Benchmarking of Flexibility and Needs - 2000

ITRC interviewed irrigation district personnel from 60 agricultural districts representing approximately 91% of the irrigated acreage within the U.S. Department of the Interior Bureau of Reclamation’s (USBR) Mid-Pacific Region. Data were analyzed to determine the degree of water delivery flexibility provided to farmers and the extent of existing and planned district modernization. The interview process defined needs for direct technical assistance and training. These needs varied by district and area in California. The Irrigation Training and Research Center (ITRC) concluded that training programs should incorporate some common classes using the Water Delivery Facility and other resources located on campus at California Polytechnic State University, San Luis Obispo, in addition to small specialized training efforts customized for single or small groups of districts. The data also indicated that more Rapid Appraisal Process (RAP) visits are needed to determine possible physical and managerial improvements (modernization and efficiency) for districts to accommodate the ever-changing needs of the consumers. Direct technical assistance to individual districts has been and will continue to be a key element of continuing success in modernization. This report summarizes the results and provides brief comments on various aspects of those results

Comparison of Measured and FAO-56 Modeled Evaporation from Bare Soil

This paper evaluates how well the FAO-56 style soil water evaporation model simulates measurements of evaporation (E) from bare soil. Seven data sets were identified from the literature and in all but one case, the individuals who took the measurements were contacted and they provided the writers with specific weather and soils data for model input. Missing weather and soils data were obtained from online sources or from the National Climatic Data Center. Simulations for three possible variations of soil data were completed and compared. The measured and the FAO-56 simulated E/ETo and cumulative evaporation trends and values were similar. Specifically, the average evaporation weighted percent difference between the measured and the simulated cumulative evaporation was between –7.5 and –0.5%. This evaluation suggests model accuracy of about ±15% with the use of sound weather data and a fairly generalized understanding of soil properties in the location being evaluated

Evaporation Estimates for Irrigated Agriculture in California

All California irrigation districts that receive either federal or state water are now required to prepare Water Conservation Plans. For the first time in the history of most districts, they are developing an elementary water balance. The term elementary should be emphasized, because there are significant weaknesses in our knowledge of subsurface flows and some components of Evapotranspiration (ET). Irrigation districts generally use published typical values of ET for their water balance computations

Evaporation Research: Review and Interpretation

Literature regarding evaporation from soil, wet plant surfaces, and sprinkler droplets was examined, normalized, and interpreted. Much of the evaporation literature is difficult to compare and interpret; this paper offers comparisons and discussions of various findings by others as well as by the writers. Techniques of measuring and estimating evaporation from irrigation and rainfall are discussed. The partitioning between increased evaporation and decreased transpiration from a variety of research is quantified. Factors that impact the various forms of evaporation are listed and quantified. This review and summary will provide practitioners and researchers with theoretical and practical guidance on measurement techniques and estimates of evaporation under a wide range of conditions