SHALLOW GROUND-WATER RECHARGE, REGIONAL GROUND-WATER DIVIDES, AND AQUIFER STORAGE IN THE GREAT LAKES BASIN

In 2005, the Great Lakes Basin Pilot study of the National Water Availability and Use Program was begun by the U.S. Geological Survey (USGS) to examine the ground-water resources, water use, and water availability in the Great Lakes Basin. Three retrospective analyses were done using existing data and reports to estimate regional characteristics of the aquifers in the Great Lakes Basin. (URLs at the end of the following paragraphs refer to USGS reports from those analyses.)

Long-term average ground-water recharge characteristics to shallow aquifers were determined from base-flow estimates previously derived by means of a model based on an empirical relation between measured base flow and surficial geological materials. Estimated recharge ranged from 1.6 to 16.8 inches per year and is based on the assumption that recharge is approximately equal to base flow. (http://pubs.usgs.gov/sir/2005/5284/)

In 2005, the Great Lakes Governors (U.S.) and Premiers (Canada) signed agreements that include a ban on new diversions of water outside the Great Lakes Basin. It is well documented that, in some areas of the Great Lakes watershed, pumping has altered the regional ground-water drainage divide between the Great Lakes and the Mississippi Basins. This study examined regional and local studies to estimate the location of regional ground-water divides on the U.S. side of the Great Lakes Basin. (http://pubs.usgs.gov/sir/2006/5102/)

The Great Lakes Basin has at least seven principal aquifers that supply ground water to the citizens in the U.S. Hydraulic properties of many of the regional aquifer systems in the Great Lakes have been examined by regional studies by the U.S.G.S. and others, but a regional compilation of those properties had not been done. This study compiled the values of hydraulic properties, including hydraulic conductivity and storage, into a single document and made estimates of ground water in storage in principal aquifers on the U.S. side of the Great Lakes Basin. (http://pubs.usgs.gov/sir/2006/5180/)