Mead Lake 2013 TMDL Implementation Evaluation Monitoring - WCR_05_CMP14


Mead Lake is an eutrophic impoundment in Clark County and in 2008 a TMDL was completed and approved for the lake. The goal of the TMDL was to reduce total phosphorus (TP) loading by ~4500 lbs/year or a 35% reduction. Clark County has been implementing BMPs for the past several years and has achieved substantial reduction in TP loading to Mead Lake from the watershed (based on model results). Clark County LCD has installed BMPs in the headwaters of the watershed to reduce barnyard and feedlot runoff from a very large operation. The County has also installed BMPs in other parts of the watershed and is planning to work with three additional operations this summer. These operations are located in relatively close proximity of each other and provides an opportunity to monitor site specific improvements as well as overall watershed improvement. However, there are concerns that new additional sources of TP are occurring in the watershed. Substantial acreage has been converted from protected land use such as woodland, wetland and fallow fields to cropland. These additional sources were not accounted for in the TMDL and may offset the gains in TP reduction implemented by Clark County. Staff in Western District would like to obtain funding to evaluate loading from the watershed and water quality conditions in the South Fork Eau Claire River and Mead Lake. Monitoring results will be used to determine if existing BMP implementation has improved water quality conditions and will provide a bench mark or baseline to evaluate proposed BMP installation. Results may also be useful in assessing new TP sources in the watershed and may be useful in determining if additional loading reductions are needed to improve water quality.


The overall goal of this project is to evaluate the success of the Mead Lake TMDL and determine if additional TP load reductions are needed from the watershed. There are multiple objectives of this project. 1) Data collected will be used to determine if the installation of BMPs have reduced TP loading from the watershed and if water quality conditions improved in Mead Lake. The data will help evaluate the accuracy of the TP load reduction goal developed in the 2008 TMDL. The information may help in assessing new TP sources in the watershed. 2) Data collected will provide a baseline to document current water quality conditions and will allow for a comparison following additional BMP installation. This study will allow for an overall watershed and a site specific evaluation.


Water chemistry samples will be collected from two sites in Mead Lake. TP, chlorophyll, secchi readings and dissolved oxygen and temperature profiles will be collected biweekly from May through October. A total of 22 sampling events are planned. Eight in lake water chemistry samples will be collected in FY14 and 14 samples will be collected in FY 15. Load monitoring will start in May and continue through calendar year 2013. Monitoring is planned to continue into calendar year 2014. TP, SS and streamflow will be collected bi-weekly for a total of 16 sampling events. Streamflow will be collected more frequently to establish a stage discharge relationship with the pressure transducer. Macroinvertebrate samples collected in 2013 will be resurveyed at three sites on the South Fork Eau Claire in fall of 2014 to document if community changes occurred as a result of BMP installation. A final report will not be completed until Post monitoring data is collected at a later date.

Study Design

This study will include two components. 1) Assess water quality of Mead Lake 2) Asess TP loading from the South Fork Eau Claire River Watershed to Mead Lake and Assess Water Quality of Mead Lake - Department staff will monitor in water quality conditions in Mead Lake. Monitoring will include collecting TP, chlor and secchi readings from two inlake sites biweekly from May through October. Vertical profiles of water chemistry parameters (dissolved oxygen, temperature, conductivity and pH) will be collected during each visit. Department staff will also train citizen volunteers to collect self help data. Self help monitoring will continue beyond this study and will be used to monitor changes in lake water quality. Assess TP loading from Watershed - Western District water resources staff will install a pressure transducer to be used with streamflow measurements to establish a stage discharge relationship. TP and SS data will be collected bi-weekly and used with streamflow measurements to estimate annual TP loading.

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