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The focus of the WRMT is the (~200?) mile stretch of the Rio Grande River from Laredo to Brownsville. The Rio Grande demarcates the Texas-Mexico border, a region which is experiencing rapid growth in population and increased demands for water. Numerous state, regional, and local planning efforts are underway to respond to the competing needs for surface water, the deteriorating water quality in the Rio Grande Basin, and the development of additional water supply resources especially during drought periods. A complex binational water allocation system, local and regional flooding issues, and conflicting stakeholder interests further challenge the border region water dilemma. Effective management of water resources in the area requires the integration of complex domains that include water supply, water quality, water use, and management of floods and droughts.

Most of the study area is a relatively flat delta plain, with elevation under 300 meters and an average slope of 0.005 m/m. The western edge of the study area is marked by the Sierra Los Picachos mountains in Mexico, which rise to an elevation of over 1,500 meters.

The majority of the population is concentrated four cities, two in Texas and two in Mexico. Due to the dynamics of international trade, these cities are paired across the border and are known as "twin cities". The Texas city of Brownsville is mirrored by Matamoros and Laredo is paired with Nuevo Laredo. Outside these two international metropolitan areas, the population is sparse and generally concentrated near the border.

Land Use

Land use data describe the vegetation, water, natural surface, and cultural features on the land surface. The majority of the study area is pastureland, primarily used for ranching, with very little urban land use. In the eastern portion of the study area, the predominant pastureland fades into cropland, the primary land use of the Lower Rio Grande Valley. Largely due to the mountainous regions to the west, the Mexico portion of the study area has a much greater forested area.

Hydrology

The hydrology of the study area is largely controlled by man-made dams erected for water supply and management. Falcon International Reservoir, the upgradient limit of the study area, is the primary water source for the entire downgradient region in both the U.S. and Mexico. It therefore provides almost all of the flow in Segment 2302 of the Rio Grande. A number of intermittent streams in the U.S. contribute runoff following rainfall events, while two rivers contribute runoff from Mexico on an intermittent basis.

Due to heavily regulated water rights along the Rio Grande, water released from Falcon Reservoir is tightly managed. Water is only released after a request from a water rights holder, primarily for municipal, agriculture, and industrial use. Because agriculture makes up a large portion of this use, this discharge increases drastically during the spring planting season. Inflow from Mexico is intermittent, primarily limited to heavy rainfall events.

Drought

During the past decade, the study area has undergone the worst drought since the 1950’s. Falcon Reservoir, the primary water source for municipal, industrial, and agricultural uses for both U.S. and Mexico along the final 300 miles of the Rio Grande, has not been at full capacity since 1992 and is currently (2001) at approximately 15% capacity.

Water rights along the Rio Grande are tightly controlled by a 1944 treaty which regulates ownership of water in the river and the Amistad-Falcon dam system. The main source of water for this system is the Rio Conchos, which drains much of the Mexican state of Chihuahua, and is the largest tributary of the Rio Grande. The 1944 treaty states that one third of the water from the Rio Conchos and the other Mexican tributaries belongs to the U.S. It also states that Mexico is required to deliver 350,000 acre-ft of water and the U.S. is required to deliver 1.5 million acre-ft of water annually.

Since the drought began in 1992, Mexico has increased reservoir storage in the Rio Conchos basin and failed to provide the appropriate quantity of water, generating a water debt of approximately 1.4 million acre-ft. The Rio Conchos discharges to the Rio Grande over 400 miles upstream. Promises by the Mexican government to repay the debt will result in greatly increased storage in Amistad and Falcon Reservoirs, but will not directly impact flow in the Rio Grande in the study area.

Colonias

The boom of low-wage families settling in the border region has created a multitude of unincorporated communities which are marked by inadequate infrastructure, typically lacking clean water, sewage, paved roads, garbage disposal, and even numerical addresses. As of 1998, Texas border colonias were estimated to house approximately 340,000 people and be growing at a rate of about 10 percent a year.

Water availability in colonias is often limited to shallow dug wells. Wastewater is generally flushed into a covered hole in the ground or discharged to the ground surface. The result is significant contamination of the shallow groundwater and runoff into the Rio Grande. This environment makes colonias a breeding ground for diseases associated with pathogenic bacteria.

The problem is compounded by the lack of health services in colonias, where health problems are likely even higher than reported. For example, in Hidalgo county - which has the highest hepatitis and typhoid fever rates in Texas – each primary care provider sees over 7,500 patients, compared to the national average of 1,000 patients per provider. Additionally, in a 1994 study, 38 percent of Rio Grande Valley residents did not have health insurance - compared to 17.8 percent for the state as a whole - indicating that many colonia residents’ health problems go untreated, and therefore unreported.