Monbulk Creek Smart Water
– areas of investigation (workstreams)

1. Flow regime:
Can networked SCMs and RTC technology improve the flow regime in Monbulk Creek?

The project will measure changes in flow regimes and water quality within the stormwater network and the creek itself. While the flow regime changes are of primary interest to this study, it is essential to track water quality, given its potential to impact on ecological responses. We will monitor flow in the three stormwater pipes (which drain the most urban parts of the catchment) and three stream sites (two major tributaries and the catchment outlet). We will sample water quality at all sites during dry-weather and wet-weather events.

Analysing the flow regime (hydrologic and hydraulic) impacts of RTC In Year 1, we will use existing sophisticated RTC-modelling tools we have developed to simulate the RTC network under a range of scenarios. We will then translate the predicted flow outcomes into estimates of wetted habitat availability and other hydraulic metrics such as area of slackwater, to understand the hydraulic impacts, using a detailed survey of Monbulk Creek and its tributaries, which will be used to develop a TUFLOW model of the entire stream network. This will be undertaken in combination with Workstream 3, given the importance of habitat availability to understanding platypus foraging behaviour.

The project will develop control rules to govern the operation of the innovative SCMs and network. The best performing control rules (in terms of degree of replication of the natural flow regime, amount of potable water savings for households, etc) will be tested in the catchment, with help by the South East Water engineers who will program the network of actuator-controlled SCMs according to the identified controlled rules. The modelled hydrological outcomes will be evaluated against the core hydrologic monitoring and hydraulic metrics derived from the streamflow data. These data will be used to evaluate the performance of the RTC implementation, comparing flows in reaches with and without baseflow-supplementation by the RTC systems, using Bayesian models, taking into account both temporal and spatial autocorrelation.

2. Social sustainability:
In what ways do household water practices support or challenge the social sustainability of networked rainwater tanks being co-managed for private and public good?

Installing RTC technology on household tanks makes new connections between individuals and agencies, private and public spaces, and household and institutional practices in co-managing urban water. This workstream will investigate the ways in which RTC technology transforms, and is transformed by, household practices. The exploratory, qualitative design of this study will enable in-depth inquiry into the diversity of household engagement with RTC technology as it transitions from novel to routine or rejected technology.

This study will firstly elicit and track household practices over a roughly two-year period through repeat interviews (i.e. before/after RTC installation) with 20-30 households (group or individual). To investigate a range of household experiences, a purposive sampling strategy will be designed for maximum variation within the sample, in relation to: type of occupancy, domestic setting, type of home, environmental commitment, and location within the catchment. Secondly, all households involved in the piloting of the RTC technology will be invited to respond to “domestic probes”, a social research method originating in technology design in which participants are set a short, playful task (e.g. the taking of a photo, or a response to an object) to generate evocative insight into the ways in which they engage with a specific technology in the domestic setting. Interview transcripts and written, drawn or recorded responses to domestic probes will be uploaded and analysed in nVivo through an iterative, inductive coding process.

3. In-stream response:
Do the increased baseflows and reduced stormflows benefit platypus foraging habitat?

Based on extensive hydrological (MUSIC) modelling of the catchment, we predict that the RTC SCM network could be capable of doubling autumn baseflows downstream of the two public storages, resulting in increased wetted area in the channel, providing increased foraging habitat in those reaches at a critical time of the year for platypus. This workstream will assess changes in a) in-stream habitat (in conjunction with Workstream 1), b) macroinvertebrate abundance and assemblage composition and c) platypus foraging behaviour in the affected reaches compared to the control reach.

In-stream habitat: We will map instream habitat (i.e. ‘riffles’, ‘pools’ and ‘runs’) along three study reaches, each 1km long, in combination with the hydraulic assessment and TUFLOW model development in Workstream 1. Along each reach, physical habitat will be digitally mapped using low-flying drone photogrammetry survey (1-cm resolution) to build a 3D digital terrain model that can be integrated into the TUFLOW hydraulic model to classify the reach sections into pools, riffles and runs based on depth and velocity. Any gaps in the photogrammetry (particularly deep pools) will be filled with manual feature survey at low flow.

Macroinvertebrate abundance and assemblage composition: We will assess the potential for increased wetted habitat to provide food sources for platypus by comparing macroinvertebrate abundance and assemblage composition between permanently inundated channel habitat and seasonally inundated habitat. Macroinvertebrates will be sampled in each reach in autumn before RTC releases (when seasonally inundated habitat is dry), during spring before RTC releases (when seasonally inundated habitat is wet) and in the autumn after RTC releases (when seasonally inundated habitat will be wet in the two downstream reaches). To assess the effect of platypus predation on macroinvertebrate assemblage composition and abundances estimated from these samples, the project will conduct an exclosure experiment, setting replicate cages with the same surface area as the suction sampler in the stream channel. These will be deployed 4 weeks before macroinvertebrate surveys over the three seasons, with abundance and assemblage composition compared between caged and non-caged samples.

Platypus foraging behaviour: Platypus foraging behaviour (time spent foraging in permanently or seasonally inundated habitats) will be assessed using 12 Radiometry Long-Wave Infrared (LWIR) cameras. Cameras will be deployed for 1 month during each of the three macroinvertebrate sampling seasons, targeting permanently or seasonally inundated habitats. This will allow an assessment of the frequency with which platypus use permanently inundated versus seasonally inundated habitat for foraging, which will then be related to the hydraulic model predictions of the extent of suitable habitat for platypus foraging under a range of flow scenarios, including real-time control release strategies or potential impacts of a loss in baseflows under a changing climate. To help relate the outcomes of this short-term study in the context of the longer-term trajectory of the Monbulk Creek platypus population, Melbourne Water will continue to collect live-trapping and eDNA data as part of their 20+ year Melbourne Urban Platypus Program.

Project summary  |  Why this project is needed