Design of furrow systems with tailwater reuse

The application efficiency of furrow irrigation systems can be greatly improved when tailwater can be captured and reused. The design of such a system is somewhat more complex than the procedure for traditional furrow and cutback systems because of the need to utilize two sources of water simultaneously.

The major complexity of reuse systems is the strategy for recirculating the tailwater One alternative is to pump the tailwater into the primary supply and then increase the number of operating furrows to utilize the additional flow. Or, tailwater can be used to irrigate separate sections of the field or even other fields. In any case the tailwater reservoir and pumping system need to be carefully controlled and coordinated with the primary water supply.

To illustrate the design strategy for reuse systems, a design procedure for a common configuration outlined by Walker and Skogerboe is presented. The reuse system shown is intended to capture tailwater from one set and combine it with the supply to a second set. A similar operating scenario prevails for each subsequent pair until the last set is irrigated when some of the tailwater must be either stored until the next irrigation, dumped into a wasteway, used elsewhere or used to finish the irrigation after the primary inflows have been shut-off.