A hydraulic control is typically only defined, or found, in relation to the formation or presence of a pool. In other words, you are unlikely to have a true hydraulic control (that creates a continuous, flat water surface elevation) without having a pool. If you have a pool, a hydraulic control is likely present, but it may be hard to determine the control type - cobble or boulders are easy to visually assess, but if a streambed consists mostly of sand and gravel while curving gently upwards at the end of a pool, it can be considered a hydraulic control, though it is harder to identify.

Tom,

Based on your response here, when you say "if a streambed consists mostly of sand and gravel while curving gently upwards at the end of a pool, it can be considered a hydraulic control"--our question is, should the sand/gravel slope following a pool always be considered a hydraulic control? We have the opposite question of the original post: Can you have a pool without a hydraulic control? (when there is no cobble or boulder boundary (or other barrier type) at the end of the pool)

Hello,

Can you ask this on a separate post, and if possible, provide a photo?

Thanks,

Tom