Can the HGM classification of small, non-peat forming wetlands distinguish wetlands from surface water geochemistry?

We report the results of a detailed 12-month study of 23 freshwater wetlands and one larger synoptic characterization of 55 freshwater wetlands to test whether a hydrogeomorphic (HGM) classification of the wetlands into lotic (attached to streams) and terrene (groundwater fed) classes meaningfully discriminated wetland surface water chemical composition in the mountainous Catskill-Delaware watersheds of southeastern New York State. Most of these hillslope wetlands are underlain by thin, largely siliceous mineral soils and have minimal peat cover. Nonparametric one-way ANOVA (Kruskat-Wallis) tests based on measurements of SC, Ca²⁺, Mg²⁺, Na⁺, DOC, TDN, TDS, Si, SO₄^2-, PH, DO, K⁺, Cl^-, NH₄⁺, NO₃^-, TDP, and HCO₃^- failed to reject the null hypothesis that the surface water chemistry of lotic and terrene wetlands was identical. Results of the statistical tests showed that the only significantly different chemical species in surface waters from the two HGM landscape classifications were SC, Na⁺, and Cl₂^-, which was clearly related to individual wetland proximity to road salt additions. Isotopic analyses of ²H and ¹⁸O for 30 synoptic wetland surface waters also failed to demonstrate significant differences for any of the HGM wetland classes. Based on the results of these data, we caution that landscape position, landform, water flow path, and water body type may not be accurate in making wetland classifications for HGM assessment in all locations. Underlying geology should be considered before making assumptions that water chemistry will differ by landscape position, and wetland functions dependent on water chemistry should be evaluated accordingly.