Floodplain-river ecosystems: Fragmentation and water resources development

Floodplain-river ecosystems are natural fragmented systems because of periodic hydrological connections. The integrity of these ecosystems is thought to be dependent, in part, upon exchanges of energy and matter between patches, such as the main river channel, adjacent floodplain surface and other morphological features, during periods of connection. Flow regulation and its associated infrastructure change the natural character of fragmentation in floodplain-river ecosystems, and have important consequences for their overall productivity. This paper considers the influence of water resources development on the character of fragmentation in a large lowland river in SE Australia. Large-scale water resources development in the Macintyre River, Australia, has significantly altered the spatial and temporal patterns of hydrological connections. The construction of weirs and other embankments on the lower Macintyre River floodplain prevents water movement through a series of anabranch channels thereby reducing the availability of these floodplain patches by 55%. In addition, because of flow regulation, hydrological connections to these channels occur up to 22% less often. Data are presented showing the impacts of these changes on the potential supply of dissolved organic carbon from the anabranch channels during periods of inundation over a 98-year period. Reductions of up to 98% of potential dissolved organic carbon supply from some anabranch channels were noted.