Neva Marsh:  A Riverine Wetland in the Flint Hills of Central Kansas

The Neva Marsh is managed by Emporia State University as one of the University's Natural Areas. The wetland site was developed through the Natural Resources Conservation Service, Wetlands Reserve Program (Howard,2009).  It functions as a riverine wetland in that its main water source is rainwater and ground water with occasional flooding of the Cottonwood River. Riverine wetlands are located near a slope within a stream corridor where groundwater flow is transected and collects into a depression (Brinson, 1993). The water’s presence in the depression creates anerobic conditions that develops a hydric soil . The condition of hydric soils inhibits the growth of some indigenous plants while promoting the growth of hydrophytic plants (NRCS, 2008). The western 4ha. of the current marsh (yellow triangle in Figure 1) has always existed as wetland. The eastern 17ha. was been drained and tilled for crops, but was recently restored to wetland conditions. Construction on the restoration began in October of  2005. A retaining wall was built from east to west with earthen dikes on both sides forming an enclosed basin.  The water level in the basin reached depths of approximately 0.3m. Borrows were placed on the discharge side of the retaining wall to slow the migration of water that leaves the basin. Their intention is to allow favorable habitat and cover for wildlife while slowing the effects of sediment migration (NRCS 2007) 

Location and Site Description

The 21ha. site is located in Chase County KS, 2.4 km west of Cottonwood Falls in Kansas. It is situated on the margin of the Cottonwood River flood plain (yellow triangle in Figure 1). The river meanders from west to east along a path just north of the marsh area. Directly east, a bend in the Cottonwood River extends to within 250 meters from the marsh. Along the southern border of the marsh, Permian limestone and shale strata rise 150 meters above the flood plain. Twelve springs issue from limestone formations and serve as the main water source for the marsh (note the white arrow in Figure 1). At the hilltop and to the south, a small spring feeds a pond used for livestock. Downhill and to the west from the pond is a second spring fed pond that drains north to the Cottonwood River. Prather Creek and Chase County State Fishing Lake, located on the hilltop south of the stock ponds, are fed by a large spring. Drainage from the State Fishing Lake follows Prather Creek, 950 meters east of the Neva Marsh, to discharge into the Cottonwood River.

Figure 1. The Neva Marsh and surrounding water bodies.

 The Cottonwood River 

The Cottonwood River segment from Diamond Creek to Cottonwood Falls has a drainage area of 3279km2 and receives on average 211m3/s of flow (USGS 2001). 

Bedrock Hydrology

Ground water flow is typically influenced by land surface topography but can also be is dominated stratigraphic or structural features in rock formations (Fan 2007). At the Neva site, the underlying rock formations are limestone and shale of Early Permian age. The layers observed along the southern boundary of the site are composed of Council Grove Group strata, and include the Grenola Limestone through Wreford Limestone formations (KGS, 1968; Figure 2)

Figure 2. Underlying and adjacent bedrock units (KGS, 1968)

Resitant limestone and fine-grained shale layers restrict ground water flow to fissures and fractures in the formations (Cooke, 2006). Mechanical/bedding plane interfaces provide openings for water to move through (Figure 3). Weathering enhances the cracks allowing more water to pass through the rocks. Chemical dissolution occurs if the water is acidic and contacts the carbonate constituents of the limestone which further enlarges the space. Water motion can manipulate grains to grind at the rocks surface which wears the fissures deeper into the rock (Eaton, et al. 2007). Fissures eventually branch out.

Peritidal carbonate rocks will promote multiple smaller fractures due to varied conditions such as fossils, wavy textures, and breccias. Basinal carbonates offer fewer horizons and bedding planes that facilitate fracturing (Graham Wall, 2006). The difference in the sedimentary conditions also thwarts the vertical direction of water flow, in that; the deeper the rock, vertical fractures occur less often. Water then seeks to continue down gradient in the superior layer and continues to flow in multiple layers. Overtime the mechanisms will continue to increase the conductivity of the aquifer. Eventually, water escapes to the surface through a fracture or other conduit that is down gradient from the aquifer. Artesian pressure may force water upwards into an opening.

The Alluvial Aquifer

The unconsolidated alluvial sediments in the Cottonwood River Valley aquifer system are approximately 12 meters thick (Figure 4). The upper 1.5 meters of topsoil are underlain by 5 meters of silty clay, and 5.5 meters of sand, gravel, and broken limestone.  A water table depth of approximately 2.4 m bls was measured in 1951.  A low head dam at Cottonwood Falls was observed to raise the water table level two to three miles up stream (Oconnor, 1951)


The soil in the Neva Marsh is classified as Osage hydric. A soil comprised of 60 percent fine clay and silt as a result of long periods of standing water. The soil’s low permeability, hydraulic conductivity of 0.01 - 0.42 µm/s, most likely prohibits vertical infiltration of recharge to the underlying alluvial aquifer (Watts,2009). The Cottonwood River reached flood stage every 1-2 Years over the last 17 year period. The river crested between 3.0 - 5.0m. A flood stage of 2.7m will bring river water into the marsh (NWS, 2010).

Sources of Recharge to the Neva Marsh


The Cottonwood River segment from Diamond Creek to Cottonwood Falls has a drainage area of 3279km2 and receives on average 211m3/s of flow (USGS 2001). The river reached flood stage every 1-2 Years over the last 17 year period. The river crested between 3.0 - 5.0m. A flood stage of 2.7m will bring river water into the marsh (NWS, 2010).

Springs .

The primary source of water for the Neva Marsh is 12 springs that issue from the upland rock layers on the south margin of the site. The spring water accumulates at the base of the hillslopes and travels via a drainage ditch located along the road into a culvert near center of the marsh’s southern edge. Water that passes through the culvert flows toward the west, fills the retention area, and discharges over wood blocks placed opposite the culvert. Beyond the culvert a slight depression slows the water’s path before it drains north via a small stream to the Cottonwood River (NRCS 2007). 


The ultimate source of water recharge to the upland and alluvial systems is rainfall. Chase County receives on average 32 inches of rain per year. Most of the rain that falls at the Neva Marsh does not move vertically through the upper alluvium, but is retained at the site  by the clay-rich top soil. The upper layers of the dominated by clayey which allows water to run off or accumulate in depressions at the surface. Thus, a large portion of water travels the sloping drainage zones to surface bodies. Some of the water is used by vegetation (Watts, 2009). Precipitation infiltrates into rock formations through outcrops, then travels from East to West along the dipping structural trend as observed in the high volume springs at the head of the Cottonwood River. The uplands in this study area experience a flow to the northeast caused by a structural change influenced by the Elmdale Dome (Moore, 2001). 

Regional Water Supplies

The nearby cities of Cottonwood Falls and Strong City draw municipal water from the alluvial aquifer to supply 1400 people with 109 gallons per day per capita(KSDA 2007). Cottonwood Falls maintains three domestic wells in the alluvium north east from the marsh. The well locations are shown in Figures 1 and 3. The wells supply 90, 90, and 160 gpm.

The upland area is primarily used for pasture and remains grassland. Therefore, spring water is diverted to ponds for stock.

Soy beans and corn are grown on the alluvial plain. Kansas Department Agriculture reports 52ha. as irrigated with an annual use of 17 hectare meters (KSDA 2007a).

Water Quality

The surrounding calcium carbonate rocks produce elevated hardness levels. Alluvial aquifer chemical levels illustrated in Figure 5 are nearly the same today as the concentrations in 1948 (Water Report Cottonwood Falls 2009).

The Kansas Watershed Association and the Environmental Protection Agency has deemed the Lower Cottonwood watershed area as impaired, with low priority. Fecal coli measures high in the Upper Cottonwood River Watershed and Diamond Creek due to a large number of feedlots. Upstream influence causes impairment of the beginning segment of the Lower Cottonwood River Watershed; however, organic constituents become diluted at this point (EPA WaterLINK, 2009). The Neva Marsh area experiences some levels of chlordane and imazapic which are constituents of insecticides and herbicides respectfully. The chemicals are water soluable, and will break down in sunlight. However, they can bind to soils. The NRCS reports the contaminant level as less than a the maximum contaminant limit(NRCS 2007).


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