Instructor Materials - Module 4
Groundwater Flow at Woburn Wells G & H
Using this Module
In this module students learn some of the fundamental concepts of groundwater flow including measurement of water levels, hydraulic heads, construction of potentiometric surfaces, delineation of flowpaths, and calculation of ground-water flow velocities and traveltimes.The goals of this module are to learn how to contour irregularly spaced data (water-level measurements made in observation wells), how to draw flowpaths on a contoured water-table map, how to measure hydraulic gradients from a contoured water-table map, and how to compute flow velocities and traveltimes using Darcy's law. The goals are applied to examining flowpaths of groundwater moving from the W.R. Grace and Beatrice properties and to computing traveltimes along these flowpaths.
Module Design
This module was developed for an undergraduate course in environmental geology, a first course in ground-water hydrology, or as part of the sequence of modules in a mock-trial course contained within this website. The module requires students to contour irregularly spaced data (x, y, z) for construction of water-table maps, calculation of hydraulic gradients, and estimation of groundwater flow velocities and traveltimes.
The EXCEL spreadsheet requires students to contour two sets of water-level data collected by the U.S. Geological Survey. One set of data was collected prior to wells G and H operating and the potentiometric surface represents the configuration of the water table during times between 1964 and 1979 when wells G and H were not operating. The other set of data was collected after wells G and H had pumped for 30 days at their average operating rates and the potnetiometric surface approximates the typical configuration of the water table when wells G and H were operating together between 1964 and 1979. These two contour maps with selected flowpaths drawn on them and and a map of the drawdown created by pumping wells G and H after 30 days of continuous pumping represent three of the major pieces of evidence to be interpreted by students and presented in the mock trial. The traveltimes of along flowpaths emanating from the Beatric property and from the Grace property also are important to the mock trial.