Existing approaches to reporting environmental watering performance do not account for partially successful watering events. The environmental water needs of most of our river systems have been quantified, and in many cases, significant water assets have been set aside, or reassigned to help achieve environmental outcomes. Despite having a significant public water asset tied to important environmental outcomes, assessing and reporting environmental watering performance is usually based on a simplistic binary pass or fail reporting approach.
Environmental watering requirements are typically described as a spell analysis in terms of fixed parameter values for flow magnitude, spell duration, spell timing, spell count and independence between spells. Traditional environmental watering performance reporting requires all of these parameter values to be achieved in order to report a successful year. We present a method by which each parameter is represented by a continuous function (not a single fixed value). By defining the parameter values as continuous functions the value of partially meeting the preferred watering requirement can be quantified. The continuous function approach allows the relative importance of each parameter to be captured as a continuous function and report an overall performance measure per year as a continuous range from 0-100%, not simply a pass or fail. For example, a flow requirement may prescribe three events per year to allow three fish spawning opportunities. If the observed flow only achieved two events in a year, traditional reporting approaches would report a failed year. Using the continuous function approach we could define the value of two events as 50% of the preferred (three events), and this water year would then report an overall 50% performance score, not ideal, but not a complete fail.
We have applied the continuous function approach across over 200 environmental water requirements across Victoria and the Qld Murray Darling Basin.