Design of Tailwater Recovery Systems Accounting for Irrigation System Operation and Performance

Abstract

The design of tailwater recovery system design for furrow irrigation was examined. The analysis expands on procedures developed by previous authors and aims to account for the operation and performance of the irrigation system on tailwater system design. The method is demonstrated with a hypothetical test case which was examined under a range of inflow rates per furrow and target application depths. While the required tailwater sump capacity largely depends on the area to be irrigated and the maximum target irrigation depth, capacity requirements will increase if large imbalances between inflows and outflows occur by design. Imbalances can be reduced by a judicious selection of unit inflow rate and tolerated runoff fractions, but when the supply inflow rate is fixed, adjustments to the unit inflow rate may be limited or not feasible. Because pump-back depends on the runoff fraction, it is desirable to limit runoff losses subject to their impact on irrigation system performance. Because of the uncertainty and variability of infiltration and runoff, a tailwater system will inevitably be subject to imbalances. If runoff from the initial irrigation set can be measured and the tailwater pump-back rate can be adjusted, the configuration of the tailwater system can be modified before pump-back begins to mitigate imbalances caused by infiltration variability.