Ecohydrology across scales

Lake Ontario and Toronto, Canada © Peggy2012CREATIVELENZ

The University of Waterloo’s ecohydrology research group focuses on the effects of environmental change on water quality as the world faces mounting water-related challenges

Physical water shortages, such as those currently experienced by the inhabitants of Cape Town, South Africa, are widely recognised. The degradation of water quality, however, may pose even more widespread threats to biodiversity, ecosystem functions, food production, human health, and economic growth. Not surprisingly, therefore, water quality issues figure prominently in the United Nations 2030 Sustainable Development Goals (SDGs).

These issues are not limited to developing countries, however. In Canada, for example, harmful and nuisance algal blooms are a recurrent phenomenon in many freshwater bodies, even in the iconic Laurentian Great Lakes, while there are over 150 drinking water advisories across the country, mostly affecting First Nations communities.

Globally, awareness is also growing that climate change adaptation must be an integral part of planning and implementing effective water management policies and practices. In many areas of the world climate warming is causing more severe wet weather events. The resulting more intense flooding brings about a variety of environmental and economic impacts, including the deterioration of water quality and ecological impairment of rivers, wetlands, and lakes.

Research advancing the predictive understanding of the sources and fate of contaminants along the aquatic continuum, as well as smarter ways to assess and monitor the state of water resources, is crucial for the development of sustainable solutions for a safe water future.

Ecohydrology Waterloo-style

Ecohydrology comes from the contraction of ecology, which studies the interactions between organisms and their physical environment, and hydrology, the science of water. Because human activities – agricultural, industrial, and domestic – all depend on water, ecohydrology is intimately linked to social and economic wellbeing.

The ecohydrology research group (ERG) at the University of Waterloo, Canada, carries out fundamental and applied research in support of the wise use of water resources – that is, one that balances society’s water needs with those of natural ecosystems.

The group was established in 2011 and forms a cornerstone of the university’s Water Institute. What sets ERG apart is the vast range of spatial and temporal scales covered by its research activities, from molecular-level studies on the processes that determine the chemical forms and bioavailability of nutrients and pollutants, to global-scale assessments of anthropogenic perturbations of the hydrological and biogeochemical cycles.

Processes: mechanisms and rates

A distinctive strength of ERG is in the field of biogeochemical kinetics, which aims to unravel the reaction pathways and networks that govern the chemical state and evolution of natural waters, and predict the rates at which the corresponding reactions take place in the environment.

ERG’s focus is on reaction processes that are involved in the mobility and environmental fate of nutrient elements (carbon, nitrogen, phosphorus, silicon, sulphur, and iron) and contaminants, most notably the toxic metalloids arsenic, chromium, and selenium, as well as hydrocarbons and microplastics.

Fig. 1 Contaminant transformations are studied in custom-made reactors under variable geochemical and microbial conditions (Courtesy: Dr Ekaterina Markelova)

Research highlights include the discovery of novel interactions between arsenic and sulphur in reducing environments, such as wetland soils and polluted aquifers, with profound implications for source water protection and the design of remediation technologies to remove arsenic from drinking water. Related work explores how soil micro-organisms cope with elevated concentrations of harmful metalloids, while other projects look into the mechanisms that cause the sequestration of nutrients in lake sediments or, conversely, promote their release back to the overlying water column where they can contribute to excessive algal growth.

Many of these projects benefit from in-house developed reactor systems in which biogeochemical processes and their rates are investigated in detail under environmentally relevant conditions (Fig. 1), as well as from field-based measurements and remote sensing data. The knowledge and observational data acquired in the process-oriented studies are subsequently incorporated in quantitative models.

Models: integrated and scale-adaptive

Another hallmark of ERG is the development of models that couple biogeochemical reaction systems to transport processes in soils, groundwater, rivers, lakes, and coastal ecosystems. In particular, ERG researchers have developed very sophisticated reactive transport models to interpret high-resolution chemical distributions and flux measurements in soils and sediments.

In a recently completed study such a model was used to delineate the circumstances under which stream sediments act as a source or a sink of nitrite, a reactive and toxic intermediate in the nitrogen cycle.

Fig. 2 Remote sensing data are used to drive and validate coupled hydrodynamic and biogeochemistry models that simulate past and future lake water quality at daily to decadal timescales. Data shown are for the Laurentian Great Lakes (Courtesy: Dr Homa Kheyrollah Pour)

In other studies, models coupling biogeochemical reactions to hydrodynamic simulations are helping to assess the vulnerability of water quality in lakes and reservoirs to future changes in climate and upstream land use (Fig. 2).

Coarser (so-called ‘parsimonious’) mass balance models are providing estimates of the long-term accumulation and permanency of contaminant legacies in agricultural and urban landscapes.

Along similar lines, dynamic phosphorus and nitrogen budgets have been reconstructed for the Mediterranean Sea since 1950, plus projections from now until the middle of the century.

Modelling efforts have also yielded the first geographically explicit, global assessments of the effects of damming on nutrient delivery by rivers to the world’s coastal zone. The results help explain why nearshore marine biological productivity is increasingly limited by the availability of phosphorus, rather than nitrogen. Coastal management should therefore focus on phosphorus abatement strategies in order to control coastal eutrophication.

ERG researchers further contribute to improving the theoretical foundations of ecohydrological modelling, for example, by deriving thermodynamically consistent representations of microbially mediated reaction processes or by developing new, multi-objective model calibration protocols.

Actionable research

By combining laboratory-based studies, field observations, and numerical modelling, ERG researchers are closing major gaps in our understanding of how anthropogenic pressures are changing the environmental flows of water, nutrients, and contaminants at the local to global scale.

This understanding in turn enhances the depth and rigor with which risks to water quality and aquatic ecosystem services can be assessed, under current and anticipated future stressors.

As a logical outcome, ERG’s research is becoming ever-more integrated with economic cost-benefit analyses, the development of innovative water quality sensors and sensor systems, and the establishment of sustainable socioecological goals and policy-relevant environmental indicators.

Read more about the work of Professor Dr Philippe Van Cappellan and the work of the Ecohydrology Group in Pan European Networks: Science & Technology, issue 23

Special Report Author Details
Author: Philippe Van Cappellen
Organisation: Department of Earth and Environmental Sciences, University of Waterloo
Website: Visit Website
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