Water mass balances for the Rio Grande/Bravo from Fort Quitman, Texas to Foster Ranch near Langtry, Texas: An assessment of factors

Ramiro Lujan, University of Texas at El Paso


Water availability is declining in many regions of the planet, particularly in arid and semi-arid regions. Water bodies located in these regions, like the Rio Grande/Bravo at the U.S.-Mexico border, are subjected to high water demands. This research project makes an assessment of the spatial and temporal variability of elements intervening in the water mass balance for the section of the Rio Grande/Bravo between Fort Quitman and Langtry, Texas during the time period extending from January 1990 through December 2005. This document mentions the main Rio Grande/Bravo stakeholders from the U.S. and Mexico, and describes issues related to water ownership in the U.S. and Mexico and the allotment for the surface waters of Rio Grande/Bravo according to the U.S.-Mexico 1944 Water Treaty. Results from this study indicate that surface runoff and groundwater inflows constitute an important source of water to the lower river reaches. Evapotranspiration along the Fort Quitman and Amistad reach is around 140 Mm3/year. The largest fraction (93 %) of it takes place along the Fort Quitman-Presidio reach where salt cedar bosques are most extensive. Estimated groundwater recharge rates over the very large semi-arid sub-basins of the Rio Grande/Rio Bravo watersheds are in the range of 3.4–7.8 mm/yr, a very significant source of water. The water balance shows that Rio Grande/Bravo flows into Amistad Reservoir rely heavily on discharge from aquifers and monsoonal storm surface runoff from the large drainage basins. Groundwater extractions within the river's basin and out of basin water transfers for Rio Grande/Bravo water users create a significant impact on the river's water resources. Groundwater extractions from the Upper Rio Grande/Bravo reach should be limited and regulated in order to avoid a drastic reduction of water availability on this region. Water allocation procedures allocate this water to surface right holders without specifying its origin or importance. International treaties cover only some surface water sources, while ignoring groundwater and storm water input. Lack of an exhaustive understanding of the current water flows, combined with the lack of treaties might lead to a situation where locally regulated groundwater pumping increases result in reduced river stream flows with losses to downstream users. Groundwater removal far from the river may occur decades prior to the associated reduction in river flows. The disparity existing in the legal frameworks governing the Rio Grande/Bravo water resources require a better and extensive research about the intervening factors.

Subject Area

Environmental management|Water Resource Management|Environmental science|Environmental engineering

Recommended Citation

Lujan, Ramiro, "Water mass balances for the Rio Grande/Bravo from Fort Quitman, Texas to Foster Ranch near Langtry, Texas: An assessment of factors" (2012). ETD Collection for University of Texas, El Paso. AAI3512740.