East River Watershed in Upper Colorado River Basin. Mountainous watersheds, such as the East River watershed (shown), store and release water from snow, with meltwater mediating coupled hydrologic-biogeochemical reactions across multiple spatial and temporal scales. The Watershed Function SFA is developing and testing new approaches at this watershed in the Upper Colorado River Basin. This basin, perhaps the most important in the western United States, supplies water to more than one in 10 Americans and irrigation water and nutrients to more than 5.5 million acres of land, generates more than 4,200 megawatts of hydroelectric power, and supports a diversity of ecosystems that provide other societal benefits. [Image courtesy Sam Faivre]
Biogeochemical dynamics from genome to watershed scales
Climate change, extreme weather, land-use change, and other perturbations are significantly reshaping interactions among the vegetation, soil, fluvial, and subsurface compartments of watersheds throughout the world. Watersheds are recognized as Earth’s key functional unit for managing water resources, but their hydrological interactions also mediate biogeochemical processes that support all terrestrial life. These complex interactions, which occur within a heterogeneous landscape, can lead to a cascade of effects on downstream water availability, nutrient and metal loading, and carbon cycling. Despite significant implications for energy production, agriculture, water quality, and other societal benefits important to U.S. Department of Energy (DOE) energy and environmental missions, uncertainty associated with predicting watershed function and dynamics remains high. To address this uncertainty, the Subsurface Biogeochemical Research program, within DOE’s Office of Biological and Environmental Research (BER), is supporting the Watershed Function Scientific Focus Area (SFA).
The Watershed Function SFA is developing a scale-adaptive approach, which posits that the integrated watershed response to disturbance events can be adequately predicted through consideration of interactions and feedbacks occurring within a limited number of subsystems. Hypothesis-based research is being performed to improve understanding of hydrological, ecohydrological, and organo-mineral dynamics and interactions in select subsystems. Watershed simulators using adaptive mesh refinement will be used to investigate how coupled and distributed subsystem processes integrate within a “watershed reactor” to yield a cumulative downgradient response.
System-of-Systems Watershed View. The Watershed Function SFA takes a “system-of-systems” perspective and a scale-adaptive approach to quantify how fine-scale processes occurring in different watershed subsystems contribute to the integrated, time-dependent export of water, nitrogen, carbon, and metals. Example subsystems shown include hillslopes with strong gradients in vegetation composition; flow paths for water and nutrients that bridge hillslopes and floodplains; and floodplain compartments, such as active and abandoned river channels, hyporheic zones, shale outcrops, and alluvial sediments. Dynamic processes impact individual subsystems and linkages between subsystems. Click image to enlarge.
The Watershed Function SFA seeks to determine how perturbations to mountainous watersheds (e.g., floods, drought, and early snow melt) impact the downstream delivery of water, nutrients, carbon, and metals over seasonal to decadal timescales. Scale-adaptive approaches are being developed and tested to quantify:
Hypothesis-Based Research. Watershed Function SFA research activities address four hypotheses that underpin how mountainous watersheds respond to episodic through decadal perturbations such as drought, early snow melt, and long-term warming.Click image to enlarge.
Led by Berkeley Lab, the multidisciplinary, multi-institutional SFA team combines expertise in reactive transport and watershed modeling, environmental genomics and ecosystems biology, plant physiology, environmental geophysics, vadose zone hydrology, low-temperature and isotope geochemistry, data science, and environmental synchrotron science. Funded partners include the University of California, Berkeley; Colorado School of Mines; Fort Lewis College; University of Arizona; Desert Research Institute; Navarro, Inc.; and Subsurface Insights. The project involves key collaborations with investigators from 25 additional laboratories, universities, state and federal agencies, and stakeholder groups, providing extensive leveraging of support from BER and others.
The Watershed Function SFA is well aligned with the mission of BER’s Climate and Environmental Sciences Division “to advance a robust, predictive understanding of Earth’s climate and environmental systems and to inform the development of sustainable solutions to the nation’s energy and environmental challenges.”
Research Activity Focus. SFA research activities focus on (a) perturbations impacting precipitation form, timing, and infiltration; (b) vegetation controls on fluid and nutrient fluxes; and (c) impacts to biogeochemical transformations of organic matter and minerals. Such processes are represented within (d) numerical models that simulate hydrobiogeochemical functioning within the watershed reactor over a scale of hundreds of square kilometers.
Click images to enlarge.