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Reading Water

Reading Water

Learning to read water is much like learning to read. First you have to know your A,B,C’s. Next, you start putting together sounds, and soon your first small words. Then come bigger words, sentences, phrases, paragraphs, and finally complete books. It takes time to become profiecint at reading water, just as it does in reading books. There are still going to be words you come across that you dont know the meaning of, much like finding a feature in moving water that doesn’t make sense. Do your best to use context clues and the words you do know, to get the meaning of what you’re reading.

In analyzing and understanding moving water, the A,B,C’s are the individual features in moving water. Rocks, waves, current lines, holes, pillows, eddys, etc. Understanding how water reacts with the features, and how it behaves when in interacts with these features will help you on your way to reading water. As rescuers we rely heavily on an ability to size-up a scene and determine our rescue options. Setting down-stream safety and upstream spotters centers on a good understanding of moving water. Knowing “when to go” ultimately comes down to someone’s reaction after reading water.

Identifying hazards. The more familiar you become with hazards in a river the easier it will be for you to see them coming and avoid them. Hazard ID may also dictate the deployment of a rescue, and the egress / regress options. Here are a few visual cues that can alert you of potential hazards.

Horizon line: Evidence of a significant drop in gradient; a line across the river where your downstream view terminates.

Bump, hump or dome: Indicates a rock under the surface that creates a hole when water passes over and falls back onto itself.

Pillow: Indicative of water hitting and obstacle and recoiling off of it. Think of a pillow as a buffer between the rock.

Lack of a pillow: If a rock or obstacle is in view above the surface and there is no pillow, then the water is passing somewhere sub-surface, and could be evidence of an undercut rock or sieve.

Surface obstacles: Can be hazards themselves, but can also harbor a safe eddy on the downstream side.

Strainer: Branches sticking out of the water are an easy I.D., but a more subtle identifier could be a hump or horizon line. (Often times near the shore or upstream of a rock).

The above list is by no means exhaustive, but it is a start to understanding moving water and the hazards it can create.

Some basic Hydrology 

Rapids are formed by a combination of three factors: gradient, volume, and obstacles/constriction. Together these factors compose the majority of rapids you’ll encounter. A waterfall is an example of the first two: some amount of water flowing over steep gradient. Classic whitewater rapids on rivers typically combine all three. There are places in some rivers where only volume and gradient are present. Typically these sections are relatively flat.





Water doesnt like voids. If there is a void, water tries to fill it. When water passes over a subsurface rock and plunges downward, it creates a void that it then tries to fill. Water falls back in on itself and creates a hole or reversal. The more uniform (ledge-like) the rock creating the hole is, the more retention power the hole has.



Water typically moves to the outside of a river bend. As a result, the larger features of a rapid can often be skirted by moving toward the inside of a turn in the river. Sometimes the inside is impassible due to shallow water.

Keep in mind that water-levels can change features and hazards. What was once an exposed rock, could become a keeper hole at higher flows. Water is dynamic, and while the rocks don’t always move, the water constantly is and it is strong. Don’t underestimate the  force of moving water.

Challenge yourself to get better at reading water. Take time to look at river features and describe what’s happening. Play the ‘what-if’ game. “If I were over there, then…”  The more features you see and analyze, the better you will become at reading water. Developing an ability to read water will make you a better rescuer, guide or boater. Want some help? Come take a course with us at Sierra Rescue. Bear in mind reading water is only half the battle. Sure you scout and have a detailed understanding of what the water is doing and the line you want to take. Now the hard part is getting there safely!