A simple field model to predict seepage and water table height in a canal command area

We developed a semi-analytical model to predict seepage, recharge and water table position behaviour in a canal command area. Model divides the total time into n time steps (i = 1 to n) of one year each to calculate the mound height as a function of time and space from an ephemeral analytical rechar ge model. After each time step i the water table is leveled off at h (m, i) up to the extended orthogonal canal reach (ECR). Recharge coefficient vari ed from 0.02-0.25 in different months of a year. Predictions of the model were tested at the research farm of Haryana Agricu ltural University, Hisar, India, under ten years of irrigation using measur ed yearly average and monthly data for depth to water table at orthogonal d istances of 100, 300, 700, 1200 and 2700 m from the canal. Good agreement w as observed not only in yearly prediction of depth to water table W (mean e rror < 9.3 %) but also in monthly prediction of W (mean error < 6.25 %). Th is model can be used to i) determine the need for lining of canal I waterco urses; ii) separate out the recharge contribution of canals, watercourses a nd of rainfall cum irrigation / returns; iii) predict the canal influencing zone in terms of orthogonal canal reach CR and extended orthogonal canal r each ECR; and iv) predict the conveyance efficiency of canal and watercours es in terms of seepage rate and percent seepage losses. Since the input par ameters of climate. soil and canal used by the model are easily available a nd measurable under field conditions, and the calculations can be easily do ne on a programmable calculator, the model is simple, cheap, and practical that can be executed even in remote areas.