go to chapters:
1. Overview
2. Study Area Description
3. Geomorphology and Sediment Cones
4. Environmental Resources
5.Problems and Opportunities
6. Recommendations
7. References
8. Appendices
Chapter 5 Watershed Problems and Opportunities
5.1 Problems
Historically, the Forgotten River Reach of the Rio Grande has been subject to higher spring time flows due to snowmelt within the upper Rio Grande Basin and intermittent tributary flows from isolated thunderstorms throughout the Forgotten River Reach’s adjacent watersheds during the monsoon season. Changes to the natural hydrologic regime from irrigation and flood damage reduction structures upstream of the Forgotten River Reach have dramatically changed river’s flow regime and the vegetation communities within the study area.
The Bureau of Reclamation’s Rio Grande Project furnishes a full irrigation water supply for about 178,000 acres of land and electric power for communities and industries upstream of the Forgotten River Reach. Drainage water from project lands provides a supplemental supply for about 18,000 acres in Hudspeth County, Texas. Project lands occupy the river bottom land of the Rio Grande Valley in south-central New Mexico and west Texas. About 60 percent of the lands receiving water are in New Mexico; 40 percent are in Texas. Water is also provided for diversion to Mexico by the IBWC-United States Section to irrigate about 25,000 acres in the Juarez Valley.
Physical features of the project include Elephant Butte and Caballo Dams, 6 diversion dams, 139 miles of canals, 457 miles of laterals, 465 miles of drains, and a hydroelectric powerplant. The project is operated as two divisions: The Water and Land Division, and the Power and Storage Division.
Invasive species removal and control needs to be managed to minimize the negative impacts to both the terrestrial and aquatic habitats within the study area and to maximize the river’s surface water quality and availability. Native plant communities need to be reintroduced but in order to do so, actions need to be taken to again mimic the historic flow regime.
The Rio Grande throughout its course has been declared an Endangered River five times since 1993 by the American Rivers and the World Wildlife Fund. The TCEQ, Environmental Defense Fund, and the Corps partnered in 2005-2007 to conduct a study of the Forgotten River Reach of the Rio Grande from Fort Quitman to Presidio, Texas. As a part of the study, the University of Texas Center for Space Research created a substantial geospatial database of ecological, water quality, and socioeconomic attributes, which is a part of this report (Appendix A).
Prior to the advent of intensive irrigation in the El Paso/Juarez Valley, and since the construction of Elephant Butte Dam in 1915, the character of the Rio Grande has dramatically altered from a bimodal snowmelt runoff and monsoon driven hydrologic system to a system regulated and characterized by consistent flow regimes tied to the irrigation season, and which is largely unable to move sediment. The reach is now an aggrading reach whose bed is substantially higher than prior to dam construction upstream (Schmidt et al. 2003). These changes in river hydrology largely facilitated the invasion of tamarisk throughout the reach (U.S. and Mexico sides), with an estimated 16,000 acres of tamarisk in monotypic stands currently existing in the floodplain and terraces of the reach, and another 20,000 acres of salt cedar mixed with other shrubs and trees (UTCSR 2006). The consequences of this noxious shrub invasion is increased salinization of soils and water, substantial loss of habitat quality for many faunal species, displacement of native flora, increased surface and groundwater loss due to evapotranspiration losses by salt cedar, and loss of agricultural productivity. Seventeen faunal or fish species are Federally or state listed in the study area and the entire reach is declared an impaired stream by TCEQ for total dissolved solids, bacteria, and chloride salts.
5.2 Opportunities
The TCEQ partnership with the Environmental Defense Fund, is working to identify ecosystem restoration projects within the Forgotten River Reach. Environmental Defense Fund has created a booklet entitled The Forgotten River Chronicles to educate the public on the rich history of this area and on the ecosystem restoration opportunities within the Forgotten River. Through this and other outreach programs, the citizens in the area are learning the importance of preserving floodplains. Opportunities now exist to preserve more of the local floodplains as wetland or riparian habitat or open space, as well as to increase the river’s channel capacity to ensure that more water reaches downstream water users. Such uses are consistent with the ecosystem restoration missions that Federal agencies, such as the Corps, participate in. (return to table of contents)
