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Drought Along the Rio Grande Highlights Water Management Complexities

[From: Arizona Water Resource - Summer 2013] On Saturday, June 1, 2013, water was released from Elephant Butte Reservoir in South Central New Mexico into the Rio Grande. It took more than two days to travel the 80 miles to fields near Las Cruces, as water soaked into the parched riverbed. Waiting for the flow were chile, pecan, cotton and alfalfa growers in Southern New Mexico, Western Texas and Mexico, as well as the city of El Paso, Texas, which depends on the Rio Grande for half its water supply.

The Rio Grande is the fifth largest river in the United States, flowing roughly 1,900 miles from the Rocky Mountains in Southwestern Colorado to the Gulf of Mexico. In its journey, the Rio Grande serves as an 800-mile natural boundary between the United States and Mexico, and supplies thousands of acres of irrigated farmland, some Native American Pueblos, and cities like Albuquerque, New Mexico, and El Paso. The river is also the lifeline for the endangered Rio Grande silvery minnow.

This year threatens to be one of the driest in the 100-year record of river flow. When water was released from Elephant Butte in early June, the reservoir was at six percent of its storage capacity. Drought conditions have afflicted the entire Rio Grande basin since 2002. But the past three years have been particularly dismal, with two consecutive winters of reduced storm activity and snowfall in Colorado and Northern New Mexico. Snowmelt from the higher elevations is the major source of water for this river, but during the winter of 2012-13, precipitation was only 45 percent of average. The cumulative effect of years of below average snowpack and prolonged drought have left Rio Grande reservoirs at less than 25 percent of their storage capacity. These conditions have gradually shortened the irrigation season, reduced water allotments for farmers, and pushed municipal water authorities to find alternative water sources and encourage additional conservation measures.

Drought brings the complexities of water management in the Southwest into high relief. Balancing the needs of irrigators from different jurisdictions with the necessities of urban residents and the environment is an ongoing challenge. In New Mexico, the Rio Grande is controlled by a series of dams and diversion structures. Flows are highly variable, so the system relies on reservoirs that store water for release to irrigators and other users. The reservoirs are managed in order to ensure delivery to Texas at Elephant Butte according to the terms of the Rio Grande Compact, an agreement between Colorado, New Mexico and Texas.

In the Middle Rio Grande area, the Middle Rio Grande Conservancy District (MRGCD) provides irrigation water to 70,000 acres, including 8,800 acres of Pueblo Indian lands. The District extends along the river from the Cochiti Dam in Sandoval County south through Bernalillo, Valencia and Socorro counties to the Elephant Butte Reservoir, a stretch that includes the City of Albuquerque and habitat for federally protected endangered species. With record-breaking low stream flows and reservoir storage, the irrigation season that normally stretched from March to October is expected to last no longer than 50 days this year. El Vado Reservoir, which supplies water for the District, was at 22 percent of capacity in May and the stored water was expected to be gone by the first week of July. Once the reservoir is empty, the District has to rely on the river’s natural flow—a dire prospect since river flow has plummeted with the prolonged drought. The average June flow in the Albuquerque stretch of the river is roughly 2,500 cubic feet per second, but by the end of May this year the flow was only 350 cfs.

The six Pueblos in the Middle Rio Grande area have federally recognized rights to river water for irrigation, domestic and ranching purposes, and have contracts with the MRGCD for water deliveries. While some of their rights share the same priority with other District contract holders, a portion of their rights are "prior and paramount" owing to the Pueblos’ ancestral settlement in the area. This means that in times of shortage they are entitled to receive some water when others may have to do without.

In Albuquerque, a "drought watch" is in effect, meaning that fines are doubled for allowing water to flow into the street or onto neighboring property and for using sprinklers between 11 a.m. and 7 p.m. Albuquerque Bernalillo County Water Utility Authority is encouraging its customers to achieve even greater conservation than they have in previous years. The Authority is also helping to keep the river flowing by leasing 40,000 acre-feet of its San Juan-Chama project allotment to the Bureau of Reclamation, which needs the additional water for the Rio Grande silvery minnow. The San Juan-Chama project imports water from the Colorado River system.

The minute silvery minnow is a recurrent figure in conversations among water managers and farmers. The fish was classified as an endangered species in 1994, as it is found only in the Middle Rio Grande and now occupies less than five percent of its natural habitat. To preserve its remaining habitat and allow for its survival, the Biological Opinion issued by the U.S. Fish and Wildlife Service in 2003 requires Reclamation—which operates the dams—to keep the Rio Grande flowing continuously to Isleta Diversion Dam. Below Isleta to Elephant Butte, flow maintenance is conditional; in a dry year, the river is allowed to dry in a controlled manner after June 15. This year, even with the addition of 40,000 acre-feet of imported water, there was not enough water in the river to meet requirements. Given the recurrent drought conditions, the U.S. Fish and Wildlife Service approved a contingency plan to reduce water flows beginning the first week of June in an effort to stretch dwindling water supplies for the endangered minnow. The plan falls short of water flow mandates in the 2003 Biological Opinion but was considered the only viable option given the extenuating circumstances.

Downstream, irrigators in the Elephant Butte Irrigation District (EBID) and El Paso County Water Improvement District No. 1 (EPCWID) face equally daunting challenges: This season they will receive only 145,000 acre-feet of water, which is about 20 percent of their water allotment in average years. While a full allotment is 36 inches of water per acre, this year farmers can expect to receive 3.5 inches of water per acre. To maintain their production farmers in Southern New Mexico and West Texas are turning to groundwater.

Groundwater pumping is an expensive option, however, inaccessible to many small farmers. Dependence on groundwater pumping could also have damaging consequences. The river and the aquifer are connected, so without a flowing river, the aquifers that feed the wells lack recharge and increased groundwater extraction progressively draws down water levels. In addition, as wells draw from deeper levels, salinity increases and farms’ yields decrease. For these reasons, groundwater pumping is not a long-term sustainable solution to continuing drought.

Much like farmers, urban water utilities are supplementing surface water allotments by pumping groundwater. El Paso Water Utilities, which typically relies on river water for half of its water supply, is increasing supplies with new and renovated wells and increased production at its desalination plant. Although the city has avoided mandatory water restrictions, it exhorts customers to adopt its water saving recommendations.

In recent years tensions between competing water users over water rights have come to a boiling point as the drought diminishes supplies. Texas is now suing New Mexico for not delivering what it considers it is owed under the Rio Grande Compact. Signed in 1939, the Compact divides the Rio Grande waters among the states of Colorado, New Mexico and Texas. By the terms of the compact, Colorado and New Mexico must deliver specified amounts of water to Elephant Butte and Caballo Reservoirs for use in Southern New Mexico and West Texas. The current legal dispute between Texas and New Mexico erupted when irrigation releases to southern New Mexico were curtailed, driving irrigators to pump more groundwater. Texas alleges that unsupervised groundwater pumping by New Mexico farmers below Elephant Butte is reducing the amount of Rio Grande water reaching Texas farmers, thereby depriving the state’s agricultural lands and cities of water to which they are legally entitled.

Texas has also asserted that Mexico is not living up to the terms of the 1944 treaty that allocates water between the United States and Mexico. By the terms of the treaty, Mexico is obliged to provide Texas a specified amount of water over a five-year period from its reservoirs along the Lower Rio Grande. These reservoirs store water from Mexican streams that feed the Lower Rio Grande where it forms the border with Texas. Water users in Texas are pressing their claim through ongoing discussions involving the U.S. State Department and the Mexican government.

The current dry spell in the Rio Grande Basin is not unprecedented and will not be the last of its kind. Climate projections described in a Bureau of Reclamation Report to Congress suggest that temperatures throughout the basin could increase by 5–6 degrees, while annual precipitation will remain variable with a decrease of 2.3-2.5 percent by 2050. This would cause a decrease in the river’s average annual runoff by 7.3–14.4 percent. In practice, these numbers mean that the 21st century will present water managers and water users along the Rio Grande with a suite of even greater challenges than they now face.

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