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
Figure 1. The Neva Marsh and surrounding water bodies.
The Cottonwood River
Figure 2. Underlying and adjacent bedrock units (KGS, 1968)
The Alluvial Aquifer
Sources of Recharge to the Neva Marsh
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).