An Evaluation of the SCS Design Criteria
ABSTRACT RECENT advances in the theoretical description and model simulation of surface irrigation now permit the evaluation of existing procedures and development of new and improved procedures for design and management of surface irrigation systems. Such developments are now underway, but their refinement and adoption by institutions and individuals may require considerable time. In the meantime, existing procedures will continue to be used. This paper summarizes an evaluation of that portion of the USD A Soil Conservation Service (SCS) irrigation guide dealing with ponded level borders. The evaluation indicates that while the current SCS guide will produce systems that perform essentially as expected under most conditions there are other conditions in which the field performance may be substantially less satisfactory than expected. These situations tend to be those where factors combine to retard the advance of surface flow and thus reduce the uniformity of application. The purpose of this paper is to alert users of the current SCS design guide for level borders to this possibility and to advise caution under these conditions until appropriate revisions are available.