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Lake Response Model: Phosphorus and water loading estimates to Langton Lake were used as <br />inputs to a lake response model (Appendix A, Table 5). Wisconsin Lake Model Spreadsheet <br />(WiLMS), (Panuska, et. al., 1994) comprises ten empirical lake models, developed using <br />monitoring data from various lakes throughout North America, Canada and Northern Europe. <br />The lake models predict either springtime or mean growing season (May - September) in -lake <br />total phosphorus concentrations. The group of lakes models used is representative of a cross- <br />section of many lake types and characteristics and published extensively in lake management <br />literature. <br />The measured growing season mean phosphorus level along with lake morphometry and <br />watershed loadings was used as an input to the WiLMS model. These data are used to run all of <br />the lake response models. The in -lake total phosphorus concentrations predicted by each lake <br />response mode are then compared to actual monitoring data from the receiving water. The model <br />that provides the best match to the actual monitored in -lake total phosphorus concentration is <br />usually selected as the one, which best represents system conditions. <br />Among several candidate models, the Rechow, 1979 general model fit the measured data best, <br />estimating a P concentration of 74 ug /l for a normal year precipitation of 28 inches. Using the <br />same model, hypothetical changes in phosphorus concentrations resulting from percent reduction <br />in phosphorus loadings were calculated. It was found that in order to drop the total phosphorus <br />concentration to 67 ug /1, to bring it up to category C in the lake water quality report card, a <br />reduction of about 8 -10% in phosphorus loading would need to be achieved. <br />What the Information Tells Us About Langton Lake <br />The most significant findings regarding Langton Lake and its watershed are as follows: <br />• Langton Lake enjoys relatively good water quality for a very shallow urban lake. <br />This is reflected by the prevalence of a diverse community of native rooted aquatic <br />vegetation and moderately good water clarity. Major positive influences on the lake's <br />City of Roseville 47 <br />Parks Natural Resource Management <br />