For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Tables Table 1. Streamflow-gaging stations and statistical data used to analyze regional skew in California and to determine flood frequency for the Sacramento-San Joaquin River Basin, California …………………………………………………… 23 Table 2. Basin characteristics for analyzing regional skew in California ………………… 23 Table 3. Basin characteristics for sites used in the regional skew analysis, California …… 24 Table 4. Results of trend tests for annual peak discharge at selected sites in California … 24 Table 5. Key dam sites and drainage areas, periods of estimated unregulated annual-maximum-daily discharge, and periods of concurrent unregulated annual-maximum-daily and peak-discharge data ………………………………… 25 Table 6. Unregulated, annual-maximum-daily discharge for key dam sites, California …… 26 Table 7. Regional skew models for California ……………………………………………… 38
AbstractImproved flood-frequency information is important throughout California in general and in the Sacramento-San Joaquin River Basin in particular, because of an extensive network of flood-control levees and the risk of catastrophic flooding. A key first step in updating flood-frequency information is determining regional skew. A Bayesian generalized least squares (GLS) regression method was used to derive a regional-skew model based on annual peakdischarge data for 158 long-term (30 or more years of record) stations throughout most of California. The desert areas in southeastern California had too few long-term stations to reliably determine regional skew for that hydrologically distinct region; therefore, the desert areas were excluded from the regional skew analysis for California. Of the 158 long-term stations used to determine regional skew, 145 have minimally regulated annual-peak discharges, and 13 stations are dam sites for which unregulated peak discharges were estimated from unregulated daily maximum discharge data furnished by the U.S. Army Corp of Engineers. Station skew was determined by using an expected moments algorithm (EMA) program for fitting the Pearson Type 3 flood-frequency distribution to the logarithms of annual peak-discharge data.The Bayesian GLS regression method previously developed was modified because of the large cross correlations among concurrent recorded peak discharges in California and the use of censored data and historical flood...
Back cover: Left, Collection of water samples during high flow conditions on the Sacramento River; right, Collection of samples of aquatic organisms and assessment of habitat conditions at a northern California headwaters stream.
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