The Ord River estuary: a regulated wet-dry tropical river system

Abstract

The lower Ord River is a wet-dry tropical river functioning as a perennial dry tropical river as a result of regulation. It is currently one of the few heavily regulated rivers in Australia's tropical north, providing water for hydroelectrical production and irrigation. Current plans call for an increase in the area of irrigated land surrounding the lower Ord River and its estuary. The estuary is highly turbid and subject to very strong tides. It can be conceptualised as five connected physical zones - the Riverine Zone, the Tidal Freshwater Zone, the Transitional (Maximum Turbidity) Zone, the Estuary Mouth, and the Tidal Creeks and Flats Zone - distinguished by geomorphology, flow and tidal influence. Each of these physical zones functions as a distinct biogeochemical and ecological functional zone. Here, we describe how these zones function, how they interact, and how the estuary as a whole may respond to the changes expected in the mid-term future.