Mark Cable Rains

Integrating geographically isolated wetlands into land management decisions

Wetlands across the globe provide extensive ecosystem services. However, many wetlands - especially those surrounded by uplands, often referred to as geographically isolated wetlands (GIWs) - remain poorly protected. Protection and restoration of wetlands frequently requires information on their hydrologic connectivity to other surface waters, and their cumulative watershed-scale effects. The integration of measurements and models can supply this information. However, the types of measurements and models that should be integrated are dependent on management questions and information compatibility. We summarize the importance of GIWs in watersheds and discuss what wetland connectivity means in both science and management contexts. We then describe the latest tools available to quantify GIW connectivity and explore crucial next steps to enhancing and integrating such tools. These advancements will ensure that appropriate tools are used in GIW decision making and maintaining the important ecosystem services that these wetlands support.

Water Sources and Hydrodynamics of Closed-Basin Depressions, Cook Inlet Region, Alaska

Among the most prevalent wetland and deep-water habitats in Alaska are ponds, many of which are subarctic ponds occurring as moraine, ice-scour, or dead-ice depressions. Many are closed-basin depressions, where surface-water inflows and outflows are negligible. The objective of this study was to quantify the water sources and hydrodynamics of these subarctic ponds, particularly with respect to the role they play in groundwater recharge. There are two types of ponds on the study site. Perched-precipitation ponds have inflows by melt water and direct precipitation, outflows by evapotranspiration and groundwater recharge, and are seasonally inundated because surface water is perched above the water table and infiltration through the low-permeability surficial deposits to the water table is slow. Flow-through ponds have inflows by melt water, direct precipitation, and groundwater discharge, outflows by evapotranspiration and groundwater recharge, and are perennially inundated because of groundwater throughflow. Both are groundwater recharge focal points. This is particularly true for perched-precipitation ponds, where net groundwater recharge rates were 215% larger than in flow-through ponds, and 332% larger than in the broader landscape. Most of the additional groundwater recharge occurs immediately following breakup, as aeolian-transported snow trapped in the depressions melts which results in enhanced groundwater recharge rates.

Controls on Water Levels and Salinity in a Barrier Island Mangrove, Indian River Lagoon, Florida

We examined controls on water levels and salinity in a mangrove on a carbonate barrier island along the Indian River Lagoon, east-central Florida. Piezometers were installed at 19 sites throughout the area. Groundwater was sampled at 17 of these sites seasonally for three years. Head measurements were taken at the other two sites at 15-minute intervals for one year. Water levels in the mangrove are almost always lower than lagoon water levels. Spectral analysis of water levels showed that mangrove groundwater levels are not tidally influenced. Salinities vary spatially, with values of ∼10xa0psu in uplands, ∼30xa0psu in regularly-flushed mangroves, and ∼75xa0psu in irregularly-flushed mangroves. Cation and anion concentrations and stable isotope compositions indicate that water salinities are largely controlled by enrichment due to evapotranspiration. A shore-perpendicular electrical resistivity survey showed that the freshwater lens is restricted to uplands and that hypersaline waters extend deeply below the mangrove. These results indicate that evapotranspiration lowers water levels in the mangrove, which causes Indian River Lagoon water to flow into the mangrove where it evapoconcentrates and descends, forming a thick layer of high-salinity water below the mangrove.