Advancing a Watershed Hydro-Biogeochemical Theory: Linking Water Travel Time and Reaction Rates Under Changing Climate

Project: Research project

Project Details

Description

Mountain watersheds are often regarded as the 'water towers for humanity' (Viviroli et al. 2007). In thewestern USA, mountain snow packs are estimated to feed about three fourth of freshwater and more than60 million people (Bales et al. 2006). They also represent the dominant-yet-vulnerable control on wateravailability. Here we choose Coal Creek, Colorado, a high-elevation (~ 2,700 – 3,700 m) mountainouscatchment that has already seen 4 decades of continued temperature increases (> 5?C based on SNOTELmeasurements) and declines in snow fractions ( ~ 70% in 1980 to ~50% in 2018). We ask the overarchingquestion of how and how much do hydrological and biogeochemical functioning co-evolve in awarming climate? In particular, how do hydrological characteristics (water storage, flow paths, and traveltime) change in response to a warming climate? What are the corresponding alterations in biogeochemicaland chemical weathering rates at the watershed scale? What is the general rate law that causally linksmetrics of hydrological and biogeochemical rates to measures of external hydroclimatic conditions andinternal watershed structure characteristics? Using a combination of field measurements, transit time andage modeling, and process-based watershed hydro-biogeochemical modeling, we aim to develop a generalrate law at the watershed scale, establishing a largely-unknown linkage between the extensively studied hydrology travel time theory and the recently developed theory on old and new water fraction characteristics affectingbiogeochemical and weathering rates. Reaction rate laws are generally derived and parameterized in small-scale and often well-mixed systems that have often been found non-applicable at the watershed scale. TheCoal Creek watershed will serve as a model watershed to develop the general watershed-scale rate law,which will be further tested in a constellation of catchments within the USA and across the globe where the PIshave been engaged. These additional sites differ in the levels of snow dominance and geology, topography, and landcover conditions. The general law may be modified and expanded to ultimately encompass a variety ofenvironmental conditions.The proposed work will offer mechanistic understanding of how a warming climate alters waterflow, storage, and travel time characteristics; and how and how much such alterations speed up reactionsthat drive the evolution of catchments and ultimately Earth surfaces. Although these aspects have beenextensively studied within disciplinary boundaries, the inter-linkage is not clear and the hydro-biogeochemistry community is often puzzled by watershed process coupling, feedbacks, and emergentbehaviors, all of which are important for projecting to the future. This work aims to unravel such linkagesby integrating existing knowledge and approaches, crossing hydrology and geochemistry boundaries, andadvancing new fronts regarding climate change influences on water quantity and quality. The outcome of thiswork will advance our forecasting capabilities for water, mass, and energy in the rapidly changing planet.Notably, the developed general rate law will illustrate the first-order principles of hydro-biogeochemicalprocess coupling. Ultimately, it will help develop forward projections to provide insight for adaptation,management, and prevention of water quantity and quality-related catastrophes.The proposed work continues our exploratory project on concentration discharge relationships atCoal Creek, CO. It will extend comprehensive data collection of soil, geologic and hydrologic characteristics, isotopic analyses andmodeling of hydro-biogeochemical processes at the watershed scale. More importantly, this work will extendthe insights gained from Coal Creek to other sites that are impacted by decreasing snow fractions, andadvance the theory that hydrological and biogeochemical coupling are both influenced by Earth system changes.
StatusFinished
Effective start/end date9/15/199/14/23

Funding

  • Biological and Environmental Research: $540,000.00

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