Water Power From Small Streams 



How you may estimate fairly accur- 

 ately the capabilities of any stream 



tiic capauiiiLics oi any ; 



By H. B. Richmond 



r-rw 



kHE very stream to run my lighting 

 generator!" How many times have 

 you thought that, when unex- 

 pectedly you came upon a little stream in 

 the woods? But have you really any idea 

 of just how much power can be obtained 

 from a stream? Let us consider the situa- 

 tion, so that the next time you see a stream 

 you will be able to estimate instead of specu- 

 late how much work it is capable of doing. 

 We will not bother about the refinements 

 of stream gaging, or the intricacies of the 

 design of turbine blades. Just enough of 

 the fundamental principles to enable us to 

 arrive at the desired result will be sufficient. 

 That result is power, and the two items 

 which make it up are the quantity of water 

 flowing and the distance it falls. Quantity 

 is measured in gallons per second, cubic 

 feet per second, or other convenient units. 

 The distance through which the water falls 

 is known as the head and is measured in 

 feet. Power may then be said to be the 

 product of the quantity Q by the head H. 

 If we accept the cubic foot per second as 

 the measure for Q, the foot as our measure 

 for H, and the horsepower as our measure 

 for power we have the equation P = ^ 

 This assumes that all the water power may 



be converted into work, which unfortu- 

 nately is not true. In large installations it 

 is not uncommon to utilize 80 per cent of 

 the water, but for small streams it would 

 not be wise for us to count on much over 

 one-half. Taking allowance for this factor 

 our equation would become, say P = ^. 



Now all this is very fine if we know Q and 

 H. Fortunately it is not very difficult to 

 get an estimate of these quantities. If the 

 water is coming over a single fall it is not 

 at all hard to estimate or to actually 

 measure the height in feet. If there are a 

 series of falls to be utilized the sum of the 

 heights of the several falls would be the 

 height to use. This, of course, implies that 

 the stream would be dammed at the last 

 fall so that the water would back up to the 

 level of the first fall, or that the dam would 

 be placed at the first fall and then the 

 stream carried on a level through a pen- 

 stock to a point above the last fall. 



It is not such an easy matter to determine 

 the quantity of water flowing. A very 

 simple way to get an estimate is to drop a 

 small piece of wood in the stream a little 

 distance above the falls and note the speed 

 with which it is carried down the stream. 

 I dropped a chip in a little woodland 



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