Developed by:

Jane HerbertMichigan State UniversityKellogg Biological Station andExtension Land & Water Unit

Dr. Paul SeelbachMichigan Department of Natural ResourcesInstitute for Fisheries Research

Introduction

In 2008, the Michigan Legislature enacted historicnew laws to manage large quantity water withdrawalsusing hydrologic and ecological sciences as theframework for policy development. Implementationof these state laws largely fulfills Michigan’scommitment, under the new Great Lakes—St.Lawrence River Basin Water Resources Compact(signed in 2008), to responsibly manage the abundantwaters and water-dependent natural resources of theGreat Lakes region. The compact contains thefollowing important principles:• The term waters means the Great Lakes and allstreams, rivers, lakes, connecting channels and otherbodies of water, including tributary groundwater,within the basin.• Surface waters and groundwater function togetheras one common hydrologic system.• Society’s goal is a wise balancing of waterresources among varied human users and the needsof aquatic ecosystems.• Adaptive use of the best available sciences mustunderpin management programs.

This document answers some common backgroundquestions about Michigan’s new water laws tomanage large quantity withdrawals and the newWater Withdrawal Assessment Process.

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What is the Water Withdrawal Assessment Process?It is an assessment of the ecological impacts of aproposed large quantity water withdrawal on nearbystreams and rivers. As stated in Public Act 179 of2008, “Large quantity withdrawal” means 1 or morecumulative total withdrawals of over 100,000 gallonsof water per day average in any consecutive 30-dayperiod that supply a common distribution system.The process was developed in 2006 by a statewideGroundwater Conservation Advisory Council1 and theMichigan Legislature. It is science-based and, as such,is subject to improvements as more data becomeavailable. It takes into consideration the relationshipsbetween groundwater withdrawals, nearby streamflow and fish populations. It determines thelikelihood of a withdrawal causing a serious impact ona nearby stream or river and it provides guidancetowards minimizing the impact. For a detailedexplanation of the deliberations and development ofthe Water Withdrawal Assessment Process, pleaserefer to the Council’s final report2 .

How does this process determine how much water isavailable? The process first determines the level offlow necessary to protect stream and riverecosystems and the fishes that inhabit them. It thenassesses the impact of proposed large quantitywithdrawals. The process operates at two levels: anInternet-based, screening-level tool and/or a moredetailed site review by Michigan Department ofEnvironmental Quality (MDEQ) staff. If the estimatedimpact of a proposed water withdrawal is minimal, aperson may register the use and proceed to developit. Starting July 9, 2009, all proposed large quantitywithdrawals must use the screening level tool (orcomplete a site specific review) before registering ause. The free screening level tool is available onlineat www.miwwat.org.

C onsidering aquatic ecosystems:The basis for Michigan’s new WaterWithdrawal Assessment Process

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Do these new laws change my riparian rights? No,the Riparian Doctrine of reasonable use is still thebasis for Michigan water law. Every Michiganlandowner has a qualified (not absolute) right to thereasonable use of the water adjacent to or under hisor her property. A landowner may defend this rightthrough the court system.

Impacts of groundwater wells onnearby river and stream flows

Previous (2006) Michigan water withdrawallegislation provided a rebuttable presumption3 thatwells deeper than 150 feet or farther than one-quarter mile from streams or rivers did not cause anadverse impact on the aquatic ecosystem. However,in practice, the impact of wells on nearby streamsand rivers is more complex than these interim rulesimplied. Pumping rate and duration, well depth,aquifer characteristics and other landscape featuresdetermine the impact on nearby streams and rivers.The 2008 legislation addresses these concerns.

How will the Water Withdrawal Assessment Processhelp determine impacts? The online screening toolincorporates generalized modeling principles ofpumping well behavior using statewide data. Itconsiders well depth, aquifer characteristics, distancefrom nearby streams, and pumping rate andfrequency to estimate stream-aquifer interactions. Itdistributes the estimated impacts of well pumpingamong neighboring streams based on distance.Closer streams may have more water depletion,distant streams less depletion. The more detailed sitereview by MDEQ staff follows similar steps but usesmore specific and localized hydrologic data.

Do groundwater aquifer characteristics and suppliesdiffer across Michigan? Yes. Groundwater may bestored in bedrock aquifers or in overlying “glacialdrift” aquifers. Drift aquifers are composed primarilyof sand and gravel deposits left by the glaciers. Bothtypes of aquifers can vary greatly in actual depth andcapacity to store and transmit water.

How are these aquifer variations reflected in thescreening tool? The geography of these aquifers hasbeen mapped, but not in detail. Estimates of aquifercharacteristics and depths were obtained from theMichigan Groundwater Inventory and Map Project,located at http://gwmap.rsgis.msu.edu.

Streams and index flows

One goal of the Water Withdrawal AssessmentProcess is to maintain current flow regimes fordifferent types of streams and rivers across Michigan.An important element of the process is attention tosummer low flows. The median stream flow for thesummer low-flow month is called the index flow. Thismedian value means that during the low-flow month,half the time stream flow is less than the index flowand half the time it is more. It represents the centerof the range of natural low flows typicallyexperienced by fish populations in that particularstream or river. Index flows are calculated for about7,000 stream and river segments across Michigan andare incorporated into the screening tool as referencepoints for current flow conditions.

Why use the summer low-flow month as the indexflow? The main component of stream flow duringthe summer low-flow month is groundwater.Summer is the season of lower precipitation, higherevapotranspiration and less runoff directly tostreams. Late summer is a naturally stressful time forfish populations, as streams and rivers are shallowand experience their highest temperatures andlowest dissolved oxygen levels. In short, the summerlow-flow month is often the worst case habitatscenario for fish populations. It can be a limitingperiod for resident fish communities, as well as forother riverine animals and plants. Therefore, theindex flow is a sensitive measure of possible effects ofwater withdrawals. In Michigan the summer low-flowmonth is almost always August or September.

U.S. Geological Survey stream gaging stations arenot present on every stream. How is the index flowestimated for streams without gaging stations?There are 147 gaged stream segments in Michiganthat have at least 10 years of record (although notalways the most recent 10 years). However, there are7,000 stream and river segments incorporated intothe screening tool. To estimate flow for the ungagedstream and river segments, a statistical model usingwatershed characteristics such as geology, soils,drainage area, land cover and precipitation, has beenbuilt to reproduce the range of index flows observedacross the selected 147 gaged stream segments.These same watershed characteristics have beenmapped for the remaining ungaged segments andthese data are fed into the statistical model toproduce estimates of index flows for ungaged stream

and river segments. Existing withdrawals are takeninto account to the extent that they are reflected inthe data from the 147 gaged streams.

Are surface water withdrawals also assessed? Yes. Alarge quantity surface water withdrawal from a riveror stream has greater potential for impact because itis a direct gallon-for-gallon reduction of the indexflow. Pumping from a groundwater aquifer typicallyhas less impact than pumping from surface water,depending on distance from the stream, depth of thewell and aquifer characteristics.

Can the screening tool assess the impact ofwithdrawals on lakes and wetlands? No, not directly.The screening tool assesses the late summer waterbudget for the entire area drained by each particularriver segment, but it does not provide assessmentsfor specific lakes and wetlands. One charge to thenew Water Resources Conservation Advisory Councilis to examine whether and how the definition ofAdverse Resource Impact (defined below) should bemodified to address potential impacts to inland lakesand other aquatic systems.

Stream flows and fish populations

The term Adverse Resource Impact (ARI) is themaximum allowable reduction in index flow based onthe impacts to a stream’s characteristic fishpopulation. This standard applies to all Michiganstreams and rivers, based on classification of habitattype. In other words, different types of streams andrivers can sustain different amounts of index flowreduction before an ARI occurs.

Why were fishes used as the environmentalindicators of ARI in streams? Stream and riverecosystems are made up of physical, chemical andbiological components, some of which are suitable asindicators of stream health. Fishes are commonlyused because they are high on the food web and thusconsidered integrators of habitat and food webqualities.

What is a characteristic fish population? The speciesof fish that are expected to occur in better thanaverage numbers in a certain habitat type of streamor river. To determine characteristic fish populations,

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Figure 1. Distribution of Michigan’s11 stream and river habitat types.

Source: Zorn, T.G., P.W. Seelbach, E.S. Rutherford, T.C. Wills, S. Cheng, and M.J. Wiley. 2008. A regional-scale habitat suitability model to assess the

effects of flow reduction on fish assemblages in Michigan streams. Michigan Department of Natural Resources, Fisheries Research Report, Ann Arbor.

Figure 1. Distribution of Michigan’sFigure 1. Distribution of Michigan’s11 stream and river habitat types.11 stream and river habitat types.

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1 Michigan’s 2008 water use legislation includes Public Acts 179 through 190. Public Act 189 establishes a newWater Resources Conservation Advisory Council to oversee implementation of the new laws.

2 Final Report to the Michigan Legislature, in response to Public Act 148 of 2003 (February 2006) available on-lineat www.michigan.gov/wrcac.

3 A rebuttable presumption, in this context, is defined as a legal assumption that can be contested by apreponderance of scientific evidence.

the screening tool uses Michigan Department ofNatural Resources (MDNR) fish survey data collectedat more than 1,700 survey sites across Michigan from1980 to 2005. These data were summarized toprovide a statistical description of each species’habitat needs in terms of stream catchment area,index flow and summer water temperatures.

How do I find the habitat type of a stream or river?Michigan’s streams and rivers have been classifiedinto 11 habitat types according to watershed size,characteristic fish populations and summer meanwater temperature. Using this system, each of the7,000 stream and river segments have been classifiedand mapped (Figure 1). Information on a specificstream or river habitat type may be found within thescreening tool on the Water Withdrawal AssessmentProcess web site.

Are characteristic fish populations to be expected,even in a channelized county drain or a man-madeirrigation ditch? Yes. Altered streams and ditches aresurveyed on a regular basis by MDNR fishery surveys.Many altered systems support diverse and abundantfish populations.

Are these water bodies included in the assessmentprocess? Yes. Natural streams, modified streams andman-made ditches are all included. Some Michiganstreams and rivers have naturally small index flows.These water bodies may not appear to flow duringthe driest periods of the year, but are still consideredto be permanently flowing.

How do I find the characteristic fish population for awatershed of interest? Information on thecharacteristic fishes that are common to each of the11 habitat types may be found in the online screeningtool. However, the actual fish populations in any onestream segment may vary.

What is a fish response curve and how is it used inthe assessment process? A fish response curvepredicts the response of a characteristic fish

population to decreasing index flows due to waterwithdrawals. Fish curves are generated using thestatistical habitat information described above andare incorporated into the model. They are used indetermining risk of creating an ARI due to a proposedwater withdrawal. The tool uses 11 fish responsecurves – one for each of the 11 habitat types depictedin Figure 1.

The online assessment tool expresses risk of ARIwith four zones — A through D. How do these zonesrelate to a proposed large quantity withdrawal? AllMichigan streams and rivers are classified by size andwater temperature. Each stream type has differentcharacteristic fish populations that responddifferently to the loss of water. For each type, amaximum amount of water can be withdrawn beforean ARI occurs. When using the online assessmenttool, the risk of ARI is marked by Zones A through D.Zone A (green) has little risk of causing an adverseresource impact, while Zone D (red) means anadverse resource impact will occur. Zones B and C liebetween these extremes, indicating increasing risk.The tool advises the user what zone his/her proposedwithdrawal falls into and provides instruction on nextsteps.

Do these risk zones allow a percentage loss of fishpopulations? Yes. Human water uses are balancedagainst aquatic ecosystem uses. However, the tool isdesigned to prevent substantial damage to theecological integrity of Michigan’s streams and riversand to increase awareness, caution, conservationpractices and protection as the risk of ARI increases.

Where can I find more information about Michigan’snew Water Withdrawal Assessment Process? Moreinformation may be found on the MichiganDepartment of Natural Resources Web page atwww.michigan.gov/wrcac.