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Lake Response Model: Phosphorus and water loading cstimates 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., I994) 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 browing seasan (May-September) in-lake <br />tatal phosphorus concentrations. The group of lakes models used is representative of a cross- <br />section of nnany jake types and characteristics and published extensively in lake mana�ement <br />literature. <br />The measured �'owing season mean phosphorus level along with lake morghometry and <br />watershed loadin�s was used as an input to the WiLMS model. These data are used to run all of <br />the lake response modeis. The in-lake total phosphorus concentrations predicted by each lake <br />response mode are then compared to actual monitoring data frozrt the receiving water_ The madel <br />that provides the best rnatch to the actual monitored in-lake total phosphorus concentration is <br />usually selected as the one, which bcst represents system conditions. <br />Among several candidate modcls, the Rechow, 1979 general model fit the measured data best, <br />estimating a P concentration of 74 ua/1 for a normal year precipitation of 28 inches. Using the <br />same model, hypothetical chan�es in phosphorus concentrations resultin� frorr► percent reduction <br />in phosphorus loadings were caJculated. It was found that in order to drop the total phosphorus <br />concentration to 67 ug/l, to brin� it up to category C in the lake water quality report card, a <br />reduction of about 8-l0�lo in phosphorus loadin� would need to be achieved. <br />What the Inforrnation Tells Us Abotit Langton Lake <br />The most significant findings re;arding Langton Lake and its watershed are as follows: <br />• LanQton 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 ciarity. Major positive inF�uences on the lake's <br />condition include the relatively small watershed of the lake and the treatment benefits <br />of the detention basin servin; the industrial portion of the �vatershcd. <br />City of Roseville 4� <br />ParAs Natiiral Resoi�rce rYlnnagerne►it <br />