|
|
| Water in the Lower Rio Grande/Río Bravo Basin |
Whether the Lower Rio Grande/Río Bravo Basin moves toward a more sustainable future concerning its water resources is largely a question of management. Potentially, the river can supply enough water, of acceptable quality, to support the domestic water needs of 4.9 million people projected to be living in the Lower Rio Grande/Río Bravo Border Region in 2030. To make this possible, agricultural use of water will have to be reduced significantly. Market mechanisms and mutually beneficial arrangements between cities and irrigation districts can bring about more efficient water use, making the rural-urban reallocation one of cooperation rather that conflict. However, without changes in water management to reflect minimum ecological water needs, not enough water will be left instream to maintain riverine and riparian ecosystems. As new wastewater treatment plants continue to come on line, water quality in the river may improve, although these improvements could be offset by increased concentration of pollutants due to decreased stream flow caused by increased water use. The complex array of local, state, regional, federal and international institutions involved in water management presents a formidable challenge, yet greater institutional cooperation and improved region-wide water management will be fundamental to maneuvering the Lower Rio Grande/Río Bravo Basin toward a more sustainable future.
- Population will double by the year 2030, while surface water supply will stay at current levels or decrease.
- Rapid growth and development in the San Juan and Conchos River basins in Mexico could significantly reduce the amount of water these two tributaries contribute to the mainstem of the Lower Rio Grande/Bravo.
- The adequacy of the existing water supply system under drought conditions is being tested for the first time. During the drought of record in the 1950s only 500,000 people lived in the same area where 2 million live today. Amistad reservoir did not yet exist, and Falcon reservoir came on line in the middle of the drought.
- Low flow conditions present a significant threat to water quality. For example, at Anzaldúas Dam in Mexico during the years low flow years 1982-1984 conductivity values-- an indicator of salinity-- were high enough to indicate that the water should not be used for irrigation in soils with poor drainage.
- During "normal flow" years "hot spots" of chemical pollution exist, particularly down steam from major urban areas along the river, but the greatest overall threats to river water quality are increasing salinity and fecal coliforms.
- Under reduced flow conditions, dissolved oxygen (BOD) standards will likely not be met.
- Significant changes in fauna appear to be correlated with decreasing streamflows, the proliferation of exotic species, pollution, and increased salinity.
- Transfers of agricultural water to municipal use occur in Texas through an existing water market and joint infrastructure improvements on the part of cities and irrigation districts. No such redistribution occurs in Mexico.
- The system is flexible - small increases in irrigation efficiency can release significant amounts of water for other uses. A reduction of water use by agriculture by less than 20 percent would enable the domestic water demands of a doubled population to met in the year 2030.
- The existing regional water market in the Texas part of the basin holds great potential for more efficient use of water.
- Tremendous opportunity exists for "win-win" arrangements in which municipal water suppliers agree to finance improvement in irrigation efficiency in return for the rights to the water saved.
- Significant (20 to 40 percent) long-term reductions in water supply would likely have a small overall impact on the regional economy because new irrigation technology and cropping patterns would be adopted.
- Binational cooperation is limited to joint management of two large reservoirs and distribution of their waters between the two countries. No efficient mechanism exists for binational protection of the river and its environment. Nor does joint water or drought planning exist.
- While opportunities exist to achieve greater efficiency of water use, the water saved will almost certainly be allocated to human uses, leaving the ecosystem in continued decline.
|
|
| Page Updated/Reviewed: 01/12/2007 8:40 AM |
|
|
