Peter, An alternative for larger flows is to choose a regular part of the river/stream say 20 m long and measure the cross-sectional area (take several measurements of depth and a representative width). Toss in a float (an orange is quite easy to see) and time it over the 20 m. You may want to average a number of attempts. Then:
Flow = TF*(cross sectional area * length)/time Where TF (say 0.8 although I hope others will correct me on this) is a twiddle factor to account for the fact the orange is moving in the fastest part of the water. Obviously this is a once off measurement and may not be representative at all. Many of our rivers in Ireland are flashy (this has its own difficulties for hydro installations) and it would be much better to use long term records if they are available. Kind Regards, Martin *********************************************** Martin J. Leahy DPhil (Oxon) CPhys MInstP FRAMI Millstream Energy, The Millstream, Abbeyfeale, Co. Limerick IRELAND Email: [EMAIL PROTECTED] 086 6055572 TEL: 00353 61 213056 FAX: 00353 61 202423 *********************************************** -----Original Message----- From: Peter Schneider [mailto:[EMAIL PROTECTED] Sent: 12 May 2005 22:24 To: microhydro group Subject: [**Possible SPAM**] [microhydro] Re: weir method on natural weirs? 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] Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links ------------------------ Yahoo! Groups Sponsor --------------------~--> What would our lives be like without music, dance, and theater? Donate or volunteer in the arts today at Network for Good! http://us.click.yahoo.com/TzSHvD/SOnJAA/79vVAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
