Headwaters are the source of a river. Most large river systems have multiple headwaters.
In modelling, headwater inflow data relate to the parts of a river and its tributaries above the first river gauge. Headwater inflow data are an estimate of how much water flows in each tributary of a river. We calculate headwater inflow using rainfall and evaporation data, and by calibrating gauge flow.
We build the headwater components of our models with:
- measured river flow data
- rainfall runoff modelling
- storage inflow calculations.
You can learn more about headwater and how we estimate and assess inflows from the Australian Modelling Practice Notes.
In modelling, a ‘reach’ is the stretch of river between 2 gauges. Reach components of our model are those data that relate to particular reaches.
They can include gauged and other inflow data.
Learn more about modelling a reach water balance in the Australian Modelling Practice Notes.
These are data that relate to infrastructure such as dams and weirs that store water or regulate water flow.
Data about water storage characteristics are readily obtainable. They include:
- when the storage was built
- when and how it was upgraded (for example, by raising an embankment)
- total volume – usually, the volume at which the spillway overflows
- total surface area – also usually related to volume at the point the spillway overflows
- stage-storage data (that is, how much water is stored at different heights)
- volume-area data for calculating evaporation
- spillway capacity
- controlled release volume or discharge rate
- release volume or discharge rate as the result of flood
- ‘dead storage’ volume or the volume of water stored below the level of the lowest outlet, which is the minimum supply level.
Temporal data about water storage could include:
- inflow volume or rate
- storage volume over time
- release and extraction volume or rate
- seepage volume or rate
- spill volume or rate.
If we don’t have access to storage inflow data, we estimate storage inflows.
Where a dam is decades old, we might be able to calculate inflows based on historical flow records from before the dam was built.
If not, we can calculate storage inflows by balancing inputs like inflows and rainfall with outputs like evaporation and seepage. We call this Storage Inflow Derivation (SID).
We can also use the results of SID to calibrate a rainfall-runoff model for residual inflows.
You can learn more about SID from the Australian Modelling Practice Notes.
Diversion components are data relating to water extraction for:
- town water use
- environmental releases
- historical water ordering
- on-farm storage.