Scientific and Technological Tools to Implement Iowa Nutrient Reduction Strategy
New scientific tools and techniques and an improved understanding of the physical, chemical and biological processes are needed to predict nutrient mobilization, fate and transport in Iowa. It also is important to improve scientific understanding of the benefits derived from best management practices (BMPs), from individual practices through watershed-integrated approaches.
Four research projects focus on developing scientific and technological tools to aid in the implementation of the Iowa Nutrient Reduction Strategy. A science- and process-based framework using an integrated watershed approach will improve understanding of the complex nutrient management issues in Iowa, and the basis for possible solutions.
The first project will quantify the benefits of BMPs and land management practices, and associated hydrology on nutrient loading to water resources using hydrodynamic modeling tools. Modeling will be used to quantify the prediction of nitrogen reductions. The second project will quantify the benefits of BMPs and land management practices, and associated hydrology on sediment and phosphorus loading based on field observations. The third project will further refine a web-based database, called the Water Quality Information System, developed in 2014. The fourth project involves measurement of field data parameters to support modeling, including field monitoring of nitrogen, sediment and phosphorus inputs and outputs for select BMPs installed in priority watersheds.
A total of 65 water quality sensors are being deployed this spring. In addition, turbidity sensors are being deployed at 10 new sites with equipment purchases funded by Iowa Department of Natural Resources. These sensors will help quantify statewide stream phosphorus loading using turbidity as a surrogate. This will provide an inexpensive way to quantify phosphorus loading, which ordinarily would require frequent sample collection and lab analysis. Five are deployed in Mississippi River tributaries and five in Missouri River tributaries.
Water quality sensors were retrieved beginning in October. During the winter months, field staff conduct equipment maintenance, calibration and data quality review, and some sensors are returned to the manufacturer for routine maintenance. Redeployment of sensors at about 70 sites will begin around March 2018, depending on weather and ice conditions. These sites include urban and rural locations, where sensors assess both point and nonpoint sources.
The IIHR sensor network includes water quality sensors deployed at nearly 80 sites. Recent enhancements of the system include instrumentation deployed in Iowa Watershed Approach watersheds. In addition to these new sites, a dissolved phosphorus sensor has been deployed in the English River at Kalona. Provisions have been made to deploy additional phosphorous sensors on the South Fork of the Iowa River at Kalona and the Big Spring Fish Hatchery at Elkader. Infrastructure is being installed for 2018 sensor deployments at the Geisler Farm in Calhoun County where an INRC-funded research project will begin in early 2018. Infrastructure also is being installed for a project being conducted in collaboration with Iowa DNR. At these sites, turbidimeters will be installed in six Mississippi River tributaries and four Missouri River tributaries to test the idea that turbidity data will act as a proxy for both sediment and phosphorus transport. This will provide a mechanism to inexpensively quantify phosphorus loading, which ordinarily would require frequent sample collection and lab analysis.
Monitoring of the Slough Creek CREP wetland is ongoing. This quarter, the wetland was drawn down to help establish vegetation, which presented an opportunity to conduct water monitoring in a low-pool condition for the first time. As the wetland refills, water quality data from the sensor deployments should provide information on the role of macrophytic plants in nutrient sequestration. In another project, to support the modeling in the Iowa Watershed Approach project, water quality data collected in Clear Creek is being analyzed to estimate tile drainage contribution to both streamflow and nitrogen load at the watershed scale. These findings will be used to improve tile drainage representation in the watershed models used by IIHR. The 2016 IIHR water monitoring report is online at http://iwqis.iowawis.org/assets/monitoring-report-2016.pdf. The 2015 report also is available at the same page.
Work continues to monitor the Slough Creek CREP wetland for nitrate, dissolved oxygen, temperature and conductivity. The two water quality sensors deployed upstream and downstream of the wetland have provided continuous measurements since 2014 of incoming and outgoing NOx (nitrite + nitrate) concentrations, along with other water quality variables. A coupled hydrologic and water quality model that was built to simulate and evaluate the nutrient removal dynamics of an Iowa wetland under variable hydrologic conditions shows nitrogen load reductions of 57 percent (2014), 59 percent (2015) and 21 percent (2016), for a three-year average of 46 percent. In another project, recent work derived a new way to estimate phosphorus concentrations without expensive lab testing for total phosphorus. By using turbidity, o-phosphorus and stream discharge, total phosphorus loads are accurately estimated. These three parameters can be remotely and continuously monitored using sensor technology. To this end, two real-time ortho-phosphorus measurement devices were deployed on the Iowa River near New Providence, and the English River at Kalona. In addition, one unit is deployed at the Cedar Rapids Wastewater Treatment Plant and one will be deployed at the groundwater spring at the DNR Fish Hatchery near Manchester. These new deployments of continuous sensors will add to existing information about phosphorus loss in Iowa.
Several projects continue. One deals with phosphorus loads, which usually are linked to mobilization of sediment to waterways. Recent work indicates that in some parts of Iowa, phosphorus loading also may be closely linked to drainage hydrology and baseflow. A new project builds on earlier work conducted in the Turkey River watershed by using focused and high frequency monitoring to delineate the phosphorus load between dissolved and particulate forms. This project will be conducted in both heavily tile drained watersheds (i.e. Des Moines Lobe) and in southern Iowa streams (Southern Iowa Drift Plain) to evaluate how phosphorus delivery mechanisms vary across Iowa. Traditional event sampling equipment will be used to support continuous monitoring. Monitoring devices will be deployed in the spring as soon as weather and stream conditions allow.
During the last quarter, a coupled hydrologic and water quality model was built to simulate and evaluate the nutrient removal dynamics of an Iowa wetland under variable hydrologic conditions. The Slough Creek CREP wetland in north central Iowa was selected for this analysis, because it is well instrumented and drains primarily agricultural, tile-drained land characteristic of much of Iowa. Two IIHR water quality sensors deployed upstream and downstream of the wetland have provided continuous measurements of incoming and outgoing nitrite + nitrate concentrations, along with other water quality variables, dating back to 2014. Hydrologic and water quality simulations of the Slough Creek wetland were performed with commercially available modeling software. Overall, simulated and measured nitrite + nitrate concentrations downstream of the wetland compared well.
Several projects are underway. For one project, the main objective is to characterize nitrate-nitrogen flux in Iowa streams. This data has a variety of uses vital to the success of the Iowa Nutrient Reduction Strategy. Most important is documenting water quality improvements as a result of voluntary practice implementation by Iowa farmers. The Iowa Water Quality Information System (IWQIS) website now reports nitrate-N concentrations and loads from continuous sensors located at more than 50 sites across Iowa. Sensors in 14 of the largest streams capture N loads from approximately 82% of the state’s area. Continuous monitoring is being used to quantify nitrate load reductions associated with a CREP wetland and document changes over time. In another instance, continuous nitrate-N sensor data is being used to quantify nitrate reductions associated with in-stream processes. The Iowa Water Quality Information System online tool is available at http://iwqis.iowawis.org.
Several projects are underway. In one, trends in the available nitrogen data from the Iowa Department of Natural Resource’s ambient water quality program, called STORET, are being studied. Nutrient grab samples are collected at stream monitoring sites throughout the state monthly, with 63 of the STORET sites evaluated in this study. Detailed analysis will be used to document trends in the daily nitrogen load and yield. Some analyses will look at impacts from percent row crop of corn and soybean, estimated annual runoff coefficients, soil type, land use and landform region. In another project, the Iowa Water Quality Information System online tool available at http://iwqis.iowawis.org has continued to improve and evolve. As redeployment of continuing field sensor sites and installation of new sensor sites has progressed during the spring 2016 season, the statewide distribution of water quality data sites has expanded significantly, allowing the public to access the extensive network of data collected by the IIHR Water Quality Network.
Four projects are underway. Modeling tools are being used in the Upper Roberts Creek watershed to study the potential impacts on watershed nitrogen loads if there was widespread use of cover crops, and nitrate removal wetlands were constructed. In another project, researchers are analyzing soil samples to estimate the total phosphorus concentration in soils at the floodplains, streambed and banks of the Turkey River. This is helping to identify where the greatest amount of erosion is occurring. In the third project, the Iowa Water Quality Information System online tool is available at http://iwqis.iowawis.org. It offers access to real-time nutrient data with a range of water-related information such as precipitation, stream flow and soil moisture. Improvements to the system are ongoing. The Iowa Institute of Hydraulic Research network of 26 water quality stations was fully deployed for the 2015 water season. Planning has begun to site an additional 15 water quality monitoring stations for the 2016 water season. Coverage will include all of Iowa’s major rivers.