Understanding Ground Water Level Trends: A Key to Managing Water Use

The Department of Natural Resources (DNR) monitors the use of the State's water and allocates that resource to assure that there is water of sufficient quality and quantity to supply the needs of future generations. The primary tool used by the Department for assessing future ground water availability is the observation well network. Under the observation well network program, ground water levels are routinely measured in 600 wells statewide. The primary objective is to provide estimates of changes in water supply. In addition, these data help the Department resolve well interference complaints, other allocation issues, and are useful to ground water researchers. The U.S. Geological Survey (USGS),lo cal units of government, and others involved in ground water use data from the observation well network. Systematic records of ground water levels measured in each of the wells in the network form the database. Water levels in aquifers fluctuate in both a long and short term sense, primarily in response to changes in precipitation and/or pumping. A plot of these fluctuations through time is called a hydrograph. The changes tell something about an aquifer's recharge and discharge rates, the geological properties of the aquifer and overlying materials. The purpose of this report is to provide a historical overview of ground-water trends and levels throughout Minnesota. To accomplish this, we present a historical background of the observation well program, a hydrogeological primer on aquifers, a description of seasonal and long term trends in ground water levels, and finally, a statewide overview of ground water levels.