Water resource development and hydrological change in a large dryland river: the Barwon-Darling River, Australia

Water resource development has had a major impact on the hydrology of the B arwon-Darling River, a large dryland river in southeast Australia. Flows ar e highly modified through the presence of nine headwater dams, 15 main chan nel weirs and 267 licensed water extractors. Median annual runoff has been reduced by 42% over a 60-year period. Small flood events (e.g. Average Recu rrence Interval of <2 years) have suffered the greatest impact with reducti ons in magnitude of between 35 and 70%. At a number of stations, the season ality of hows has also been affected with a distinct shift in seasonal flow peaks relating to irrigation diversions. Overall, flows show a marked incr ease in predictability and consistency (sensu Colwell R.K. 1974. Predictabi lity, constancy and contingency of periodic phenomena, Ecology 55, 1148-115 3). There has also been a change in the shape of the hydrograph. Both long- and short-term hydrological changes in the Barwon-Darling, associated with water resource development, may prove to be critical for the ecological he alth of the system. (C) 2000 Elsevier Science B.V. All rights reserved.