Irrigation and drainage in the new millennium

Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Includes bibliographical references.A field investigation on a new vineyard in the Murrumbidgee Irrigation Area showed that improved subsurface drainage systems reduce salt loads in drainage water whilst providing waterlogging and salinity control. By only draining the rootzone the drainage volume and salinity were greatly reduced. Improved design and management options were tested against the current practice of deep pipe drains (1.8 m depth) widely spaced (20 m apart) allowed to drain continuously. This drain configuration was managed to prevent flow when the water table was deeper than 1.2 m from the soil surface, and not during irrigations. This resulted in a 50 % reduction in the drainage salt load. Shallow (0.7 m depth) closely spaced drains (3.65 m apart) were also tested and reduced the drainage salt load by 95 % when compared to the unmanaged deep drains. This improved design and management will significantly reduce the amount of salt that requires disposal. This work, together with other field and modeling studies, has been used to develop a set of guidelines for subsurface drainage with the aim of improving drainage water quality