|ZERIHUN, DAWIT - U OF AZ, TUCSON, AZ
Submitted to: Environmental and Water Resources Institute World Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2008
Publication Date: 5/15/2008
Citation: Bautista, E., Strelkoff, T., Clemmens, A.J., Zerihun, D. 2008. Surface volume estimates for infiltration parameter estimation. Environmental and Water Resources Institute World Congress Proceedings. CDROM. 10 pp.
Interpretive Summary: Surface volume estimations are needed as part of volume balance calculations commonly in surface irrigation engineering analyses. Volume balance calculations are used to predict irrigation flows and performance and also to estimate infiltration properties from irrigation evaluation data. Surface volume estimates typically are based on formulae that assume steady-state conditions. In many field situations, flow depths evolve slowly with time, and in such cases, steady-state formulas will result in significant surface volume estimation errors. This article presents an alternative method for estimating flows depths needed to calculate surface volumes and examines the resulting prediction errors under a wide range of conditions. The method should be of interest to NRCS irrigation specialists and other irrigation professionals as it improves significantly the accuracy of surface volume calculations.
Technical Abstract: Volume balance calculations used in surface irrigation engineering analysis require estimates of surface storage. These calculations are often performed by estimating upstream depth with a normal depth formula. That assumption can result in significant volume estimation errors when upstream flow depth evolves slowly with time and cannot be used under zero-slope conditions. This article examines the errors incurred when calculating upstream depth with an approximation to the zero-inertia equation instead of the normal depth formula. The approximation, which uses an empirical adjustment factor, gives reasonable results under a wide range of hydraulic conditions.