AMARILLO – Evapotranspiration-based irrigation scheduling can save water and money for producers, but the networks of weather stations necessary to gather the data are in danger of being lost, according to a recent study.
Based upon producer information from the Texas Panhandle and the Winter Garden area, such scheduling has resulted in reduction of irrigation pumping by an average of 2 inches per crop season, without crop-yield loss, said Dr. Dana Porter, Texas AgriLife Extension Service engineer in Lubbock.
This water savings, based on recent average pumping costs on irrigated acreage in the Texas Panhandle, amounts to an approximate savings of $18 million in energy pumping costs alone.
At the recent High Plains Irrigation Conference and Trade Show in Amarillo, Porter presented the results from an assessment of Texas evapotranspiration networks by a team comprised of AgriLife Extension, Texas AgriLife Research and the U.S. Department of Agriculture-Agricultural Research Service personnel.
Evapotranspiration is a science-based measure of a crop’s total water demand through evaporation and plant transpiration to the atmosphere, she explained. The statewide assessment of evapotranspiration networks or weather station networks was designed to evaluate their and other data sources’ suitability in irrigation scheduling.
The data recorded by the ET networks, as they are known, includes air temperature, humidity, solar radiation and wind speed, among other factors. The accuracy of the evapotranspiration estimates depends on the accuracy of meteorological data used for calculation.
“These stations are sited to agricultural conditions to collect weather data to estimate crop water use and information for irrigation scheduling, particularly to fine-tune irrigation scheduling to match the crop water needs,” Porter said.
While the data are used by agricultural producers, they are also used by water districts for water allocations, the general public for landscape irrigation and for drought-mitigation operations, she said. Agricultural researchers, environmental researchers and others need the data as well to evaluate conditions of their studies or interpret outcomes of their studies.
Porter said in the study, they identified existing evapotranspiration networks, reviewed their operations, data collection procedures and methods of evapotranspiration calculation. In addition, they conducted sensitivity analyses to determine the accuracy of data and sensors, as well as the maintenance necessary to achieve accurate evapotranspiration estimates.
The study found there are numerous weather networks that make weather data available, but they were established for a variety of reasons and serve different primary purposes and audiences than for agricultural and water conservation use, she said.
Some of these uses included weather-based research, preparation for severe events, water-source monitoring (pollution, quantity), air pollution monitoring, weather forecasting and severe weather warnings.
Systems aimed at agriculture are considered Ag Met Networks, which collect and disseminate data to calculate evapotranspiration and crop-water use, Porter said. Examples of these are the Texas High Plains ET Network based in Amarillo and the Texas ET Network based in College Station.
Consultations were held with network managers to determine detailed information on the parameters of the networks, including staffing, annualized programming costs, products available, cost of storage and media type, sources of funding and number of stations.
A common concern identified was funding stability and staffing issues related to the networks.
“One of the problems we’ve identified is the general instability of funding or lack of sufficient funds to maintain the staffing, the equipment and the operations for adequate and reliable information from these units statewide,” Porter said.
“In the past, we’ve been able to maintain these networks based on research funds, what’s called soft funding. For nearly 20 years we’ve been piecing together projects to hire staff who are needed, as well as to buy equipment, calibrate sensors, pay for required maintenance travel and pay for telecommunications costs associated with data acquisition.”
The problem now, Porter said, is that the grant funds have been exhausted, and “we’ve pursued a number of other avenues to secure funding unsuccessfully, and we have not been able to accomplish a long-term solution.”
The study concluded that agricultural-based data for computation of reference evapotranspiration must be validated, she said, and that non-agricultural-based data sources, especially, should be verified for quality assurance/quality control and siting conditions before they can be used in evapotranspiration calculations.
This validation is not a quick or easy process necessarily and typically requires qualified personnel to make that determination, Porter said. The study also indicated that the use of bad or inadequate data can lead to poor estimates and water-policy decisions.
Weather-station network personnel should understand the equipment, sensors, calibration, importance of appropriate siting, effects of microclimate, data quality and standardization before trying to provide evapotranspiration calculations, Porter said.
The group’s final recommendation is that meteorological parameters and reference evapotranspiration estimates should be maintained on a statewide basis, particularly for the irrigated regions since irrigated agriculture consumes such a large portion of the water resources in Texas.
These accurate ET data are necessary for “ground-truthing” validations in research, water planning and water resource allocations (permitting and regulation), as well as for farm-level irrigation water planning, scheduling and management, Porter said.
“ET networks should be supported through adequate and sustainable means to reduce risks associated with losses of short-term grant funding and loss of faculty/managers and other support staff.”