II.8.3 - Spill

Flow Archive Spill

When spill is allocated from Flow Archive files, it is identified as a percent of daily averaged flow over multi-day periods. Consequently, for use in CRiSP.1, archive derived spill must be allocated to specific days and hours of the day. Special adjustments to spill allocations in years of low and high water are not implemented at this time. CRiSP.1 considers three types of spill:

Planned Fish Spill is requested by the fisheries agencies. The schedule for this can be obtained from the Flow Archive Files or can be set in the Spill Schedule Window.

Overgeneration Spill occurs when electrical generation demand is less than that available in flow. This is obtained from the Flow Archive File only.

Forced Spill occurs when river flow exceeds powerhouse capacity. This is calculated by CRiSP.1.

First, Planned Fish Spill is allocated. For each period, planned spill is distributed over scheduled spill days and fish spill hours (within those days) using the following steps.

2. Total modulated flow in the period that occurs in fish spill hours on planned spill days is calculated and designated

   flow_available (in kcfs units).

3. The requested spill in a period is designated

   spill_request (in kcfs units).

4. Percent spill during Fish Hours is calculated as

   spill_daily_percent = spill_request/flow_available.

5. If spill_daily_percent > 100%

   then spill_daily_percent = 100%

   of the flow available in the request periods and the rest is discarded and a warning message is generated.

Second, Overgeneration Spill identified in the flow models for 2 or 4 week periods is evenly distributed over all days in the periods. The following calculations are made on a daily basis.

2. Overgeneration Spill is added to Planned Fish Spill in Fish Hours every day in a period to yield total spill.
3. If Total Spill in Fish Hours is now greater than the total flow over the hours then the excess is distributed over the rest of the day.
4. If Total Spill for the entire day is greater than the total daily modulated flow then the spill is set to the total daily modulated flow.

Third, Forced Spill occurs when river flow exceeds powerhouse capacity. Forced Spill is calculated on the dam time slice periods. This is typically a 2 hour interval. CRiSP.1 uses the following logic:

2. Calculate the quantity

   flow - powerhouse capacity/flow = possible forced spill

3. Then, if

   possible forced spill > total fish & overgeneration spill

   assign

   total spill = possible forced spill.

   Otherwise the forced spill is assimilated into fish and overgeneration spills.

Planned Spill can be set by specifying spill information with the Spill Schedule Tool. The following information is entered:

• fraction of flow spilled
• days over which the spill fraction applies
• days in which actual spill occurs, i.e. the planned spill
• hours of planned spill for the indicated days.

Spill Caps

The maximum allowable planned spill is set by spill caps at each dam. If planned spill exceeds the cap then spill is limited to spill cap. Forced spill can exceed the spill cap. Spill cap is under the DAM button.

Spill Efficiency

The fraction of fish passed with spilled water is defined by one of seven possible empirical equations that can be selected by the user.

Table 40 Equations used in spill efficiency
Equation number	index	Equation form
eq (146)	a
	b
	c
	d
	e
	f
	g

where

• Y = fraction of total fish passed in spill
• X = fraction of water spilled
• a and b = regression coefficients
• e = error term (var) selected from random distribution.