I am very happy to announce that the paper: The Role of the Hydrographer in Rating Curve Development has now been published in Confluence: Journal of Watershed Science and Management. Marianne Watson, Robin Pike, and I all learned a lot from each other in the process of writing this paper, resulting in a product that is greater than the sum of the inputs....

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An image of blind people, rating curve, and Goldilocks.

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....

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An illustration of stage-discharge rating curves.

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...

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An image showing drones for 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...

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An image showing stage discharge rating curve.

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....

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