Nitrate Levels in Water Threatened Iowa Town

Joel DeJong,  NW Iowa Crops Specialist


The city of Rock Valley in Sioux County has continually had high nitrate levels in their drinking water.  Water quality requirements for communities in Iowa mandate that continually testing higher than standard levels for water contaminants will cause the Department of Natural Resources to enforce changes in the city's water system to insure that levels of this contaminant can be controlled for the future - which could cost a small community like Rock Valley about 5 million dollars to build a nitrate treatment facility.  Rock Valley is on a lot of sand in the soil horizon, so nitrate can move through the profile quite rapidly, if found in excess in the surface.  Identification of where the nitrate is originating from, and reduction of nitrate into city wells used for supplying the community with water was needed to avoid the higher cost of installing an N treatment facility.


The city of Rock Valley put together an advisory team to work on this problem in 2000.  On that team were city staff, along with representatives of their engineering firm, NRCS, Iowa Geological Survey Bureau, DNR, and ISU Extension.  This committee determined funds were available through NRCS to hire a coordinator to work on this project in the watershed area surrounding Rock Valley.  The Iowa Geological Survey Bureau drilled several monitoring wells to identify where the recharge for the city wells came from - and discovered that most was from within Rock Valley, but high risk areas around the town created some of the problem, also.  ISU's part of this plan was to help educate as to the concerns of nitrate contaminant, help train the 3 different project coordinators over the project, offer nutrient management workshops and individual assistance with agricultural producers in the watershed, hold demonstrations of reduced N use on lawns, and continue to help the planing group with project carry-out.  The planning committee continues to meet and give direction for the project.

The city of Rock Valley has saved about 5 million dollars because they have not had to install an N treatment plant.  Nitrate levels have been reduced in almost all wells, and sites for future low nitrate well locations have been identified.  Well monitoring shows where high N plumes exist, and the surface treatments in those areas are now designed to reduce this problem further.  Nitrate levels in Rock Valley's water are now consistently below the safety standard.  It is also thought that since water quantity was never a problem for the city, and now that water quality looks to be making great progress, the city might be able to sell water to the local rural water organization to further bring in some income.

Several livestock sites of concern now have better manure management storage and application plans in place, one site was moved from a high risk area to another much further away from the city well site.  Over 300 acres around wells have been seeded to native grasses to reduce N flow through the soil profile, and upstream in the watershed area more buffers and conservation practices have been put into place to reduce N movement into the stream flowing into Rock Valley's watershed.  Nutrient management plans are now a part of several producer's operations on 1295 acres, as well.  In town, more slow-release fertilizer is being sold - reducing the amount of N being used on lawns.  The city also uses lower N levels on all of their city parks and ball fields - also helping to reduce excess N levels in soil water.

This project has allowed several different partners to work together for the benefit of an Iowa community.  In the process it has made all of the partners more familiar with what each brings to the table.  A team approach to this problem has been very effective.  This has been a rather unique method for solving a nitrate problem in this community - but it has given a successful model that might be followed in other communities in the future.

Submitted February 25, 2004

POW #'s 150, 103

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