Watershed Scaling Effects Measured Via Nested High Frequency Sensors

Issue

Measurement of nutrient concentrations in Iowa surface waters has informed ongoing efforts to reduce nutrient loading through the Iowa Nutrient Reduction strategy.  However, much of that monitoring takes place near the outlet of a watershed. While this strategy allows comparisons of watersheds and assessments of changes in concentrations over time, it does not allow for insights into the dynamics of nutrient processing within the watershed. 

Objective

The work proposed involves placement of in situ water quality instrumentation near the mouth, in the middle and in the headwaters of several Iowa watersheds.  These sets of instruments will allow scientists to assess how nutrients react within the watershed, and, in combination with flow measurements, determine where nutrients originate. In addition, the high time resolution of these instruments will allow study of the impact of extreme precipitation events on nutrient and sediment movement.

Approach

This grant will also support development of a method combining the use of the in situ nitrate sensors with a USGS statistical model to provide a standard method of calculating annual nutrient and sediment loads for the state. Different forms of nutrients (nitrate, ammonia, organic nitrogen, orthophosphate and particulate phosphorus) will be included in the output.