GSC-SSSENR

Groundwater Seepage Calculator: Steady-State Single-Event Non-Redistribution (GSC-SSSENR). This web application utilizes steady-state sediment temperature profile to estimate groundwater seepage flux. Users are encouraged to familiarize with the theory beforehand. The only assumed parameters in the steady-state models are volumetric heat capacity of water (ρfcf) and thermal conductivity (k) of the saturated porous media. Solution of the analytical equations for steady-state conditions depends on input of values for the volumetric heat capacity of water and the thermal conductivity of sediment. The value of the volumetric heat capacity of water will vary between 4.19x106 and 4.12x106 J/m3-°C as a function of salinity from freshwater (salinity 0 ppt) to seawater (salinity 35 ppt) at 20°C. Sharqawy et al. (2010) provide a review of mathematical relationships that can be used to calculate values at other temperatures and salinity. A description of the factors that influence sediment thermal conductivity has been summarized in Stonestrom and Constanz (2003). The grain size of sediment materials and the organic matter content are two important factors that influence the value of this parameter. Stonestrom and Constanz (2003) provided a review of measured or estimated values for a variety of porous materials and a commonly recommended default value for sediments is 1.84 J/m.s.°C. This value is representative of a sandy sediment with little or no organic matter. However, Duque et al (2016) have shown that use of this default value can lead to overestimation of calculated seepage flux by a factor of 30%, which can be significant in locations with seepage flux on the order of 1 cm/day or less. Characteristics of the sediment material will be influenced by the local surficial geology, sediment depositional environment, and the presence of vegetation or other sources of organic matter. In order to provide an updated point of reference for selection of sediment thermal conductivity for a range of depositional systems for inland and coastal environments, a review was conducted of studies where sediment thermal conductivity was measured directly or specifically optimized during model calibration. These results are summarized in the table at left, which indicates that the common default value of 1.84 J/m.s.°C represents the high end of the distribution. The sediment origin, type and texture descriptors listed in the table can be used to select a value that seems appropriate for the investigated water body. Alternatively, measurements of thermal conductivity on sampled sediment cores can provide a more direct assessment of the value(s) to use for modeling.