2002 Natural Resources Management

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The relatively low water quality grades for Bennett and Langton lakes are not unusual in an urban environment. Shallow lakes (i.e., those with mean depths of less than 10 feet) like Bennett Lake and Langton Lake are extremely productive environments, meaning that even under pristine conditions they are rich in aquatic vegetation. The main reason for this is sunlight can penetrate to the bottom almost anywhere in the lake at adequate intensities to support both vegetation rooted to the lake sediments well as other types of plants like algae that float in the water column. In addition, nutrients washed into the lake from the surrounding watershed — whether held in the lake sediments or suspended in the water column — are available to support plant growth. In contrast, deeper lakes often have a significant portion of the lake bottom that does not receive enough sunlight to support plant growth. Also, the deep portion of a lake is separated from the upper shallow portions of a lake for much of the growing season through a process known as thermal "stratification ". With the warmer water layer on top and cooler layer on the bottom, relatively little water is exchanged between the two layers for most of the recreation season. The deeper portion of these types of lakes can act as "storage" for excess nutrients, holding high concentrations in areas of the lake that are too deep to allow the light intensities necessary to support algae growth. Each of the two lakes is described in detail below in terms of its basin and watershed characteristics as well as its ecology, use and quality. LANGTON LAKE Lake and Watershed Overview Figure 5.1 shows the location of Langton Lake and the approximate bounds of its watershed. Langton Lake occupies a total surface area of 23 acres. Average depth of the lake is around 3 feet, while the maximum depth is around 5 feet. City of Roseville 38 Parks Natural Resource Management