More Like this

1. Toward catchment hydro‐biogeochemical theories

   https://doi.org/10.1002/wat2.1495  

   Li, Li; Sullivan, Pamela L.; Benettin, Paolo; Cirpka, Olaf A.; Bishop, Kevin; Brantley, Susan L.; Knapp, Julia L. A.; van Meerveld, Ilja; Rinaldo, Andrea; Seibert, Jan; et al (December 2020, WIREs Water)

   Abstract Headwater catchments are the fundamental units that connect the land to the ocean. Hydrological flow and biogeochemical processes are intricately coupled, yet their respective sciences have progressed without much integration. Reaction kinetic theories that prescribe rate dependence on environmental variables (e.g., temperature and water content) have advanced substantially, mostly in well‐mixed reactors, columns, and warming experiments without considering the characteristics of hydrological flow at the catchment scale. These theories have shown significant divergence from observations in natural systems. On the other hand, hydrological theories, including transit time theory, have progressed substantially yet have not been incorporated into understanding reactions at the catchment scale. Here we advocate for the development of integrated hydro‐biogeochemical theories across gradients of climate, vegetation, and geology conditions. The lack of such theories presents barriers for understanding mechanisms and forecasting the future of the Critical Zone under human‐ and climate‐induced perturbations. Although integration has started and co‐located measurements are well under way, tremendous challenges remain. In particular, even in this era of “big data,” we are still limited by data and will need to (1) intensify measurements beyond river channels and characterize the vertical connectivity and broadly the shallow and deep subsurface; (2) expand to older water dating beyond the time scales reflected in stable water isotopes; (3) combine the use of reactive solutes, nonreactive tracers, and isotopes; and (4) augment measurements in environments that are undergoing rapid changes. To develop integrated theories, it is essential to (1) engage models at all stages to develop model‐informed data collection strategies and to maximize data usage; (2) adopt a “simple but not simplistic,” or fit‐for‐purpose approach to include essential processes in process‐based models; (3) blend the use of process‐based and data‐driven models in the framework of “theory‐guided data science.” Within the framework of hypothesis testing, model‐data fusion can advance integrated theories that mechanistically link catchments' internal structures and external drivers to their functioning. It can not only advance the field of hydro‐biogeochemistry, but also enable hind‐ and fore‐casting and serve the society at large. Broadly, future education will need to cultivate thinkers at the intersections of traditional disciplines with hollistic approaches for understanding interacting processes in complex earth systems. This article is categorized under:Engineering Water > Methods 

   more » « less
2. Luquillo Experimental Forest: Catchment science in the montane tropics

   https://doi.org/10.1002/hyp.14146  

   McDowell, William H.; Leon, Miguel C.; Shattuck, Michelle D.; Potter, Jody D.; Heartsill‐Scalley, Tamara; González, Grizelle; Shanley, James B.; Wymore, Adam S. (April 2021, Hydrological Processes)

   Abstract Catchments in the Luquillo Experimental Forest (LEF) of Puerto Rico are warm, wet and tropical with steep elevational relief creating gradients in temperature and rainfall. Long‐term objectives of research at the site are to understand how changing climate and disturbance regimes alter hydrological and biogeochemical processes in the montane tropics and to provide information critical for managing and conserving tropical forest ecosystems globally. Measurements of hydrology and meteorology span decades, and currently include temperature, humidity, precipitation, cloud base level, throughfall, groundwater table elevation and stream discharge. The chemistry of rain, throughfall, and streams is measured weekly and lysimeters and wells are sampled monthly to quarterly. Multiple data sets document the effects of major hurricanes including Hugo (1989), Georges (1998) and Maria (2017) on vegetation, biota and catchment biogeochemistry and provide some of the longest available records of biogeochemical fluxes in tropical forests. Here we present an overview of the findings and the data sets that have been generated from the LEF, highlighting their importance for understanding montane tropical watersheds in the context of disturbance and global environmental change. 

   more » « less
3. Catchment processes can amplify the effect of increasing rainfall variability

   https://doi.org/10.1088/1748-9326/ac153e  

   Müller, Marc F.; Roche, Kevin R; Dralle, David N. (January 2021, Environmental Research Letters)

   null (Ed.)
4. Catchment Coevolution and the Geomorphic Origins of Variable Source Area Hydrology

   https://doi.org/10.1029/2023WR034647  

   Litwin, David_G; Tucker, Gregory_E; Barnhart, Katherine_R; Harman, Ciaran_J (June 2024, Water Resources Research)

   Abstract Features of landscape morphology—including slope, curvature, and drainage dissection—are important controls on runoff generation in upland landscapes. Over long timescales, runoff plays an essential role in shaping these same features through surface erosion. This feedback between erosion and runoff generation suggests that modeling long‐term landscape evolution together with dynamic runoff generation could provide insight into hydrological function. Here we examine the emergence of variable source area runoff generation in a new coupled hydro‐geomorphic model that accounts for water balance partitioning between surface flow, subsurface flow, and evapotranspiration as landscapes evolve over millions of years. We derive a minimal set of dimensionless numbers that provide insight into how hydrologic and geomorphic parameters together affect landscapes. Across the parameter space we investigated, model results collapsed to a single inverse relationship between the dimensionless relief and the ratio of catchment quickflow to discharge. Furthermore, we found an inverse relationship between the Hillslope number, which describes topographic relief relative to aquifer thickness, and the proportion of the landscape that was variably saturated. While the model generally produces fluvial topography visually similar to simpler landscape evolution models, certain parameter combinations produce wide valley bottom wetlands and non‐dendritic, trellis‐like drainage networks, which may reflect real conditions in some landscapes where aquifer gradients become decoupled from topography. With these results, we demonstrate the power of hydro‐geomorphic models for generating new insights into hydrological processes, and also suggest that subsurface hydrology may be integral for modeling aspects of long‐term landscape evolution. 

   more » « less
5. Oxidative dissolution under the channel leads geomorphological evolution at the Shale Hills catchment

   https://doi.org/10.2475/10.2016.02  

   Sullivan, Pamela L.; Hynek, Scott A.; Gu, Xin; Singha, Kamini; White, Timothy; West, Nicole; Kim, Hyojin; Clarke, Brian; Kirby, Eric; Duffy, Christopher; et al (December 2016, American Journal of Science)