Oversupply – variable success
About Oversupply
Downstream from water storages, streams are often used to deliver water for consumptive users (irrigators). This can result in extended periods of elevated flows. The oversupply model is similar to the low flow model, but instead of reporting the period above a minimum threshold, the oversupply model reports the period below a maximum threshold.
Water requirements
This model captures the total duration of flow below a prescribed elevated flow threshold across a user prescribed period of the year (typically, Autumn-winter, summer-spring).
Model purpose
The purpose of the model is to represent a common way to prescribe oversupply or elevated flows. The model extends this traditional prescription to also allow the consideration of the prevailing climate as well as the representation of partial success.
Development context
This model was developed initially in the eFlow Projector application (Marsh et. al. 2021) to support performance reporting by the Victorian Environmental Water Holder.
Spatial application
This model can be applied anywhere that elevated flow requirements can be described in terms of magnitude, duration and timing.
Model description
Ecohydrological rules
The flow time series is analysed to identify all event opportunities within the prescribed sub-period of the year (typically, Autumn-winter, summer-spring), where the flow is below the specified threshold. The best set of event opportunities is combined to provide an overall magnitude and duration score for the period. The output is an overall performance (0 to 100%) for each water year of the record.
Assessment method
A continuous yearly value is determined by combining all scores (magnitude and duration) into a summary score. These results are then aggregated to a binary yearly result, then to a temporal result based on the defined assessment parameters.
The temporal results are then analysed across locations to report an overall landscape risk by considering the simultaneous occurrence of failures across the system.
Inputs
Data
- Daily flow data
Parameter Sections
- Data – parameters to describe the variable season. This includes the start month (to determine the year) and the success % of each month. A binary season can be achieved by using only 0 and 100% season scores.
- Rules – the rules for each possible climate type. This included a magnitude (flow threshold) and duration (% of season) target.
- Partial tables – the tables to define how partially achieving the rules can still carry some level of success. This includes a table for both magnitude and duration.
Outputs
- Yearly time series of performance, including the magnitude, duration, compliance and summary scores
- Events file containing all events identified, including start date, end date and duration.
- Yearly time series of assessment results
- Temporal time series of assessment results
- Spatial time series of assessment results
User interface
Underlying code
This plugin is written in Python and its underlying code is publicly available from the Eco Risk Projector computation repository.
References
Marsh, N., Marsh, Z., Stacey, M., and Toomey, M. (2021) Eflow Projector: Assessing th Perfomance of environmental watering, Proceedings of the 10th Australian Stream Management Conference 2020, Kingscliff, NSW
Source: Victorian Environmental Water Holder. https://www.vewh.vic.gov.au/news-and-publications/stories/understanding-flows-some-terminology-explained 
Australian Bass. Source: Fishes of Australia, Creative Commons Attribution 3.0 Australia License. https://fishesofaustralia.net.au/home/species/3233
Australian bass (Macquaria novemaculeata) spawning and juvenile movement
Northern snake-necked turtle (Chelodina oblonga)
Mary River turtle (Elusor macrurus) and white-throated snapping turtle (Elseya albagula)