The effect of river regulation on floodplain wetland inundation, Murrumbidgee River, Australia

Abstract

River regulation by headwater dams has altered the flow regime of rivers worldwide. For floodplain rivers, reduced connectivity between the main channel and floodplain wetlands has led to a decline in ecological health. Current river restoration theory advocates a return towards a more natural regime of floodplain wetland inundation. However, for many rivers, a poor understanding of the natural floodplain wetland inundation regime has hampered effective restoration management. This paper describes a technique for quantifying the effect of flow regulation on the inundation regime of floodplain wetlands on an extended reach of the Murrumbidgee River, Australia. A series of Landsat Thematic Mapper (TM) images, captured before and after a set of floods, was analysed to describe the relationship between flow and inundation for a 640 km river reach. These data were combined with historical regulated and modelled natural daily flow data to show that river regulation has reduced the duration and frequency of wetland inundation by ∼40%. For the majority of wetlands the capture of small and medium floods in the headwater dams reduced wetland inundation substantially. However, for low connecting wetlands in reaches upstream of the main irrigation off-takes, summer irrigation flows have increased inundation.Extra keywords: integrated quantity quality model, IQQM, Landsat Thematic Mapper, modelled natural flow, remote sensing.

Quantifying flooding regime in floodplain forests to guide river restoration

“…High flows affect floodplain habitats and ecosystem processes directly through flooding and indirectly by controlling floodplain topography via depositional and erosional processes (Gurnell et al, 2012). The operation of flood control and other large dams has dramatically reduced peak flows, ultimately causing a decline in flood-dependent species (Dister et al, 1990;Auble et al, 2005;Frazier and Page, 2006;Burke et al, 2009;Stallins et al, 2010;Johnson et al, 2012). To help mitigate the loss of floodplain communities due Elementa: Science of the Anthropocene • 2: 000031 • doi: 10.12952/journal.elementa.000031 to flow regulation, many scientists, NGOs, and government agencies have proposed a full suite of potential solutions, including controlled flow releases to approximate natural flow regimes to help restore downstream in-channel and riparian ecological processes (Richter, 2010;Arthington, 2012;Olden et al, 2014;Warner et al, 2014).…”

The effects of climate change on ecologically-relevant flow regime and water quality attributes

“…Specific ecological responses have not been predicted from the changes observed, however, it is possible to postulate the types of effects that might result from the predicted changes based on previous studies. Modification of mean annual flows, high flows and high flow spells would suggests changes to primary production (Robertson et al 2001), floodplain connections (Bunn and Arthington 2002;Page et al 2005;Frazier and Page 2006) and riparian vegetation (Poff and Zimmerman 2010). Changes to the low flow spells suggests changes to the availability of habitat (Bunn and Arthington 2002) and the ability for fish to migrate to spawn (Freeman et al 2001).…”

Allochthonous DOC in floodplain rivers: identifying sources using solid phase microextraction with gas chromatography

“…Prior to regulation, flows were highly variable and exhibited maximum discharge in winter and spring. The main impact of flow regulation has been on the frequency and duration of small to moderate flows that are derived from upper catchment rainfall (Page, 1988 ;Frazier and Page, 2006). (Table 1).…”