The water table in unconfined aquifers is often believed to be a subdued replica of the topography or land surface. However, this assumption has not been widely tested and in some cases has been found to be in error. An analysis of ground water rise in regional unconfined aquifers, using both a two-dimensional boundary element model and a one-dimensional Dupuit-Forchheimer model, reveals the conditions under which the water table does or does not closely follow the topography. A simple decision criterion is presented to estimate in advance under which conditions the water table is expected to be largely unrelated to the topography and under which conditions the topography controls the position of the water table.

Extensive portions of the southern Everglades are characterized by series of elongated, raised peat ridges and tree islands oriented parallel to the predominant flow direction, separated by intervening sloughs. Tall herbs or woody species are associated with higher elevations and shorter emergent or floating species are associated with lower elevations. The organic soils in this ''Ridge-and-Slough'' landscape have been stable over millennia in many locations, but degrade over decades under altered hydrologic conditions. We examined soil, pore water, and leaf phosphorus (P) and nitrogen (N) distributions in six Ridge and Slough communities in Shark Slough, Everglades National Park. We found P enrichment to increase and N to decrease monotonically along a gradient from the most persistently flooded sloughs to rarely flooded ridge environments, with the most dramatic change associated with the transition from marsh to forest. Leaf N:P ratios indicated that the marsh communities were strongly P-limited, while data from several forest types suggested either N-limitation or co-limitation by N and P. Ground water stage in forests exhibited a daytime decrease and partial nighttime recovery during periods of surface exposure. The recovery phase suggested re-supply from adjacent flooded marshes or the underlying aquifer, and a strong hydrologic connection between ridge and slough. We therefore developed a simple steady-state model to explore a mechanism by which a phosphorus conveyor belt driven by both evapotranspiration and the regional flow gradient can contribute to the characteristic Ridge and Slough pattern. The model demonstrated that evapotranspiration sinks at higher elevations can draw in low concentration marsh waters, raising local soil and water P concentrations. Focusing of flow and nutrients at the evapotranspiration zone is not strong enough to overcome the regional gradient entirely, allowing the nutrient to spread downstream and creating an elongated concentration plume in the direction of flow. Our analyses suggest that autogenic processes involving the effects of initially small differences in topography, via their interactions with hydrology and nutrient availability, can produce persistent physiographic patterns in the organic sediments of the Everglades.

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Over the last one hundred years, compartmentalization and water management activities have reduced water flow to the ridge and slough landscape of the Everglades. As a result, the once corrugated landscape has become topographically and vegetationally uniform. The focus of this study was to quantify variations in surface flow hydrology in the ridge and slough landscape

By using analytic elements to model steady state, two‐dimensional, Dupuit‐Forchheimer groundwater flow and its contribution to surface water flow, average base flows and groundwater flows in a groundwater and surface water system can be represented. Changing boundary conditions are modeled by adding or removing streams from the groundwater flow domain according to the availability of water in the stream. This dynamic representation of boundary conditions allows for the anticipation of unknown effects due to future aquifer stresses or stream withdrawals. The model does not account for transient streamflow but significantly improves the realism of steady state surface water and groundwater interactions by simulating average base flows and limiting the infiltration rates of losing streams. When steady state groundwater flow is modeled without considering the limits of available streamflow, recharge rates or hydraulic conductivities that are estimated during model calibration can be substantially in error. The capability to model groundwater and surface water conjunctively is accomplished without substantial increases in model complexity or data requirements.

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