Determination of velocity dispersion profiles in open canals using different interpolation methods

Abstract

The purpose of this study was to estimate co-speed curves (velocity dispersion profiles) in the cross-section of an open canal using point flow velocities by 10 different interpolation methods and to determine the best of these by comparing them with each other. Firstly, velocity dispersion profiles were obtained for two trapezoid section concrete-lined irrigation canals according to measured point velocity values, using the inverse distance to a power, Kriging, minimum curvature, natural neighbor, nearest neighbor, polynomial regression, radial basis function, triangulation with linear interpolation, local polynomial and moving averagemethods. Then the cross validation test was applied to determine the best of these methods. In this test, interpolation methods were compared with each other in terms of the correlation between the actual and predicted value in verification points (r), minimum error (Emin), maximum error (Emax), mean error (ME), mean absolute error (MAE), mean relative error (MRE) and root mean square error (RMSE). The result was that the ‘triangulation with linear interpolation’ method was determined as better than other methods at predicting velocity dispersion profiles in both open irrigation canals (r = 0.946 and 0.941, Emin = -0.322 and -0.552, Emax= 0.027 and 0.059, ME = -0.074 and -0.119, MAE = 0.084 and 0.131, MRE = 0.124 and 0.127, RMSE = 0.140 and 0.224). Key words: Open canal, velocity dispersion profile, interpolation, performance.