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o Geologic atlas updated in 1991 <br />o Few observation wells <br />Model Application <br />We know that MM3 has an average error of +/- 17 feet and we know the sources of the error. What <br />does this mean for the way the model is applied? <br />The Metropolitan Council recognizes the error in the model compared to the real world. This error can <br />be minimized when comparing model output to model output. Drawdown shows you the change <br />between two conditions, the starting and ending place doesn't matter as much as the difference <br />between the two conditions. <br />Table 1: Uses for "out of the box" MM3 <br />Acceptable <br />Marginally Acceptable* <br />Not Acceptable <br />Compare regional scenarios <br />General well field placement <br />Localized well field <br />optimization <br />Compare sub -regional <br />scenarios <br />Estimate groundwater/surfac <br />water connections <br />Site specific evaluations <br />Identify areas where more <br />information is needed <br />Wellhead protection plans <br />Predicting time dependant <br />water table elevations <br />Identify possible problem <br />areas <br />*The model can be used as a "back of the envelop calculation" giving the user an idea of a starting place for further analysis. <br />Calculations using Metro Model 3 <br />MM3 is currently used by the Metropolitan Council for two specific calculations: <br />1. Drawdown <br />2. Available Head <br />These two calculations are visible in the drawdown figures provided in the Master Water Supply Plan. <br />Drawdown Calculations <br />The drawdown is the difference in head between two points in time. The drawdown (Dd) is calculated <br />as the difference between the model head at 2010 pumping rates (H2010) and the model head at 2040 <br />pumping rates (H2040). The model resulting from the 2010 pumping as reported in SWUDS was <br />designated as the initial condition. This means areas with drawdown are showing an increase in <br />pumping from 2010 pumping conditions. <br />Dd = H2010 — H2040 <br />The 2040 projected drawdowns are relative to the modeled 2010 pumping as reported in DNR SWUDS. <br />This has been a point of discussion and the idea that the most people felt comfortable with is modeling <br />the 2010 pumping as reported in SWUDS to use as a baseline condition. This links the model to a <br />