The East River, Colorado, Watershed: A Mountainous Community Testbed for Improving Predictive Understanding of Multiscale Hydrological–Biogeochemical Dynamics

Abstract

Extreme weather, fires, and land use and climate change are significantly reshaping interactions within watersheds throughout the world. Although hydrological-biogeochemical interactions within watersheds can impact many services valued by society, uncertainty associated with predicting hydrologydriven biogeochemical watershed dynamics remains high. With an aim to reduce this uncertainty, an approximately 300-km 2 mountainous headwater observatory has been developed at the East River, CO, watershed of the Upper Colorado River Basin. The site is being used as a testbed for the Department of Energy supported Watershed Function Project and collaborative efforts. Building on insights gained from research at the "sister" Rifle, CO, site, coordinated studies are underway at the East River site to gain a predictive understanding of how the mountainous watershed retains and releases water, nutrients, carbon, and metals. In particular, the project is exploring how early snowmelt, drought, and other disturbances influence hydrological-biogeochemical watershed dynamics at seasonal to decadal timescales. A system-of-systems perspective and a scale-adaptive simulation approach, involving the combined use of archetypal watershed subsystem "intensive sites" are being tested at the site to inform aggregated watershed predictions of downgradient exports. Complementing intensive site hydrological, geochemical, geophysical, microbiological, geological, and vegetation datasets are long-term, distributed measurement stations and specialized experimental and observational campaigns. Several recent research advances provide insights about the intensive sites as well as aggregated watershed behavior. The East River "community testbed" is currently hosting scientists from more than 30 institutions to advance mountainous watershed methods and understanding.

Hyporheic Zone Microbiome Assembly Is Linked to Dynamic Water Mixing Patterns in Snowmelt‐Dominated Headwater Catchments

“…Here we have focused our analyses on an upland catchment (East River) within the Upper Colorado River Basin to understand how seasonally dynamic hydrology affects patterns of hyporheic mixing, pore water biogeochemistry, and microbial community assembly. Such catchments are at the forefront of climate change effects, with changes in vegetation and the timing and extent of snowmelt exacerbated relative to lower elevation locations (de Valpine & Harte, ; Elmendorf et al, ; Harte & Shaw, ; Hubbard et al, ; Klein et al, ; Panetta et al, ; Shaver et al, ). Understanding how hydrologic shifts could influence microbiome assembly within the riverbed may be critical for predicting how solutes are processed and transported through these ecosystems under different climate change scenarios.…”

Taxonomically and metabolically distinct microbial communities with depth and across a hillslope to riparian zone transect

“…Water runoff and infiltration transform and transfer solutes and particles from headwaters to streams and lakes, and from the surface to the subsurface. Currently, there is relatively little known about how hydrobiogeochemical functions are partitioned across ecosystem compartments and the extent to which environmental factors select for distinct microbial communities that mediate biogeochemical transformations and impact water quality and other watershed outputs [2].…”

“…The gradients affecting microbial communities within these deeper zones are influenced by above-ground factors such as precipitation, but are also determined by the geochemistry of the underlying bedrock and groundwater [8,9]. Here, we investigated a well studied headwaters mountainous catchment in the East River of Colorado, where intersecting research activities are focused on developing a predictive understanding of geological, hydrobiogeochemical and ecological process interactions [2]. We analyzed genome resolved metagenomes to evaluate the connections between microbial composition, metabolic capacities and the spatial organization of these attributes along a hillslope to riparian zone transect and as a function of depth below ground surface.…”

“…From the perspective of vegetation, slope, underlying bedrock and weather conditions, the transect is typical of a substantial fraction of the watershed. The East River watershed in the Upper Colorado River Basin serves as a testing ground for the Department of Energy Watershed Function Project (watershed.lbl.gov) and its associated research community [2]. The watershed is approximately 300 km 2 with an average elevation of 3266 m. It has an average annual temperature~0°C, with average minimum and maximum temperatures of −9.2°C and 9.8°C, respectively.…”

“…The watershed is approximately 300 km 2 with an average elevation of 3266 m. It has an average annual temperature~0°C, with average minimum and maximum temperatures of −9.2°C and 9.8°C, respectively. The bulk of the 600 mm yr −1 of average precipitation is in the form of snow, which covers the surface between September and May [2,11]. In early spring, groundwater reaches the surface, but the lowest level of the water table depends on the location along the hillslope.…”