WERA202: Climatic Data Application in Irrigation Scheduling and Water Conservation
Statement of Issues and Justification
Although the need for multistate coordination of irrigation water resources has always existed, recent droughts and a boom in the population of many western states has made this coordination even more imperative. Although agricultural acreage in many areas is on the decline, agriculture is still the major user of water in many states. In the West, it is estimated that 90% of the freshwater drawn from well and surface sources is for agriculture.Irrigation scheduling models that have been developed help growers estimate when and how much irrigation water to apply to their crops. Most, if not all, scheduling models use weather data (real time and/or historic) and these data are usually managed by state or regional personnel. Unfortunately, the weather data formats vary from location to location and normally the scheduling model will only utilize weather data in the format of the local weather data system. Differences in the weather data collected include time steps (hourly vs. daily), sequencing (the order in which the data are stored), and varying degrees of quality control (ranging from none to intense data scrutiny). Thus, there exists a need to coordinate the weather data collection, storage formats as well as the development of scheduling models themselves. This committee has already provided much coordination among the member states and this effort should continue.
Crop water use, or evapotranspiration (ET), is usually estimated by calculating evapotranspiration for a reference crop (ETo/ETr/ETs) and then multiplying that by a crop coefficient (Kc) to estimate water use for a specific crop (ETc). Since the formation of the WERA 202 committee, (formerly the WCC-202 committee) a new standardized format for estimating reference crop water use has been published (FAO 56 and the ASCE/EWRI standardized reference ETs). These equations use the Penman-Monteith equation to standardize the way researchers estimate reference crop water use around the world. However, with a new standardized reference ET equation, questions have arisen about the usefulness of crop coefficient data developed and used with the other ET equations. Furthermore, there is now a desire to standardize Kc development in order to better allow these data to be used with the new standardized ET equation.
Finally, the use of irrigation scheduling models by growers varies from county to county, state to state and region to region. There continues to exist a need and desire to coordinate, discuss and review methods used in various states to provide clientele with the best possible information to help them better use their irrigation water resources. One example of the need for better irrigation scheduling information and methods is the Environmental Quality Incentive Program (EQIP) program offered through the USDA Natural Resource Conservation Service (NRCS). This program has begun providing cost-share money to producers to improve their irrigation water management. To be paid, the producers have to show documentation of irrigation water management for the entire growing season. This has created a demand for irrigation water management training for producers and NRCS staff. These demands have increased the need for crop specific irrigation scheduling information specifically accurate crop water use estimates.
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