Prior Lake - Spring Lake Watershed District 2009 Water Quality ...

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focused entirely on capturing water quality data from streams so that potential sources ofpollution could be identified.With only one year of data, it is difficult to make conclusive statements on the state of streamwater quality in the PLSLWD. As more data are collected, conclusions that are more accuratewill be drawn. Generally speaking, the data collected in 2009 appears to suggest that waterquality is relatively good. This could be due to the very dry spring and summer, which resultedin minimal run‐off and clear streams. It is too soon to determine whether the streams arenormally clear during this time of year. Large late summer and fall rain events brought adifferent view of water quality. While some streams remained clear, others showed significantchanges in water quality. As turbidity values passed 1000 FNU’s and dissolved oxygen nearedzero mg/L, potential problem areas were more clearly identified.III. Method of StudySince a program to establish Total Maximum Daily Loads (TMDLs 1 ) had already begun, thePLSLWD needed to gather as much data about the watershed as possible in a relatively shortamount of time. In order to have quality data upon which the TMDL program could rely, thePLSLWD prepared a comprehensive monitoring plan that provided detail regarding siteselection, types of monitoring, sampling parameters, flow and precipitation data, samplefrequency, and quality assurance/quality control. The following provides a brief description ofeach of these program components.a. Site Selection:Initially, nearly all accessible road/stream intersectionswere identified as the monitoring sites. Several siteswere determined too dangerous for safe parking,however, and were thus removed from consideration,leaving a total of thirty‐four locations that wereultimately monitored in 2009. The thirty four sites weregrouped into three categories, including: Lake Input,Upper Watershed, and Prior Lake Outlet Channel (PLOC).The “Lake Input” group consisted of twelve sites (redpoints on figure 2). Flow from these sites dischargedirectly into Spring, Upper Prior, or Lower Prior Lakes.Figure 2 ‐ Synoptic Monitoring Locations1 A Total Maximum Daily Load, or TMDL, is both a study and a calculation. The calculation is based on themaximum amount of a pollutant that a waterbody can receive and still safely meet water quality standards. Thestudy determines what needs to be done in the watershed in order for the stream to reach that standard(http://www.epa.gov/OWOW/tmdl).Page 2 of 15
The “Upper Watershed” consisted of fourteen sites (green points on figure 2). The UpperWatershed is in the southern section of the PLSLWD, and though the stream segments here donot directly discharge, their flow does eventually reach the lakes. Eight sites were chosen alongthe PLOC (yellow points on figure 2). The Lake Input and PLOC sites are located in areas thatare predominantly urbanized, compared to the Upper Watershed which is primarily rural andagricultural land uses. See Appendix 1 for detailed site descriptions and locations.b. Monitoring StudiesMonitoring equipment was leased from the Scott Watershed Management Organization(WMO). Two types of monitoring studies were conducted based on the objectives of thePLSLWD and the capabilities and limitations of the available equipment. These types includeddeployment monitoring and synoptic monitoring.Deployment monitoring consisted of monitoring a stream site for an extended period of timeusing a Hydrolab MS5 Multi‐parameter Sonde (sonde). A sonde is a portable monitoring deviceused to record water quality instantaneously or continuously in awaterbody (figure 3). For the deployment monitoring study,sondes were anchored into the stream and recorded datacontinuously in 15‐minute intervals for up to two weeks at a time.Parameters monitored in the PLSLWD included specificconductance, temperature, turbidity, and dissolved oxygen.Often two sondes were deployed simultaneously to compare twodifferent sites along the same stream, but were also occasionallyplaced in different streams. For example, during one storm event,a sonde was placed upstream and another was placedFigure 3 ‐ Sondedownstream of Buck Lake to determine what, if any, water qualitychanges could be attributed to it flowing through the lake (figures 4 & 5). The deploymentstudies were also useful for examining natural daily fluctuations in dissolved oxygen. Becausedissolved oxygen is lowest before sunrise, it would be very difficult to capture the lowest dailyvalues without deploying the sondes. Refer to Appendix 4 for all deployment monitoring resultsand figures.Page 3 of 15
Page 1 and 2: Prior Lake ‐ Spring Lake Watershe
Page 3: I. IntroductionThe Prior Lake ‐ S
Page 7 and 8: SSWCD staff worked collaboratively
Page 9: IV. Resultsa. IntroductionWater qua
Page 12 and 13: Figure 6 - 2009 Maximum Turbidity V
Page 14 and 15: Figure 7 - Red points indicate that
Page 16 and 17: Figure 8 - Red points indicate that
Page 18 and 19: Appendix 1 ‐ Synoptic Site Locati
Page 24 and 25: Appendix 2: Synoptic Data ‐ Sorte
Page 36 and 37: Site # & DateSampledAppendix 3: Syn
Page 48 and 49: Appendix 4 - Synoptic Graphs and Fi
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Appendix 4 - Synoptic Graphs and Fi
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Appendix 5 ‐ Deployment Data 2009
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