Abstract
Wetlands provide many benefits, including flood attenuation, groundwater recharge, water-quality improvement, and habitat for wildlife. As their structure and functions are sensitive to changes in hydrology, characterizing the water budgets of wetlands is crucial to effective management and conservation. The groundwater component of a budget, which often controls resiliency and water quality, is difficult to estimate and can be costly, time-consuming, and invasive. This study used a GIS approach using a digital elevation model (DEM) and the elevations of lakes, wetlands, streams, and hydric soils to produce a water-table surface raster for a portion of the Itasca Moraine, Minnesota, U.S. The water-table surface was used to delineate groundwatersheds and groundwater flow paths for lakes and wetlands, and map recharge and discharge rates across the landscape. Specific conductance and pH, which depend on the hydrological processes that dominate a wetlands water budget, were measured in the field to verify this modeling technique. While the pH of surface waters varied in the study area, specific conductance increased from 16.7 to 357.5 μS/cm downgradient along groundwater flow paths, suggesting increased groundwater interaction. Our results indicate that basic GIS tools and often freely available public-domain elevation datasets can be used to map and characterize the interaction of groundwater in the water budgets of lakes and wetlands, as exemplified by the Itasca Moraine region. Combining this with grid cell-by-cell water balance provides a means to estimate recharge and discharge, thereby affording a way to quantify groundwater contribution to and from lakes and wetlands. Applied elsewhere, this cost-efficient technique can be used to assess the vulnerability of lakes and wetlands to changes in land use, groundwater development, and climate change.
Highlights
Wetlands provide benefits to society, such as flood attenuation, groundwater recharge, water-quality improvement, and habitat for wildlife, including those that are threatened or endangered [1]
Effort was made to select an adequate distribution of lakes and wetlands across the study area and a small kayak was used so that measurements could be taken in a variety of locations within each waterbody
The best-fit interpolated water-table surface was subtracted from the digital elevation model (DEM) to map the depth to the water table, which shows a few scattered areas where the interpolated water-table surface lies above the surface topography (Figure S5), it occurred in less than 2% of the groundwatershed raster cells
Summary
Wetlands provide benefits to society, such as flood attenuation, groundwater recharge, water-quality improvement, and habitat for wildlife, including those that are threatened or endangered [1]. For. For lakes lakes and wetlands in glacial terrain, groundwater groundwater interacts interacts in in one one of of three three ways ways (Figure (Figure 1): 1): and wetlands in glacial terrain, through recharge (flow from surface water), discharge (flow from groundwater to surface through recharge (flow from surface water), discharge (flow from groundwater to surface water), water), or or aa combination combination where where recharge recharge and and discharge discharge will will occur occur in in different different locations locations within the same surface water body (flow-through). This interaction within the same surface water body (flow-through) This interaction commonly commonly corresponds with with topographic topographic position, position, it it depends depends largely largely on corresponds on where where the the lake lake or or wetland wetland lies within the larger-scale groundwater-flow system [3].
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