Recommendations for Monitoring Program for Tuppal and Bullatale Creeks

"February 2005".

Project Number: Development of a wetland and floodplain monitoring plan for restoration of flows to Tuppal and Bullatale Creek Systems M/BUS/77 GZ150.

MDFRC item.

Tuppal and Bullatale creeks are ephemeral floodrunners that link the River Murray to its major anabranch, the Edward River. Historically, these creeks received most of their annual discharge in spring when the River Murray was in high flow, then dried to pools as the water level in the River Murray lowered. Today, the creeks are managed so that their hydrological patterns differ markedly from the natural regime. The Tuppal Creek channel is usually dry, save for some remnant waterholes, whilst most of Bullatale Creek flows throughout the year. The health of the iconic Barmah–Millewa Forest is threatened by unseasonal flooding, as identified in the Living Murray Initiative. One of the major causes of unseasonal flooding (summer flooding) is rainfall rejection. Tuppal and Bullatale creeks have been identified as possible diversionary thoroughfares of rainfall rejection flows. The main purpose of this report is to recommend a monitoring program to assess the impacts of three flow scenarios on Tuppal and Bullatale creeks: Low flow release from MIL irrigation system into Tuppal Creek (Scenario I). Divert rainfall rejection flows into Tuppal and Bullatale creeks (Scenario II). Natural spring flooding event affecting both creeks (Scenario III). To develop a monitoring program it is useful to follow the adaptive management framework. This approach emphasises the need for an understanding of current condition so that the ecological implications of altered flow patterns can be predicted. There are many knowledge gaps associated with the current condition of Tuppal and Bullatale creeks; however, it is possible to predict major outcomes and responses, identify key response indicators and make recommendations for a monitoring program. Scenarios I and II introduce temporary flow to Tuppal Creek. These scenarios will have implications for water quality, the extent and distribution of waterholes, groundwater quality and levels, riparian vegetation, in-channel cumbungi and red gum saplings, bank erosion, fish and macroinvertebrates. The long-term effect of altered flow patterns will depend on the size of flows and the frequency of them. In general, ecological responses are likely to be restricted to the riparian fringe. Scenario II is the only managed intervention affecting Bullatale Creek and its impacts will be restricted to the creek below current inflows from Lower Toupna Creek. Water quality, channel morphology, fish, macroinvertebrates and riparian vegetation are the parameters most likely to respond to this flow change. In general though, ecological responses to Scenario II are likely to be minimal. Scenario III is expected to have a dramatic impact on Tuppal and Bullatale creeks and the floodplain; ecological responses are likely to be widespread and long lasting. Creek productivity will increase, channels may migrate, instream vegetation may be scoured from the channel bed and large scale movements of fish and other aquatic fauna is likely to occur. Temporary wetlands will form on the floodplain in which macroinvertebrates will emerge, waterbirds will forage and frogs will breed. Native vegetation along the riparian zone and in floodplain forests will also benefit greatly. The following indicators are expected to provide measurable responses to flow changes in Tuppal and Bullatale creeks: Hydrology Waterhole distribution Water quality Groundwater level Sulfidic sediments Channel morphology Habitat complexity Vegetation (riparian, in-channel cumbungi and red gum, in-channel submerged and floodplain) Aquatic fauna (fish and macroinvertebrates) Floodplain fauna (birds, frogs and macroinvertebrates). The number of knowledge gaps in regard to current condition must be addressed during the initial stages of the monitoring program. Providing infrastructure for the measurement of parameters such as surface water/groundwater links is required. Comprehensive baseline data on ecosystem components such as waterhole distribution and fish diversity is essential in Before-After-Control-Impact (BACI) assessment. Billabong Creek is probably the most suitable ‘reference' stream for gauging the impacts of management interventions in Tuppal and Bullatale creeks.