GGSD Program Details for TIMELAG

TIMELAG

Category	Aquifer test analysis
Platform	DOS
Status	Public domain
Description	TIMELAG is a program to estimate hydraulic conductivity from a single-well test. The method involves instantaneous raising or lowering of the water level in a well and measuring the water-level recovery through time based on Hvorslev (1951) and more recent extensions. The method involves fitting a line to reduced field data, using linear least-squares regression on a semi-log scale. The induced change in water level must be instantaneous as the derivation of the theoretical basis requires the head in the aquifer to be constant. The well must be constructed so that neither the screen nor the filter pack inhibit ground-water movement. Also, the well should not be developed to the extent that a zone of increased permeability exists around the well. The program allows the standpipe and the well intake (screened or open portion of the well) to have different radii. Interactive data entry and editing, reading from and writing to a data file, graphic display and inspection of the observed time-water level data pairs, and writing results to a file for printing and inclusion in reports.
Cost	US Dollars 50
Data formats supported	Geophysics : LOG
Supplier in United States of America	International Ground Water Modeling Center