Vertical leakage and vertically averaged vertical conductance for Karst Lakes in Florida

Abstract

Abstract. In the karst lake district in peninsular Florida in the southeastern United States, as many as 70% of the lakes lack surface outlets, and groundwater outflow is an important part of the water budgets of these lakes. For 11 karst lakes in the Central Lake District, vertical leakage from the lakes to the upper Floridan aquifer averages 0.12 to 4.27 rn yr -•. The vertically averaged vertical conductance Kv/b , a coefficient that represents the average of the vertical conductances of the hydrogeologic units between the bottom of a lake and the top of the upper Floridan aquifer, was determined to range from 0.0394 to 1.00 yr -• for these lakes. For six of the lakes, various hydraulic parameters previously calculated by other investigators are shown to be equivalent to the Kv/b values calculated in this study. If Kv/b is determined for a lake, then vertical leakage can be estimated for other conditions of lake stage and hydraulic head in the upper Floridan aquifer, using Kv/b for the lake and Darcy's equation written for vertical flow. The methodology described in this paper for quantifying Kv/b , which requires only limited data (i.e., vertical leakage, lake stage, and hydraulic head in the upper Floridan aquifer), could be used to investigate the apparent association between relatively large Kv/b values and lake level instabilities at some lakes in the Central Lake District and similar hydrogeologic settings. This methodology for calculating vertical leakage is applicable to the Central Lake District in Florida and to other similar lake and groundwater systems. IntroductionIn water budget calculations for lakes, groundwater outflow can be a significant component of the water budget. In seepage lakes, from which losses occur by seepage into the groundwater [Wetzel, 1983], groundwater outflow can be quite large. Even in drainage lakes, from which losses also occur by surface water flow from an outlet, the groundwater outflow component can be relatively large [Deevey, 1988]

Modeling of Seasonal Lake Level Fluctuations of Titan's Seas/Lakes

“…The lakebed seepage rate can be calculated by a vertical application of Darcy's law (Motz, ) as where b is thickness of the layer between lakebed and methane table and Δ h v is the height difference between lake level (lake stage) and hydraulic head of the methane table. The hydraulic conductivity K is 10 6 times smaller ( K = 3 × 10 −8 m/s =3 × 10 −6 cm/s) than in Case 1.…”

Wetland-Groundwater Interactions in Subtropical Depressional Wetlands

“…Other processes that could lead to variability in estimated K values for a given wetland include errors in water budget components, cycles of vegetative growth and die-back, and cattle stocking rates and associated hydraulic impacts (e.g., compaction and physical mixing). Motz (1998) attributed measured temporal variability (coefficient of variation between 0.09 and 0.56) in hydraulic resistance for karst lakes to errors in water budget components. Identifying and quantifying all the mechanisms responsible for temporally variable K values was outside the scope of this study, but further research should quantify impacts of cattle and plant growth cycles on wetland hydraulic properties related to groundwater recharge.…”

A Heuristic Approach to Estimating Spatial Variability of Vertical Leakage in the Recharge Zone of the Gambier Basin Tertiary Confined Sand Aquifer, South Australia

“…The tracer-based approaches involve one or more of the following: environmental or injected tracer techniques [1]; advection-diffusion modelling of pore water chloride profiles [2]- [4], adoption of the compartmental mixing model approach [5]. Hydraulic based approach to the assessment of site specific vertical leakage from Darcy's equation involve: vertically averaged conductance [6]; based on vertical hydraulic gradient and Darcy flow equation [7]; equivalent hydraulic conductivity approach [8]; adaptation of radial flow theory from pumping test data [9]; analytical solution to pressure perturbation and fluid leakage through the aquitard [10]. Hydraulic-based quantification of vertical leakage can be difficult since the key parameter, vertical hydraulic conductivity can vary considerably.…”