Catchment Science Research Articles

Advances in Catchment Science, Hydrochemistry, and Aquatic Ecology Enabled by High-Frequency Water Quality Measurements.

High-frequency water quality measurements in streams and rivers have expanded in scope and sophistication during the last two decades. Existing technology allows in situ automated measurements of water quality constituents, including both solutes and particulates, at unprecedented frequencies from seconds to subdaily sampling intervals. This detailed chemical information can be combined with measurements of hydrological and biogeochemical processes, bringing new insights into the sources, transport pathways, and transformation processes of solutes and particulates in complex catchments and along the aquatic continuum. Here, we summarize established and emerging high-frequency water quality technologies, outline key high-frequency hydrochemical data sets, and review scientific advances in key focus areas enabled by the rapid development of high-frequency water quality measurements in streams and rivers. Finally, we discuss future directions and challenges for using high-frequency water quality measurements to bridge scientific and management gaps by promoting a holistic understanding of freshwater systems and catchment status, health, and function.

The pan-Arctic catchment database (ARCADE)

Abstract. The Arctic is rapidly changing. Outside the Arctic, large-sample catchment databases have transformed catchment science from focusing on local case studies to more systematic studies of watershed functioning. Here we present an integrated pan-ARctic CAtchments summary DatabasE (ARCADE) of > 40 000 catchments that drain into the Arctic Ocean and range in size from 1 to 3.1 × 106 km2. These watersheds, delineated at a 90 m resolution, are provided with 103 geospatial, environmental, climatic, and physiographic catchment properties. ARCADE is the first aggregated database of pan-Arctic river catchments that also includes numerous small watersheds at a high resolution. These small catchments are experiencing the greatest climatic warming while also storing large quantities of soil carbon in landscapes that are especially prone to degradation of permafrost (i.e., ice wedge polygon terrain) and associated hydrological regime shifts. ARCADE is a key step toward monitoring the pan-Arctic across scales and is publicly available: https://doi.org/10.34894/U9HSPV (Speetjens et al., 2022).

Analysis of oxygen isotopes of inorganic phosphate (δ18Op) in freshwater: A detailed method description for obtaining oxygen isotopes of inorganic phosphate in environmental water samples

The ability to identify the origin of phosphorus and understand processes controlling P cycling is essential for designing effective mitigation and restoration of eutrophic freshwater ecosystems. The oxygen isotope composition of orthophosphate (δ18Op) has significant potential as a tracer for P entering freshwater ecosystems. However, methods of analysis of δ18Op are still in their preliminary stages and have proven challenging to implement for new practitioners. In order to achieve progress in developing the application of δ18Op signatures as a tracing tool, there is a need to eliminate the methodological challenges involved in accurately determining δ18Op. This protocol article describes the various steps needed to concentrate and isolate orthophosphate in freshwater samples into an adequately pure Ag3PO4 analyte, without isotopic alteration during processing. The protocol compiles the disperse experiences from previous studies, combined with our own experience. The twofold aim of the paper is toprovide a baseline for an increasing standardisation of the silver phosphate purification method associated with analysis of the oxygen isotope composition of orthophosphate (δ18Op), and to foster new research in the applicability of δ18Op signatures for P source tracing in catchment science.

Multidecadal biological monitoring and abatement program\ assessing human impacts on aquatic ecosystems within the Oak Ridge Reservation in eastern Tennessee, USA

AbstractHuman activities can be powerful drivers of ecosystem change within catchments. While most long‐term catchment studies have been conducted at pristine sites, such studies are less common from sites more impacted by human activity. The Oak Ridge National Laboratory's Biological Monitoring and Abatement Program (BMAP) was developed in the mid‐1980s to (1) assess compliance with environmental regulations, (2) identify causes of adverse ecological impacts, (3) provide data for human and ecological risk assessments, and (4) evaluate the effectiveness of remedial actions taken to mitigate the impacts of contaminants in soils, groundwater, and surface water by documenting ecological recovery on the Oak Ridge Reservation (ORR), a federally owned 33 476‐acre site in eastern Tennessee, managed by the US Department of Energy. The ORR is composed of multiple watersheds containing many small to mid‐size streams. BMAP uses an integrated approach for determining stream health; its databases include long‐term seasonal records of contaminant concentrations in water and biota, data from aquatic toxicity testing, and surveys of macroinvertebrate and fish assemblages from impacted and reference streams. These long‐term data provide valuable records of degradation and recovery in catchment ecosystems. Our objective here is to describe our study system and data series in order to increase awareness of the availability of these long‐term data to the catchment science community.

Advances in Catchment Science through Integrated Hydrological Modelling and Monitoring

Environmental research is rapidly evolving toward an integration of different disciplines, and this is also reflected in hydrology and the hydrological modelling community [...]

Long‐term hydrological, biogeochemical, and climatological data from Walker Branch Watershed, East Tennessee, USA

AbstractIn 1967, the original Walker Branch Watershed (WBW) project was established to study elemental cycling and mass balances in a relatively unimpacted watershed. Over the next 50+ years, findings from additional experimental studies and long‐term observations on WBW advanced understanding of catchment hydrology, biogeochemistry, and ecology and established WBW as a seminal site for catchment science. The 97.5‐ha WBW is located in East Tennessee, USA, on the U.S. Department of Energy's Oak Ridge Reservation. Vegetation on the watershed is characteristic of an eastern deciduous, second‐growth forest. The watershed is divided into two subcatchments: the West Fork (38.4 ha) and the East Fork (59.1 ha). Headwater streams draining these subcatchments are fed by multiple springs, and thus flow is perennial. Stream water is high in base cations due to weathering of dolomite bedrock and nutrient concentrations are low. Long‐term observations of climate, hydrology, and biogeochemistry include daily (1969–2014) and 15‐min (1994–2014) stream discharge and annual runoff (1969–2014); hourly, daily, and annual rainfall (1969–2012); daily climate and soil temperature (1993–2010); and weekly stream water chemistry (1989–2013). These long‐term datasets are publicly available on the WBW website (https://walkerbranch.ornl.gov/long‐term‐data/). While collection of these data has ceased, related long‐term measurements continue through the National Ecological Observatory Network (NEON), where WBW is the core terrestrial and aquatic site in the Appalachian and Cumberland Plateau region (NEON's Domain 7) of the United States. These long‐term datasets have been and will continue to be important in evaluating the influence of climatic and environmental drivers on catchment processes.

Hydrological consequences of changes forest cover on watersheds of the Amur river basin

Observing the geographic environment change of watersheds is very important for understanding problem of influence on streamflow, which ranks fourth out of 23 hydrological problems highlighted at Vienna Catchment Science Symposium in April 2018. Watersheds of the Middle and Lower Amur, where main part of streamflow is formed, are covered with forests of various structures. Annual forest fires in the Amur basin lead to sharp decrease in transpiration and summarize evaporation, an increase in volume and rate of surface streamflow (slope) into river beds and, as a consequence an increase in river runoff. An increase frequency of fires entails a change in forest species composition. Despite fact that species of the stand within watershed grow up in same conditions (environment, climate, weather, fires) – total value of the areas of coniferous forests has a decrease, in contrast to deciduous species. This is consistent with the conclusions of Russian hydrologists about shift in Russia of the boundaries of middle taiga on north, which is justified by them using climatic models. Reduction of coniferous forests, which have a deeper root system and larger area of contact with atmospheric precipitation, contributes to a faster runoff of rainwater, contributing an increase streamflow. Moreover, a positive trend is also noted in synchronous dynamics of peaks of rain floods on the Amur near Khabarovsk. This corresponds to assessment of spatio-temporal variations of global terrestrial water storage changes of the Amur according measurements of the Earth’s gravitational fields by GRACE satellite, carried out by foreign researchers. It has been suggested that with a descending trend in areas of coniferous forests, conditions will persist, contributing to increase in streamflow during the period of monsoon and frontal cyclonic rains.

Toward Better Understanding of Terrestrial Processes through Long‐Term Hydrological Observatories

Core Ideas Awareness of hydrological observatories needs to be increased. These 23 papers document hydrological observatories on four continents. Hydrological observatories can help to solve relevant and important scientific questions. Observation of hydrological processes has a long‐standing tradition covering various climatic, hydrologic, geologic, and geomorphologic conditions. Hydrological observations are either organized in dedicated observatories focused on hydrology or within larger environmental observatories that address processes from the atmosphere to the groundwater. In this special section, we document hydrological observations currently conducted in long‐term hydrological observatories and other multidisciplinary observatories across the world. Besides monitoring basic climatic and hydrological variables, dedicated experiments are performed in many of these observatories. Hydrological observatories have proven to be crucial for the advance of the hydrological and greater Earth surface and environmental sciences. The accrued benefits include the development of integrated hydrological models that consider complex feedbacks between hydrological compartments. It is of utmost importance to increase awareness and knowledge of these infrastructures to optimize exploration of new hypotheses in hydrology and neighboring and allied disciplines. This special section consists of 23 papers documenting hydrological observatories on four continents covering diverse environmental conditions and research aspects of catchment science. We expect that the use of worldwide long‐term hydrological observatories across multiple compartments will help to solve important relevant scientific and societal questions.

Form and function relationships revealed by long‐term research in a semiarid mountain catchment

Fifteen years of cumulative research in the Dry Creek Experimental Watershed in southwest Idaho, USA, has revealed relationships between catchment form and function that would not have been possible through independent short‐term projects alone. The impacts of aspect and elevation on incident energy and water, coupled with climate seasonality, have produced tightly connected landform properties and hydrologic processes. North‐facing hillslopes have steeper slope angles, thicker soil mantles, finer soil texture, and higher water holding capacities than their south‐facing counterparts. This trend is modulated by elevation and vegetation; higher elevation sites, where aspect differences in vegetation are less evident, exhibit less distinct hydrologic properties. The storage of water first as snow, then as soil moisture determines how upland ecosystems survive the seasonal and persistent water stress that happens each year, and sustains streamflow throughout the year. The cumulative body of local knowledge has improved general understanding of catchment science, serves as a resource for conceptual and numerical evaluation of process‐based models, and for data‐driven hydrologic education. WIREs Water 2018, 5:e1267. doi: 10.1002/wat2.1267This article is categorized under: Science of Water > Hydrological Processes Science of Water > Water and Environmental Change

How landscape organization and scale shape catchment hydrology and biogeochemistry: insights from a long‐term catchment study

Catchment science plays a critical role in the protection of water resources in the face of ongoing changes in climate, long‐range transport of air pollutants, and land use. Addressing these challenges, however, requires improved understanding of how, when, and where changes in water quantity and quality occur within river networks. To reach these goals, we must recognize how different catchment features are organized to regulate surface chemistry at multiple scales, from processes controlling headwaters, to the downstream mixing of water from multiple landscape sources and deep aquifers. Here we synthesize 30‐years of hydrological and biogeochemical research from the Krycklan catchment study (KCS) in northern Sweden to demonstrate the benefits of coupling long‐term monitoring with multi‐scale research to advance our understanding of catchment functioning across space and time. We show that the regulation of hydrological and biogeochemical patterns in the KCS can be decomposed into four, hierarchically structured landscape features that include: (1) transmissivity and reactivity of dominant source layers within riparian soils, (2) spatial arrangement of groundwater input zones that govern water and solute fluxes at reach‐ to segment‐scales, (3) landscape scale heterogeneity (forests, mires, and lakes) that generates unique biogeochemical signals downstream, and (4) broad‐scale mixing of surface streams with deep groundwater contributions. While this set of features are perhaps specific to the study region, analogous hierarchical controls are likely to be widespread. Resolving these scale dependent processes is important for predicting how, when, and where different environmental changes may influence patterns of surface water chemistry within river networks. WIREs Water 2018, 5:e1265. doi: 10.1002/wat2.1265This article is categorized under: Science of Water > Hydrological Processes Science of Water > Water and Environmental Change Science of Water > Methods

Demonstrating the value of community-based (‘citizen science’) observations for catchment modelling and characterisation

Despite there being well-established meteorological and hydrometric monitoring networks in the UK, many smaller catchments remain ungauged. This leaves a challenge for characterisation, modelling, forecasting and management activities. Here we demonstrate the value of community-based (‘citizen science’) observations for modelling and understanding catchment response as a contribution to catchment science. The scheme implemented within the 42km2 Haltwhistle Burn catchment, a tributary of the River Tyne in northeast England, has harvested and used quantitative and qualitative observations from the public in a novel way to effectively capture spatial and temporal river response. Community-based rainfall, river level and flood observations have been successfully collected and quality-checked, and used to build and run a physically-based, spatially-distributed catchment model, SHETRAN. Model performance using different combinations of observations is tested against traditionally-derived hydrographs. Our results show how the local network of community-based observations alongside traditional sources of hydro-information supports characterisation of catchment response more accurately than using traditional observations alone over both spatial and temporal scales. We demonstrate that these community-derived datasets are most valuable during local flash flood events, particularly towards peak discharge. This information is often missed or poorly represented by ground-based gauges, or significantly underestimated by rainfall radar, as this study clearly demonstrates. While community-based observations are less valuable during prolonged and widespread floods, or over longer hydrological periods of interest, they can still ground-truth existing traditional sources of catchment data to increase confidence during characterisation and management activities. Involvement of the public in data collection activities also encourages wider community engagement, and provides important information for catchment management.

Constitution of a catchment virtual observatory for sharing flow and transport models outputs

Predicting hydrological catchment behaviour based on measurable (and preferably widely available) catchment characteristics has been one of the main goals of hydrological modelling. Residence time distributions provide synoptic information about catchment functioning and can be useful metrics to predict their behaviours. Moreover, residence time distributions highlight a wide range of characteristic scales (spatial and temporal) and mixing processes. However, catchment-specific heterogeneity means that the link between residence time distributions and catchment characteristics is complex. Investigating this link for a wide range of catchments could reveal the role of topography, geology, land-use, climate and other factors in controlling catchment hydrology. Meaningful comparison is often challenging given the diversity of data and model structures and formats. To address this need, we are introducing a new virtual platform called Catchment virtual Observatory for Sharing flow and transport models outputs (COnSOrT). The goal of COnSOrT is to promote catchment intercomparison by sharing calibrated model outputs. Compiling commensurable results in COnSOrT will help evaluate model performance, quantify inter-catchment controls on hydrology, and identify research gaps and priorities in catchment science. Researchers interested in sharing or using calibrated model results are invited to participate in the virtual observatory. Participants may test post-processing methods on a wide range of catchment environments to evaluate the generality of their findings.

Examination of aerial diatom flushing across watersheds in Luxembourg, Oregon and Slovakia for tracing episodic hydrological connectivity

Abstract Hydrological processes research remains a field that is severely measurement limited. While conventional tracers (geochemicals, isotopes) have brought extremely valuable insights into water source and flowpaths, they nonetheless have limitations that clearly constrain their range of application. Integrating hydrology and ecology in catchment science has been repeatedly advocated as offering potential for interdisciplinary studies that are eventually to provide a holistic view of catchment functioning. In this context, aerial diatoms have been shown to have the potential for detecting of the onset/cessation of rapid water flowpaths within the hillslope-riparian zone-stream continuum. However, many open questions prevail as to aerial diatom reservoir size, depletion and recovery, as well as to their mobilisation and transport processes. Moreover, aerial diatoms remain poorly known compared to freshwater species and new species are still being discovered. Here, we ask whether aerial diatom flushing can be observed in three catchments with contrasting physiographic characteristics in Luxembourg, Oregon (USA) and Slovakia. This is a prerequisite for qualifying aerial diatoms as a robust indicator of the onset/cessation of rapid water flowpaths across a wider range of physiographical contexts. One species in particular, (Hantzschia amphioxys (Ehr.) Grunow), was found to be common to the three investigated catchments. Aerial diatom species were flushed, in different relative proportions, to the river network during rainfall-runoff events in all three catchments. Our take-away message from this preliminary examination is that aerial diatoms appear to have a potential for tracing episodic hydrological connectivity through a wider range of physiographic contexts and therefore serve as a complementary tool to conventional hydrological tracers.

Merging perspectives in the catchment sciences: the US-Japan Joint Seminar on catchment hydrology and forest biogeochemistry

Japan has strong research programmes in the catchment sciences that overlap with interests in the US catchment science community, particularly in experimental and field-based research. Historically, however, there has been limited interaction between these two hydrologic science communities because of differences in language, culture, and research approaches. These differences highlight a potential for scientific discovery through coordinated interactions. In this vein, US--Japan Joint Seminars have been held about once a decade since the early 1970s (Yevjevich and Downs, 1971; Bras et al., 1988; McDonnell et al., 2001). In addition, beginning in 2000, Hydrological Processes began hosting annual special issues of the Japanese Society of Hydrology and Water Resources, which furthered the infusion of Japanese research into the English literature (Board of JSHWR, 2000; Tsujimura et al., 2012) and has helped increase participation of Japanese researchers in North American and European scientific conferences. In March of 2013 at the East--West Center in Hawaii (www.eastwestcenter.org), the fourth US--Japan Joint Seminar was held to continue the tradition of fostering interaction, exchanging ideas, and establishing collaborations between the US and Japan in the catchment sciences. This commentary summarizes the goals and outcomes of the meeting and establishes a vision for intercontinental catchment science research in the future.

Www.daylighting.org.uk: case study website supporting research into daylighting urban rivers

Deculverting, or 'daylighting', involves opening up buried watercourses and restoring them to more natural conditions. It is often claimed to provide multiple benefits to society, the environment and the economy. However, the outcomes and objectives of deculverting projects are rarely published, which makes it difficult to evaluate their true effectiveness, determine the best methods to use, or provide quantitative evidence to encourage future projects. At the Catchment Science Centre, we have developed www.daylighting.org.uk in response to this research need. This map-based website of international daylighting case studies records the project drivers, costs and the environmental, social and economic objectives and outcomes. Practitioners are encouraged to enter their own case study details and add to our findings.

Catchments in the future North: interdisciplinary science for sustainable management in the 21st Century

Catchments in the future North: interdisciplinary science for sustainable management in the 21^st Century

Storage-discharge relationships at different catchment scales based on local high-precision gravimetry

In hydrology, the storage-discharge relationship is a fundamental catchment property. Understanding what controls this relationship is at the core of catchment science. To date, there are no direct methods to measure water storage at catchment scales (101–103 km2). In this study, we use direct measurements of terrestrial water storage dynamics by means of superconducting gravimetry in a small headwater catchment of the Regen River, Germany, to derive empirical storage-discharge relationships in nested catchments of increasing scale. Our results show that the local storage measurements are strongly related to streamflow dynamics at larger scales (> 100 km2; correlation coefficient = 0.78–0.81), but at small scale, no such relationship exists (~ 1 km2; correlation coefficients = −0.11). The geologic setting in the region can explain both the disconnection between local water storage and headwater runoff, and the connectivity between headwater storage and streams draining larger catchment areas. More research is required to understand what controls the form of the observed storage-discharge relationships at the catchment scale. This study demonstrates that high-precision gravimetry can provide new insights into the complex relationship between state and response of hydrological systems. Copyright © 2012 John Wiley & Sons, Ltd.

Catchment science and policy for agriculture and water quality

► This paper prefaces 12 state-of-the-science contributions relating to water quality policy and management in agricultural catchments. ► The contributions relate to examples in the European Union on uncertainty, scale and economic perspectives. ► Policy uptake, biophysical and confounding influences on mitigation measures, policy participation and ecosystems services provision are reviewed.

Relating in situ hydraulic conductivity, particle size and relative density of superficial deposits in a heterogeneous catchment

Summary Estimating the permeability of superficial deposits is fundamental to many aspects of catchment science, but can be problematic where insufficient in situ measurements are available from pumping tests in piezometers. Consequently, common practice is to estimate permeability from the material description or, where available, particle size distribution using a formula such as Hazen. In this study, we examine the relationships between particle size, relative density and hydraulic conductivity in superficial deposits in Morayshire, Northern Scotland: a heterogeneous environment typical of many catchments subject to previous glaciations. The superficial deposits comprise glaciofluvial sands and gravels, glacial tills and moraines, raised marine sediments, and blown sands. Thirty-eight sites were investigated: hydraulic conductivity measurements were made using repeated Guelph permeameter measurements, cone resistance was measured in situ with a Panda dynamic cone penetrometer; material descriptions were made in accordance with BS5930:1999; and disturbed samples were taken for particle size analysis. Overall hydraulic conductivity ( K ) varied from 0.001 m/d to >40 m/d; glacial till had the lowest K (median 0.027 m/d) and glacial moraine the highest K (median 30 m/d). However, within each geological unit there was great variability in measured hydraulic conductivity values. Multiple linear regression of the data indicated that log d 10 and relative density (indicated by cone resistance or BS5930:1999 soil state description) were independent predictors of log K and together gave a relationship with an R 2 of 0.80. Material description using the largest fraction (e.g. sand or gravel) had little predictive power. Therefore, in heterogeneous catchments, the permeability of superficial deposits is most strongly related to the finest fraction ( d 10 ) and relative density of the material. In situ Guelph permeameter measurements at outcrops with good geological characterisation provide an easy and reliable method of determining the permeability of particular units of superficial deposits.

Hydrological connectivity and microbiological fluxes in montane catchments: the role of seasonality and climatic variability

There has been an upsurge of interest in the concept of hydrological connectivity to understand various aspects of catchment science (Bracken and Croke, 2007; Ali and Roy, 2008). Much of this work focuses on the dynamic role of connectivity in explaining the nonlinearities in catchment hydrological response; as the transient connection of hillslopes to channel networks is at the heart of important issues such as flood generation (e.g. Lane et al., 2004), diffuse pollutant fluxes (e.g. Jordan et al., 2007) and the trigger of many important ecological events (e.g. Tetzlaff et al., 2007a). These issues come together when considering the risk of microbiological pollution of surface waters by faecal pathogens which may include bacteria, viruses and protozoan parasites from warmblooded animals (Geldreich, 1996). This is an important applied topic with implications for human health, although one, poorly understood and an area where insights from process hydrology have not contributed as much as they might (Kay et al., 2007). Runoff processes in urban, agricultural and more extensively managed ‘wild’ landscapes play a crucial role in connecting pathogen reservoirs in the landscape to the river channel network (Kay et al., 2005). Managing this pollution risk requires different approaches under different land uses; however, there is a particular challenge in relatively undisturbed montane regions where the spatial distribution of pathogenic agents mainly relates to the distributions of wild animal populations which are often unknown. Yet in many such regions, water bodies are used for recreational activities and water supplies for dispersed populations usually have limited treatment. Thus, microbiological pollution may have significant health risks in areas often mistakenly considered ‘pristine’. If policies such as the European Union’s Water Framework Directive (WFD) are to be implemented, integrated catchment management of diffuse pollution requires that these issues receive more attention (Kay et al., 2010). The relationship between microbiological pathogens and hydrological connectivity in montane regions introduces complexities, particularly in terms of the seasonal influence of temperature and moisture availability on microbial survival and reproduction. There is already an identified need to develop appropriate metrics to quantify hydrological connectivity in different environmental settings (Ali and Roy, 2008). Such metrics have generally focused on physical and chemical parameters, which may differ greatly in different catchments. For example, assessing connectivity in overland flow dominated catchments (e.g. Birkel et al., 2010) will require approaches that differ from those applicable to catchments dominated by sub-surface flows (e.g. Lehmann et al., 2007). Here, we highlight the critical importance of seasonality in understanding how hydrological connectivity influences landscape and riverscape interactions to control fluxes of microbiological pollutants in a montane catchment in Scotland.