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Analyzing peatland discharge to streams in an Alaskan Watershed: An integration of end-member mixing analysis and a water balance approach
Citation:
Gracz, M., M. Moffett, D. Siegel, AND P. Glaser. Analyzing peatland discharge to streams in an Alaskan Watershed: An integration of end-member mixing analysis and a water balance approach. JOURNAL OF HYDROLOGY. Elsevier Science Ltd, New York, NY, 530:667-676, (2015).
Impact/Purpose:
Peatlands in south central Alaska form the predominant wetland class in the lowlands that encompass Cook Inlet. These peatlands are also in areas of increasing human development in Alaska. Currently Alaska peatlands are extensive and largely pristine. This study focused on obtaining measures of functional aspects of these peatlands to help environmental managers and wetland scientists better understand processes and ecoservices that peatlands in this landscape provide. This research piece focused on making a quantitative determination of the contribution of peatlands to the summer baseflow water of an anadromous fish stream that is a tributary of the Anchor River in southcentral Alaska. Measures of peatland processes will help determine expectations for wetlands of this area.
Description:
Some authors report that peatlands do not contribute substantially to flow during the dry season (Boelter & Verry 1977, Ingram 1983, Holden et al. 2004), while others report that watersheds with a higher cover of peatlands produce more flow during droughts (Ackroyd 1967, Newson 1980, Brandesten 1988). The differences are likely due to hydrogeologic setting and the difficulties of quantifying diffuse porewater contributions from extensive peatlands (Holden et al. 2004). Here we employ a PCA-based end-member mixing analysis (EMMA) with a sensitivity analysis of a peatland water budget to quantify diffuse porewater contributions to dry-season stream flow in a watershed where potential end-members have similar chemical composition with respect to major ions. EMMA is adapted by using chemical analysis of trace elements and spatially distributed stream-sampling at a single point-in-time during the dry-season. The water budget shows that extensive peatlands can potentially produce a substantial quantity of pore water discharge during a dry period. The mixing model calculations show that 55% of stream flow during a dry-period originated near the surface of the peat. The peatland contribution likely moderates warming stream temperature during a critical time for commercially important fish such as king salmon (Oncorhynchus tshawytscha). This abstract does not necessarily reflect EPA policy.
