ONE-DIMENSIONAL SOIL MOISTURE FLOW MODELING OF RIDGETOP WETLANDS USING HYDRUS-1D

The Daniel Boone National Forest is home to hundreds of natural and constructed wetlands, hosting a diverse assemblage of wildlife and capable of storing hundreds of thousands of gallons of water, though the volume of precipitation necessary to form a ridgetop aquifer without a wetland and the subsurface movement of water is at present poorly understood. Through understanding the natural processes impacting these wetlands, effective strategies for their management and maintenance promoting environmental health may be implemented. Extensive soil moisture, temperature, precipitation and water level data encompassing several years has been collected from these wetlands via soil and atmospheric monitoring stations. Thermal properties of the soil were measured as well as saturated hydraulic conductivity from permeameters. The sensor data obtained was used to input a representative soil column into HYDRUS-1D to attempt to calibrate a vertical flow scenario capable of estimating vertical recharge within the wetlands. Sensor data shows that wetland soils ephemerally saturate both in the spring and summer as a result of precipitation events. The rate, depth, and rate of saturation due to vertical infiltration as opposed to seepage from surface water storage is however unclear. Our model closely matched sensor data for storm periods where vertical infiltration was the only process. The rate of vertical infiltration and saturation was controlled by the properties set for the underlying subsoil. In cases where the underlying subsoil was less permeable, saturated conditions occur more quickly. Given variable soil properties this process is important for creating the sustained saturated conditions found in sensor data. Such modeling is instrumental in further understanding characteristics of a natural wetland, and applying these features to the invasive species-rich constructed wetlands as well as poorly understood natural wetlands.