North Region: Environmental Flow Assessment

Dr Richard Hunt, DERM, Mareeba, Qld.

Barron River

Barron River – most regulated system in the Wet Tropics

  Tinaroo Falls Dam   Irrigated agriculture   Town water supply   Hydroelectric facility at Barron Falls

Test site Ref site

Barron River at Bilwon: Test site

Flaggy Creek: Reference site

In-stream carbon sources are important for the food web

Stable isotope analysis of terrestrial and aquatic primary producers, and consumers. δ13C ratio remains stable as it passes through the food chain. Benthic algae important carbon source for consumers in Barron main channel.

Can flow regulate instream primary production?

Indicator 1. Algal growth: artificial substrates

Riffle habitat: bedrock and sand. Temporally and spatially replicated experimental units.

Algal biomass

Indicator 2. Ecosystem metabolism: primary production determined from diurnal change of dissolved oxygen

  Run/pool habitat

GPP: first flow pulse

  Volumetric

  Fish, prawns and other consumers depend upon algal carbon sources   River flows can have a strong effect on in-stream primary production   Very important how water is delivered – not just quantity   Natural flow regime provides a template for effective flow management

Mitchell River

Mitchell River: large unregulated catchment

Mitchell River

  Collaboration with Griffith University (TRaCK)   Improve understanding of natural functioning of food webs   Importance of dry season and wet season production

Discharge and water temperature

Dry season primary production

Food webs for early and late dry season: dry season

External sources of carbon major contributor to fish communities Local sources of carbon maintain dry season production

Wet season very important for large mobile consumers: fish and prawns

Algal production in the Floodplain

Terrestrial vegetation via insects

Increased connection with marine production

Productivity of these river systems depend upon floodplain inundation and connectivity