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Department of Water Resources California Cooperative Snow Surveys WATER SUPPLY INDEX (WSI) FORECASTS 2024 Water Year Hydrologic Classification Indices 2024 Water Year Forecast as of March 1, 2024 SACRAMENTO RIVER UNIMPAIRED RUNOFF - SACRAMENTO RIVER INDEX (SRR) Probability of Exceedance Forecast Date 99% 90% 75% 50% 25% 10% -------------------------------------------------------------------------------- Dec 1, 2023 6.1 (35%) 8.1 (46%) 10.1 (57%) 13.9 (79%) 20.2(114%) 26.6(151%) Jan 1, 2024 6.8 (39%) 8.4 (48%) 10.1 (57%) 13.0 (74%) 17.6(100%) 22.7(129%) Feb 1, 2024 7.4 (42%) 9.2 (52%) 11.6 (66%) 14.3 (81%) 19.0(108%) 23.5(133%) Mar 1, 2024 13.0 (74%) 14.3 (81%) 15.4 (87%) 16.9 (96%) 20.7(117%) 24.2(137%) Sacramento River Runoff is the sum of unimpaired flow in million acre-feet at: Sacramento River above Bend Bridge Feather River at Oroville (aka inflow to Lake Oroville) Yuba River near Smartville American River below Folsom Lake Also known as the "Sacramento River Index", this index was previously used to determine year type classifications under SWRCB Decision 1485. Also previously referred to as the "4 River Index" or "4 Basin Index". Water Year Runoff through end of last month: 2024 (current year) = 7.3 MAF 97% of average 2023 (last year) = 8.2 MAF 110% of average Previous Water Year Total Runoff: 2023 = 24.1 MAF 136% of average 1977 (Min) = 5.1 MAF 29% of average 2017 (Max) = 37.8 MAF 214% of average 1991-2020 average = 17.7 MAF SACRAMENTO VALLEY WATER YEAR TYPE INDEX 40-30-30 (SVI) Probability of Exceedance Forecast Date 99% 90% 75% 50% 25% 10% -------------------------------------------------------------------------------- Dec 1, 2023 4.67 5.30 5.97 7.22 9.28 11.35 Jan 1, 2024 4.89 5.41 5.95 6.91 8.45 10.10 Feb 1, 2024 5.06 5.64 6.46 7.36 8.97 10.51 Mar 1, 2024 6.89 7.32 7.72 8.23 9.58 10.80 Index = 0.4 * Current Apr-Jul Runoff (1) + 0.3 * Current Oct-Mar Runoff (1) + 0.3 * Previous Year's Index (2) Notes: (1) Runoff is the sum of unimpaired flow in million acre-feet at: Sacramento River above Bend Bridge Feather River at Oroville (aka inflow to Lake Oroville) Yuba River near Smartville American River below Folsom Lake (2) Maximum 10.0 for previous year index term Previous Water Year Indices: 2023 = 9.32 118% of average 1977 (Min) = 3.10 39% of average 1983 (Max) = 15.29 193% of average 1991-2020 average = 7.91 Year Type Classification: Index based on flow in million acre-feet: Wet Equal to or greater than 9.2 Above Normal Greater than 7.8, and less than 9.2 Below Normal Greater than 6.5, and equal to or less than 7.8 Dry Greater than 5.4, and equal to or less than 6.5 Critical Equal to or less than 5.4 This index, originally specified in the 1995 SWRCB Water Quality Control Plan, is used to determine the Sacramento Valley water year type as implemented in SWRCB D-1641. Year types are set by first of month forecasts beginning in February. Final determination is based on the May 1 50% exceedence forecast. SAN JOAQUIN VALLEY WATER YEAR TYPE INDEX 60-20-20 (SJI) Probability of Exceedence Forecast Date 99% 90% 75% 50% 25% 10% -------------------------------------------------------------------------------- Dec 1, 2023 1.64 1.98 2.35 2.91 4.08 5.21 Jan 1, 2024 1.64 1.92 2.23 2.63 3.58 4.52 Feb 1, 2024 1.83 2.18 2.63 3.13 3.91 4.59 Mar 1, 2024 2.45 2.81 3.08 3.43 4.13 4.74 Water Year Index based on flow in million acre feet Index = 0.6 * Current Apr-Jul Runoff (1) + 0.2 * Current Oct-Mar Runoff (1) + 0.2 * Previous Year's Index (2) Notes: (1) Runoff is the sum of unimpaired flow in million acre-feet at: Stanislaus River below Goodwin Reservoir (aka inflow to New Melones Res.) Tuolumne River below La Grange (aka inflow to New Don Pedro Reservoir) Merced River below Merced Falls (aka inflow to Lake McClure) San Joaquin River inflow to Millerton Lake (2) Maximum 4.5 for previous year index term Previous Water Year Indices: 2023 = 6.40 197% of average 2015 (Min) = 0.81 25% of average 1983 (Max) = 7.22 222% of average 1991-2020 average = 3.26 Year Type Classification: Index based on flow in million acre-feet: Wet Equal to or greater than 3.8 Above Normal Greater than 3.1, and less than 3.8 Below Normal Greater than 2.5, and equal to or less than 3.1 Dry Greater than 2.1, and equal to or less than 2.5 Critical Equal to or less than 2.1 This index, originally specified in the 1995 SWRCB Water Quality Control Plan, is used to determine the San Joaquin Valley water year type as implemented in SWRCB D-1641. Year types are set by first of month forecasts beginning in February. Final determination for San Joaquin River flow objectives is based on the May 1 75% exceedence forecast. SACRAMENTO VALLEY & SAN JOAQUIN 8 RIVER INDEX Previous month: Feb 3910 TAF This index is the sum of the previous month's unimpaired runoff for the 8 rivers that are included in the above SACRAMENTO RIVER UNIMPAIRED RUNOFF and the SAN JOAQUIN VALLEY WATER YEAR TYPE INDEX A listing of reconstructed indices based on historical observed runoff is posted at http://cdec.water.ca.gov/water_supply.html The official year types are based on May 1 forecasts, not the observed runoff. If you have any questions contact the Snow Surveys and Water Supply Forecasting Staff Andy Reising (916) 914-0050 Andrew.Reising@water.ca.gov Anthony Burdock (916) 914-0051 Anthony.Burdock@water.ca.gov Jacob Kollen (916) 914-0028 Jacob.Kollen@water.ca.gov Jordan Thoennes (916) 885-8992 Jordan.Thoennes@water.ca.gov Steve Nemeth Stephen.Nemeth@water.ca.gov If you would like to receive notifications of forecasts and/or other DWR Products click on the following link to subscribe or manage your existing subscriptions: https://public.govdelivery.com/accounts/CNRA/subscriber/new