Squeezing Extra Drops out of the Rio Grande
By Danielle Supercinski
Since its creation in 2001, the Rio Grande Basin Initiative (RGBI) has addressed numerous issues to meet present and future water demands along the river through efficient irrigation and water conservation measures.
Population growth and urban water demands in the Rio Grande Basin are expected to double in the next 50 years. Irrigated agriculture currently claims more than 85 percent of the water in this highly productive agricultural area. Drought and water shortages are persistent problems as well.
Texas Agricultural Experiment Station researchers, Texas Cooperative Extension specialists and county agents from Texas A&M University System Agriculture and New Mexico State University College of Agriculture and Home Economics work jointly on this project effort. Collaborating with local irrigation districts, agricultural producers, homeowners, 19 external agencies and other universities, roughly160 Texas and New Mexico RGBI participants are dedicated to expanding efficient use of available water resources and creating new water supplies for the Rio Grande Basin.
“The Rio Grande Basin Initiative has been very valuable because it has provided an opportunity to bring together all the things we know about water conservation into one package through research and development of new water practices,” said B.L. Harris, RGBI project manager and associate director of Texas Water Resources Institute. “This research is coupled with an effective educational program to demonstrate and train people to implement the best and most appropriate practices to conserve water.”
Significant water savings and accomplishments have been achieved through the initiative’s nine research and education tasks, Harris said.
Economists and engineers have developed evaluation tools to guide irrigation districts in water-use efficiency infrastructure and cost-of-saving-water analysis. RGIDECON©, the rapid assessment tool (RAT) and geographic information systems (GIS) are three of the main tools developed. To date, $54.4 million of rehabilitation projects (federally authorized and overseen by the U.S. Bureau of Reclamation) have been analyzed with RGIDECON©. The goal has been, and remains, to help local stakeholders in attaining the most economical approach to water conservation, while recognizing pertinent operational, political and institutional considerations. Engineers developed the RAT to aid irrigation district decision-making regarding infrastructure rehabilitation. They also developed maps and GIS databases for irrigation districts, consulting firms and public agencies to use in developing project applications, and analyzing conditions, water losses and potential water savings.
“The Rio Grande Basin Initiative provides an opportunity for us to work with other agencies and universities to help develop the justification and documentation needed to guide the use of public expenditures for improving the overall water delivery infrastructure in the Basin,” Harris said.
Researchers have established on-farm monitoring of crop water use and have taken extensive soil samples to determine nitrogen content with soil depth, depth of rooting and other soil properties necessary for use in adapting the Crop Production and Management Model (CroPMan) to the area to help producers in scheduling irrigations. CroPMan also allows producers to access economic trade-offs of allocating limited water resources between various crops at varying stages of crop growth.
Water is the primary factor limiting production of many crops in the Lower Rio Grande Valley of Texas. Sugarcane, grown on 44,000 acres in the Valley in 2005, required roughly 200,000 acre-feet of irrigation water to produce. Researchers found that using improved furrow irrigation techniques and scheduling based on the results of this project would save 10 to 15 percent of this irrigation water or between 20,000 and 30,000 acre-feet.
Researchers created the Precision Irrigators Network (PIN) to include growers in the research process. Researchers estimate that on a “typical” 100 acre field, water savings can amount to 6 to 8 inches of water per acre per year, or 163,000 to 217,000 gallons per year. The Texas Water Development Board estimates that on 620,000 acres of irrigated land in the Rio Grande region alone, 311,000 to 413,000 acre-feet of water per year could be saved.
The use of flexible, plastic polypipe and water metering devices to replace inefficient and leaky ditches and siphon tubes has steadily increased in the Lower Rio Grande Valley and in nearby Mexico. Three demonstrations conducted in Mexico showed that 30 percent water could be saved by using polypipe. The use of pressurized irrigation systems, polypipe and measuring devices has slowly been adopted by Mexican producers with the help from RGBI.
Extension specialists have conducted in-home water conservation demonstrations in nine Rio Grande Basin counties in Texas and five in New Mexico to determine how much water families of four use in 30 households in Texas and 15 households in New Mexico. Extension specialists educated the families on water conservation measures, provided the families with in-home water audits and then lists of recommended behavior and fixture changes, and in some cases water conserving fixtures were installed. The goal of the study is to evaluate effectiveness of various levels of intervention and show water and economic savings when conservation methods are implemented. Preliminary results show that water use can be reduced by 25 percent with education interventions alone.
RGBI funding is also focused on coordinating basinwide activities related to the Pecos River Basin, a major sub-basin of the Rio Grande and documenting potential and realized water salvage from large-scale saltcedar management programs. Several research and monitoring efforts are ongoing, including saltcedar transpiration estimates from sap flow measurements and determining fate of salvaged water through flow nets. To date, more than 13,000 acres of saltcedar have been treated with herbicides within the Pecos River Basin of Texas, some with state funding. Current research indicates that potential water salvaged from saltcedar is at least 2 feet per acre per year. Assuming this minimum amount of salvage, more than 26,000 acre-feet of water has been salvaged from these saltcedar control programs.
Increased use of soil testing as a standard best management practice will improve overall production economics and provide added protection for critical and limited water resources. A four-county soil-testing program was conducted fall through winter of 2001 thru 2004 in Cameron, Hidalgo, Starr and Willacy counties. Projected fertilizer savings based on soil tests were an estimated 1,742,321 pounds of nitrogen and 2,345,310 pounds of phosphorus. These reductions in nutrient loading represent a reduced threat for potential impacts to surface and groundwater resources. The total economic impact from the project was estimated at $1,072,344 based on average per pound costs for nitrogen and phosphorus.
Within its environment, ecology and water quality protection task researchers determined that the levels of Giardia and Cryptosporidium in river water are much higher during the non-irrigation season compared to the irrigation season. Genetic typing has identified human-specific and zoonotic (capable of transmission between animals and humans) strains of Giardia and Cryptosporidium in water samples. These data will be used to assess the human and animal health risks associated with the use of winter return flows. This information will also help develop strategies that can safely extend municipal and agricultural water supplies.
Other projects under this task focus on maintaining agricultural productivity and urban landscapes with alternative irrigation water sources. Texas presently reclaims 5 percent of its wastewater, with the potential to increase water conservation by reclaiming greater quantities of wastewater for beneficial use. Further research is focused on salty groundwater, graywater and concentrate as alternative water sources for irrigation in rural and urban areas. The research strategy is to remove salts prior to irrigation to levels acceptable for salt tolerant crops. More than 70 different landscape plant species have been evaluated for salt tolerance. In El Paso the urban landscape area irrigated with moderately salty reclaimed water has increased from 150 acres to 325 acres during the past 7 years.
Initiative researchers have collected natural resource information for counties along the Rio Grande and organized into spatial databases that provide GIS coverage for a particular county. To date, 16 Texas counties have been analyzed and mapped. Stakeholders can access and identify environmental, natural resource and socioeconomic information for each county. Natural resources, socioeconomic and health related conditions in the Pecos Basin counties have also been collected and processed for web hosting to complement work completed for Rio Grande Basin counties. These systems help planners in these water short areas.
Over the past three years, RGBI participants have had an estimated 90 refereed journal articles, 80 Extension publications, 36 magazine and newspaper articles, and more than 300 reports, presentations and papers to help guide and direct educational efforts in the Rio Grande Basin.
RGBI has been a model program of collaboration and partnerships, focused on water conservation outcomes and accountability. In the past year, the RGBI has received several awards commemorating these partnerships and collaborations.
“One of the keys to a project of this type is widespread and collective collaboration with so many groups,” Harris said. “Water management districts, ag producers, municipal water users and others involved on both sides of the border working together collaboratively is an absolute must.”
The RGBI project is going into its fifth year of research and educational efforts towards efficient irrigation in the Rio Grande Basin. Project efforts have produced numerous accomplishments, and they continue producing significant water savings and measurable outcomes. The RGBI is a federally funded, administered by the Texas Water Resources Institute, in collaboration with New Mexico State University, and funded through the U.S. Department of Agriculture Cooperative State Research, Education, and Extension Service.
More detailed information regarding the RGBI and its progress and accomplishments can be found at http://riogrande.tamu.edu.
Make every drop count!
