Mean annual discharge flow rates for tributaries of the Minnesota River vary widely (click here for a table). In the western portion of the basin, the highest mean flow occurs in the Chippewa River (315 cfs), followed by the Lac Qui Parle River (134 cfs), the Redwood River (125 cfs), the Yellow Medicine River (123 cfs), and the Pomme de Terre River (110 cfs). In the eastern portion of the basin, the highest mean flow occurs in the Blue Earth River (606 cfs), followed by the Le Sueur River (476 cfs), the Watonwan River (336 cfs), and the Cottonwood River (322 cfs). Thus, the flows entering the Minnesota River from the eastern portion of the basin (1740 cfs) are about twice the flows entering from the western portion of the basin (807 cfs).
Water quality monitoring data in the Minnesota River and its major tributaries have been collected on a nearly regular basis since the 1960's to 1970's. During a four year period beginning in 1989, the Legislative Committee for Minnesota Resources provided special funding to the Minnesota Pollution Control Agency for intensive monitoring of the Minnesota River basin.
Percent of water quality monitoring samples taken in the Minnesota River tributaries at various locations from 1968-1994 that violate water quality standards for fecal coliform bacteria, turbidity, nitrate and nitrite nitrogen, dissolved oxygenand and five day biochemical oxygen demand (BOD5). Percent of samples for total phosphorus that exceed 0.25 mg/L, the mean concentration in the river is also calculated. Data are also summarized according to the season of sampling. Seasonality effects are important, as climatic events from March to April may include snowmelt runoff and precipitation on bare soil, while events from June to July may include intensive precipitation on soil covered by a partially well developed crop canopy. In July to August period stream flows decreases. Winter months when stream flow is minimal include months from November to February. Seasonal patterns in turbidity are evident in the monitoring data. Click on a location below for a table.