Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin Water Use for Agriculture in Priority Rivers Basins Section 1 Executive Summary Introduction Water Resources – A Global Perspective Section 2 Africa: – Niger River Basin – Lake Chad Basin – Zambezi River Basin Section 3 South Asia: – Indus River Basin Section 4 East Asia and the Pacific: – Mekong River Basin – Yangtze River Basin Section 5 Australia: – Murray-Darling Basin Section 6 Europe and Central Asia: – Great Konya Basin Section 7 North and Middle America: – Río Grande Basin Section 8 Main Conclusions Literature cited in the study 1 Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin CONTENTS 1 The Río Grande Basin............................................................................................................ 3 1.1 Management of the Río Grande Basin........................................................................... 4 1.1.1 International Boundary and Water Commission................................................. 4 1.1.2 The NAFTA institutions ..................................................................................... 5 1.1.3 Conflicts in the basin........................................................................................... 6 1.2 Features of the Río Grande Basin.................................................................................. 7 1.2.1 Ecoregions in the Río Grande Basin ................................................................... 7 1.2.2 Recreation and wildlife enhancement ................................................................. 7 1.2.3 Current water situation........................................................................................ 8 1.3 Irrigation development................................................................................................... 9 1.4 Agriculture................................................................................................................... 12 2 Conclusions for the Río Grande Basin ............................................................................... 18 2.1 Irrigated agriculture .....................................................................................................18 2.2 Future water demand ................................................................................................... 18 2 Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin 1 THE RÍO GRANDE BASIN The Río Grande Basin encompasses 465,998km2 and covers portions of three US states and five Mexican states. Although the Río Grande is shown as a continuous river, the flow from the Colorado Mountains at times is strongly reduced near Fort Quitman, approximately 125km south of El Paso. The new perennial flow then begins again at the confluence with the Río Conchos from the Mexican side, approximately 454km downstream from El Paso. The flow of the Río Grande that originates from the watershed in the southern slopes of the Colorado Mountains and the mountain ranges of northern New Mexico is stored at Elephant Butte Dam (design capacity 3.25km3) located in New Mexico (see Figure 1.1). The water is used to irrigate the Mesilla, the El Paso and the Juarez Valleys. The Río Grande below the El Paso- Hudspeth county line consists mostly of return flow and occasional excess water and runoff from the adjacent areas. The Bureau of Reclamation designates the Río Grande between Elephant Butte Dam and Fort Quitman as the middle Río Grande, whereas in Texas this section is considered part of the Upper Río Grande reach. In any case, the El Paso to Fort Quitman segment of the Río Grande consists largely of the tail waters of the water supply from Elephant Butte Dam. Annual rainfall in this segment of the Río Grande Basin averages 200mm. The Río Conchos from Mexico is the major entry into the Río Grande below Fort Quitman and flows in just below Presidio (or Ojinaga, Mexico), 454km south of El Paso. This flow continues to Amistad Dam (design capacity 6.27km3), located 500km below Presidio. There is no major tributary that flows into the Río Grande from the US side, until the inflow of the Pecos River at Langtry, Texas, and the Devils River at Amistad Reservoir. The Conchos basin itself is heavily regulated, with several large reservoirs, primarily to supply irrigation districts. Most of the municipalities in the Conchos basin meet demand using local groundwater reserves. Downstream of the confluence, the river flows through a series of large protected natural areas, including the Big Bend Ranch Texas State Park, the Cañon de Santa Elena and Maderas del Carmen protected areas in Mexico, and Big Bend National Park. Downstream of Big Bend National Park to Amistad Reservoir, the river has been designated a Wild and Scenic River under US federal law. River rafting is a popular and economically significant activity in this stretch. The flow of the Pecos River is regulated at Red Bluff Lake on the New Mexico-Texas border, consisting mostly of saline irrigation return flow. The flow of the Pecos River that enters the Río Grande is a mixture of return flow and runoff from far west Texas. The Bureau of Reclamation designates this segment of the Río Grande as a part of the lower Río Grande system, whereas in Texas this segment is commonly referred to as the Upper Río Grande reach. Annual rainfall in this section of the Río Grande averages 250–300mm. The Río Grande between Amistad Dam and Falcon Reservoir (capacity 3.94km3) is a long stretch extending over 481km. There is no major tributary, but there are numerous creeks and drains that flow into the Río Grande after storms. In Texas, this segment of the Río Grande is commonly referred to as the Middle Río Grande reach. Annual rainfall in this section increases to 500mm. The Río Grande below Falcon Reservoir to the Gulf of Mexico is the heart of the Lower Río Grande, and flows over 442km. The Río Salado from Mexico is a major tributary that flows directly into Falcon Reservoir, and the Río San Juan flows into the Río Grande below Falcon. There are two major drainage courses on the US side: the Main Floodway and the Arroyo Colorado. The latter is of particular importance, because it flows directly into the Laguna 3 Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin Atascosa National Wildlife Refuge. The natural drainage flow is away from the Río Grande eastward toward the Laguna. This area lies outside the Río Grande Basin and is a part of the Nueces River Coastal Basin. Figure 1.1 The Río Grande/Río Bravo Basin 4 Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin 5 Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin 1.1 Management of the Río Grande Basin 1.1.1 International Boundary and Water Commission The International Boundary and Water Commission/Comisión Internacional de Límites y Aguas (IBWC/CILA), established in 1944, is the official agency for communication between the Mexican and United States governments regarding water issues along the international border. The jurisdiction of the IBWC/CILA covers the boundary areas of the Río Grande/Río Bravo in Texas and Río Colorado in California, the terrestrial line that divides Mexico and the United States, as well as water infrastructure along the border. The functions of the IBWC/CILA are to: • observe the fulfillment of international treaties related to boundaries and international waters of Mexico • participate in diplomatic negotiations leading to international agreements on the subject • operate and maintain dams, hydrometric stations and other international works along the border, in close coordination with corresponding federal or state entities • carry out water accountancy leading to an appropriate distribution of water, in accordance with current international treaties 6 Water Use for Agriculture in Priority River Basins – Section 7 North and Middle America The Río Grande Basin • collaborate with other federal and state agencies in environmental affairs along the northern border of Mexico. In addition, the Commission has the authority to settle differences that may arise between the governments with respect to interpretation and application of the 1944 Treaty. The mandate of the Commission is quite narrow. There are many important water issues, such as groundwater appropriation, drought management and water conservation, which were not included in Commission responsibilities. 1.1.2 The NAFTA institutions The North American Free Trade Agreement (NAFTA) includes side agreements for the establishment of international institutions to address environmental concerns in the border region between the United States and Mexico. These institutions do not have a direct impact on water management policies, as they are concerned primarily with water pollution, wastewater treatment, and solid waste infrastructure. However, through certification and funding of projects leading to conservation and reduced pollution of the existing water supply, they may indirectly contribute to an increase in the amount of usable water. The Border Environmental Cooperation Commission The mission of the Border Environmental Cooperation Commission (BECC) is to coordinate, evaluate, and facilitate environmental infrastructure projects along the border. The