Water Withdrawal Assessment Tool can help local planning officials plan for the future: Part 1

Michigan’s Water Withdrawal Assessment tool screens large quantity water withdrawals to prevent adverse impacts to stream and river ecology. The Web-based system also provides valuable information that planners can use to prevent water availability issues.

Michigan is water rich with abundant surface water and groundwater for recreation, drinking, industry and agriculture. Even in the midst of plentiful supplies, there are parts of the state where increasing competition for water, especially groundwater, is currently or will in the future make it harder to extract those resources without impacting other users and the environment.

The web-based Michigan Water Withdrawal Assessment Tool (WWAT) is one resource local planners can use to assess their current situation and future vulnerability.

To understand the tool and how it can be useful to planners, a little history is in order. In 2005, leaders in the Great Lakes states agreed to a formal compact prohibiting most new or increased diversions (moving water outside of the Great Lakes basin) and responsibly managing the water resources within it. As part of that agreement, each state agreed to regulate large-quantity withdrawals, those using 100,000 gallons or greater per day (a pumping capacity of 70 gallons per minute or more).  Large-quantity withdrawals are typically related to agricultural irrigation, industrial and public water supply uses. The compact was ratified in Michigan by passage of Public Act 190 of 2008 (MCL 324.32701).

Under the Michigan law, all new or increased large quantity withdrawals are prohibited from causing an Adverse Resource Impact (ARI).  In simple terms, an ARI is defined as causing harm to a local river or stream ecosystem by overly decreasing its flow during the low-flow period (usually August). Groundwater and surface water are interconnected, so large water wells can cause an ARI in addition to direct withdrawals from lakes and streams. More than 5,300 watersheds covering the state are classified according their size and temperature class to determine the total water withdrawal available before reaching the ARI level. 

To help farmers, industries and others proposing new or increased large-quantity withdrawals, Michigan state agencies, Michigan State University Extension and the MSU Water Resources Institute developed the research-based Water Withdrawal Assessment Tool. The system allows large water users to click on the location where the withdrawal is proposed and enter basic information.  The tool then computes the potential effect on nearby streams and rivers, determining the probability of an ARI occurrence. Based on those results, the applicant may proceed (if an ARI is unlikely), or they may be subject to additional review if the tool calculates that the new withdrawal is likely to produce an ARI.

Under Michigan law, new or increased water withdrawals of 100,000 gallons per day or more must register using the withdrawal tool and apply the tool to screen for potential ARIs. Some watersheds in the state are currently near, at or exceed the ARI level, meaning that a combination of stream characteristics and cumulative water withdrawal rates may affect fish populations and ecology. All are located in agricultural areas in the Southern Lower Peninsula.

Michigan law prohibits local units of government from regulating large-quantity water withdrawals. That responsibility lies exclusively with the state.  Even so, the Water Withdrawal Assessment Tool provides excellent information that can help local governments plan future development in a way that reduces the potential for water use conflicts and impacts on rivers and streams.

Just how planners can take advantage of WWAT data is the subject of Part 2 of this article.

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