• Hydrograph partitioning of a sub-arctic glacial watershed, Interior Alaska: A geochemical analysis
    • Tiffany Gatesman
    • February 06, 2015

Alaska’s rivers are strongly influenced by snow and glacier melt, which contribution to larger-scale watershed runoff is rarely quantified. Anticipated future changes of snow and glacier melt due to climate warming ultimately impacts the ability of managers and communities to plan and adapt to short- and long-term variations in runoff. An understanding of the contributing sources of river discharge via geochemically-based hydrograph separation techniques can help refine runoff forecasts and projections. Increased glacial runoff may also increase suspended solids, primarily inorganic silts and clays associated with mechanical and chemical erosion.

Field measurements, laboratory and modeling analyses equip us to address three main objectives: a) Quantify contribution of glacier melt, snow melt and rainfall to lowland streamflow; b) Assess hydrologic pathways of glacier wastage within a watershed underlain by discontinuous permafrost; and c) Describe variations in streamflow suspended load. Geochemical field samples include end-of-winter snow pack cores, rain, surface water, glacier surface meltwater, glacier terminus runoff, winter baseflow and groundwater from the Jarvis Creek watershed (634 km2), Interior Alaska. Geochemical composition of runoff has been measured continuously during the thawed season since 2011. Water samples are analyzed for major ions (Ca2+, Mg,2+ Na+, K+, NH4+, Cl-, F-, SO42-, PO42-, NO3-), oxygen (δ18O) and deuterium (δD) stable isotope ratios and suspended colloid characterization. Preliminary results show significant seasonal δ18O variability in Jarvis Cr. runoff and distinct chemical signatures in contributing sources. Finally, the measurements and laboratory analyses of stable isotope and dissolved ion concentrations will inform our end-member volumetric mixing models to allow us to quantify the contributing sources to streamflow while gaining a fundamental knowledge about the regional hydrologic system.

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