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.

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Water-Table Fluctuation (WTF) Method

MRC Approach of Heppner and Nimmo (2005)

The Master Recession Curve (MRC) approach of Heppner and Nimmo (2005) was based on research conducted at a fractured rock site in Pennsylvania, USA. Development of the MRC using this approach begins by graphing the water-table elevation versus the decline rate for all time steps during which the water table was declining. The MRC curve can be constructed through this scatter plot using one of three methods: (1) a linear best fit to the data, (2) a power best fit to the data, or (3) by dividing the elevation range into “bins” and take the average decline rate for points in each bin. The linear and power best fits to the data yield a smooth MRC but require manual setting of minimum and maximum decline rates. Dividing the elevation range into bins results in a less smooth but entirely data-based MRC. More data produces a better MRC. The figure is an example showing the observed water-table elevation versus the water-table decline rate based on the bin-averaged method to produce the MRC.

Master recession curve approach (Heppner and Nimmo, 2005) to the water-table fluctuation method for estimating recharge

After the MRC is developed it is applied to the water-level data set one data point at a time to predict the elevation at the following time step in the absence of recharge. This predicted water-table elevation is then compared to the observed elevation, with the difference between the two values is the DH(t_j). If the predicted water level was greater than the observed water level, DH(t_j). A detailed description of the MRC approach for estimating recharge is provided by Heppner and Nimmo (2005).