For the parallel pipe drains of Problem 17.5, the length of drain is 7230 ft. The surface gradient is 0.5%. The water table is generally parallel to the ground surface. Determine the peak discharge due to deep percolation and upstream slope. Also design the drain. n = 0.011.

Problem 17.5

For an agricultural drainage system, design the drains (determine the drain spacing) for the following conditions:

1. Depth from surface to impervious layer = 30 ft

2. Depth of drains from surface = 8 ft

3. Root zone or water-table requirement = 4 ft below the surface

4. Uniform hydraulic conductivity = 10 ft/day

5. Water application is as follows:

6. Each irrigation application, as well as spring snowmelt, contributed to a deep percolation of 1 in. (Adapted from the Bureau of Reclamation, 1984.)