Hydrology Corner Blog: Best practices

Women in Water, Week 1: Paving the Way

As part of our Women in Water series, started on International Women’s Day, we are interviewing women across the world who are dedicated to the protection of the water and the environment, and the use of technology to do so. This week, we met with Donna Hollis, an AQUARIUS user from TasWater, and Alice Ohrtmann, a Linko user from Rock River Water Reclamation District.

Reality by the Numbers – What the Spreadsheet Has Done to Us

There is a hidden cost behind the reliance on spreadsheets that is invisible to those who are dependent on them. Most people use spreadsheets for multiple purposes, so using spreadsheets to manage water data seems “free” relative to the cost of purpose-built software for data management. A National Public Radio Podcast about spreadsheets was recommended to me by colleagues at the CWRA conference in Lethbridge last week.

Water Data Truth

Internet Truth vs Verifiable Truth – The Importance of Traceable Provenance in Water Information

The most passionate people involved in the water monitoring industry all care deeply about the preservation of traceable provenance for their data. To people on the outside this can seem like an indulgence that adds a burden of work to the data management process with little apparent benefit. The benefit is ‘verifiable truth’, a distinction with little value. Until it matters!

Rating Curve Blind Man Elephant & Goldilocks - Hydrology Corner Blog

Rating Curves, Blind Men, an Elephant, and the Goldilocks Principle

While there must be an underlying true relation between water level at a given place and time and the corresponding discharge, our experience of that truth is limited to gauging observations from which we must infer the totality of the relationship. It is generally true that if you give the same set of data to “n” different hydrographers they will produce “n” different discharge hydrographs. There is no assurance that any of the hydrographs are actually true. Each hydrographer is making inference about what they believe to be true based on a relatively few gaugings.


Stage-Discharge Rating Curves – Geophysics or Religion?

Almost everything we know about our global freshwater resources is due to the humble stage-discharge rating curve. The vast majority of all flow data ever produced is the derived result of a transform from a variable that is easy to monitor continuously (stage) to a variable that is impossible to directly measure continuously (discharge). This means we are dependent on rating curves for advancements in hydrological science; for flood forecasting; for drought management; for engineering designs that provide us with physical safety, transportation, water supply and waste disposal; for water management policies and decisions that ensure energy and food security.


Extreme Gauging – How to Extend Rating Curves With Confidence

Extreme flows are extremely hard to gauge, hence we get very few gaugings to accurately define the top-end of stage-discharge rating curves. This is a problem. Whereas empirically calibrated functional relationships can be trustworthy for the purpose of interpolation, they can be notoriously unreliable for extrapolation. One needs to be very careful about extrapolating any rating curve to an ungauged extreme.

International Rating Curve Standards

Rating Curves Workshop – International Best Practices Explored in New Zealand

Stage-discharge rating curves define a unique relation between water level and discharge, enabling continuous derivation of streamflow from water level record. This is important because water level (which is relatively easy to monitor) is only locally relevant whereas discharge (which is relatively difficult to measure directly) is the integral of all runoff processes upstream of the gauge. The vast majority of all streamflow data that has ever been produced is a derived result of a rating curve. In other words, almost everything that we know (or rather that we think we know) about hydrology is a result of rating curves.

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…