A Wetland Restoration Project: Water Budget and Nutrient Analysis of a Drained Carolina Bay

Abstract

Hydrology is the most important variable in the creation and maintenance of wetlands and wetland processes. As part of a wetland restoration project, the hydrological conditions are being measured to evaluate the restoration plan as well as to predict off-site impacts of restoration. This study developed a water budget, which accounts for all water inputs and outputs, for a drained Carolina bay in Robeson County, NC during a 13-month period. Sources for water inputs and outputs were measured or determined by difference, to establish the current hydrological conditions. Precipitation was the major source of water input totalling1014 mm of water. The main sources of output were evapotranspiration and surface outflow, with 845 mm and 727 mm respectively. Groundwater inflow was estimated to range from 171 to 563 mm, which indicates that Juniper Bay has a significant groundwater inflow that could possibly influence the restoration project. The water budget indicates that the bay is now acting as a discharge wetland, but will act as a flowthrough wetland once restoration is complete, which may cause off-site impacts.

Nutrient cycling is strongly influenced by the hydrologic conditions of an ecosystem. A study was conducted to determine the inputs and outputs of nutrients to determine if these nutrients may cause a water quality issue. The nutrients NH4+-N, NO3--N, TKN, PO43-, TOC, Ca2+, Mg2+, K+, as well as Na+ were measured in precipitation, groundwater and surface water. During 2002 to 2003 there was very little change in the surface water nutrient concentrations except during rain events of greater than 5 centimeters in a day. During these large rain events the nutrient concentrations rose by at least 2 times and in some instances rose by as much as 4 times the base flow conditions for TOC and calcium. In most instances the surface water levels of P and N were below the levels that cause water quality degradation. However, during large rain events there could possibly be periods of high nutrient levels and short-term eutrophication. Nutrient levels in precipitation on average were quite low, except for PO43-, NH4+-N, NO3-N, and TKN indicating possible deposition of nutrients from outside sources.