GROUNDWATER—SURFACE WATER INTERACTIONS IN AN UPLIFTING ALASKAN VALLEY

The hydrology of the Mendenhall Valley, near Juneau, AK, is extremely heterogeneous involving glacial, weather, groundwater, forest, and urban hydrological processes. Additionally, the entire valley, like much of Southeast Alaska, is experiencing uplift at rates estimated as high as 2.5 cm yr-1. The objective of this project was to evaluate how climatological and geological changes, i.e., uplift, have impacted the valley’s hydrological system, particularly with respect to the groundwater-surface water interactions of Duck Creek. Climate changes have generally resulted in increased liquid water in the valley as a result of slight increases in precipitation and accelerated glacial melt. Perhaps the most pronounced geological change in the valley is Interestingly, despite the augmented water to the valley, Duck Creek runs dry with increasing frequency. We installed a network of wells throughout the valley, four wells were instrumented with pressure transducers, three of which were continuously data-logged since the summer 2002 and one well has been monitored for several decades. Valley stream discharges (Mendenhall River, Duck Creek, and Jordan Creek) and the Mendenhall Lake stage were continuously monitored by the USGS. Weather data were collected by the National Weather Services at the mouth of the Valley. Using a suite of data analyses and models we have shown that isostatic rebound is the most probable contributor to Duck Creek’s current problem of seasonally running dry. This finding is particularly interesting in light of considerable habitat restoration efforts that have been ongoing since 1994.