Comparison of Selected Methods for Estimating Groundwater Recharge In Humid Regions

Method:	Category:	Spatial Scale:	Temporal Scale:	Quantity Estimated:	Ease of Use:	Data Needs:	Cost:
HELP3 Model	Water Budget	Point to Regional	Day to Years	Potential Recharge	Easy	Low to Moderate	Moderate
The Hydrologic Evaluation of Landfill Performance (HELP3) model was developed by the U.S. Army Waterways Experiment Station to compute the water balance of landfills on a daily time scale. It estimates potential recharge at a point in the watershed, but areal estimates can be obtained by summing recharge rates computed for homogeneous subdivisions of the watershed. The model requires imputs of daily meteorological data, soil properties, and land cover, though meterological data can be synthesized by HELP3 from the WGEN weather-generation model and default properties are built in for soil and land cover types. If default properties are used, recharge estimates can be made quickly and for low cost, though the method is more difficult and costly if site-specific input data are collected. The DOS and UNIX computer codes are distributed free by COE, and Windows-based interface has been developed by Waterloo Hydrogeologic which saves time.