Data are being collected to develop a suspended sediment concentration model.
|Hydrologic Unit Code (HUC):||07120002|
|Datum:||624 feet above NAVD88|
|Drainage Area:||449 square miles|
|County in which site is located:||Newton|
|Site managed by:||Indianapolis Office|
Originating in northwestern Indiana, the Iroquois River flows for 103 miles prior to joining with the Kankakee River. This site monitors a drainage area of 449 square miles (650 sq. mi. total drainage area). The Iroquois River is a part of the Mississippi River Basin.
In Indiana, the Iroquois River has been largely channelized. The river has little relief, leading to low velocity. The Iroquois River lies in the Central Till Plain physiographic region of Indiana; the surficial geology of this region is characterized by soils consisting mainly of silty clay loam and silt loams. This site monitors a heavily agricultural area characterized by row crop farming.
The super gage, Iroquois near Foresman, deploys a multi-parameter sonde to collect continuous measurements of water temperature, specific conductance, pH, dissolved oxygen, and turbidity. An additional monitor continuously measures nitrate plus nitrite. Measurements are collected every 15 minutes and update to the web hourly. Additionally, hydrologic technicians collect water-quality samples to represent a variety of hydrologic and seasonal conditions. Samples are analyzed for concentration of suspended sediment, nitrogen, and phosphorus.
Concentrations from laboratory analysis and corresponding values from in-stream instruments are mathematically combined to develop a statistical surrogate model. Then, the model is used to compute real-time concentrations based on continuous in-stream sensor readings of another, more easily measured value. For example, turbidity is a typical in-stream measurement used as a surrogate for suspended-sediment concentration. Daily, monthly, and annual loads can be computed and compared to understand seasonal and annual variability.
The Upper Iroquois Watershed is an area of concern for many agencies and organizations. The Iroquois River Conservancy District recently performed an environmental impact review to document natural resources in the study area, and to outline potential permitting challenges associated with those resources. Several improvements to watershed resources were indicated by the review including: obstruction removal (logjams), eroded stream bank repair, two-stage ditch construction, enhancement of floodway conveyance, and upstream flood storage management. All of the recommended projects directly affect flashiness and flooding of the river and/or the amount of sediment in the water.
In 2015, the Iroquois River Conservancy District asked the USGS to install, operate, and maintain a super gage on the Iroquois River at Foresman, IN. The super gage will quantify concentrations and loads of sediment and nutrients being transported by the Iroquois River. The gage may also document water quality improvements in nutrient concentrations and loads attributable to conservation cropping and best management practices in the Iroquois River watershed.