The Mt Lofty Ranges (MLR) catchments provide significant water resources for the environment, recreational activities, agriculture, industries, and potable water supplies. The water resources of the MLR were prescribed in 2005 which requires local natural resource management (NRM) boards to prepare a Water Allocation Plan (WAP) for prescribed resources. The WAP sets sustainable limits for allocation of water and provides for ongoing water management. This requirement and recognition of the need for increased environmental flows for the MLR culminated in the release of the draft WAP for the western MLR in 2010 and the eastern MLR in 2011. The draft WAPs have endeavoured to take into account the needs of all water users.
Within the WAPs, environmental water requirements (EWRs) specify ‘the water regime needed to sustain the ecological values of ecosystems, including their processes and biological diversity, at a low level of risk’. EWRs are described at the biotic functional group level (e.g. fish, macroinvertebrates and water-dependent plants) by determining the flow-dependent ecological processes that are required to support each group, and the water regime required to support those processes. In the current WAPs, water quality is not considered an issue if the flow regime is deemed adequate.
The Goyder Institute has identified areas to improve information to support water allocation planning in the MLR. These include the development of robust models based on better understanding of hydro-ecological processes, particularly under low-flow situations. In this regard, the present project aimed at developing a method less reliant on expert opinion, more repeatable and transparent and more strongly based on empirical evidence. Existing environmental water requirements were revised, based on a review of literature, existing and new field-based monitoring data and an assessment of the water quantity requirements of ecosystems.
The project has established a network of hydrological and ecological monitoring sites, and complements current monitoring programs of the Adelaide and Mount Lofty Ranges Natural Resource Management Board (AMLRNRMB), South Australian Murray-Darling Basin Natural Resource Management Board (SAMDBNRMB) and Environment Protection Authority (EPA) (i.e. vWASP, eFlows, EPA macroinvertebrate, hydrology and fish monitoring sites), providing scientific evidence and data to improve predictive modelling capacity.
A modelling framework was developed to assess quantitatively whether water-use scenarios maintained and/or improved current conditions. Several approaches were used in combination to develop flow-response models for vegetation, macroinvertebrates and fish under this framework. Trait-based models were developed for macroinvertebrates and fish, using multivariate statistics and generalised linear modelling to develop empirical relationships between the target biota and hydrological variables. The level of intermittency over 10 years was modelled as the key hydrological variable driving change in temporary rivers.
There is clear evidence that further increases in water abstraction would increase the level of intermittency in MLR streams, leading to further ecological degradation of water-dependent ecosystems.
This project adds further weight to the evidence already identified in the current WAPs that returning low flows and thereby reducing intermittency is an essential part of maintaining, and potentially improving healthy, resilient ecosystems in the MLR.
This work has demonstrated the use of empirical data in modelling responses to water-use scenarios and in quantifying the ‘maintain and improve’ components of water allocation planning objectives. It has consolidated datasets and knowledge from across the region and brought together multiple research agencies.