Electric Power Foregone to Lock Flushby Oregon Natural Resource Council
Restoring the Lower Snake River, Appendix to Section 2
Transportation (pp. 19-21)
In this appendix section, additional information is provided on electric power foregone to lock flush and on local property tax supports for Lower Snake ports.
KEY REPORT RESULT: (bluefish recommends: Economic & Environmental Impacts of Extended Lock Outage by Dr. Ken Casavant, Freight Policy Transportation Institute, 8/11)
River transportation on the Lower Snake is expensive and heavily subsidized. Although river shippers pay only $1.23 per ton from Lewiston, Idaho to Kennewick, Washington, taxpayers and electric ratepayers pay an additional $12.66. The total cost to ship one ton of goods on the Lower Snake is $13.88. In comparison, rail costs only $1.26.
Electric power foregone to lock flush
Foregone power per lock flush
the method for calculating this loss at any given lock is straightforward:
Acre-feet of water diverted x Power head x 0.87 = loss in kWh
for example given a typical system lock with a volume of 133 acre-feet and a power head of 100 feet,, the calculation is: 133 x 100 x 0.87 = 11,571 kWh. So the opportunity cost in electric power of operating this lock is 11,571 kWh per flush. This formula is applied in the table below to establish loss in kWh per lock flush for the four Lower Snake River dams.
Forgone hydropower per lock flush at each dam, in kWh
|DAM||ACRE-FEET||POWER HEAD||K FACTOR||LOSS/FLUSH|
Source: Report of the Secretary of the Army on Civil Works Activities, Walla Walla District Army Corps of Engnieers 1993 & calculated as described.
Total number of lock flushes with lost water
Operating a lock does not always entail losing water. Some lock operations do not require flushing water, and some water would be lost during high flows whether or not the locks were in operation. Taking these into consideration, we calculate for commercial and recreational lock flushes the amount of water lost to power generation.
LOCK OPERATIONS THAT REQUIRE FLUSHING
If the lock is empty and a vessel arrives from downstream then the lock will be filled in operating, not flushed. In such a case the next vessel through in either direction will account for flushing the lock. There are four possible permutations of the relative positions of barges and locks. In three of these, operating the lock involves a flush. So three-fourths of lock operations are counted as lock flushes in developing this estimate.
When water is spilled over the dams during spring high water, there is no foregone power generation ascribable to lock flush. So lock flushes during the high-water month of May are not included in our estimate.
Power foregone to lock flush: calculations
Fiscal 1994 monthly commercial and recreational lock flushes data provided by the Corps of Engineers is presented in the two tables below (not shown). Several operations are performed on this data:
POWER VALUE LOSSES TO LOCK FLUSH FOR THE FOUR SNAKE RIVER DAMS ARE: (assuming 1.6 cents/kWh)
(Two tables associated with above calculation are not shown here but conclusion is included:)
IN TOTAL: LOWER SNAKE TOTAL, COMBINED COMMERICAL & RECREATION FLUSH Fiscal 1994
Total lock flushes with lost water: 4,493
Acre-feet of water diverted: 590,480
Forgone kWh (millions): 50.56 Value of foregone power: $809,021
Sources: Vessel & Lockage Summary, Walla Walla District, Army Corps of Engineers & Calculated
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