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Water Quality Monitoring

Regular monitoring of the water quality of Rice Lake is done on a monthly basis from early spring through late fall each year.  The water monitoring is done by a group of RLA members and the North Fork Crow River Watershed District at two sites on the lake. 


Water temperature, water clarity (Secchi disk reading), pH, conductivity and dissolved oxygen along with a water sample are collected at each location each month.  The water sample is sent to the RMB Environmental Laboratories for analysis to determine chlorophyll A, phosphorus and total suspended solid material. 


Water quality monitoring continues monthly from May through October. The tables and graphs below show the results of water sampling over the years.

Trophic State Index Average

Phosphorus, Chlorophyll-a (algae concentration) and Secchi depth are related. When phosphorus increases, more food is available for algae, so algal concentrations increase. When algal concentrations increase, the water becomes less transparent and the Secchi depth decreases.


The resulting numbers from these three measurements cover different units and ranges and thus cannot be directly compared to each other or averaged. In order to standardize these three measurements to make them directly comparable, they are converted to a trophic state index.  The goal for Rice Lake is a TSI Average of 40 or below.  As can be seen by the chart below the TSI seems to slowly be improving but we have a ways to go. The assessment of water quality trends by the MN DNR shows the trend is improving water quality.


(Primary site only. For detecting trends, a minimum of 8-10 years of data with 4 or more readings per season are recommended)

Years Monitored: 2001 - 2022 
Total Phosphorus: Improving with 95% confidence. 
Chlorophyll-a: No significant trend exists. 
Secchi Depth: Improving with 90% confidence. 
Trophic State Index: Improving with 95% confidence. 

For more information about water quality monitoring and the Trophic State Index, click the button below:

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