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

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.

[1]  R. Sparks,et al.  THE NATURAL FLOW REGIME. A PARADIGM FOR RIVER CONSERVATION AND RESTORATION , 1997 .

[2]  K. Page,et al.  Stratigraphic architecture resulting from Late Quaternary evolution of the Riverine Plain, south‐eastern Australia , 1996 .

[3]  M. Simons,et al.  IQQM—A hydrologic modelling tool for water resource and salinity management , 1996 .

[4]  R. Kingsford.  Ecological Impacts and Institutional and Economic Drivers for Water Resource Development--a Case Study of the Murrumbidgee River, Australia , 2003 .

[5]  N. Poff,et al.  A Special Section on Dam Removal and River Restoration , 2002 .

[6]  John R. Jones,et al.  Flooding to Restore Connectivity of Regulated, Large-River Wetlands Natural and controlled flooding as complementary processes along the lower Missouri River , 1998 .

[7]  N. Poff,et al.  How Dams Vary and Why It Matters for the Emerging Science of Dam Removal , 2002 .

[8]  U. Uehlinger,et al.  Using artificial floods for restoring river integrity , 2003, Aquatic Sciences.

[9]  John Louis,et al.  Relating wetland inundation to river flow using Landsat TM data , 2003 .

[10]  Richard T. Kingsford,et al.  Ecological impacts of dams, water diversions and river management on floodplain wetlands in Australia , 2000 .

[11]  C. Nilsson,et al.  Fragmentation and Flow Regulation of River Systems in the Northern Third of the World , 1994, Science.

[12]  M. Thoms.  Floodplain–river ecosystems: lateral connections and the implications of human interference , 2003 .

[13]  W. Junk.  The flood pulse concept in river-floodplain systems , 1989 .

[14]  S. Briggs,et al.  Relationships Between Hydrological Control of River Red Gum Wetlands and Waterbird Breeding , 1997 .

[15]  W. Dietrich,et al.  Downstream Ecological Effects of Dams: A geomorphic perspective , 1995 .

[16]  I. Chaubey,et al.  FLOOD PULSE DYNAMICS OF AN UNREGULATED RIVER FLOODPLAIN IN THE SOUTHEASTERN U.S. COASTAL PLAIN , 2000 .

[17]  T. McMahon,et al.  Effects of regulation on the flow regime of the river Murray, Australia , 1995 .

[18]  C. Nilsson.  REMEDIATING RIVER MARGIN VEGETATION ALONG FRAGMENTED AND REGULATED RIVERS IN THE NORTH: WHAT IS POSSIBLE? , 1996 .

[19]  Richard E. Sparks,et al.  Need for Ecosystem Management of Large Rivers and Their Floodplains These phenomenally productive ecosystems produce fish and wildlife and preserve species , 1995 .

[20]  W. Graf.  Dam nation: A geographic census of American dams and their large‐scale hydrologic impacts , 1999 .

[21]  T. Wong,et al.  A model of flood wave speed—Discharge characteristics of rivers , 1984 .

[22]  F. Douglas Shields,et al.  Can Large Rivers Be Restored?Most restoration projects are only attempts to rehabilitate selected river sections to a predetermined structure and functio , 1995 .

[23]  Geoffrey E. Petts,et al.  WATER ALLOCATION TO PROTECT RIVER ECOSYSTEMS , 1996 .

[24]  B. Biggs,et al.  Relationships between benthic biota and hydrological indices in New Zealand streams , 1997 .

[25]  K. Walker,et al.  Environmental effects of flow regulation on the lower river Murray, Australia , 1993 .

[26]  P. Frazier,et al.  Floodplain Formation and Sediment Stratigraphy Resulting from Oblique Accretion on the Murrumbidgee River, Australia , 2003 .

[27]  Dlwc.  State of the rivers report: Murrumbidgee Catchment 1994-1995 volume 2 , 1996 .

[28]  J. Stanford,et al.  The serial discontinuity concept of lotic ecosystems , 1983 .

[29]  K. Tockner,et al.  An extension of the flood pulse concept. , 2000 .

[30]  Nick J. Mount,et al.  The effect of altered flow regime on the frequency and duration of bankfull discharge: Murrumbidgee River, Australia , 2005 .