Ottawa County groundwater has quality and quantity concerns
Some groundwater in Ottawa County has become impaired with wells pulling up salty water. Concerns also center on quantity, with overall lowering of groundwater levels.
There may be a looming shortage of safe-to-drink groundwater in Ottawa County as both quantity and quality issues have arisen in some areas. Ottawa County contracted with Michigan State University’s (MSU) Institute for Water Research (IWR) to study a number of groundwater related problems that parts of the county have experienced in recent years.
In the Allendale area, there was a new subdivision in which water wells could not deliver the quantity of groundwater desired. In the central part of the county, water wells that tap the bedrock Marshall Formation started to deliver very salty water.
At the Ottawa County “Seventh Annual Water Quality Forum” on November 1, David Lusch, Distinguished Senior Research specialist, reported the findings of MSU’s year-long investigation of these issues. One of the main findings is that the static groundwater level under Ottawa County is going down. That means groundwater is being pumped out faster than it is being replenished.
Lusch said there are generally two groundwater aquifers under Ottawa County. First is groundwater found in the glacial overburden, and second is groundwater in the bedrock. Glacial overburden is the sand, gravel, clay, and loam on top of bedrock – deposited by the last glacier.
In the southeast and northeast areas of the county, the glacial overburden consists of fine-texture deposits which do not allow much deep infiltration of precipitation that can recharge groundwater. In the face of this limited recharge capacity, the increasing groundwater withdrawals remove water at a rate faster than it can be replenished.
Some water users have installed deeper wells which extend down into the bedrock Marshall Formation, a thick sandstone. In several areas in central Ottawa County demand for groundwater is high enough that very salty water from deep within the Marshall Formation has been pulled into these wells. The more groundwater is pumped in these areas, the more salty water will move into those wells. This naturally occurring brine water is in the same groundwater resource that chemical and salt companies in Midland, Manistee, and Ludington use to extract various chemicals and salts.
Principle among the study’s findings, however, is when comparing the average Static Water Level (SWL) for 1966-1999 to the average SWL for 2000 to 2012, there has been a 10 to 12 meter (33 to 40 foot) drop in bedrock groundwater levels, and a 3 to 9 meter (10 to 30 foot) drop in glacial groundwater levels. These are modest, but significant, declines in the SWL.
Also the drop in SWL does not appear to be the result of less rain, since the weather records show there has been more precipitation from 2000 to 2012 than there was 30 years ago.
Continuing to pump out more groundwater than is being replenished is not sustainable over the long term, Lusch cautions. Lusch indicated there will need to be more study to know how much longer the community can continue to pump groundwater at a rate faster than it is replenished.
Part of the study being done by IWR also includes exploring various public policy alternatives to address these issues. Michigan State University Extension is part of the study team and when enough facts are known for the community to take action, MSU Extension Educators will assist them in defining possible solutions.