River Thames Conditions

15 Apr 2024
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Good afternoon.

I am new to the River Thames, and am getting an understanding of the "river conditions" that appear to be given daily by the EA on an advisory basis. I view them on the River Thames Guide APP. I see this morning for the 1st time (for me) that some reaches have "No current data". I am not sure whether they are referring to "current" flow or "current" up to date!

Anyway, my question is, is the colour of current condition defined by a flow meter in each reach, or is there a human that looks at the flow each day, and uses his or her judgement on whether it is a "Red Board" flow, or Yellow or Green? I look forward to hearing from those that may know.



Active member
27 Mar 2012
Bedfordshire and Surrey
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River conditions are defined by the number of weir gates open on each stretch of river. Every set of weirs on the Thames is individual and has a different number of individual weir gates. As the river level goes up some weir gates are opened to maintain the river level, once a certain number of weir gates are open this triggers a change in the conditions from green to yellow or to red. The weir gates are called tackle and when the gate is open it is drawn.
River flow is measured as a flow rate volume in cubic metres per second as flow speed varies greatly with the rivers width and depth.