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2002 Natural Resources Management
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2002 Natural Resources Management
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7/13/2012 10:46:09 AM
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The emergent population is dominated by cattails, though some small pockets <br />of arrowhead and bulrush were noted near the fishing pier. <br />Large water level fluctuations appear to have played a major role in limiting the <br />development of a diverse native emergent community. This is not unexpected, since <br />Bennett Lake has served an important stormwater management function for over 750 <br />acres of the City. <br />It is unclear how the aquatic vegetation community has changed over time. Clearly, historically <br />high nutrient loadings and water level fluctuations have created a very resistant aquatic <br />vegetation community dominated by a few aggressive species. <br />Sediment Assessment <br />Samples of lake sediment were also taken to attempt to gain a preliminary indication of the <br />degree of enrichment of the sediments within Bennett Lake. As mentioned earlier in this report, <br />the degree of lake sediment enrichment can be important, especially in shallow lakes, because <br />the condition of the lake can be affected both by the phosphorus carried via runoff into the lake <br />from the watershed as well as by the phosphorus released by the sediments within the lake. <br />Lakes that have received large loadings of phosphorus over a long period of time tend to have <br />much more enriched sediments than those that have not. <br />Sediment samples were taken at the locations shown in Figure 5.2. The maximum depth of <br />sediment sampling was approximately 5 feet because of limitations of the sampling equipment. <br />Approximately the top 2 inches of sediment were sampled, since this is roughly the profile <br />identified as contributing the bulk of recyclable phosphorus in many lakes. Somewhat <br />surprisingly, the sediments sampled generated results that suggested the potential in -lake pool of <br />mobile phosphorus is relatively small, equal to about 25% of the estimated loads contributed by <br />the watershed. There are two likely reasons for this. First, the estimated watershed load is high <br />because of the large amount of developed land discharging stormwater to the lake. Second, the <br />deeper sediments in the lake are usually the most enriched but were not sampled effectively <br />because of equipment limitations. <br />City of Roseville 52 <br />Parks Natural Resource Management <br />
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