Confluence: Pooling Resources to Monitor and Model the Lower Minnesota River

A partnership of federal, state, and local agencies developed a water-quality model of the lower 40 miles of the Minnesota River. The lower Minnesota River lies at the juncture of two contrasting landscapes: a predominantly agricultural watershed to the west and an expanding metropolitan area to the east. The reach is listed as impaired for not meeting water-quality standards for dissolved oxygen, turbidity, bacteria, PCBs, and mercury. Excessive nutrients and sediment are also concerns. The lower Minnesota River receives pollutant loads from point sources, including two major wastewater treatment facilities, and nonpoint sources, such as runoff from rural and urban areas. A water-quality model was needed for facility and watershed planning. The partners chose the CE-QUAL-W2 model and designed a three-year monitoring program to support the model. Long-term monitoring programs for the river, tributaries, and discharges were enhanced to fulfill data requirements of the CE-QUAL-W2 model. More intensive monitoring was added at low river flows during summer to capture water quality under critical conditions. Special field studies were implemented to guide decisions and support model inputs. These included extensive work on oxygen and phosphorus dynamics. The project demonstrates the benefits of designing a multi-year monitoring program to support a specific model framework.