Closing the Gap: Hydrological Science and Practice

The NASH symposium this year was held at the joint CWRA/CGU national convention in Banff, Alberta.

This was the first joint convention between the Canadian Geophysical Union – the home of Canadian research hydrologists – and Canadian Water Resources Association – the home of Canadian water resources engineering practitioners. There has always been a big gap between research and practice in hydrology. Practitioners need to be better informed about the state of the art in process understanding and researchers need to be better informed about the nature of the problems faced by practitioners.

In particular, it is apparent that static, textbook, approaches to water resource engineering are incapable of meeting current expectations for adaptive management of water resources.

Many assumptions implicit in traditional solutions are demonstrably false (e.g. stationarity in the climate signal); our current understanding of scaling, thresholds, and non-linearities in natural systems is at a level of sophistication that was inconceivable when most water resource engineering text books were printed; data rich in information about the structure and behavior of aquatic systems are now available that have not been previously considered as tools for water resource management (e.g. stable isotopes); and water resources management practice is being pushed into landscapes that were out of scope of the seminal studies on which water resources engineering practices are based (e.g. recently de-glaciated landscapes).

The conference had 8 parallel sessions forcing tough choices between many equally compelling subject areas. For me the priority was – of course – the NASH symposium, of which I will write more in future blog posts. For now, I will just describe three out of dozens of examples of the opportunities for improving the knowledge-base for water resources management.

The session on tracing and fingerprinting sediment sources and transfers in watersheds discussed the use of radionuclides, DNA and stable isotopes as tracers.

Apparently, a residual of atmospheric depositions of radionuclides from cold war nuclear testing provides a unique marker in the upper soil horizon. Measurements of Cesium 137 concentration in suspended sediments provide a marker of sediment source. High concentrations mark hillslope erosional sources and low concentrations mark fluvial erosional sources. Microbial Source Tracking and detection techniques use DNA analysis of microbes sampled from the water column to trace their origin. The origin of fecal coliform contamination can be traced back to a specific feedlot. The ratio of 15N to 13C provides a signature of the source of nutrients in the aquatic ecosystem allowing for an improved understanding of the role of anadromous species such as Salmon as key species in aquatic ecology.

The Keynote address by Dr. Jeff McDonnell discussed recent advances in understanding of how water moves through hillslopes.

This research is based on the use of the stable isotopes 18O and 2H as markers of the residence time of water in the catchment. The use of this data has contributed to a greater understanding of the role of the lower boundary of the soil profile as a control on the throughflow recession rate. It turns out that these boundary conditions are at the heart of thresholds, hysteresis, and continuity in flow pathways. It also turns out that trees primarily use tightly bound soil water not mobile water as commonly assumed. This research demonstrates that many commonly held assumptions may need to be challenged with respect to forest stand management, slope stability, and water quality management in small watersheds.

David Sauchyn’s presentation ‘informing adaptation to the hydrologic impacts of climate variability and change’ provided a very large scale perspective on temporal change in water availability.

His research is based on streamflow reconstruction over the past thousand years using dendrochronology. It can be shown that there are several periodic cycles in water availability including the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The challenge for anyone trying to make inference from observational records is that the PDO signal has a period of about 60 years. Disentangling the PDO signal from the influence of climate change and of land-use change therefore becomes, at best, very, very, difficult for almost all observational periods of record.

This is a very exciting time for all of us working at the intersection of the science and practice of hydrology. Even if you did not previously think you are at this intersection, you may be closer than you think. The need for a deeper, more complete, understanding of watershed behavior is growing in proportion to the increasing stresses on water availability. This improved understanding will be built on new sources of data and expert interpretation of what this data means.

About Canadian Water Resources Association (CWRA) – The CWRA is a national organization of individuals and organizations from the public, private and academic sectors that are committed to raising awareness of the value of water and to promoting responsible and effective water resource management in Canada. CWRA membership consists of water users and water resource professionals including managers, administrators, scientists, academics, students and young professionals.

About Canadian Geophysical Union (CGU) –  The CGU began as a society dedicated to the scientific study of the solid earth and has evolved into one that is concerned with all aspects of the physical study of Earth and its space environment, including the Sun and solar system. To express this broader vision of the geophysical sciences, the Union has adopted a sectional structure that allows individual sections to function as semi-autonomous entities.

About North American Stream Hydrograhers (NASH) – The aim of the North American Stream Hydrographers (NASH) is to bring researchers and practitioners together into a community of practice for advancing the science of stream hydrography. We exist at arm’s length from the day-to-day pressures facing monitoring agencies, and advocate the development and sharing of best practices, informed by a long-range perspective of desired outcomes for hydrometric data. Such a perspective is essential to reflect more comprehensively the timescales of relevance when monitoring the hydrological cycle.

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