Ecology and management of Ephemeral Deflation Basin Lakes

"June 2004".

Project Number: Deflation Lake Ecology Study or Ecology & Management of Ephemeral Deflation Basin Lakes - MDBC Project R10011 M/BUS/7 EW28A (J102).

MDFRC item.

Ephemeral Deflation Basin Lakes (EDBL) are a critical component of lowland river floodplain ecosystems that provide habitat for large numbers of animals and plants and provide a number of environmental services, including water purification and flood mitigation. EDBL also represent a valuable resource for human activities with many being used as water storages to supply domestic and agricultural needs. Water resource development has altered the hydrological cycles of many EDBL, such as the Menindee Lakes in western New South Wales. The Menindee Lakes is an integral part of the Murray-Darling Basin’s water supply infrastructure. Flow regulation since the late 1960s has altered the periodicity of flooding and complete drying events experienced by each of the Menindee lakes. The lakes are now wetter for longer and the dry periods much shorter. Such changes of the hydrological cycle are considered a key threat to wetland ecosystem integrity and have been associated with declines in wetland water quality, diversity and productivity. The cycle of wetting and drying is believed to be key to the rehabilitation of these systems within the current supply regimes. At present, however, our conceptual understanding of how hydrological change impacts on EDBL ecosystem integrity is fragmented, and much of the available information is derived from non-arid zone systems. This study sought to provide information linking hydraulic regime and ecological processes within the Lakes, which can be used to support the development of environmentally sensitive management processes. The specific objectives of the project were to develop an understanding of the ecological responses of EDBL water quality and biota to flooding and drying through a mixture of field surveys, targeted experiments and modelling, and to produce management guidelines for water regime management of these systems. This report addresses the first of these aims. Guidelines for the management of EDBL are presented as a separate document (Scholz and Gawne 20041).