Passive Capillary vs Conventional Drainage of Push-Up Greens

Technical Info

Dr. Ed McCoy

Ohio State University

Passive Capillary Drainage (PCD) of push-up putting greens essentially consists of installing fibrous capillary drainage elements to a depth of 9 to 10 inches and at a spacing of 3 feet within areas of a putting green in need of drainage. Additionally, a 3/8-inch wide sand curtain extends from the base of the push-up green top dressing layer to the fibrous drainage element. Alternatively, the conventional pipe-drainage approach for push-up green drainage consists of corrugated plastic pipe at 14 to 16 inch depth and 6 foot spacing across the green. The 2 inch diameter pipe with sand-slot perforations is placed in a 4 inch wide trench commonly backfilled with a 6:2:2 sand:soil:peat blend. This analysis compares drainage rates of the PCD system using the DS38t drainage element with rates of a conventional greens drainage approach.

PCD-vs--Conventional1My analysis uses two pieces of information: 1) measurement and calculation of the flow capacity of the DS38 drainage element, and 2) an analysis of water flow through the push-up green soil profile to the drainage array. A measurement of the flow capacity of the DS38 drainage element was conducted at two slopes and this data was used with Manning’s equation to describe flow capacity at all slopes. The results of the flow capacity measurement and calculation are shown in the figure below. This analysis uses the flow capacity value at 2% slope having a value of 0.11gal min.

Analysis of water flow through the push-up green soil profile to the drainage array was conducted using a mathematical simulation of water flow in soil where both the PCD and conventional drainage systems are placed in a 12 foot wide by 35 inch deep push-up green soil profile consisting of a 4 inch sand cap over a clay loam soil. Additionally, both systems are uniformly wetted and flow is initiated by a l inch rain. This 12 foot section of a push-up green would be drained by 2 conventional pipes and 4 capillary drainage elements.

The figure below shows cumulative drainage as a function of time for the conventional system using run-of-pipe length of 30, 60 and 90 feet. The steeper portions of the curve correspond to higher drainage rates following the rain; and as excess water is removed from the green, the drainage rate slows. In this case, drainage from the push-up green is entirely controlled by the rate at which water arrives at the pipe array. The 2-inch diameter drainage pip has adequate flow capacity so as to not inhibit overall drainage. Further, drainage ends after about 15 hours.