Research about Jasper, Iowa

USGS2011

Impacts of Land-Cover Change on Suspended Sediment Transport in Two Agricultural Watersheds

Suspended sediment is a major water quality problem, yet few monitoring studies have been of sufficient scale and duration to assess the effectiveness of land-use change or conservation practice implementation at a watershed scale. Daily discharge and suspended sediment export from two 5,000-ha watersheds in central Iowa were monitored over a 10-year period (water years 1996-2005). In Walnut Creek watershed, a large portion of land was converted from row crop to native prairie, whereas in Squaw Creek land use remained predominantly row crop agriculture. Suspended sediment loads were similar in both watersheds, exhibiting flashy behavior typical of incised channels. Modeling suggested that expected total soil erosion in Walnut Creek should have been reduced 46% relative to Squaw Creek due to changes in land use, yet measured suspended sediment loads showed no significant differences. Stream mapping indicated that Walnut Creek had three times more eroding streambank lengths than did Squaw Creek suggesting that streambank erosion dominated sediment sources in Walnut Creek and sheet and rill sources dominated sediment sources in Squaw Creek. Our results demonstrate that an accounting of all sources of sediment erosion and delivery is needed to characterize sediment reductions in watershed projects combined with long-term, intensive monitoring and modeling to account for possible lag times in the manifestation of the benefits of conservation practices on water quality.

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USGS2001

Ground water near Newton, Jasper County, Iowa

The U.S. Geological Survey, in cooperation with the city of Newton, Iowa, conducted an investigation of the ground-water resources of Jasper County, Iowa, near Newton during 1999-2001. The purpose of the investigation was to provide additional information on the South Skunk River alluvial aquifer from which Newton obtains its present municipal supply and to summarize the available information on other groundwater resources in the county. The South Skunk River alluvial aquifer consists of unconsolidated deposits of sand and gravel of glacial and fluvial origin. These deposits overlie bedrock composed primarily of shale and limestone of Pennsylvanian or Mississippian age. Information on the South Skunk River alluvial aquifer and other Jasper County alluvial aquifers is limited to a few test holes in a few locations. Additional thickness and lithologic information was collected using seismic refraction and test hole drilling to increase the understanding of the South Skunk River alluvial aquifer near Newton. Water-level and water-quality information also was collected. The alluvial deposits along the South Skunk River near Newton range from less than 30 to more than 60 feet thick. Three areas of deposits exceeding 60 feet thick occur near the present city of Newton well field about 5,000 feet west of the present well field, at the present well field, and about 5,000 feet southeast of the present well field. Ground water in the South Skunk River alluvial aquifer near the Newton well field flows toward the municipal well field. Ground-water levels on the well-field side of the South Skunk River were lower than water levels in the river, indicating flow from the river toward the well field. The water quality in the South Skunk River and the alluvial aquifer was similar, except most ground-water samples contained low dissolved oxygen concentrations. The low dissolved-oxygen concentrations in ground water resulted in high concentrations of iron and manganese in some locations and reduced forms of nitrogen.

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