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q~ is the index flow, which is given by
| Equation 2 |
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where:
I is the inflow to the reach during the time-step,
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- Computes an initial storage estimate by using inflows to fill the reach up to but not exceeding the dead storage level;
- Computes a revised storage estimate based on any remaining inflows and fluxes, but ignoring outflows; or
- If the revised storage estimate is above dead storage, then outflows are computed. Otherwise, the initial storage estimate is used and outflows are set to zero.
Initial Estimation of Storage Constant (k)
An initial value of k can be determined by
- For linear routing (ie m=1) k is equal to the wave travel time divided by the number of divisions. The wave travel time is how long the wave takes to move through the reach
- For non-linear routing, (m≠1) k can be calculated using the known wave travel time per division and the chosen value of m for a representative flow rate
Equation XXXXXX
| Anchor | ||||
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| Parameter | Description | Units | Range | Default | |||||
|---|---|---|---|---|---|---|---|---|---|
| General configuration | |||||||||
| Avg. Reg. Flow | Average regulated flow is used to calculate travel time for orders in the ordering phase. It is not used in the flow distribution phase.
| megalitres per day | real ≥ 0 | 0 ML/d | |||||
| Elevation | Note that while it is usual to use zero storage as the reference point for the elevation of a link or node, there is no convention for a link as to whether that should be at the start or end of the reach, or some point in between. Source has no mechanism for indicating the fall across a reach. | ||||||||
| Initial conditions | If necessary, one of these parameters may be used to seed a reach with either an initial flow or storage (see below) so that reach behaviour is fully defined from the first model time-step. | ||||||||
| Initial flow | megalitres per day | real ≥ 0 | 0 ML/d | ||||||
| Initial storage | The amount of water deemed to be in the link on the first time-step. For example, if there is a lag of two days, and there is 10ML in the link at the start of the run, then 5ML is deemed to be flowing out each day (total initial storage divided by lag). | megalitres | real ≥ 0 | 0 ML | |||||
| Reach length | Source simulates evaporation and rainfall using the user defined reach length and a reach width (based on simulated flow and a user defined rating curve) to calculate surface area. | metres | real ≥ 0 | 0 m | |||||
| Routing parameters | |||||||||
# Divisions | Number of reach divisions. Conceptually, this parameter describes the number of times that a reach is replicated. The effective length of a reach is determined from its behaviour, which is controlled by the combination of the storage exponent m, the inflow bias x and the storage constant K. Specifying multiple reach divisions implies applying the same set of behavioural parameters multiple times. In other words, if the effective length of a single-division reach is 500 metres (as derived from its behavioural parameters), changing the # Divisions parameter to 2 implies a combined effective length of 1000 metres. If you want to sub-divide a 500 metre reach into two 250 metre sections, you must also change the behavioural parameters to achieve this. | whole units | integer ≥ 1 | 1 | |||||
| Inflow bias (attenuation factor, x) | The weighting factor x is used to adjust the bias between inflow and outflow rate and allows for flow attenuation. A recommended starting value is 0.5. | dimensionless | real 0 ≤ x ≤ 1 | 0 | |||||
| Generic | |||||||||
| Storage constant (k) | When using linear routing (m = 1), the units of the storage constant k are in seconds and the wave travel time is equal to k times the number of divisions. When using non-linear routing (m ≠ 1), a starting value could be calculated using Equation XX in the scientific reference guide. | k units | real ≥ 0 | 0 | |||||
| Storage exponent (m) | If m=1, linear (Muskingum) routing is implied, otherwise non-linear routing is implied. . m=0.74 is a good starting value for a natural channel. | time-steps | real 0 < m ≤ 1 | 0 time-steps | |||||
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