7/29/2019 November 2012 Wallaces Farmer

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More than meets the eyeBy KATHLEEN CHESTER

TECHNOLOGY has found its way intonearly every aspect of daily life, andfarming and conservation are no ex-

ception. While the human eye can identify

when soil is leaving the farm field in areaswhere gullies cut through cropland, in-stalling soil-saving practices everywhere agully can be seen isnt necessarily effective.

Velvet Buckingham, environmentalspecialist with the Iowa Departmentof Agriculture and Land Stewardshipsdivision of soil conservation, says thehighest amount of contaminants dontalways come from the visible areas suchas the 3-foot deep gullies. Sediment canbe leaving the land at a higher rate on asloping piece of land that doesnt appearto be delivering as much as the gully, butin reality it is delivering more, she says.

Buckingham, who coordinates theRathbun Land and Water Alliances ProtectRathbun Lake Project, says a more precisemeasure of potential soil loss is gainedthrough the use of geographic informationsystem, or GIS, technology. You can seesoil loss in the gullies; you cant always seeit on sloping hillsides. That is why GIS is sohelpful, she explains.

GIS is a system designed to capture,store, manipulate, analyze, manage andpresent all types of geographical data.Tyler Jacobsen, cartographer and GISspecialist for Rathbun Regional WaterAssociation incorporates the GIS with in-formation such as soil type, land use and

Key Points

Using GIS technology helps identify areasthat are main sources of sediment.

This allows erosion control plans to bedeveloped to treat worst areas first.

Also provides feedback on effectivenessof installed conservation practices.

degree of slope to create a model specifi-cally for the Rathbun Lake Watershed.

The overall objective of the ProtectRathbun Lake Project is to slow the move-ment of water and the contaminants it car-ries into Rathbun Lake, so the purpose ofthe model is to identify which acres aremost likely to lose soil during heavy rains.

Target erosion prone landJacobsen says there are several steps toidentifying this priority land (both visualand computer generated) using a combina-tion of aerial and satellite images for largemaps and models. In order to create themost accurate model, field level obser-vation by project staff confirms currentland use, which is matched to what thesatellite images show. Key componentsof the model are land use, which are fieldverified, and a GIS based version of theRevised Universal Soil Loss Equation. Thiscombines land use data with various soil,rainfall and management factors on a wa-tershed basis, explains Jacobsen.

Existing conservation practices arealso taken into consideration when cre-ating the model. The results yield a map

for a particular study area that estimatesthe amount of soil runoff with current landuse practices, Jacobsen says.

Marty Braster, environmental manage-ment specialist with the RRWA, says a wa-tershed management plan developed by

RLWA more than a decade ago has been ef-fective in guiding the water quality protec-tion activities of the Protect Rathbun LakeProject. Jacobsen completed the full as-sessment in December of 2001 and updatesthe plan on a yearly basis. Each year, weadd new field assessments and prioritymaps to areas of the watershed where weare focusing our water quality protectionefforts, he says.

How new technology helpsDue to the vast amount of land in theRathbun Lake Watershed (354,000 acres),it was divided into 61 more manageablesubwatersheds. In 2003, the project beganworking with the seven with the highestconcentration of priority land. As conser-vation practices are completed and asfunding allows, additional subwatershedsare identified. To date, landowners in 39 ofthe 61 subwatersheds have or are in theprocess of installing practices.

Of the 354,000 acres, GIS technologyhas helped identify the principal sourceof sediment from the watershed 58,675acres of priority land that is used primarilyfor row crops. This priority land comprisesjust 17% of the Rathbun Lake Watershed,yet it is the source of 73T, or more than173,000 tons, of the estimated 237,000 tons

of sediment delivered annually to the lGIS-based models and water qua

monitoring estimate the effectivenof installed conservation practices inducing the delivery of sediment and phphorus to Rathbun Lake. In additioproviding feedback on the effectivenof the installed practices, the results ofGIS analysis will be used to improve application of this technology.

Landowners apply at their local Noffices to install practices, but prioland is basically pre-approved. Sinceurgency to protect the land has beentermined, a higher percentage of cshare (75%) has been assigned to it. remaining 25% can be borrowed throthe low interest rate loan program throthe Iowa Water Quality Loan Fund.

Chester writes for RLWA.

USEFUL TOOL: Tyler Jacobsen usesGIS technology to identify priority arewhere conservation practices will savthe most soil and protect water quality

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Conservation86 www.FarmProgress.com November 2012 Wallaces Farm