Isotopic flow determination and geochemical and geomorphic impacts on vegetation for western north american springs

Аннотация

Recharge areas for most springs are rarely known because they can be sourced from proximal, shallow, atmospheric sources or long-travelled, deep, regional aquifers and alteration along the flow path is common. Stable isotopic (18O and 2 H) geochemistry of springs water can provide indications of relative flow path distance. Locally sourced springs generally have an isotopic signature similar to the isotopic values of local precipitation for that region and elevation. Springs with a different isotopic composition than local meteoric inputs likely have non-local recharge, representing a regional source. Exceptions to this rule include springs in karst terrain, geothermal locations, or travertinerich groundwater systems, where other physical or geochemical processes influence the isotopic signature of the water. In this study, we tested local vs. regional sourcing using springs isotopic data from regional studies across Western North America in Arizona, Nevada, and Alberta. These regional study sites included the Basin and Range, Transition Zone, Colorado Plateau, Cordillera, Interior Plains physiographic regions, and lowland to montane aquifers. The combination of location-specific physical data with stable isotopic groundwater data provides an effective method for flow path determination at springs with similar flow and chemistry. Springs from Arizona were found to be a mix of regional and local recharge, those from Nevada were locally sourced, and Alberta’s springs were generally sourced from regional flow systems.