Skip to main content
U.S. flag

An official website of the United States government



Heavy is a Fortran program for calculating the change in gravity caused by the change in groundwater storage as predicted by a MODFLOW groundwater-flow model. Gravity change is calculated relative to the initial time step at user-specified locations (e.g., measurement locations). At each location, the gravitational attraction is the sum of the attraction caused by storage change (confined or uncon

Gravity Data Spreadsheets

These gravity data spreadsheets are Microsoft Excel documents containing functions that convert observed meter readings to gravity using the meter calibration table (for LaCoste & Romberg relative-gravity meters), applies a tide correction, calculates and plots drift using the Roman (1946) method, and calculates average gravity differences between each station pair.


GSadjust is the first comprehensive, publicly-available graphical interface for performing drift-correction and network adjustment for combined relative- and absolute-gravity surveys (Kennedy and others, 2021). The objective of network adjustment is to determine a single, best-fit gravity value at each station based on all available observations and their respective uncertainty. Typically the obse

GSadjust: a graphical user interface for processing combined relative- and absolute-gravity surveys

GSadjust is a graphical user interface for processing relative-gravity surveys. It provides an interface for data selection, drift evaluation and correction, network adjustment, for data from modern relative (Scintrex, ZLS) and absolute (Micro-g LaCoste) gravity meters. 

Computer Programs for Telescopic Mesh Refinement using MODFLOW-96: MODTMR, TMRDIFF, and RIVGRID

MODTMR - A program for telescopic mesh refinement using MODFLOW TMRDIFF - A program to provide a means of comparing computed head or drawdown in local and regional models in applications of telescopic mesh refinement. RIVGRID - A program to construct MODFLOW data sets for head-dependent boundaries using grid-independent data sets