In water year 2020, a dry year, 11.50 MAF of river water entered the Sacramento-San Joaquin Delta; the State Water Project and Central Valley Project pumps exported 3.66 MAF of it, 32 percent, and 2.96 MAF flowed to San Francisco Bay above the outflow floor that Water Right Decision 1641 sets for the month and the kind of year. The Delta’s own farms and channels used 1.23 MAF, and net outflow to the Bay was 6.61 MAF, of which 3.71 MAF was the floor itself.
How does 2020 compare with the ten water years before it?
Over water years 2010 to 2019, exports averaged 4.46 MAF a year, 24 percent of inflow. In 2020 the share was 32 percent. On 299 days of the year a standing rule, permit term, or biological opinion held exports below pump capacity while surplus water existed; on 67 days outflow sat at or below the floor, so there was nothing to take without breaking the rule. The most common condition across the year was a rule or permit held exports.
Month by month
| Month | Inflow (MAF) | Exports (MAF) | In-Delta use (MAF) | Net outflow (MAF) | Floor (MAF) | Exports, percent of inflow | Most common condition |
|---|---|---|---|---|---|---|---|
| Oct 2019 | 1.10 | 0.17 | 0.11 | 0.81 | 0.25 | 15.7 | a rule or permit held exports |
| Nov 2019 | 0.77 | 0.29 | 0.07 | 0.40 | 0.27 | 37.9 | a rule or permit held exports |
| Dec 2019 | 1.47 | 0.65 | -0.08 | 0.89 | 0.28 | 44.3 | a rule or permit held exports |
| Jan 2020 | 1.19 | 0.40 | 0.00 | 0.79 | 0.28 | 33.2 | a rule or permit held exports |
| Feb 2020 | 0.94 | 0.22 | 0.05 | 0.68 | 0.41 | 23.1 | a rule or permit held exports |
| Mar 2020 | 0.92 | 0.28 | 0.01 | 0.63 | 0.44 | 30.8 | a rule or permit held exports |
| Apr 2020 | 0.90 | 0.17 | 0.06 | 0.68 | 0.42 | 18.6 | a rule or permit held exports |
| May 2020 | 0.80 | 0.11 | 0.14 | 0.56 | 0.44 | 13.6 | a rule or permit held exports |
| Jun 2020 | 0.85 | 0.20 | 0.22 | 0.42 | 0.24 | 24.2 | a rule or permit held exports |
| Jul 2020 | 0.93 | 0.39 | 0.26 | 0.28 | 0.31 | 41.6 | no surplus outflow above the floor |
| Aug 2020 | 0.88 | 0.44 | 0.23 | 0.21 | 0.22 | 50.3 | no surplus outflow above the floor |
| Sep 2020 | 0.74 | 0.33 | 0.15 | 0.25 | 0.18 | 45.0 | a rule or permit held exports |
MAF = million acre-feet.
What contractors were told to expect
| Contractor class | Final allocation, 2020 | Final allocation, 2019 |
|---|---|---|
| SWP Table A | 15 percent | 75 percent |
| CVP south-of-Delta agriculture | 20 percent | 75 percent |
| CVP south-of-Delta cities | 70 percent | 100 percent |
| CVP north-of-Delta agriculture | 50 percent | 100 percent |
| CVP north-of-Delta cities | 75 percent | 100 percent |
| Settlement Contractors | 75 percent | 100 percent |
| Exchange Contractors | 75 percent | 100 percent |
| Friant Class 1 | 60 percent | 100 percent |
| Friant Class 2 | 0 percent | 0 percent |
| South-of-Delta refuges | 100 percent | 100 percent |
Allocations are percentages of contract supply.
How 2020 measures against other supplies
The 3.66 MAF exported in 2020 is 83 percent of California's 4.4 million acre-foot basic apportionment of the Colorado River under the Boulder Canyon Project Act of 1928, the state's other large imported supply. The 2.96 MAF that left the Delta above the floor is 65 percent of the 4.55 million acre-foot capacity of Shasta Lake, the largest reservoir in the state; 57 percent of it passed in three months (Oct, Dec, Jan).
Frequently asked questions
How much water did the Delta pumps export in water year 2020?
3.66 MAF: 1.97 MAF at the Central Valley Project's Jones plant and 1.53 MAF at the State Water Project's Banks plant, which together serve cities and farms on both projects. That was 32 percent of the 11.50 MAF that entered the Delta in a dry year.
How much Delta water flowed to the ocean in 2020?
Net Delta outflow was 6.61 MAF. Of that, 3.71 MAF was the minimum that Water Right Decision 1641 requires to keep salt water out of the Delta and its intakes, and 2.96 MAF was above that floor, 45 percent of the outflow.
What did project contractors receive in 2020?
The State Water Project's final Table A allocation was 15 percent of contract supply. Central Valley Project south-of-Delta agricultural contractors were told 20 percent and south-of-Delta cities 70 percent. An allocation is an announcement of the share of contract supply to expect, not a delivered volume.
Explore the year on the toolkit: Delta diversions by month, the constraint calendar, allocation history.