Working in cooperation with
irrigation districts, economists and engineers have developed evaluation
tools to guide irrigation districts in water-use efficiency infrastructure
and cost-of-saving-water analysis. The Rio Grande irrigation district
economics tool (RGIDECON), the rapid assessment tool (RAT) and geographic
information systems (GIS) are three of the main tools developed during
the RGBI’s 5-year history.
To assist producers with irrigation scheduling, researchers have established
on-farm monitoring of crop water use. They have taken extensive soil
samples to determine nitrogen content with soil depth, rooting depth
and other soil properties necessary for adapting the Crop Production
and Management Model (CroPMan) to the area. CroPMan also allows producers
to assess economic trade-offs of allocating limited water resources
between various crops at varying crop growth stages.
Water is the primary factor limiting the production of many crops
in the Lower Rio Grande Valley of Texas, and researchers have found
using improved furrow irrigation techniques and scheduling for sugarcane
production can save 10 percent to 15 percent of irrigation water or
between 20,000 and 30,000 acre-feet.
RGBI researchers created the Precision Irrigators Network (PIN), which
incorporates growers into the research process by demonstrating water
saving, efficient irrigation techniques and installing techniques
and installing soil moisture sensors. Researchers estimate that on
a “typical” 100 acre-field, water savings using PIN can
amount to 6 to 8 inches of water per acre per year, or 163,000 to
217,000 gallons per year. Based on 620,000 acres of irrigated land
in the Rio Grande region alone, PIN can save 311,000 to 413,000 acre-feet
of water per year.
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 Tamaulipas, Mexico showed that irrigation
could be reduced by 30 percent by using polypipe.
Extension Specialists have conducted in-home water conservation demonstrations
in 45 households to determine the amount of water a typical family
of four uses. Extension specialists provided them with in-home water
audits and educational materials as well as list of recommended behaviors
and fixture changes. In some cases, they installed water-conserving
fixtures. Preliminary results show that educational interventions
can reduce water use by 25 percent.
RGBI funding also focuses on coordinating basinwide activities related
to the Pecos River, a major tributary of the Rio Grande. The project
is documenting how much water can be saved by large-scale saltcedar
management programs. To date,scientists have treated more than 13,000
acres of saltcedar within the basin with herbicides. 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.
Because 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, Extension specialist
conducted a four county soil-testing program. Projected fertilizer
savings based on soil tests were an estimated 1.7 million pounds of
nitrogen and 2.3 million pounds of phosphorous. These reductions in
fertilizer application represent a reduced threat for nutrient contamination
of surface and groundwater resources. The total economic impact from
the project was estimated at $1.0 million based on average per-pound
costs for nitrogen and phosphorous.
Researchers in El Paso used genetic typing to determine that the levels
of certain bacteria in river water are much higher during the non-irrigation
season. Researchers will use these data to assess the human and animal
health risks associated with using winter return flows and will help
develop strategies that can safely extend municipal and agricultural
water supplies.
Since Texas presently reclaims about 5 percent of its wastewater with
the potential to reclaim greater quantities, further research is being
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 level acceptable
for salt-tolerant crops. RGBI researchers have evaluated more than
70different landscape plant species for salt-tolerance. In El Paso,
the urban landscape area irrigated with moderately salty reclaimed
water has increase from 150 acres to 325 acres during the past seven
years.
“One of the keys to a project of this type is widespread and
collective collaboration,” Harris said. “Water management
districts, ag producers, municipal water users and others involved
on both sides of the border working collaboratively is an absolute
must.”
The RGBI is 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.
For more detailed information regarding the RGBI and its progress
and accomplishments, go to http://riogrande.tamu.edu
