Hydrology Corner Blog: rating curve

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.

Drones Hydrometry Perspective - Hydrology Corner Blog

Drones – Providing a New Perspective on Hydrometry

A different point of view changes nothing but it can change everything. Last week I wrote about how unmanned Aerial Vehicles (UAV), also known as drones, could be used for Large Scale Particle image Velocimetry (LSPIV) to get surface velocity measurements, which when combined with surveyed cross-sections can produce extreme flow gaugings. That same drone, equipped with the same camera, can also provide the cross-sectional information needed to complete the job.


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.

Ray Maynard Hydrographer - Complex Ratings & the Hydrometric Savant

Complex Rating Curves & the Hydrometric Savant

Imagine, for a minute, your stereotype of a person of learning; especially one with detailed knowledge in some specialized field of science. I expect the person filling your mind’s eye is not a ruddy-faced bloke with a substantial belly and a thick Queenslander accent wearing shorts and R.M.Williams boots. Appearances are deceiving. I first met Ray ‘Rainman’ Maynard in Nelson, New Zealand.

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.

Zen and the Art of Stream Gauging

Those who work closely with data recognize the value of incremental investment in data quality; however, there is despair that this value can be quantized in terms that are meaningful to the bean-counters who control and allocate funding for monitoring programs. The discussion prompted by ‘Economics of Data Quality’ remind me of aspects of the novel ‘Zen and the Art of Motorcycle Maintenance’ by Robert Pirsig. The story is about many things but it is mostly about a search for quality.

Water monitoring, Hydrology, Water data management software, Rating curve, Stage discharge curve

2014 NWQMC Takeaway – The Industry is Moving to Continuous Monitoring

Day 2 of the National Water Quality Monitoring Conference in Cincinnati, OH was an interesting day of presentations. The rest of the week appears to be just as fascinating. It has been great reconnecting with old peers, making new connections, and listening to the presentations on some very thought-provoking projects. The passion for water resources…

Water monitoring, Hydrology, Water data management software, Rating curve, Stage discharge curve

Three Great Reasons to Update Your Subscription to Hydrology Corner

Dear Readers, Over the past three years Hydrology Corner has grown from a ground breaking blog on hydrology topics, to a multi-author source for cutting edge news, information, and opinions about hydrological best practices. Today, we are announcing an upgrade to our email subscription services to better serve a growing readership. This new system will…

Water monitoring, Hydrology, Water data management software, Rating curve, Stage discharge curve

Neil Young & The World Bank – Water vs Energy

The recent uproar over Neil Young’s comments about Alberta’s oilsands development got me thinking about energy and water. Water is used in many of our energy generation methods. Whether it’s hydro power, thermal generation, oil extraction, etc., water is vital to most current energy production methods. That might not be a problem except water is…