Measuring and estimating water table level and drainage discharge rate in unsteady flow state

Prediction of water table depth and outflow rate of drainage system are the most important issues in the literature of the drainage engineering. Three models of Kraijenhoff Van de Leur – Maasland، de Zeeuw - Hellinga and Glover – Dumm are frequently used for prediction of water level and discharge rate under unsteady state flow condition. For comparing the ability of these models an experiment was conducted using a laboratorial physical model. Data were collected for constant and variable head conditions in accordance to the boundary conditions of each model. The results showed good agreement with the observation data. For water level rising condition the Kraijenhoff Van de Leur – Maasland and de Zeeuw – Hellinga models، underestimated the outflow rate and overestimated the water table level as compared to the observed data، also Kraijenhoff Van de Leur – Maasland model''s prediction was better than that of de Zeeuw – Hellinga model. For the falling water table state the de Zeeuw – Hellinga model prediction was closer to the observation. The prediction accuracies of all three models decreased and converged while reaching the end of the experiment.