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 [Photo: Groundwater flowing out of well.]

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

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USGS Groundwater Watch

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

 [Image: USGS active water level wells location map.]

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USGS in Your State

USGS Water Science Centers are located in each state.

 [Map: There is a USGS Water Science Center office in each State.] Washington Oregon California Idaho Nevada Montana Wyoming Utah Colorado Arizona New Mexico North Dakota South Dakota Nebraska Kansas Oklahoma Texas Minnesota Iowa Missouri Arkansas Louisiana Wisconsin Illinois Mississippi Michigan Indiana Ohio Kentucky Tennessee Alabama Pennsylvania West Virginia Georgia Florida Caribbean Alaska Hawaii and Pacific Islands New York Vermont New Hampshire Maine Massachusetts South Carolina North Carolina Rhode Island Virginia Connecticut New Jersey Maryland-Delaware-D.C.

Water-Table Fluctuation (WTF) Method

The water-table fluctuation (WTF) method provides an estimate of groundwater recharge by analysis of water-level fluctuations in observation wells. The method is based on the assumption that a rise in water-table elevation measured in shallow wells is caused by the addition of recharge across the water table.

Figure 1. Determination of water-level rise.
Determination of water-level rise.

Recharge by the WTF method is estimated as:

R(tj) = Sy* DH(tj)       (1)

where R(tj) (cm) is recharge occurring between times t0 and tj, Sy is specific yield (dimensionless), and DH(tj) is the peak water level rise attributed to the recharge period (cm).

Although simple in theory, some key assumptions and critical issues inherent in the WTF method have great bearing on its successful application: (1) the observed well hydrograph depicts only natural water-table fluctuations caused by groundwater recharge and discharge; (2) Sy is known and constant over the time period of the water-table fluctuations, and (3) the pre-recharge water-level recession can be extrapolated to determine DH(tj).

Application of the method WTM involves two steps:

Because of the simplicity of the method and wide availability of water-level hydrographs from observation wells, the WTF method has been used for many years (Meinzer, 1923; Rasmussen and Andreasen, 1959; Crosbie and others, 2005). An excellent review of the WTF method is provided in Healy and Cook (2002).

Case Studies Using the WTF Method


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Page Last Modified: Tuesday, 03-Jan-2017 20:46:59 EST