Perspective: river science for dryland river regulation

Dryland rivers are differentiated from other rivers by high flow variability. They are also particularly important for river regulation to secure supplies for irrigation agriculture and to meet other human demands. The dilemma is that river regulation not only has considerable benefits for human societies in achieving water security and providing flood protection but also represents perhaps the greatest cause of hydrological interference by humans. In Australia, the Murray-Darling basin with only 21 mm of run-off had committed over 90% of the exploitable yield to consumptive irrigation use as early as the late 1970s. Here, perhaps more so than in any other country, there arose an imperative to advance a new river science to support the environmentally sound management of regulated dryland rivers and Keith Walker was at the heart of that endeavour. In this short opinion piece, I offer observations on how his search for a "general model" has advanced over the past two decades.