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:
Temperature	Tracer	Point	Days to Years	Recharge	Moderate	Moderate	High
Measurement of temperature beneath a stream or lake can be used to infer the rate of infiltration at a point location for periods of days to years. Estimates of potential recharge can be made from by comparing measurements of temperature to values modeled for sediments of assumed thermal diffusivity with infiltration of various rates. The method requires installation of thermistors beneath streams to depths of a few inches to define diurnal fluctuations to 10's of feet to define the annual fluctuations. Analysis of the data requires analytical or numerical modeling, which can be time consuming and difficult. Cost of thermistors is low, but data-analysis cost is high.