Creating Solutions forRock Creek Lake

GIS Mapping:

Rock Creek Lake is at risk. The centerpiece of Rock CreekState Park in Jasper County, Rock Creek Lake offers visitors a

range of recreational opportunities, including the second-busiest campground in Iowa and great fishing.

However, many different factors are threatening the lake.Action is being taken to improve the lake for today’s visitors

and to preserve the lake for future generations. GIS mapping ishelping to make those improvements possible.

What’s awatershed?A watershed is an area of land thatdrains water into the lowest point -- abody of water, such as a stream, lake ormarsh. Watersheds can be as small as acity block, draining into a creek, or verylarge.

The Rock Creek Lake watershed covers26,698 acres in northeast Jasper andsoutheast Marshall Counties. The lakeitself is only 491 acres.

During a rainfall, water either travelsover the surface or seeps into theground. Water traveling over thesurface or through groundwater maypick up contaminants like sediment,chemicals and waste and deposit themin a body of water.

What’s GIS? Improving water quality b

This mapshows wherethe RockCreekwatershed liesin Jasper andMarshallCounties.

Rock Creek Lake, located in Rock Creek State Park in Jasper County,offers visitors a range of recreational opportunities, including thelakeside campground, which is consistently the second-busiest camp-ground in Iowa. The lake is known for its catfish, bass, bluegill andcrappie fishing. However, many factors are threatening the lake.Projects are being planned and implemented to improve water qualityfor today’s lake users and future generations. GIS mapping is at thecenter of these projects.

Sediment and nutrients, especially phosphorus, are the largest threatsto Rock Creek Lake, placing the lake on Iowa’s impaired waters list.High levels of nutrients can result in high levels of algae, which not onlycloud the water, but also lead to more serious problems like lowoxygen levels, more rough fish like carp, and a greater chance of toxicalgae. Sediment fills in the lake, reducing the depth of the water, andalso carries nutrients into the lake.

The Rock Creek Watershed Project was created to improve the lake’swater quality, with the main goals of reducing sediment entering thelake by 80 percent and reducing the amount of phosphorus reachingthe lake by 70 percent.

To begin working towards these goals, research was needed to deter-mine the areas in the watershed that contribute the most soil andphosphorus to the lake. To do this, a Geographic Information Systems(GIS)- based assessment of the watershed was conducted by a teamconsisting of the Iowa Department of Natural Resources (DNR), JasperCounty Soil and Water Conservation District, U.S. Department ofAgriculture (USDA), Natural Resources Conservation Service of theUSDA, and the Division of Soil Conservation of the Iowa Department ofAgriculture and Land Stewardship.

The first step in the GIS-based assessment of the watershed includedstaff reviewing aerial photography maps to determine land use in thewatershed -- pastures, corn fields, residential areas, etc. Next, staff wentout into the watershed to collect baseline data over four weeks during a

Geographic Information Systems(GIS) use graphics and data to createmaps that identify problems andevaluate possible solutions. GISmapping links spatial data -- the actualphysical location of something -- withattribute data, or information aboutthat location. For example, thephysical location of a lake is spatialdata, while the lake’s name and size isattribute data.

GIS works to combine spatial data withdifferent layers of attribute data. In theRock Creek project, for example,spatial data was combined withinformation on soil loss, best manage-ment practices and land use, amongother things.

Beach-goers enjoy a day at the lake at Rock Creek State Park.

Rock Creek Lake was constructed in 1952 as a 641-acre lake with a 24-foot maximum depth.Over the last 50 years, erosion and soil deposition have caused the lake to lose almost 40percent of its volume and 102 acres of surface area.

Sediment and phosphorus are the two major threats tothe lake’s water quality, according to a 2000 Iowa StateUniversity (ISU) study.

While agricultural practices have improved over thepast 50 years, sediment from the surrounding water-shed, which is primarily agricultural, continues to be aproblem for the lake.

Many farms in the Rock Creek Lake watershed cur-rently practice no-till and minimum till methods, butthe water quality of the lake was heavily affected in itsearly years by intensive row cropping and pasture use.Today, more than 25,000 tons of soil is still carried intothe lake every year. The ISU study suggests that 89percent of the phosphorus moving through the water-shed is attached to this sediment.

A large amount of land drains into the lake -- the watershed contains 26,698 acres, which is 54times larger than the 491-acre lake. To maintain good water quality, the recommended landto lake ratio in a watershed is 20 to 1. If there is more than 20 acres of watershed for everyacre of the lake, sediment can become a large problem, much like it has at Rock Creek.

Rock Creek Lake: A History

Rock Creek Lake, December 1965

begins with GIS mappingdriving windshield survey of the26,698-acre watershed.

Additional staff members wentout in the field to confirm landcover data and determine soilloss by collecting revised univer-sal soil loss equation (RUSLE)data on a field-by-field basis.

Staff in the field also determinedthe amount of protective vegeta-tive groundcover in pastures andgrazed timbers; the location andseverity of streambank, shorelineand gully erosion; and thelocation of livestock facilities andexisting best management prac-

A family fishes along the lake.

tices (BMPs). Best managementpractices address nonpointpollution problems and work toresolve them.

After information was collected,it was placed on baseline maps byDNR GIS staff over a period ofsix weeks. The data was used tocreate detailed maps showingcurrent land cover, soil loss,sediment delivery, the location ofcurrent BMPs and acres of landenrolled in the ConservationReserve Program.

These maps helped identifypriority areas in the watershedand priority BMPs, and where toconsider permanent conservationeasements and land purchases inthe watershed to ensure long-term water quality benefits.

Identifying and understanding pIdentifying priority areas and practicesOnce data was gathered and GIS maps were created, staffused the maps to identify existing best management practices(BMPs) and structures, like terraces and ponds. Maps werealso used to find priority areas within the Rock Creek water-shed where priority BMPs are needed most.

Priority areas were identified by the following criteria:• Areas of high potential sediment delivery based on RUSLE(revised universal soil loss equation) calculations• Areas in proximity to Rock Creek Lake

• Riparian (stream) corridors

• Areas without functioning sediment-trapping structures

The following priority BMPs were identified:• Sediment reducing structures and management practices

• Stream corridor protection

• Conservation cover establishmentand enhancement• Animal waste management systems

• Nutrient management education

Permanent conservation easementsand land purchases are also being usedin the watershed to ensure long-termwater quality benefits. The followingeasement priorities were identified:

• Sediment trapping structures

• Riparian corridor stabilization

• Critical area stabilization (for areasoutside the riparian corridor and areasnot associated with significant struc-tural BMPs)

Rock Creek LakeSediment Sources

The pictures below display types ofareas and practices within the RockCreek Lake watershed that are majorsources of sediment to Rock CreekLake.

Rock CreekQuick FactsWatershed size:26,698 acres

Lake size 2004:491 acres

Lake size 1952:602 acres

Watershed land use:60% row crop14% CRP land10% pasture4% timber2% grassland2% hayland8% farmsteads,

roads, water, etc.

• GIS maps estimatethat 80% of erosion inthe watershed comesfrom only 20% of theland area (if no conser-vation practices areused)

problem areas with GISCommunicationGIS maps of the watershed have helped toimprove communication with landowners,as they provide a detailed illustration ofthe potential for problems in specificfields and across the watershed. The mapstake complicated data and illustrate ideas,like sediment delivery rates, in an easy-to-read format. For example, newcomers tothe Rock Creek Watershed Project havegained a better understanding of projectactivities through GIS information.

FundingaccountabilityGIS mapsand data arealso used tosummarizethe accom-plishments ofthe water-shed project,includinglocatingnewly imple-mentedBMPs andsignificantland usechanges. GISis also used tocalculate theassociatedchange in soilloss to report

Additional benefits of GIS assessment• Helps define priorities of a newly developed project

• Efficiently answers the “what ifs” that may be encountered in a project

• Involves more landowners and non-traditional stakeholders in projectactivities

• Provides a better understanding of lake and watershed problems

• Provides a visual location of sediment and nutrient source areas

• Helps Soil and Water Conservation District commissioners to allocatefinancial resources to critical areas more efficiently

sediment and phosphorusdelivery reductions on a perproject or watershed scale.Using the GIS data in this waycan target the use of publicfunds to actual watershedimprovements, which in-creases project accountabilityto funding sources, projectpartners, stakeholders, govern-ing bodies and lake users.

Rock Creek Lake WatershedPotential Sheet, Rill and Gully ErosionSE Road Right-of-way Structure

GlossaryRUSLE:A calculation thatestimates soil loss fromerosion caused byrainfall on cropland.

BMP:Best management prac-tices (BMPs) addressnonpoint pollutionproblems and work toresolve them.

A giant effort to reduce sediment

Pinpointing priority areasWhile GIS is an effective resource for looking at an entire watershed, it can also be used to zoom in onareas within the watershed, like individual sites or smaller sub-watersheds. Maps of these smaller areas canbe used to research potential sites for priority best management practices (BMPs).

For example, using a sediment deliverymap, staff located areas with the worstpotential erosion and then went into thefield to discuss possible BMPs with land-owners.

Once a potential site for a BMP is located,GIS contour maps of the site can be usedto predict the sediment delivery rate,watershed area, planned pool area, landuse, revised universal soil loss equation(RUSLE) and runoff curve number(RCN) calculations, cross section eleva-tions and stage storage values.

This information can then be used tobegin the design of a project, and mapscan help show a landowner what a pro-posed project or structure may look like.Cost estimates for the project can also becreated from this information.

GIS mapping is being used to help plan anumber of projects in the Rock CreekLake watershed, including a large lake,smaller lakes and road structures.

One of the largest conser-vation projects in theRock Creek Lake water-shed is currently under-way.

A large, 22.6 acre lakewill be constructed on anew 255-acre tract ofDNR-owned land, locatedabout one mile northwestof Rock Creek Lake.

The above map shows priority areas, or areas with the highest rateof erosion, in the Rock Creek Lake watershed.

GIS maps on drainage areaand sediment delivery rateswere used to find a site forthe lake. The current sitewas chosen for its largedrainage area, and becausethe area would have a highsediment delivery rate if itreturned to cropland afterits CRP contract expires.

This large structure has a

drainage area of 1,414 acres and willfilter out sediment before it reachesRock Creek Lake, potentially reducingsediment entering the lake by 774 tonsper year.

A smaller lake structure, about two tothree acres, is planned to be built onthe same site. The structure has adrainage area of 76 acres and willreduce sediment to Rock Creek Lakeby 154 tons per year.

Rock Creek Lake WatershedPriority Areas

Using GIS to predict resultsNot only can GIS maps single out current areas creating problems in the watershed, they can also be usedto predict what areas could become problems in the future.

The GIS map to the right shows when certain areas will come out of the Conservation Reserve Program(CRP), a federal program that pays rent tofarmers wanting to remove land with a highenvironmental risk from crop production. GISmapping can calculate how much erosionwould result if the land returns to farmingproduction after the CRP contract expires.These numbers can be shared with landownersto show the importance of conservation prac-tices and to promote new CRP contracts.

GIS maps can also predict soil loss, assuming noconservation practices are present, using soilsurvey data and color infrared (CIR) aerialphotography. This helps identify areas in thewatershed that are most at risk for erosionbecause they have more erodible soil types,steeper slopes or longer slopes.

By targeting these areas for conservationimprovements, state, federal and local dollarscan be used more efficiently.

For example, in the Rock Creek Lake water-shed, GIS maps were used to identify that 80percent of the erosion came from a small area(less than 20 percent) of the watershed.

Rock Creek Lake WatershedCRP Contract Expiration

Financial incentives for conservation practicesA number of cost-share, loan andother programs are available tolandowners considering installingconservation practices and man-agement techniques on their land.

Free technical assistance is avail-able from your local NRCS, DSCor Soil and Water ConservationDistrict staff, as well as DNRprivate lands biologists andforestry staff.

For more information on theseprograms, contact the followingorganizations:

U.S. Department of AgricultureFarm Service Agencywww.fsa.usda.govNatural Resources Conservation Service (NRCS)www.ia.nrcs.usda.gov

Iowa Department of Agriculture and Land StewardshipDivision of Soil Conservation (DSC)www.agriculture.state.ia.us/soilconservation.html

Iowa DNR, Nonpoint Source Pollutionwww.iowadnr.com/water/nonpoint/

An informational brochure with additional details on financial incentivesand technical assistance is also available from the DNR by contactingKaren Grimes at (515) 281-5135 or at Karen.Grimes@dnr.state.ia.us.

A publication of theIowa Department of

Natural Resources2004

For additional copies of thispublication, please contact:

Iowa Department of NaturalResources

Wallace State Office Building502 E. 9th St.

Des Moines, IA 50319-0034(515) 281-5918

www.iowadnr.com

Produced by:Jessie Rolph,

DNR Information SpecialistPhotography:

Clay Smith, DNRContributors:

Keri Batterson, Rock CreekWatershed Coordinator

Chris Ensminger,DNR GIS Specialist

The publication of this documenthas been funded by the Iowa

Department of Natural Resourcesthrough a grant from the U.S.

Environmental Protection Agencyunder the Federal Nonpoint

Source Management Program(Section 319 of the Clean Water

Act).

Federal regulations prohibitdiscrimination on the basis of

race, color, national origin, sex,or handicap. If you believe you

have been discriminated againstin any program, activity or

facility as described above, or ifyou desire further information,

please write to the addressabove.

For more information

GIS maps help landowners’conservation efforts

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New technology is allowing ToddLenz to carry on a family farm-ing tradition.

Lenz, whose family farms land inthe north and northwest areas ofthe Rock Creek Lake watershed,is a believer in using conserva-tion practices. With the help ofGIS mapping, the Lenz family isimplementing new conservationprojects on their land.

“It goes way back, pastmy dad’s generation,”Lenz said of conserva-tion. “You’re not goingto grow anything ifthere’s not soil there.”

When the family hadan area they wanted toaddress with a newpractice, field staffwere brought in tocreate project mapsand give cost estimates.

“If I can see it on paper, it helps mevisualize things a lot better,” Lenz said.“(Maps) help sell projects to farmers.”

GIS maps detailing soil loss informationhave been used to help locate and plana number of pond structures on thefamily’s land.

The ponds, located in priority areas,have helped stabilize erosion, created arecreation area for the family, given anew home to wildlife and allowednative prairie plants to return to pas-tures.

The Lenz family uses a number ofother conservation practices, includingterraces, contour farming and water-ways, and 90 to 95 percent of the landis farmed as no-till.

“There’s not a lot of effort to returnyour investment,” Lenz said. “You canbe well-paid by being conservation-minded.”

Keri BattersonRock Creek Watershed Coordinator(641) 792-4116Keri.Batterson@ia.nacdnet.net

Ubbo AgenaNonpoint Program Coordinator, DNR(515) 281-6402Ubbo.Agena@dnr.state.ia.us

Three generations of conservation:Nathan, Todd and Dwight Lenz near oneof their ponds.

Prairie flowers look out over one of the Lenz’s ponds.