NOTE: Hydrology Pages are currently Under Construction
The San Juan Recovery Implementation Program Hydrology Committee provides oversight regarding the hydrologic data and
models used by the SJRIP. The San Juan Basin Hydrology Model simulates flow in the San Juan River below Navajo Dam on a daily time-step. The primary purpose of the model is to support San Juan River Recovery Implementation Program goals to recover populations of the endangered razorback sucker and Colorado pikeminnow in the San Juan River while proceeding with water development in the Basin. The model is used in Endangered Species Act section 7 consultations to determine the level of impact, if any, of a proposed action that deplete river flows on the Reclamation’s ability to meet the flow recommendations below Navajo Reservoir. Note that model results are not the sole criteria used to determine the level of a proposed project’s impact and that model assumptions and model uncertainty are considered when interpreting results. The SJBHM was used to evaluate and develop the current flow recommendations and will be used in developing future revisions to the flow recommendations. In addition, the model will be used to develop and evaluate the revised hydrologic baseline. The model currently uses natural flow data based on historic depletions (1929-2006); however, alternative inflow hydrologies may be evaluated in the future to evaluate current and/or future water availability under different climate change scenarios.
The Bureau of Reclamation is primarily responsible for the development and maintenance of the SJBHM. As of September 2009, the SJBHM is currently being revised. This work is expected to take until December 2010 for the full integration of a new hydrologic baseline. Projected milestones for this and other future model work will be posted soon.
San Juan Basin Background
The San Juan River Basin drains an area of approximately 25,000 square miles, an area equal to that of West Virginia. About 39 percent of the drainage is in New Mexico, 23 percent in Colorado, 20 percent in Arizona, and 17 percent in Utah. The San Juan River is the second largest tributary to the Colorado River. Its source is on the Continental Divide in southern Colorado, and it flows approximately 350 river miles westerly to its confluence with Lake Powell.
Elevations vary from about 3,700 feet above sea level at the confluence with Lake Powell to over 14,000 feet on the crests of mountain peaks in the San Juan range. Precipitation varies from more than 60 inches annually in small areas along the high peaks, to less than 10 inches in extensive parts of the Basin, to less than one-tenth inch in others.
San Juan Recovery Implementation Program Background
The purpose of the San Juan River Basin Recovery Implementation Program is to protect and recover endangered fishes in the San Juan River basin while water development proceeds in compliance with all applicable Federal and State laws. Endangered species include the Pikeminnow (formerly known as the Colorado Squawfish), or Ptychocheilus Lucius, and the Razorback Sucker, or Xyrauchen Texanus. It is anticipated that actions taken under this Program also will provide benefits to other native fishes in the basin and prevent them from becoming endangered in the future.