The hydrogeology and hydrology of the River Bain catchment, Lincolnshire
A catchment model, which has the objective of simulating streamflow and calculating groundwater recharge of a small undeveloped catchment «100 km2), is described. The model accepts input daily data of rainfall and potential evapotranspiration, and it consists of two parts. Firstly, the modified Stanford Model to simulate the land phase processes, and secondly the Penman-Grindley soil moisture balance to calculate recharge. Several assumptions have been made so that the model can be applied on a rural catchment from which rainfall data is routinely collected on a daily basis. In order to estimate recharge accurately the volumes of interception and surface runoff have to be estimated first. This is done by the modified Stanford Model. The root constant parameter in the Penman-Grindley soil moisture balance provides a realistic formulation for recharge calculations. The root constant is easily estimated from the crop cover and hence can be used to simulate the effect of changing land use on the hydrologic regime. The model has been developed on a small catchment (63 km 2 ) of the River Bain above Goulceby in East Lincolnshire. Simulation of streamflow is indicated to be more accurate in the low- to medium flow ranges than in the high flow range. Although the time step of one-day adopted in the rr.odel is sufficient for accurate calculation of recharge, it is not sufficient for accurate simulation of surface runoff which characterises the high flow events. In addition to simulation of recharge and streamflow, the model can also be used to study the effect of variation of certain parameter on the hydrologic regime.