexico.  The river flow provides water for multiple uses, including cities, irrigated agriculture, recreation, and the riverine ecosystem.  The Rio Grande flow system is controlled by a series of reservoirs on the main stem and its tributaries which are managed by different agencies for multiple purposes.  Over the past 10-12 years, the water management agencies have worked collaboratively to develop and implement a comprehensive model for river and reservoir water operations.  The model, known as URGWOM (Upper Rio Grande Water Operations Model) links inflows and reservoir operations to downstream demand for the Rio Grande and its main tributaries from Del Norte, Colorado to Fort Quitman, Texas.  It simulates river routing, river gain/loss, reservoir storage and release, flood control operations, diversions, crop consumption, return flow, riparian ET, and open water evaporation as well as the shallow groundwater system and its interaction with deep aquifer.  In addition to simulating the physical system, URGWOM contains rules for water accounting and legal constraints such as reservoir authorizations and the Rio Grande Compact.  URGWOM is currently used to prepare the Middle Rio Grande basin annual operating plan, water accounting for Rio Grande compact purposes, daily reservoir operations in New Mexico upstream of Elephant Butte Reservoir, and for basin planning studies.  This presentation provides an overview of Upper Rio Grande hydrologic system and its representation in URGWOM.