Groundwater Recharge

Daily streamflow data is used to evaluate the baseflow component also referred to as groundwater inflow or recharge to the stream which is usually considered equal to the general groundwater recharge across the watershed less any groundwater withdrawals from pumping.  Annual precipitation in Loudoun County is typically 41 inches while the general recharge rate is less than 11 inches per year. (Loudoun, 2023).

Calculations done on a monthly basis using daily flow data reveal that over a 53-year period of record at Catoctin Creek and Goose Creek, there has been a 5 and 10 percent decrease in the recharge rate, respectively.