how to utilize the gravity on transporting water from on point to other point?

Question

In agriculture we need to supply water for plants from 100 to 200 meters so i planned to built tank where water is staked in a tank with certain height so water from tank flows to the distance required with out external force ,But the problem is i dont know how exactly to calculate the Required height of tank which gives required force

Answer 1

The factor is about 0.433 pounds per square inch per 1 foot of elevation. A 20 foot elevation drop gives about 8.6 psi. This doesn't sound like much, but it does add up. my advice is to keep it contained in a pipe. By running it in a ditch, all the head pressure is dissipated, so you then need a pump to move it.

Using the pressure to distribute requires a more costly piping system, but your maintenance and water loss will be less in the long run. Do keep in mind, that you have friction loss in any pipe (or ditch), that will lower your dynamic pressure (pressure while drawing water). Maximizing your pipe size for the required flow will help to minimizing your friction loss.

Answer 2

Firstly, you find out which is the highest point of elevation of area of your agricultural land. To find out highest point you can take the assistance of any surveyor. If you think that is not possible you can do it by using water level method (water filled in long 1/4" tube and shift it along the area and measure the level at each point and shift and measure etc.) and at highest point you can build the tank. If you are able to build tank at highest point make sure to give vent points at every certain points to avoid any air entrapment. This is very important.
If you think that is not possible to build tank at highest elevation then you can not possibly give water to all of your plants by gravity force. You have no other choice than fix centrifugal or reciprocal type pumps of your requirement.
Method for calculation of pressure or elevation is, for every 10 meters of height 1 KG/cm² or 14.2 psi of pressure we can assume. From 100m to 200 m you have a elevation difference of 100 meters that is accounts for 10 KG/cm² (142 psi or pound per squire inch.) so you have to select a pump which can give you minimum 11 KG/cm² of pressure. This is required only when you are unable to build tank at the highest elevation. I hope this will clear to if you have an engineering background.

Answer 3

For every 1 foot of elevation increase water provides about 1/2 pound / in^2 of pressure increase. So unless you are planning high flow rates through small pipes, this should be all you need to know.