In Ireland, the EPA had a super booklet about building those weirs. They are very accurate indeed and you can probably make one that is accurate to within less than 5% with ease. And I am betting you can find instructions on the web for making 90 degree and half 90 (which is not 45 if I remember correctly) weirs. And really, why go more accurate than that? A stream flow varies between morning and evening and even with how cool the weather is in both summer and winter. A half decent wier is way more accurate than any other measuring system for flow as far as I know. Brian White --- In [email protected], "Peter Schneider" <natural. [EMAIL PROTECTED]> wrote: > > Dear all, > I often come across the problem to determine the approximate flow of a river, just to give people an indication of whether their site is worth thinking about hydro power. > Of course, the bucket-and-watch method is straightforward, but not really possible above a certain flow. > I know the weir method, but building an accurate rectangular weir takes some effort and time. Therefore I am wondering, how accurate is it to use a natural 'weir' for measurement? Usually, you would not have a sharp edge, and often not a vertical fall behind it. I know this affects the accuracy, but by how much? Is it safe to assume e.g. a maximum minus 30% for this? Does anyone have experience with this? > > Peter Schneider > Ireland > email: [EMAIL PROTECTED] > > > > [Non-text portions of this message have been removed] >
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