Hidden Features: How Subsurface and Landscape Heterogeneity Govern Hydrologic Connectivity and Stream Chemistry in a Montane Watershed

• DOI: 10.1002/hyp.70085
• Publication Date: 2025-03-14T01:21:26Z
• Authors: Keira Johnson; Kenneth H. Williams; John N. Christensen; Rosemary W. H. Ca...; Li Li; Curtis Beutler; Kenneth Swift Bird; Wenming Dong; Pamela L. Sullivan
• Keywords: Water chemistry

ABSTRACT Hydrologic connectivity is defined as the connection among stores of water within a watershed and controls flux solutes from subsurface to stream. difficult quantify because it goverened by heterogeniety in storage permeability responds seasonal changes precipitation inputs moisture conditions. How interannual climate variability impacts hydrologic connectivity, thus stream flow generation chemistry, remains unclear. Using rare, four‐year synoptic chemistry dataset, we evaluated shifts source Coal Creek, montane, headwater tributary Upper Colorado River. We leveraged compositional principal component analysis end‐member mixing evaluate how variation conditions chemistry. Overall, three main findings emerged this work. First, geochemically distinct end members were identified that constrained chemistry: reach inflows, quick slow groundwater contributions. Reach inflows impacted historic base precious metal mine inputs. Bedrock fractures facilitated much transport higher‐storage features (e.g., alluvial fans) groundwater. Second, contributions different changed over summer. In early summer, was composed all members, while late predominantly Finally, observed minimal differences proportional composition across four years, indicating spatial heterogeneity landscape geologic had greater influence than fluctuation on These indicate mechanisms controlling solute path activation) may be resilient (i.e., able rebound after perturbations) predicted increases variability. By establishing framework for assessing variable conditions, our study offers method biogeochemical resilience variations hydrometeorological