Drought Assessment: Sacramento River Basin, San Joaquin River Basin, and Tulare Lake Basin Ramesh Gautam, Mitchel Russo & Michael Anderson California Department of Water Resources Sacramento, CA CWEMF 2017 3/21/2017 1 Outline • Brief Description of Sacramento, San Joaquin, and Tulare Basins • Drought Index: Brief Introduction • Drought Index Calculation and Analysis • Findings and Conclusion 3/21/2017 2 Sacramento, San Joaquin & Tulare Basins Sacramento River Basin: Surface Area: Approximately 19.55 million acres Lakes and Reservoirs: 331 thousands acres (1.7% of total area) Main Rivers: Pit, McCloud, Sacramento, Feather, and American Major Lakes: Lake Shasta, Lake Orville, Folsom Lake, Lake Almanor San Joaquin River Basin: Surface Area: Approximately 9.79 million acres Lakes and Reservoirs : 103 thousands acres (1.05% of total area) Main Rivers: Merced, Stanislaus, San Joaquin, Tuolumne, Calaveras Major Lakes: Don Pedro, Mariposa, Millerton, Turlock Lake, Comanche Reservoir, San Luis Reservoir, Lake McClure Tulare Lake Basin: Surface Area: Approximately 9.4 million acres Lakes and Reservoirs : 222 thousands acres ( 2.36 % of total area) Main Rivers: Kings River, Kaweah River, Kern River, Tule River Major Lakes: Kern Lake, Buena Vista Lake 3/21/2017 3 Sacramento (8SI), San Joaquin (5SI), and Tulare (6SI) Precipitation Data Sacramento Basin 8 Stations (8SI): Mount Shasta City (MSC), Shasta Dam (SHA), Mineral (MNR), Quincy (QRD), Brush Creek (BCM), Sierra Ville RS (SRR), Blue Canyon (BYM), and Pacific House (PCF) Precipitation Records: [Oct 1919 to Sep 2016, 97 Years] San Joaquin Basin 5 Stations (5SI): Calaveras Big Trees (CVT), Hetch Hetchy (HTH), Yosemite Headquarters (YSV), North Fork RS (NFR), and Huntington Lake (HNT) Precipitation Records: [Jan 1905 to Sep 2016, 110 Years] Tulare Basin 6 Stations (6SI): Balch PH (BAL), Giant Forest (GNF), Ash Mountain (ASM), Springville (SGV), Pascoes (PSC), and Isabella Dam (ISB) Precipitation Records: [Oct 1921 to Sep 2016, 95 Years] 3/21/2017 4 Distribution of Monthly Precipitation 3/21/2017 5 Annual Precipitation Frequency Variation 3/21/2017 6 Standard Precipitation Index (SPI) • An Index that represents the dry or wet events at a particular location if long term precipitation records are known. • McKee et al. (1993) developed SPI for the purpose of defining and monitoring the drought in the United States. • Western Regional Climate Center, Colorado Climate Center, and National Drought Mitigation Center use SPI to monitor current status of drought in the United States. 3/21/2017 7 SPI Cont’d.. 3/21/2017 8 SPI Cont’d… 3/21/2017 9 SPI Cont’d… 3/21/2017 10 SPI Cont’d… • SPI can be computed to any time scale e. g., 3 months, 6 months, 12 months, 18months, 24 months, 36 months etc. • For Sacramento, San Joaquin, and Tulare river Basins, SPI was computed for 24 months time interval. SPI ≤ -2.0 Extremely Dry -2.0 < SPI ≤ -1.5 Moderately Dry -1.5 < SPI ≤ -1.0 Dry -1.0 < SPI < 1.0 Neutral 1.0 ≤ SPI < 1.5 Wet 1.5 ≤ SPI < 2.0 Moderately Wet 2.0 ≤ SPI Extremely Wet Ref: Nathaniel.B. Guttman, National Climatic Data Center, North Carolina, USA, Journal of American Water Resources Association,3/21/2017 Vol 35, No. 2, April 1999 11 3/21/2017 12 3/21/2017 13 3/21/2017 14 SPI Statistics at 8SI 5% 0% 4% 8% 3% ED 13% MD D 66% N W MW SPI Statistics at 6SI 0% 4% 4% 3% ED 11% 10% MD D N 67% W MW 3/21/2017 EW 15 Findings • Standard Precipitation Index is useful to evaluate the status of dryness or wetness in any basin. • SPI indicates that 2012-2016 drought was worse than 1976-1977 drought in Tulare Lake Basin. • For San Joaquin River Basin, 1976-1977 & 2012-2016 droughts were of equal severe with longer duration in 2012-2016. • In Sacramento River Basin, 1976-1977 drought was the worst of all droughts ever recorded since 1920. • 4% of the time, all three basins are found to be under extreme dry conditions • On average, 66 to 70% of the time, all basins are found to have average 3/21/2017precipitation. 16 Future Work • Classifying short-term and long term drought • Computation of SPI at all stations in CA • Clustering the stations based on SPI classifications • Identifying hotspot hardly hit by drought 3/21/2017 17 .