River corridor science: Hydrologic exchange and ecological consequences from bedforms to basins

Abstract

Previously regarded as the passive drains of watersheds, over the past 50 years, rivers have progressively been recognized as being actively connected with off‐channel environments. These connections prolong physical storage and enhance reactive processing to alter water chemistry and downstream transport of materials and energy. Here we propose river corridor science as a concept that integrates downstream transport with lateral and vertical exchange across interfaces. Thus, the river corridor, rather than the wetted river channel itself, is an increasingly common unit of study. Main channel exchange with recirculating marginal waters, hyporheic exchange, bank storage, and overbank flow onto floodplains are all included under a broad continuum of interactions known as “hydrologic exchange flows.” Hydrologists, geomorphologists, geochemists, and aquatic and terrestrial ecologists are cooperating in studies that reveal the dynamic interactions among hydrologic exchange flows and consequences for water quality improvement, modulation of river metabolism, habitat provision for vegetation, fish, and wildlife, and other valued ecosystem services. The need for better integration of science and management is keenly felt, from testing effectiveness of stream restoration and riparian buffers all the way to reevaluating the definition of the waters of the United States to clarify the regulatory authority under the Clean Water Act. A major challenge for scientists is linking the small‐scale physical drivers with their larger‐scale fluvial and geomorphic context and ecological consequences. Although the fine scales of field and laboratory studies are best suited to identifying the fundamental physical and biological processes, that understanding must be successfully linked to cumulative effects at watershed to regional and continental scales.

Using SWAT-LUD Model to Estimate the Influence of Water Exchange and Shallow Aquifer Denitrification on Water and Nitrate Flux

“…The challenges that the research community are now facing are to apply the acquired knowledge to larger scales [42]. In the SWAT-LUD model, the application of Darcy's equation and a simple denitrification equation has allowed the estimation of water exchange and nitrate attenuation in the floodplain area on the catchment scale with a limited number of parameters.…”

Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream–aquifer–land interactions (CP v1.0)

“…The interactions between groundwater and river water prolong physical storage and enhance reactive processing that alter water chemistry, downstream transport of materials and energy, and biogenic gas emissions (Fischer et al, 2005;Harvey and Gooseff, 2015). The Earth system modeling community recognizes such a gap in existing Earth system models and calls for improved representation of biophysical and biogeochemical processes within the terrestrial-aquatic interface (Gaillardet et al, 2014).…”

A New Approach to Quantify Shallow Water Hydrologic Exchanges in a Large Regulated River Reach

“…Hydrologic exchange is a concept introduced by Harvey and Gooseff [1] which combines surface water-groundwater interaction processes along river corridors at multiple spatiotemporal scales, including hyporheic exchange, bank storage, and regional groundwater discharge and recharge. River water interacts with subsurface water through the hydrologic exchange fluxes (HEFs), which facilitate the nutrient and carbon cycling, organic biodegradation, fish spawning, metal transport, and other key biogeochemical and hydroecological processes in the subsurface region of the river corridor [2][3][4][5][6][7].…”