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:
Zero-Flux Plane	Unsaturated Zone	Point	Day to Years	Potential Recharge	Difficult	High	High
The zero-flux plane (ZFP) method provides a point estimate of potential recharge based on the premise that recharge is equal to changes in soil-moisture storage below the ZFP. The ZFP separates upward movement of soil water to evapotranspiration from downward movement to the water table. The method requires data on the matrix potential of the soil to locate the ZFP and of soil-water content to measure changes in storage. The method is relatively difficult and expensive because of the instrumentation and data-collection required. Its use is restricted to conditions when a ZFP exists and locations were the water table is deeper than the ZFP.