Water Use for Agriculture in Priority Rivers Basins

Transcription

1 Water Use for Agriculture in Priority Rivers Basins Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 Section 8 Executive Summary Introduction Water Resources A Global Perspective Africa: Niger River Basin Lake Chad Basin Zambezi River Basin South Asia: Indus River Basin East Asia and the Pacific: Mekong River Basin Yangtze River Basin Australia: Murray-Darling Basin Europe and Central Asia: Great Konya Basin North and Middle America: Río Grande Basin Main Conclusions Literature cited in the study 1

2 CONTENTS Management of the Río Grande Basin International Boundary and Water Commission The NAFTA institutions Conflicts in the basin Features of the Río Grande Basin Ecoregions in the Río Grande Basin Recreation and wildlife enhancement Current water situation Irrigation development Agriculture Conclusions for the Río Grande Basin Irrigated agriculture Future water demand

3 1 THE RÍO GRANDE BASIN encompasses 465,998km 2 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 3.25km 3 ) 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 6.27km 3 ), 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 mm. The Río Grande between Amistad Dam and Falcon Reservoir (capacity 3.94km 3 ) 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

4 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

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6 1.1 Management of the Río Grande Basin 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

7 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 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 BECC is expected to work directly with states and local communities in developing appropriate and financially feasible infrastructure projects. It is obliged to evaluate the environmental impact of the projects it reviews. Approved projects are registered either as certified or certified with a recognition of sustainability. The charter of the BECC calls specifically for public input and participation at its meetings where projects are examined and certified. These provisions are an attempt to differentiate BECC projects from other international development programme projects where environmental improvement funds are used for infrastructure projects and other nonenvironmental projects favoured by influential supporters. The North American Development Bank The North American Development Bank (NAD Bank) was created to finance environmental infrastructure projects along the border. The bank has been allocated US$3 billion in capital to leverage up to US$9 billion in loans and grants from private financial agencies, as well as federal, state, and local sources. The initial US$3 billion in capital was financed and managed in equal parts by the US and Mexican governments, with each country having equal rights and obligations in fulfilling the bank s mission. Its primary goals are to fund projects for water supply, wastewater management, and solid waste management. The new focus created by NAFTA on the US-Mexico border is an opportunity for economic development, tempered by environmental awareness, in a region that has traditionally been at the periphery of national development trends in both countries. A major weakness in the BECC/NAD Bank system is the requirement to charge market interest rates for the loans offered. As such, there is no financial incentive to choose BECC financing over commercial options. NAD Bank s leveraging power could be useful for obtaining grants, which are more difficult to obtain. 7

8 Binational Environmental Agreements For several decades after the signing of the 1944 Treaty of International Waters, the US government was not directly involved in issues related to water along the border outside of the IBWC/CILA framework. Under US law, surface water is regulated by the states. Therefore, the courts and the state of Texas handled the entire adjudication system for water rights, for instance along the Lower Río Grande. However, by the 1980s, serious environmental problems along the border combined with greater public awareness of environmental issues led to attempts by both the US and Mexican governments to address these problems. As a result, the environmental agencies of both countries became directly involved in water issues. This trend is likely to increase under NAFTA and the greater attention brought to the region due to increased trade and economic development. Integrated Border Environmental Plan The Integrated Border Environmental Plan of was prepared by the US Environment Protection Agency (EPA) and SEMARNAP (the national environmental agency of Mexico). It also involved national legislators concerned with the potential impact of the North American Free Trade Agreement on the border environment. The goals of the plan include pollution reduction, improved environmental law enforcement, and greater education, awareness and training in environmental problems and their solutions. The US and Mexican governments scheduled a series of public hearings to receive comments from border residents and other interested parties about the plan, a rare event in US government policy for the region and an unprecedented practice for the Mexican government Conflicts in the basin The 1944 treaty allocates water in the Río Grande along the US-Mexico border. Each nation is entitled to all of the water reaching the Río Grande from tributaries originating on its side, along with half of the unallocated water between Fort Quitman and Falcon Dam, which is technically the lowest international storage dam. The major exceptions to this rule are the Río Conchos, Río San Diego, Río San Rodrigo, Río Escondido, and Río Salado in Mexico. The United States is entitled to one-third of the water from these rivers, with a guaranteed right of 431 million m 3 per year over a five-year average under normal climatic conditions. In recent years, the enforcement of legal water rights has become an important point of contention between the US and Mexico. Water users in each country are entitled to divert available water, as long as it is properly accounted for in the national accounts by the IBWC. Unauthorized diversions of water on the Mexican side of the river are a lingering problem, however, which was never seriously addressed in times of adequate rainfall. Rapid population growth and industrial development have dramatically changed the nature of the border, creating vast new demands for water services and causing new problems in water pollution and general environmental degradation. Public interest in environmental conditions has led to increasing pressures for public accountability of the IBWC s actions. Consequently, the Commission has moved from focusing on large-scale water infrastructure projects to a greater involvement in water quality issues, which leads to even further interest in Commission activities by local and state governments and border communities. The most important changes in the operating environment may yet be on their way. The impact of global climate change and other global environmental problems demonstrates a potential for severe, recurring droughts in the region. Responding to these conditions may necessitate major changes in the institutional structures of the region. 8

9 1.2 Features of the Río Grande Basin Ecoregions in the Río Grande Basin The following ecoregions have been identified in the Río Grande/Río Bravo Basin: Sierra Madre Oriental and Occidental Pine-Oak Forests, and Chihuahuan-Tehuácan Deserts. Sierra Madre Oriental and Occidental Pine-Oak Forests This ecoregion consists of numerous mountain peaks and ridges that extend from just over the border in the south-western United States into central Mexico. It supports a vast array of plant and animal species, many of which are restricted to single peaks or different ranges. Among these species are some important wild relatives of agricultural crops, such as agave (Agave spp.). The most species-rich plant families represented are Asteraceae, Fabaceae, Poaceae and Euphorbiaceae. In total, 12 species of oak trees are found within these conifer forests. Together, these plants support an impressive avifauna, including Mexican jay (Aphelocoma ultramarina), zone-tailed hawk (Buteo albonotatus), maroon-fronted parrot (Rhynchopsitta terrisi), and Strickland s woodpecker (Picoides stricklandi). Predators with large ranges, such as grey wolf (Canis lupis) and jaguar (Panthera onca), also frequent these habitats. General threats: Chief threats include overgrazing, clearing of forests for timber and fuelwood, and development. Other problems stem from recreational pressures and use of the area for military exercises. Chihuahuan-Tehuacan Deserts This ecoregion has an exceptionally rich desert flora and fauna, with subregional endemism in some taxa. The richest cactus communities in the world are found in the southern Chihuahuan Desert. Some of the world s richest desert mammal and reptile faunas also occur here. Among plant species are resurrection plant (Selaginella lepidophylla), creosote bush (Larrea tridentata), tarbush (Flourensia cernua), whitethorn acacia (Acacia neovernicosa), and numerous species of cacti, including several Opuntia species. Animals include desert pocket gopher (Geomys arenarius), Nelson s kangaroo rat (Dipodomys nelsoni), desert shrew (Notiosorex crawfordi), desert mule deer (Odocoileus hemionus), bighorn sheep (Ovis canadensis), pronghorn (Antilocapra americana), jaguar (Felis onca), collared peccary or javelina (Pecari tajacu), and desert cottontail (Sylvilagus auduboni). General threats: Grazing, extraction of salt, gypsum, and lime, clearing of riparian vegetation, and exploitation of water resources are the principal threats to the ecoregion Recreation and wildlife enhancement There is no simple way to assess the quantity of water used for recreation and wildlife enhancement. All three major reservoirs, Elephant Butte, Amistad and Falcon, are used extensively for outdoor recreational activities. The quantity of water evaporating from these reservoirs alone is substantial: 19, 58, and 79 million m 3 per year at the maximum water surface of 7,500, 27,000 and 36,000ha at Elephante Butte, Amistad and Falcon, respectively. The evaporation deficit at these dams is 254, 216 and 218cm per year, respectively. Evaporation from these three reservoirs alone amounts to a quantity greater than the municipal water use from the Río Grande. 9

10 The waterways along the Río Grande and its tributaries, including drainage ditches, support many wildlife species. The evapotranspiration losses from these wetlands are likely to reach substantial quantities, although these are not measured as such. In the stretch from Elephant Butte Dam to El Paso, for example, the densely vegetated areas along the Río Grande floodways are estimated at 15,000ha Current water situation The limited water resources of the arid Río Grande Basin have been developed and, in many instances, over-exploited to provide a year-round supply of water for irrigated agriculture, industry, and the growing municipalities. During the 20th century, a number of large reservoirs were built on the Río Grande and its major tributaries, and extensive well fields were drilled in the basin s aquifers. The dams, while providing storage, have greatly reduced the downstream flow of the main stream and its tributaries. In some areas, groundwater pumping has reduced or even eliminated spring flow or allowed the infiltration of saline water into freshwater zones. In a vigorous effort to move away from dependence on the rapidly diminishing Hueco Bolson aquifer, the city of El Paso now gets about half of its annual water supply from the Río Grande. It has secured this supply by leasing or otherwise acquiring irrigation water rights in the El Paso County Water Control and Improvement District No. 1. El Paso s switch to surface water has not been easy. Barriers have included difficulties in negotiating acquisition of irrigation rights and poor water quality in the river during times of low releases from the upstream reservoirs. And, even with the move to surface water, El Paso still depends primarily on local groundwater for the remainder of its supply. The aquifers are being mined at dangerously high rates, however, as Cd. Juárez and El Paso have grown over the last few decades. Many observers have predicted that, at current pumping rates, the Hueco Bolson may run dry for all practical purposes in 20 years. Juárez is completely dependent on the Hueco Bolson, and is now being forced to investigate other local (as well as more distant) groundwater sources. El Paso, meanwhile, is looking west, to rural counties, for future groundwater. It has purchased a number of water ranches from which it hopes to export groundwater to the city. This move has predictably caused serious conflict with the rural counties, especially because Texas does not regulate groundwater pumping under state law. Essentially, Texas still relies on the law of the big pump, more formally known as the rule of capture. Under this doctrine, a landowner can pump as much groundwater as he wants, even if a neighboring landowner is damaged. Reductions in the flow of the Conchos River at its confluence with the Río Grande have caused serious binational issues in the last few years. Due in part to drought, increased use of water in the Conchos basin, and a reservoir management strategy designed to preserve Conchos water for irrigation uses in Chihuahua, the flow of the Conchos has dropped well below the minimum million m 3 /year (over a five-year period) required by the 1944 US/Mexico water treaty. Most of the municipalities and industries in the Conchos basin currently depend on groundwater to supply demand. While complete hydrogeological studies of most of these aquifers are lacking, Mexico s National Water Commission (Comisión Nacional de Aguas [CNA]) has identified several that are over-exploited (i.e. annual pumping exceeds annual recharge) and is developing plans to help cities implement conservation measures and/or find new groundwater or surface water supplies. Reduced flow from the Conchos has greatly reduced water storage in Amistad and Falcon, with the reservoirs reaching the lowest levels since they were brought into operation in the 1960s, 10

11 severely constraining water supply for municipalities and irrigators on both sides of the Río Grande. On the US side, the river is already over-appropriated (i.e. paper water rights exceed, some say almost double, the amount of water routinely available in the system), and the low reservoir levels have made the situation much more volatile. Persistence of low rainfall patterns, however, and Mexico s decision to store water in the reservoirs in the parched Conchos basin, have resulted in greatly reduced inflows to and storage in the Amistad/Falcon system, constraining water supply for both municipalities and irrigators in the middle and lower Río Grande. By 1995, the situation forced the International Boundary and Water Commission to negotiate an emergency minute order under the 1944 Treaty in order to allow Mexico to borrow water for Tamaulipas municipalities. The agreement was never implemented as late 1996 and early 1997 rains alleviated the immediate pressures on the municipalities. Nevertheless, in Nuevo Leon and Tamaulipas, irrigation was curtailed and many dry-land farmers did not even plant crops. For example, in 1995/96, estimates put crop losses at 240,000ha of sorghum, corn, bean, and wheat crops; Tamaulipas corn production dropped by 44 per cent in the 1994/95 season, and 1995/96 was also extremely difficult. In 1996, the Mexican government was forced to import almost US$2 billion worth of grain to alleviate growing food shortages, with much of the grain going to northern Mexico. 1.3 Irrigation development The water released from Elephant Butte Dam has averaged 842 million m 3 annually. A large portion of this flow is diverted to irrigate crop lands in New Mexico. The remainder and return flow then reach El Paso at an annual rate of 547 million m 3. When the flow reaches the American Diversion Dam, 332 million m 3 is diverted annually to the American canal, which is the main supply canal for the El Paso Valley. The diversion to Mexico amounts to 65 million m 3 annually, which is used to irrigate the Juarez Valley along with shallow groundwater and municipal sewage. After diversion, the flow of the Río Grande is reduced to 155 million m 3 annually. The flow gradually increases again due to the collection of return flow and municipal sewage water discharged from several plants from El Paso and adjacent communities. The sewage water from Cd. Juarez is discharged into irrigation canals and to a limited extent to drainage ditches, but not directly into the Río Grande. When the flow reaches Fort Quitman, storm runoff from small creeks is added to the flow of the Río Grande. The Río Conchos, originating from the Mapimi drainage basin of the State of Chihuahua, carries an average annual flow of 909 million m 3 at the point of inflow into the Río Grande near Ojinaga, Mexico. This flow is slightly greater than the annual release from Elephant Butte Dam, and forms the main flow of the Río Grande in the stretch between Presidio and Amistad Dam. The Pecos River and the Devils River contribute 274 and 353 million m 3 annually to the flow of the Río Grande, respectively. All of these flows are stored at Amistad International Reservoir. The discharge from Amistad Dam has averaged 2.06km 3 annually since its construction in About half of this release is taken into the Maverick Canal, 28km south of Del Río, for hydraulic power generation and irrigation. The return flow from the power plant goes back into the Río Grande, and the remainder is used for irrigation through the Maverick Extension Canal. The combination of the base flow, return flow, and the inflow from creeks bring the flow of the Río Grande back to over 2km 3 annually at Eagle Pass. The diversion below Eagle Pass but above Laredo is minimal, and the Río Grande gains flow and reaches 2.8km 3 per year at Laredo. Below Laredo, there are several rivers and streams that flow into the Río Grande. The Río Salado from 11

12 Mexico is one of the larger rivers and has contributed to the flow of the Río Grande at an annual rate of 472 million m 3. The combined flow reaches 3.0km 3 annually at Falcon International Reservoir. Below Falcon, the Río San Juan (434 million m 3 /year) flows into the Río Grande from the Mexican side at Camargo. Río Grande water is diverted between Río Grande City and Anzalduas Dam at a rate of 292 million m 3 /year for irrigation. The major diversion to Mexico is at Reynosa. The US side of the diversions are at Anzalduas Dam, Progreso and San Benito at a combined diversion flow of 919 million m 3 per year. When the Río Grande reaches Brownsville, the flow decreases to 1.18km 3 /year, which includes erratic floodwater after storms. 12

13 Table 1.1 Summary of water use in the Río Grande Basin, New Mexico 1995 Category Withdrawal surface water Withdrawal groundwater Total withdrawal Depletion surface water Depletion groundwater Total depletion Return flow surface water Return flow groundwater Total return flow Public water supply Domestic (self-supplied) Irrigated agriculture 1, , Livestock (self-supplied) Commercial (self-supplied) Industrial (self-supplied) Mining (self-supplied) Power (self-supplied) Reservoir evaporation Total 1, , , ,141.8 Table 1.2 Summary of water use in the Río Pecos Basin, New Mexico 1995 Category Withdrawal surface water Withdrawal groundwater Total withdrawal Depletion surface water Depletion groundwater Total depletion Return flow surface water Return flow groundwater Total return flow Public water supply Domestic (self-supplied) Irrigated agriculture Livestock (self-supplied) Commercial (self-supplied) Industrial (self-supplied) Mining (self-supplied) Power (self-supplied) Reservoir evaporation Total Source: Brian and Wilson

14 Table 1.3 Statistics, Río Grande Basin, Colorado State Year Population Irrigated area (000ha) Total diversions Current useable storage , , , , % change +42% 0% % Source: Colorado Water Conservation Board 2002 Table 1.4 Projections of future water demand for Texas State, % change Population 20,864,933 39,617,389 Water use and demand per category Municipal 5218,1 8710,7 66,9 Manufacturing 2230,7 3280,6 47,1 Mining 312,1 301,3-3,5 Steam electric 749,1 1399,0 86,8 Irrigation 11944, ,7-12,3 Livestock 407,6 518,2 27,1 Total 20861, ,4 18,3 Source: Texas Water Development Board 2002 Table 1.5 Projected water demand for Texas planning areas in the Río Grande Basin % change Far West Texas (E) 628,1 722,2 15,0 Plateau (J) 55,0 68,2 23,9 Río Grande (M) 2223,5 2142,9-3,6 Coastal Bend (N) 275,9 381,9 38,4 Total 3182,5 3315,2 Source: Texas Water Development Board Agriculture Irrigated crop production dominates the use of the Río Grande surface flow. The water released from Elephant Butte Dam is used to irrigate 35,200ha of crop land in New Mexico. The remainder plus return flow from New Mexico is then used to irrigate crop land in the El Paso and Juarez Valleys. The reported irrigated crop land area for the El Paso Valley in 1989 was 17,200ha, which is about twothirds of the irrigable lands. Some lands are now classified as residential areas, or commercial lots, and others have salted out or are not being cropped. Low-density residential areas with a holding of 1ha or greater actually receive allocation of the Río Grande water, as the water right is tagged to the ownership of the land within the district boundary. The source of irrigation water below Acala (Hudspeth County) is predominantly return flow, and occasional excess spills from the El Paso Irrigation District. When these water supplies are curtailed, shallow groundwater is used to supplement irrigation. The use of the Río Grande water for agricultural purposes is limited to about 2,000ha between Fort Quitman and Amistad. However, an estimated area of 129,000ha in Mexico is irrigated by the Río Conchos before the water reaches the Río Grande. Likewise, Pecos River water is used to irrigate 5,400ha in Texas and additional unlisted areas of 14,164ha in New Mexico. Agricultural uses of the Río Grande water between Amistad and Falcon are concentrated in the Maverick Irrigation District (16,300ha) on the Texas side. On the Mexican side, the Río Salado is used to irrigate 25,500ha before reaching the Río Grande. The major agricultural uses of the Río Grande are below Falcon, totalling 310,900ha on the Texas side and 209,600ha plus 82,500ha of tributary-irrigated areas on the Mexican side. The irrigated area below Falcon accounts for 88 per cent of the Río Grande irrigated area on the Texas side, and 96 per cent of 14

15 the land irrigated directly by the Río Grande on the Mexican side. The cropped area changes depending on the year, but these changes do not affect the overall picture of the agricultural water uses. The total water use for agriculture from El Paso to the Gulf Coast averaged 1.87km 3 per year on the Texas side, and 1.36km 3 per year on the Mexican side, with corresponding irrigated areas of 354,900 and 218,300ha, respectively. The combined agricultural use of the surface water of the Río Grande is 3.23km 3, as compared to the combined estimated inflow of 4.51km 3 per year. Figure 1.2 Colorado counties Source: Table 1.6 Irrigated crops 2000 in the Upper Río Grande Basin, Colorado Crop Barley Maize 1 Sorghum Wheat Alfalfa Total County grain silage Alamosa 4,560 3,040 6,240 13,840 Conejos 3, ,424 13,144 Costillo 2,400 1,760 4,128 8,288 Río Grande 7,720 3,600 7,504 18,824 Saguache 5,600 3,200 11,904 20,704 Total 23,600 12,000 39,200 74,800 Colorado State 30, ,800 17,600 16,800 24, , ,000 Source: NASS Agricultural Statistics Data Base The maize area is planted for grain harvest but turned into silage if there are drought problems, the area for silage maize is given as an indication and not included in the total irrigated area. 15

16 Figure 1.3 Hydrological units, New Mexico State 16

17 Table 1.7 Irrigated crops 2000 in the Middle Río Grande Basin, New Mexico Crop Alfalfa Maize Cotton Pasture Wheat Pecan County Catron Chavez 22,000 4,994 1,674 1, ,060 De Baca 2, Dona Ana 4,664 2,632 5, ,435 Eddy 5, , Guadelupe Luna ,461 4,486 1, Río Arriba 1, , Sandoval 1, Santa Fe 2,324 1, , Sierra 1, Torrance 2,046 2, Valencia 5, , Total Río Grande 50,870 13,510 11,117 23,390 3,513 9,117 Total State 94,184 53,664 28,636 64,175 46,252 10,115 Source: Water Use and Conservation Bureau, Office of the State Engineer New Mexico, 2000 A map with the counties of Texas is available at 17

18 Table 1.8 Irrigated crops and water use in the Lower Río Grande Basin, Texas Crop Cotton Sorghum Maize Wheat Forage Alfalfa County (Mm 3 ) (Mm 3 ) (Mm 3 ) (Mm 3 ) (Mm 3 ) (Mm 3 ) Brewster Cameron 17, , , Crane Crocket Culberson El Paso 12, , , Hidalgo 19, , , Hudspeth 5, , , Jeff Davis Kinney Loving Maverick , Pecos 3, , , Presidio Reeves 1, , , Starr Sutton Terrel Upton 3, Val Verde Ward 1, Willacy 17, Winkler Zapata Total 83, , , , , , Area Rank Water use Rank Source: Mm 3 = million cubic metres 18

19 Table 1.8 (continued) Irrigated crops and water use in the Lower Río Grande Basin, Texas Crop Hay/past Pecan Vegetable shallow Vegetable deep Sugarcane Total County (Mm 3 ) (Mm 3 ) (Mm 3 ) (Mm 3 ) (Mm 3 ) (Mm 3 ) Brewster Cameron 4, , , Crane Crocket Culberson El Paso , , Hidalgo 5, , , , , Hudspeth 2, , Jeff Davis Kinney 2, Loving Maverick 4, , , , Pecos , Presidio , Reeves , Starr , , , Sutton Terrel Upton , Val Verde Ward , Willacy , , Winkler Zapata Total 16, , , , , ,113 1,690.6 Area Rank Wateruse Rank Source: Mm 3 = million cubic metres 19

20 Water Use for Agriculture in Priority River Basins Section 9 North America 2 CONCLUSIONS FOR THE RÍO GRANDE/BRAVO BASIN 2.1 Irrigated agriculture When assessing the results of the chapter on the Río Grande/Bravo Basin it should be kept in mind that the Mexican states that are part of the basin have been left out of this analysis, as it was impossible to obtain the necessary data. Data on irrigated agriculture have been obtained from the National Agricultural Statistical Services (NASS), but are also available from the State Department of Agriculture or the Office of the State Engineer. Sources are indicated at the bottom of the tables. Table 2.1 Major irrigated crop areas in US States in the Río Grande Basin State Colorado New Mexico Texas Total Ranking Crop Maize 13,510 13,477 26,987 7 Alfalfa 39,200 50,870 20, ,587 1 Wheat 12,000 3,513 12,948 28,461 5 Sorghum 23,363 23,363 9 Barley 23,600 34,717 4 Cotton 11,117 83, ,064 2 Pasture 23,390 16,964 26,141 8 Pecan 9,117 7,131 27,427 6 Vegetables 20, , ,955 3 Sugarcane 11,916 11, The combined value of chili, lettuce, melons, miscellaneous vegetables, and onions 2 The combined value of deep and shallow vegetables from Table 1.9 The ranking given in Table 2.1 is based on crop area, the top five crops being: alfalfa, cotton, vegetables, barley, and wheat, followed by pecan (a highly valued nut tree). As in other river basins, the first three crops generally rank among the highest water consumers. However, given that livestock rearing is the prime agricultural activity in the states of Colorado, New Mexico and Texas, a recalculation of the ranking based on the use of irrigated crops as a source of feed puts livestock rearing at the top, followed by cotton, vegetables, pecan, and sugarcane. This shows once again that the individual crop approach has to be considered with caution, since the data do not indicate whether the crop is used for human or animal consumption. Thus, the figures have to be combined in order to asses the total impact of an agricultural sector on water withdrawals. As this is the only river basin of those studied where livestock rearing is the number one agricultural activity, the ranking given in Table 2.1 has been retained for the purposes of the overall evaluation (see Section 10 Main Conclusions). 2.2 Future water demand In IWMI Working Paper No.32 Water for Rural Development, overall water scarcity levels for Mexico are given as economic, while the USA is considered as free from water scarcity. However, the observation that the IWMI report does not take regional differences into account is all the more clear for the states that border the Río Grande/Bravo. The map in Figure 2.1 indicates 20

21 Water Use for Agriculture in Priority River Basins Section 9 North America that all Mexican states bordering the Río Grande will face physical water scarcity in 2025, a situation that will affect the US side of the border as well. Figure 2.1 Projected water scarcity levels for Mexico in 2025 Source: Barker