Hello folks.

I'm new to posting on the forum, but I have been directed here in many of my searches on hydropower over the past while. Recently I've searched and skimmed the entire hydro section. It has been often informative and helpful. And sometimes amusing.

I don't have much to offer that hasn't been covered, but the methods I'm about to present are potentially significant. The write-up has been quite a chore, so I hope some find it useful.

In my review of forum topics the most frequent inquiry is whether the poster's waterway has any potential for usable power. The standard answer is head times flow and how to measure these. I didn't find anyone suggesting that in big fall sites, an adequate estimate of the head can be found by consulting Geologic Survey Maps. Of course, because the contours are limited to 10 feet or greater steps (depending on the map) they are not adequate for low head sites.

However, even in low head sites such as my own the Survey maps can be very useful.

Big brother is watching our water flow and make the data available for you, your neighbors and the authorities, here:

http://www.usgs.gov/water/I found tremendously detailed records of water flow at a gaging station 4.38 miles away, starting in 1960. Wow!

Using this data and the Survey map I'm able to extrapolate flow history for my site.

If you'd like to do the same for yours, perhaps it's best to use the above site to locate the gage closest to your hydro site. It doesn't have to be on your water way or even in your drainage area, just close enough that you expect it receives the same amount of precipitation as your site.

While you're there, explore the data available, such as daily flows, highs, lows, averages, ect. The piece of information you will need to relate all this data to your site is the total drainage area the gage covers. So, write that down.

The rest of the process is somewhat tedious, but only has to be done once and it will be useful forever. I believe Geological Survey maps can be downloaded or purchased from this site:

http://store.usgs.gov/b2c_usgs/usgs/maplocator/(ctype=areaDetails&xcm=r3standardpitrex_prd&carea=%24ROOT&layout=6_1_61_48&uiarea=2)/.do

Supplies Required:

1. Hard copy map to mark and calculate the drainage area for your hydro site.

2. Tracing paper. (Any paper you can see the map through will do.)

3. Pencil.

4. Ruler.

5. Square. (Any solid object with a 90 degree angle will do.)

Steps:

1. Locate and mark your site on the map. Using your knowledge of the terrain, follow the contours on the map to mark the high points that form the rim of the drainage basin higher than your intake or turbine site. The object is to include all the land that drains through your waterway. Mark the tops of hills and draw lines between them, that will be close enough and straight lines will help later. Also draw lines from the ends of the rims to your proposed turbine location.

2. Tape tracing paper over the map and transfer your drainage outline to it. You may want to cut this out to make it easier to work with, I did.

3. Segment your area such that it is composed of triangles. Fewer is better. Don't worry about the shape. Long and skinny. Short and fat. All good.

4. Concentrating on one triangle at a time, find the longest side. Using the base and a square draw a dotted line 90 degrees from the base to the point. Measure the length of the base and the midline. Multiply these two lengths and divide by two (2) to calculate the area of the triangle segment. Note: I measured to the closest eighth inch and recorded all results in one-twenty-eights (1/128) to keep units the same. Also if we multiply x/8 * y/8 we end up with z/64 and just changing the 64 to 128 performs (avoids) the dividing by two (2) operation. Slick! (Don't you just love math?)

5. Repeat step 4 for all triangles.

6. Add the total of all the triangles area in square inches. When the denominators are the same (common), it's easiest to add, for example: 456/128ths + 123/128ths, by ignoring the denominator: 456+123=579, until the total is done: 579/128=4 67/128 or 4.5234375. (This way it's all addition until the last one division.)

7. Find the scale on your map and convert your square inches to square miles. Mine was 1:24,000 and a quarter inch (1/4") equals approximately 520 feet, a tenth (1/10) a mile.

8. Divide your total square miles by the gaged drainage square miles given on the data site. This is the factor you can use to convert the flow data on the web site to flow data for your site.

9. For example: (Reported flow data point) * factor = (your flow data point)

Questions? No. Good. Have fun. Figure out what the flow was on your birthday, your anniversary, during hurricane Sandy or the day the driveway flooded!

You finally have the information you need to figure if your site has usable power and how best to use it if it does.

And if it turns out there isn't usable power, you'll still be able to give a definitive reply to any well meaning visitor that exclaims, "You should do something to generate electricity with that water!"

ThreeTimes