Morphological characteristics of on-farm water storages and their similarity to natural water bodies in the Border Rivers Catchment, Australia

Abstract

1. Natural wetlands throughout the world are under threat from water resource development required to support an ever increasing population. In the Border Rivers Catchment in Queensland, Australia, a large irrigation industry and highly variable flow regime have necessitated the building of large on-farm water storages. With the decline in number and size of natural wetlands, the presence of these storages on the floodplain has raised the question of their suitability as alternative habitat for aquatic fauna. This paper explores the variety of water storage types in the Border Rivers Catchment and how their morphology compares with that of natural wetlands — in particular, factors likely to influence aquatic biodiversity. 2. Storages and natural wetlands formed two distinct groups based on morphology. Storages tended to be large, deep structures with a more regular shape while natural wetlands were irregular and shallow with large perimeters. Although there was a degree of variability amongst the storage sites, a large proportion fell into one group and were considered 'typical storages'. Typical storages contained tailwater and had the following characteristics: situated 3 km from the source river, 10 years old, embankment height of 5m, area of 400 000m2, perimeter of 2.5km and capacity of 1 700 000m3. 3. Due to their uniform structure we believe that most on-farm storages are unlikely to support as diverse or abundant an aquatic population as natural wetlands. The presence of tailwater and associated chemicals is also likely to reduce the aquatic biodiversity of storages compared with natural wetlands. While they may be unsuitable as replacement wetlands, given their numbers they could provide significant aquatic habitat across the landscape, if managed effectively.