Modeling and Simulation of Baseflow to Drainage Ditches During Low-flow Periods

Quantification of baseflow to drainage ditches is essential in understanding flow dynamics in a watershed. The mass balance estimation for a stream section may not give an accurate measure of the baseflow during low-flow periods due to the lack of accuracy in flow measurements in the flumes. Modeling may be useful for estimation of baseflow during low-flow periods. In this study, numerical and analytical solutions of the Boussinesq equation were used to simulate baseflow rates during low-flow periods in two watersheds, namely the Big Ditch watershed and the Upper Embarras River watershed in Illinois, USA. Additionally, MODFLOW was also used to simulate baseflow for these periods. At each site, a stream section of 200 m was selected for baseflow simulation and six observation wells were installed at one bank of each stream section for model calibration. A total of seven low-flow periods were considered for baseflow simulation. The mean baseflow rates simulated by the numerical model were higher than that simulated by the other two models. There is no significant difference between the mean baseflow rates simulated by the analytical model and MODFLOW. It was observed that proper estimation and/or measurement of model parameters were necessary for simulation of reliable baseflow rates. Since flow measurements during low-flow periods may include possible errors, the model results might also be acceptable for all practical purpose.