Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 19, 2010
Publication Date: April 1, 2011
Citation: Clemmens, A.J., Strelkoff, T. 2011. Zero-inertial recession for a kinematic wave model. Journal of Irrigation and Drainage Engineering. 137(4):263-266. Interpretive Summary: Surface irrigation has a reputation for poor performance, yet they represent roughly half the irrigated acreage in the U.S. and 90% worldwide. It is possible to improve the performance of surface irrigation through improvements in design and operation. The process for making improvements includes evaluating an irrigation event, determining infiltration and roughness conditions, conducting analysis to provide recommendations for improvement, and implementing the recommendation. ARS developed a simulation model, WinSRFR, to assist users in this process. This paper presents a new method for calculating the surface flow after the inflow is cut off. This helps avoid anomalies in the solution, which can cause results to be difficult to interpret. This information should be useful to irrigation farmers, the Natural Resources Conservation Service, extension specialists, and agricultural consultants.
Technical Abstract: Kinematic-wave models of surface irrigation assume a fixed relationship between depth and discharge (typically, normal depth). When surface irrigation inflow is cut off, the calculated upstream flow depth goes to zero, since the discharge is zero. For short time steps, use of the Kinematic Wave model can create an incorrect water surface profile. Issues include difficulty in solving the continuity equation in the first upstream cell and a calculated adverse water-surface profile. The Kinematic Wave model produces a recession time at the upstream boundary that is too small, which can lead to incorrect calculation of recession times as water continues to recede from the surface. This problem becomes more severe for smaller values of bottom slope. In this paper, we present a zero-inertia approximation to the water surface profile at cutoff, which can be extended to the start of recession, after which calculations continue with the Kinematic-wave model. Introduction