for 1 ≤ z ≤ 50 and 0.2 ≤ cc ≤ 2.0. A pipe length of 50 m with a 1.0 m spacing yields the same amount of water as 40-m long pipes with a 2.0-m spacing, though the area required in the latter case is 60% greater. Therefore, the highest water production in this system is obtained when the pipes are placed as narrow as possible. The pipes should also be made as short as the area allows