Distribution, Transport, and Biogeochemical Transformations of Agriculturally Derived Nitrogen and Phosphorus in Cedar River Watershed

Date: 
Feb 2013

Issue

Nutrients in agricultural runoff are unintended exports that, along with erodible soils, get washed into lakes, ponds and rivers during large storm events or high floods. Nitrogen (N) and phosphorus (P) are the primary causes of eutrophication of surface water bodies. The Iowa Nutrient Reduction Strategy called for additional research on direct measurements of N and P loss, plus modeling to help determine ways to reduce losses. 

Objective

This comprehensive study of nutrient distribution, transport and biogeochemical transformations in the Cedar River watershed will lead to modeling of land-water relationships. There are three objectives. First, geo-hydrologic mapping of the Cedar River watershed will identify the probable “hot spots” of soil runoff N and P. Second, avenues of nutrient and sediment transport in the watershed caused by high intensity rain events and flooding will be determined. Third, biogeochemical transformation pathways of N and P will be studied and routes through which nutrients escape from the field identified.

Approach

The project will involve extensive fieldwork in the Cedar River watershed, followed by lab analysis of water and soil samples. Samples will be collected from 12 to 14 sites in the watershed every two weeks. Additional samples will be collected immediately after intense rain events. Soils from the surrounding agricultural fields also will be sampled. Based on the distribution of N and P in the watershed, nutrient mass balance will be calculated at the sub-watershed levels. Eventually, the high flux areas will be compared to the land use practices in nearby farm fields.

Project Updates

March 2016

FINAL REPORT

This project was designed to determine the total amount of nitrogen and phosphorus transported each year through the Cedar River Watershed, and the primary factors that cause nutrient release from sub-watersheds. Water and stream sediment sampling from 18 sites in the upper portion of the watershed was done in 2014. In 2015, primary water sampling was done at 10 new sites, with two on tributaries of the Cedar River and the others on the main channel. Data was gathered for total phosphorus, dissolved nitrogen, total suspended solids, total dissolved solids, turbidity and dissolved oxygen. The results show a large amount of nitrogen and phosphorus moves through the Cedar River from April through September. Because of high solubility, nitrogen gets into the watershed through all probable routes, including base flow. Phosphorus movement is linked to intense rain events. In some areas, a late-season peak in phosphorus input to the river occurs because of inadequate surface cover. All data is available online at www.uni.edu/hydrology.

December 2015

Two years of water and stream sediment sampling to provide a picture of nutrient loading in the Cedar River watershed is complete. Sampling from 18 sites in the upper portion of the watershed was done in 2014. In 2015, primary water sampling was done at 10 new sites, with two on tributaries of the Cedar River and the others on the main channel. Data was gathered for total phosphorus, dissolved nitrogen, total suspended solids, total dissolved solids, turbidity and dissolved oxygen. All data is available online at www.uni.edu/hydrology.

September 2015

Researchers continue to interpret data from the first year of water sampling from 18 sites in the Cedar River watershed. Since April of this year, primary water sampling has been done at 10 new sites, with two on tributaries of the Cedar River and the others on the main channel. Data are being gathered for nitrogen, total suspended sediments, temperature, pH, total dissolved solids, conductivity and dissolved oxygen. Analysis of phosphorus in water and stream sediment samples is underway. These two years of sampling will provide a complete picture of nutrient loading in the Cedar River watershed.

June 2015

Researchers continue to interpret data from the first year of water sampling in the Cedar River watershed, and are developing sub-watershed maps around each sampling site. The project is focused on nutrient load calculations for the sub-watersheds using GIS mapping tools. In addition, eight new sites have been chosen and will be sampled once every two weeks this summer. This new phase of sampling will help provide a more complete picture of nutrient loading in the Cedar River watershed. 

March 2015

Extensive fieldwork and water sampling in the Cedar River watershed involved 18 sites being sampled weekly from April through October for stream water and sediments. Lab analysis of those samples has been completed, with graphs developed that show total suspended solids, phosphorus and nitrogen. Researchers have been interpreting the data from this first year of sampling, and developing sub-watershed maps around each sampling site. They also have gathered published land use information for the watershed. This baseline data will be used to study nutrient loading to the Cedar River in relation to land use practices.

December 2014

One project involves extensive fieldwork and water sampling in the Cedar River watershed. For the first phase, 18 sites were sampled weekly from April through October for stream water and sediments. Thirty sets of samples have been collected and analyzed for total phosphorus, dissolved nitrogen, total dissolved solids, dissolved oxygen, total suspended solids and turbidity. This baseline data will be useful in studying the actual nutrient loading to the Cedar River during periods of high flow in relation to land-use practices.

September 2014

One project involves extensive fieldwork and water sampling in the Cedar River watershed. For the first phase, 18 sites are being sampled. These are located from Charles City to LaPorte City, covering the main channel Cedar, Little Cedar River, Shell Rock River, West Fork Cedar River, Black Hawk Creek and Wolf Creek. Sixteen sets of samples have been collected and analyzed for total phosphorus, total dissolved solids, dissolved oxygen and total suspended sediments. Analysis for nitrogen is underway. This baseline data will be useful in studying the actual nutrient loading to the Cedar River during periods of high flow in relation to land use practices.

June 2014

One project involves extensive fieldwork in the Cedar River watershed. Because the study area was covered by snow during most of this period, field activities were minimal. However, good progress was made in finalizing the base map and analyzing baseline samples collected in the fall of 2013. The study area has been divided into two parts. The northern half will be studied this year, and the southern half investigated next year. For the first phase, 18 sites have been selected for sampling. These are located from Charles City to LaPorte City, covering the main channel Cedar, Little Cedar River, Shell Rock River, West Fork Cedar River, Black Hawk Creek and Wolf Creek. Baseline samples collected last fall were analyzed for nitrogen, total phosphorus, chloride, sulfate, total dissolved solids and total suspended sediments. The baseline data will be useful in studying the actual nutrient loading to the Cedar River during periods of high flow in relation to land use practices.

March 2014

One project involves extensive fieldwork in the Cedar River watershed. Fourteen monitoring sites were selected last fall, with stream water collected from each site once every two weeks from mid-October until early December. Water sampling will resume in the spring, plus soil samples will be collected. The research will help identify actual nutrient losses in relation to land use practices.

Category: