YCWA Agency NGO Flow Modeling Proposal – September 9, 2014
Minimum Flows
Use the most recent set of agency/NGO minimum flows for Middle Yuba downstream of Our House,
Oregon Creek downstream of Log Cabin, and North Yuba River downstream of New Bullards Bar with
the following additions, by reach.
Middle Yuba Downstream of Our House (OH)
Oct – March
 Sediment transport: when a flow event of at least 3000 cfs (inflow into Our House Reservoir) is
forecast, open sluice gate for ~ 10 days to move sediment downstream. First event of each year.
 Whitewater recreation: provide flows between 800 and 2000 cfs on weekend days in the
following water year types, with total days per water year type as follows:
o Dry - 2 weekend days
o Below normal - 4 weekend days
o Above normal - 6 weekend days
o Wet - 8 weekend days
April – July
 Allow full ‘natural’ (without project) flow in the MYuba River on April 1 (i.e., close diversion
tunnels), in years when New Bullards storage is at 780 taf or higher at end of day on March 31.
 When New Bullards Bar storage is less than 780 taf at the end of the day on March 31, for any
OH spills on or after April 1, implement the following spill cessation steps. End when flow inflow
intersects with prescribed minimum flows. If an OH spill starts at a lower magnitude than the
highest flow in the table below, the cessation will start at the observed spill flow and go down
from that point.
Day
1
2-3
4-5
6-7
8-9
10-11
12-13
14-15
Minimum Flow – cfs
(at gage below OH)
600
500
400
300
250
200
175
150
Day, cont.
16-17
18-19
20-21
22-24
25-27
28-31
Minimum Flow – cfs,
cont.
125
100
80
60
50
40
[Note: These cessation flows represent effective flow rate changes of ~ 5-12% per day with
slower rates at the end of the cessation period. This in the range of unregulated Sierran streams
during spring run-off.]
Oregon Creek Downstream of Log Cabin (LC)
Oct – March
 Sediment transport: when a flow event of at least 1000 cfs (inflow into Log Cabin Reservoir) is
forecast, open sluice gate for ~ 10 days to move sediment downstream. First event each year.
Minus Lohman Ridge Diversion.
1
April – July
 Allow full ‘natural’ (without project) flow in Oregon Creek on or after April 1 (i.e, close diversion
tunnels), in years when New Bullards Bar storage is 780 taf or higher at end of day on March 31.
 When New Bulldards Bar storage is less than 780 taf, for any LC spills after April 1, implement
the following spill cessation steps. End when inflow intersects with prescribed minimum flows.
If a LC spill starts at a lower magnitude than the highest flow in the table below, the cessation
will start at the observed spill flow and go down from that point.
Day
1
2-3
4-5
6-7
8-9
10-11
12-14
15-17
Minimum flow
– cfs (at gage
below LC)
100
85
70
60
50
40
30
25
Day, cont.
Minimum flow
– cfs, cont.
18-20
21-23
24-27
28-31
20
15
12
10
[Note: These cessation flows represent effective flow rate changes of ~ 5-10% per day with
slower rates at the end of the cessation period. This in the range of unregulated Sierran streams
during spring run-off.]
[Note: Installation of a monitoring gage in Oregon Creek upstream of the Lohman Ridge tunnel
inflow may be needed to confirm that recession rates are following the Oregon Creek rate].
North Yuba Below New Bullards Bar
Oct – March
 Sediment/gravel and large wood restoration actions - TBD
April – July
 Use Licensee proposed spill cessation measure (FLA Measure AR4).
2