Introduction: Benefits of Flexible Water Delivery

This issue contains two papers by Merriam et al. that describe the concept and application of flexible irrigation water supplies. The papers are the final submittals of a task committee on the Benefits of Providing Flexible Water Delivery formed in 1995. The task committee presented a series of nine papers at the 27th IAHR Congress in August 1997. The purpose of the task committee was to demonstrate through case studies the economic benefits of providing flexible water availability at the farm level and the residual benefits of water conservation, reduced drainage, improved return water quality and reduced operational costs to the purveyor.

A flexible water supply allows the farmer the opportunity to choose an on-farm system that best meets the needs of the desired crop, the cost and availability of labor, and other economic or social situations. This flexibility needs to be in terms of rate, frequency, and duration of supply. A rigidly controlled rotational system can reduce the efficiency of even the most sophisticated, well-designed on-farm system. Flexible supplies can allow furrow and border strip systems to select and adjust optimum instantaneous rates to match infiltration. Flexibility in frequency can help the farmer select intervals that match both the crop needs and the availability of labor. Flexibility in duration helps to avoid overfilling the soil profile when application or infiltration rates do not match the purveyor’s delivery schedule.

Case studies and companion papers as products of the task committee were written by Cross and Burt et al. in the September/October 2000, Vol. 126, No. 5 issue of the Journal of Irrigation and Drainage Engineering. Another companion discussion paper written by Merriam was included in the March/April 2005 Vol. 131, No. 2 issue. The task committee hopes that the assembly of these five papers with a focus on flexibility of irrigation supplies provides a useful glimpse and review of the subject area.

A special thank you goes to John Merriam, professor emeritus at California Polytechnic State University, for decades of instruction and application both domestically and abroad of the concepts of flexible irrigation supplies. The Merriam Irrigation Education Foundation and the Fund for Furthering Flexible Irrigation have worked tirelessly to espouse these concepts, which continue to become more relevant as the competition for water supplies becomes more intense and the global marketing of food production becomes more complex.