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) 

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)

Soil

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

Flooding

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). 

Rainfall 

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).

References

Brinson, M.M. 1993. A hydrogeomorphic classification for wetlands, Technical Report WRP–DE–4, U.S. Army Corps of Engineers Engineer Waterways Experiment Station, Vicksburg, MS. http://el.erdc.usace.army.mil/wetlands/pdfs/wrpde4.pdf

Cooke, M.L., J.A. Simo, Chad A. Underwood, and Peggy Rijken, 2006, Mechanical stratigraphic controls on fracture patterns within carbonates and implications for groundwater flow, Sedimentary Geology, 184:225-239.

Water Report, Cottonwood Falls, 2009, Annual Water Quality Report, City of Cottonwood Falls, KS, Water Department Records.

Eaton T. , Anderson M., and Bradbury K., 2007, Fracture control of ground water flow and water chemistry in a rock aquitard, Ground Water, 45 no. 5: 610-615.

EPA WaterLINK,2009, Surf Your Watershed, http://cfpub.epa.gov/surf/huc.cfm?huc_code=11070203

Fan, Y., Toran L., and Schlische R., 2007, Groundwater flow and groundwater-stream interaction in fractured and dipping sedimentary rocks: Insights from numerical models, Water Resources Research, 43:Wo1409.

Graham Wall, B.R., 2006, Influence of depositional setting and sedimentary fabric on mechanical layer evolution in carbonate aquifers, Sedimentary Geology, 184: 203-224.

Kansas Geological Survey, 1968, Stratigraphic Succession in Kansas.  Kansas Geological Survey Bulletin 189, D.E. Zeller (ed). online at: https://www.kgs.ku.edu/Publications/Bulletins/189/index.html

Howard, D., 2009, National Resources Conservation Service, Wetlands Reserve Program http://www.nrcs.usda.gov/programs/WRP/

KSDA 2007, Kansas Department of Agriculture, Municipal Water Use Report, http://www.ksda.gov/includes/document_center/dwr/Publications/Rpt2007MunicipalPub18Feb2009.pdf

KSDA 2007a, Kansas Department of Agriculture, Irrigation Water Use Report, http://www.kwo.org/Reports%20%26%20Publications/Rpt_2007_Irrigation_Water_Use.pdf

Moore, R.C., J. M. Jewett, and H. G. O'Conner, 2001, Kansas Geological Survey, Chase County Geohydrology,URL=http://www.kgs.ku.edu/General/Geology/Chase/contents.html

NRCS, 2007, Development File, National Resources Conservation Service, Field Office, NRCS 3020 West 18th Avenue, Suite B Emporia, KS 66801-5140

NRCS, 2008, Hydrogeomorphic Wetland Classification System: An Overview and Modification to Better Meet the Needs of the Natural Resources Conservation Service Technical Note No. 190–8–76. Feb. 2008. ftp://ftp-fc.sc.egov.usda.gov/WLI/HGM.pdf

NWS,2010, National Weather Service, Advanced Hydrologic Prediction Service, http://www.crh.noaa.gov/ahps2/hydrograph.php?wfo=ict&gage=ctwk1

O’Conner , H. G., 1951, Ground-water resources of Chase County Rock Formations of Chase County, Part 3 of Geology, Mineral resources, and Ground-water resources of Chase County,http://www.kgs.ku.edu/General/Geology/Chase/pt3_avail.html

USGS, 2001,Kansas Water Science Center, Kansas Streamflow Statistics,http://ks.water.usgs.gov/studies/strmstats/ks/cs/index.php?test=basin

Watts, C.E., 2009, State Soil Scientist Kansas,Custom Soil Resource Report, Neva Marsh and Adjacent Influence, National Resources Conservation Service,Soil_Report.pdf