Geology and Geomorphology
The Spring River Basin (Figure Ge02) is located along the border between the Osage Plains and the Springfield Plateau (MDNR 1986).
The Osage Plains are a subdivision of the Central Lowland Physiographic Region and encompass the northwest portion of the Spring River Basin. This is an unglaciated area of smooth to rolling plains with low relief formed on Pennsylvanian sedimentary rock (MDNR 1986).
The Springfield Plateau forms the western-most member of the three subdivisions of the Ozark Plateau and encompasses most of the Spring River Basin. Elevations range from 1,000 to 1,700 feet above mean sea level (msl). Mississippian limestones underlay the region, and karst features are locally prominent.
The southern and eastern portions of the Spring River Basin, including the eastern and southern portions of the North Fork of the Spring River watershed and the Turkey Creek, Shoal Creek, and Center Creek watersheds, have surface layers comprised primarily of Mississippian age limestones (Figure Ge01) (MDNR 1984). A few remnants of Pennsylvanian sandstones and shales are dispersed throughout this area. A substantial portion of this area lies in the Burlington-Keokuk limestone within which most springs in the area are formed. Springs are relatively common, but generally low yielding (Table Ge01). Base flows are well sustained during dry periods.
The northwest portion of the basin, which makes up the western portion of the North Fork of the Spring River watershed, lies within deposits of shale, sandstone, siltstone, limestone, clay, and coal of Pennsylvanian age (MDNR 1984). Springs are poorly developed, infiltration to subsurface strata is limited, and base flows are poorly sustained during dry periods.
Three major soil regions are represented within the Spring River Basin; these are Cherokee Prairies, Ozark Borders, and Ozarks (MDNR 1986). Alluvial soils along major stream courses are assigned to the Cherokee Prairies category.
Soils in the Cherokee Prairies region historically supported native vegetation comprised primarily of prairie grasses. These soils range from acidic, poorly drained soils to soils which are excessively well drained, droughty, and infertile.
Ozarks soils are variable, and productivity encompasses a wide range. Ozarks soils may be stone free, but stone content can exceed 50 percent in some areas. Loess capped soils and soils located in valleys may be fertile and support improved pastures and grain farming.
The Ozark Borders region contains both forest soils and areas of transition between forest and prairie derived soils. Slope, parent materials, climate, and landforms all contribute to a wide variety of distinct soil types in this region.
Soil erosion ranges from 5 to 9 tons/acre/year from sheet and rill erosion on tilled lands, 2.5 to 5 tons/acre/year from sheet and rill erosion on permanent pasture, less than 0.25 tons/acre/year from sheet and rill erosion on non-grazed forests, and 100 to 199 tons/square mile from gully erosion. Approximately 1.4 tons of sediments/acre/year actually reach impoundments and streams within the basin. The sources of eroded sediment are derived as followed: 76% from sheet and rill erosion; 14% from gully erosion; 3% from streambank erosion; and 7% from urban and built-up areas (Anderson 1980).
Stream orders were assigned to all streams in the Missouri portions of the basin using 7.5 minute topographic maps. There are a total of 144 third order and larger streams in the basin. Of this total, 111 are third order, 20 are fourth order, six are fifth order, three are sixth order, and one (Spring River) reaches seventh order before leaving Missouri. Total stream mileages by order are: 1) third order - 593.8 miles; 2) fourth order - 256.8 miles; 3) fifth order - 106.7 miles; 4) sixth order - 225.0 miles; and 5) seventh order - 128.3 miles. Overall, third order and larger streams in the Missouri portion of the basin total 1,310.5 miles. The major streams in the basin, with their respective lengths and orders are listed in Table Ge02.
The basin has been divided into five major sub-basins, Upper Spring River, Lower Spring River/Center Creek, Shoal Creek, and upper and lower North Fork of the Spring River. Table Ge02 contains watershed areas for fifth order and larger streams in the basin summarized from Funk (1968) or as determined using available 1:100,000 scale topographic maps. The Spring River and its tributaries drain approximately 2,271 square miles in Missouri. The three sixth order streams, North Fork of the Spring River, Shoal Creek, and Center Creek drain 640, 472, and 302 square miles, respectively. The fifth order streams have watersheds ranging from 39 to 100 square miles.
Stream gradient plots for all third order and larger streams were produced using U.S. Geological Survey (USGS) 7.5 minute topographic maps. This infromation is available from the Missouri Department of Conservation's (MDC) Southwest Regional Office in Springfield, MO. Average gradients were calculated for third order and larger reaches of the Spring River, North Fork of the Spring River, Shoal Creek, and Center Creek (Table Ge03).
Channel gradients reflect the transitional Ozarks/Prairie topography of the basin. The higher gradients of Shoal Creek are more typical of those found in Ozark streams, while the lower gradients of the North Fork of the Spring River are more typical of a prairie stream. The gradients for Spring River and Center Creek are intermediate between the two.