USGS Groundwater Information
Groundwater Resources Program
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Press Release: High Plains Aquifer Groundwater Levels Continue to Decline
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USGS maintains a network of active wells to provide basic statistics about groundwater levels.
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Methods for Estimating Groundwater Recharge In Humid Regions
Recharge has been defined as the process of addition of water to the saturated zone. Because it is almost impossible to measure directly, recharge is usually estimated by indirect means. The accuracy of the indirect estimates is usually difficult to determine, so a common recommendation is that recharge should be estimated by the use of multiple methods and the results compared.
This site describes the application, data needs, strengths, and weaknesses of widely-used methods for estimating groundwater recharge that have general applicability in humid regions of the U.S. The site is designed to be a quick-reference or resource guide for selecting appropriate methods for estimating recharge in humid areas. Currently, the site provides a comparison of 15 methods. Three methods are described in detail -- Darcy method, water-table fluctuation method, and recession-curve displacement method.