I plan to construct a water storage from the rains in Himachal India and use it for a efficient farming in 1 acre of land throughout the year. I plan to construct a water storage of about 15m x 15m and around 6m deep. A water storage of around 1350 cubic metre.

1. Is that enough ??? If I use sprinklers etc.

2. How much will it cost ? three sides of the storage are underground (its a valley kind of situation) and one side is open and needs to be closed using a full retaining wall.

3. What would be the cheapest mode of constructing this ? earthwork ? how much will it cost. We have enough stones around to be used.