Project Detail

2018 Lake Tomah Follow-Up Monitoring

Purpose

Lake Tomah and tributary streams have consistently high concentrations of phosphorus. Sources of TP include current NPS, legacy issues and potentially natural sources. Previous watershed and lake monitoring estimated watershed TP Loads however more watershed monitoring is needed to determine TP load contribution from baseflow versus storm events. Previous monitoring may not have accurately assessed TP loads from larger storm and runoff events due to timing issues. This study proposes to re-assess baseflow and event loads by using fixed period sampling to assess baseflow while also targeting storm and runoff events. Fixed period monthly and storm event sampling will occur at the inflow site. Camille Bruhn, the Eau Claire biologist (Chris), and field crew (Mycal, Caitlin, etc.), and volunteer monitors will collect the samples.

Objective

The objective of this project is to build upon the work previously completed on Lake Tomah and the surrounding watershed. The City of Tomah Lake Committee, the City of Tomah, and the Monroe County Land Conservation Department are active partners and have been working to solve this water quality issue for years and this project will support their efforts to decrease the phosphorus concentrations in Lake Tomah and the surrounding tributary subwatersheds. Re-assessing the TP load into Lake Tomah from the watershed is needed to 1) document loads not assessed during events in previous studies and 2) more accurately partition the baseflow and event TP load to the lake. This information will provide a better assessment of TP load controllability. This will allow for a greater understanding of how phosphorus moves into Lake Tomah from the surrounding subwatersheds. The following WBIC will be included in the sampling efforts: 1338500 (South Fork Lemonweir River).

Outcome

This project supports the efforts of the City of Tomah Lake Committee, the City of Tomah, and the Monroe County Land Conservation Department to obtain additional information on phosphorus concentrations entering Lake Tomah. Fixed period baseflow and targeted storm and runoff event loading information can be assessed by monitoring flow and phosphorus concentrations in the South Fork Lemonweir River at County Highway CM. This will lead to a better understanding of how phosphorus moves into Lake Tomah from the watershed and what can be done to reduce phosphorus loading to the lake.

Study Design

Annual TP and sediment loads will be calculated by conducting fixed period monthly sampling and event sampling using standard flow equipment and a bridge sampling device. Tape down measurements will also be collected when flow is measured. A volunteer monitor will be used to collect the monthly grab samples. If a volunteer can not be located the sampling will need to be done by Department staff. A water level sensor and an air pressure sensor will be maintained at the previous load site to connect with the previous rating curve and continue building the curve. Streamflow monitoring will be completed during both baseflow and event flows to determine the accuracy of the depth sensor deployment and continue building the curve with higher events. Baseflow and event samples will be analyzed for TP, orthophosphate, and suspended solids; ammonia, NO2 + NO3 as Nitrogen, and TN will also be analyzed at baseflow. It is anticipated that seven events will be sampled but this will be dependent on climatic conditions. Event samples may consist of grab samples more than once throughout the event while staff are at the site. Camille Bruhn, the Eau Claire biologist (Chris), the field crew (Mycal, Caitlin, etc.), and volunteer monitors will collect the samples.

Project Type

Competitive Projects

Project Sub Type

Evaluation Monitoring

Project ID

West_11_CMP18

Year Started

2018

Status

Proposed

Reports and Documents

2018 Total Phosphorus Monitoring Report - South Fork Lemonweir River - S.Fk. Lemonweir River Station #1 Bridge On Cth Cm