Recommended environmental water requirements for the Daly River, Northern Territory, based on ecological, hydrological and biological principles

Environment Australia, 2003

Supervising Scientist Report 175
National River Health Program, Environmental Flows Initiative, Technical Report 4

Erskine WD, Begg GW, Jolly P, Georges A, O'Grady A, Eamus D, Rea N, P Dostine, Townsend S & Padovan A
ISSN 1325-1554
ISBN 0 642 24382 4

About the report

Flow regimes and environmental water requirements of the Daly River must be understood to set appropriate environmental flows and water licence conditions for large scale agricultural development and associated vegetation clearing. The Daly River provides a unique opportunity to address these issues before significant agricultural development impacts on streamflow regimes and to protect its long recognised wild river status.

Environment Australia and the Northern Territory Government, therefore, as part of the National River Health Environmental Flow Initiative, funded the following five projects:

  • Modelling Dry-season flows and predicting the impact of water extraction on a flagship species — the pig-nosed turtle (Carettochelys insculpta);
  • Tree water use and sources of transpired water in riparian vegetation along the Daly River, Northern Territory;
  • Environmental water requirements of Vallisneria nana in the Daly River, Northern Territory;
  • Periphyton and phytoplankton response to reduced Dry season flows in the Daly River;
  • Inventory and risk assessment of water dependent ecosystems in the Daly Basin.

The aim of these projects was to provide recommendations on environmental flows consistent with maintaining the biota and wider ecosystem values of the Daly River. Eight of the nine species of freshwater turtles found in the Northern Territory are present in the Daly River. Furthermore, at least two nationally threatened species of elasmobranchs, the Freshwater whipray (Himantura chaophraya) and the Freshwater sawfish (Pristis microdon), are also present. According to Pogonoski et al (2002), these species are critically endangered and vulnerable, respectively.

The recommendations derived from work undertaken for the five projects are given in table A. They need also to be accompanied by the following actions:

  • Northern Territory Government introduces integrated natural resource management for the Daly River catchment and a robust method for determining water allocations;
  • Natural estuarine biophysical processes and aquatic habitats are maintained;
  • Groundwater-dependent ecosystems are identified and protected;
  • High quality data are collected at all river gauging stations for both low and high streamflows;
  • A benchmarking and monitoring (including biomonitoring) program is designed and implemented;
  • An adaptive ecosystem management approach is implemented along with the environmental water allocations and the benchmarking and monitoring programs.