1 April 2011
Hetch Hetchy Water and Power
• Who is Hetch Hetchy Water and Power (HHWP)?• HHWP is a division of the San Francisco Public
Utilities Commission (SFPUC)• SFPUC a Department of the City and County of
San Francisco (CCSF or City)
SFPUC Customers and Resources
• SFPUC provides water to about 2.4 million people• Current water demand is about 265 mgd or
300,000 acre-feet• System storage is about 1,460,000 acre-feet
• Local Reservoirs: 227,000 acre-feet• Tuolumne Reservoirs: 660,000 acre-feet• City’s Water Bank storage in Don Pedro Reservoir
570,000 acre-feet
1 April 2011
HHWP Reservoir Operations
• How is the HHWP reservoir system operated?
• How is the storage in Water Bank incorporated in HHWP Operations?
1 April 2011
Allocation of Tuolumne River Flows
• Raker Act is the document used to allocate flows on the Tuolumne River between the Districts and the City
• Based on natural flow at LaGrange
1 April 2011
1 April 2011
Sep-
88
Oct
-88
Nov
-88
Dec
-88
Jan-
89
Feb-
89
Mar
-89
Apr
-89
May
-89
Jun-
89
Jul-8
9
Aug
-89
Sep-
89
Oct
-89
Nov
-89
Dec
-89
Jan-
90
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Flow
in 1
,000
cfs
Districts' Rights& Entitlements
Unimpaired Runoffat La Grange
Water Available to San Francisco
Maximum Districts's Rights&Entitlements
Allocation of Tuolumne River Flows
• Average flow at La Grange is 1,800,000 acre-feet• 40% of the flow is allocated to the Districts• 60% to the City. Slightly over 1 million acre-
feet per year.• The SFPUC demand is about 265 mgd,
which is about 300,000 acre-feet
1 April 2011
1 April 2011
0
1
2
3
4
5
20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74 77 80 83 86 89 92 95 98 01 04 07 10
Water Year
Flo
w i
n M
illi
on
Acr
e-fe
et
Districts Entitlement Water Available to the City
Allocation During Dry Sequences
• In 1987-92, the Districts received 85% of the allocation on the Tuolumne River
• The SFPUC 15%, averaging about 150,000 acre-feet per year which is about half of the SFPUC current demand.
• The SFPUC must rely on storage through droughts.
1 April 2011
Value of Water Bank
• SFPUC has about 1,500,000 acre-feet total storage between local storage, upcountry storage and the Water Bank.
• The SFPUC does not divert water directly from the Water Bank, however, the storage provides us with up to 25% of our water supply during multiple-year droughts.
• How does the SFPUC access that storage?1 April 2011
1 April 2011
Sep-8
8
Oct-8
8
Nov-8
8
Dec-8
8
Jan-8
9
Feb-8
9
Mar-8
9
Apr-8
9
May-8
9
Jun-8
9
Jul-8
9
Aug-8
9
Sep-8
9
Oct-8
9
Nov-8
9
Dec-8
9
Jan-9
00
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Flow i
n 1,00
0 cfs
Districts' Rights& Entitlements
Unimpaired Runoffat La Grange
Water Available to San Francisco
Maximum Districts's Rights&Entitlements
Sep-88
Oct-88
Nov-88
Dec-88
Jan-89
Feb-89
Mar-89
Apr-89
May-89
Jun-89 Jul-89
Aug-89
Sep-89
Oct-89
Nov-89
Dec-89
Jan-90
0
1
2
3
4
5
6
7
8
9
10
Flow in 1
,000 cfs
New Don PedroReservoir Inflow
Districts' Rights& Entitlements
Credit toWater Bank
Debit toWater Bank
1 April 2011
Sep-88
Oct-88
Nov-88
Dec-88
Jan-89
Feb-89
Mar-89
Apr-89
May-89
Jun-89 Jul-89
Aug-89
Sep-89
Oct-89
Nov-89
Dec-89
Jan-90
0
1
2
3
4
5
6
7
8
9
10
Flow in 1
,000 cfsNew Don PedroReservoir Inflow
Districts' Rights& Entitlements
Credit toWater Bank
Debit toWater Bank
Sep-88
Oct-88
Nov-88
Dec-88
Jan-89
Feb-89
Mar-89
Apr-89
May-89
Jun-89
Jul-89
Aug-89
Sep-89
Oct-89
Nov-89
Dec-89
Jan-90
0.0
0.5
1.0
1.5
2.0
Storag
e in Mil
lion Ac
re-feet
San Francisco'sWater Bank Account
New Don PedroReservoir Storage
1,690,000 Acre-feet
570,000 Acre-feet
Hetch HetchyReservoir Storage
Optimizing Water Supplies
• How is the HHWP reservoir system operated?
• We operate to optimize reservoir carryover storage to minimize the probability of water rationing for customers.
1 April 2011
1 April 2011
System Draft
0
20
40
60
80
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Month
Sys
tem
Dra
ft in
1,0
00 a
f
Generate aggressively in the fall assuming reservoir inflow minus deliveries to City.
Generate conservatively when space is availableto "capture" draft in Water Bank
1 April 2011
Up-country Storage, Beginning-of-month(BOM)
300
400
500
600
700
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Beginning of Month
BOM S
torage
in 1,0
00 af
Conservative Operation
Aggressive Operation
Under each scenario, up-country reservoirs are full
System Draft
0
20
40
60
80
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Month
Syste
m Draf
t in 1,0
00 af
Generate aggressively in the fall assuming reservoir inflow minus deliveries to City.
Generate conservatively when space is availableto "capture" draft in Water Bank
1 April 2011
Up-country Storage, Beginning-of-month(BOM)
300
400
500
600
700
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Beginning of Month
BOM S
torage
in 1,0
00 af
Conservative Operation
Aggressive Operation
Under each scenario, up-country reservoirs are full
Hetch Hetchy System Storage, Beginning-of-month(BOM)
800
900
1000
1100
1200
1300
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Beginning of Month
BOM S
torage
in 1,0
00 af Conservative Operation
Aggressive Operation
Water Bank storage is approximately 95,000 af less in the aggressive scenario. Although the up-country reservoirs are full, system storage is 95,000 af less due to the aggressive fall draft.
1 April 2011
System Draft
0
20
40
60
80
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Month
Syste
m Draf
t in 1,0
00 af
Generate aggressively in the fall assuming reservoir inflow minus deliveries to City.
Generate conservatively when space is availableto "capture" draft in Water Bank
