New & Noteworthy

Press Release: Study Explores Groundwater and Geothermal Energy in Drought-Stricken Eastern Oregon and Neighboring States

Technical Announcement: USGS Issues Revised Framework for Hydrogeology of Floridan Aquifer

Press Release: High Plains Aquifer Groundwater Levels Continue to Decline

Regional Groundwater Availability Study Geospatial Data

Press Release: USGS Assesses Current Groundwater-Quality Conditions in the Williston Basin Oil Production Area

Past listings...

USGS Groundwater Watch

USGS maintains a network of active wells to provide basic statistics about groundwater levels.

Other Water Topics

 Water Resources

 Groundwater

 Surface Water

 Water Quality

 Water Use

USGS in Your State

USGS Water Science Centers are located in each state.

Water-Table Fluctuation (WTF) Method

Graphical Approach for Estimating Recharge Using the WTF Method

Graphical approach to the water-table fluctuation method for estimating recharge.

In the graphical approach to determine DH(t_j) for the WTF method, the antecedent recession curves are extrapolated manually on the basis of visual inspection of the entire data set. When viewed with corresponding precipitation data, rises that are not caused by precipitation (and therefore do not indicate recharge) can be identified clearly and eliminated from the recharge calculations. Examples of rises not caused by precipitation include electrical surges, changes in barometric pressure, cessation of pumping, earth tide effects, entrapped air, temperature variations, and manual adjustment to the water-level measuring device (Freeze and Cherry, 1979). This approach involves more subjectivity than the other WTF approaches, and different users no doubt would produce slightly different recession curves. This is an especially tough problem when water levels are changing rapidly and multiple recharge events follow closely, such as in fractured rock settings.