2002 Hydrologic Report
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San Luis Obispo County Public Works Department Water Years 2001-02 and 2002-03 Hydrologic Report Final Report May 16, 2005 Executive Summary This report includes a summary of the hydrological conditions for San Luis Obispo County for the 2001-02 and 2002-03 Water Years. Data is presented for precipitation, evaporation, stream flow, groundwater and reservoir operations. The County’s data collection and record keeping program is operated by the Water Resources Unit of the County Public Works Department. The program is funded by and administered through the San Luis Obispo County Flood Control and Water Conservation District. Hydrologic data for San Luis Obispo County has been collected by various Federal, State and local agencies, including the County Public Works Department, for decades. Rainfall and temperature records for some stations date back to the late 1800’s. Much of the data has been collected by volunteer citizens throughout the County. The County Public Works Department maintains many of the records and regularly furnishes information to local public agencies, consultants and the general public. The goal of assembling and organizing the records in this report was to allow more efficient public distribution of the data. In recent years, the County has maintained the monitoring program but lacked adequate resources to publish a regular hydrologic report. Thus, this is the first such report produced in over two decades. A great deal of effort went into the preparation of this report and it was intended to serve as a boilerplate for future editions. With this in mind, an Administrative Draft version of the report was published in Adobe Acrobat format and circulated among a cross section of local professionals in August and September of 2004 to solicit comments and suggestions regarding both the usefulness of the information and the presentation format. The feedback received was generally positive and the comments have been incorporated into this final report, as appropriate. San Luis Obispo County Water Years 2001-02 Hydrologic Report Final Report 5/16/05 and 2002-03 San Luis Obispo County Utilities Division, Public Works Department Prepared by: Jeff Werst, Hydraulic Planning Unit Staff Engineer Kirsten Arnold, Hydraulic Planning Unit Civil Engineering Technician Frank Honeycutt, Hydraulic Planning Unit Senior Engineer Under direction from: Christine Ferrara, Utilities Division Manager San Luis Obispo County Public Works Director: Noel King, Director of Public Works San Luis Obispo County Board of Supervisors: Harry Ovitt, District 1 Shirley Bianchi, District 2 Peg Pinard, District 3 Katcho Achadjian, District 4 Mike Ryan, District 5 Additional copies of this report may be ordered through the SLO County Public Works Department, Utilities Division, Hydraulic Planning Unit. An electronic copy of the report is available through the County’s website at http://www.slocountywater.org/. San Luis Obispo County Water Years 2001-02 Hydrologic Report Final Report 5/16/05 and 2002-03 Acknowledgements…(It’s all About Volunteers!) Appreciation is expressed for the assistance of personnel of public agencies and private firms, and to individuals in Cities and Towns, and to ranchers in remote areas of the County who have painstakingly measured and recorded the rainfall data included in this report. Information contained in this report is generally presented on the basis of the Water Planning Areas where the data source is located. The County was divided into separate Water Planning Areas as part of the “San Luis Obispo County Master Water Plan Update, Phase 1 Data Compilation Report” prepared in August of 1998 by EDAW, Inc in association with other local consultants. We also wish to thank the well owners and operators who have assisted in the groundwater monitoring program by providing access to their wells for measuring and sampling, and who have frequently furnished important information in the form of well logs, pump test data and personal observations. We also express our appreciation to those property owners who have provided use of their land for the construction of the stream gauging stations and for the installation of recording rain gages and other equipment. The success of this program in the past years has been the direct result of the support and assistance of all of you throughout the County who have cooperated so unselfishly and we look forward to our continuing and mutually beneficial association. San Luis Obispo County Water Years 2001-02 Hydrologic Report Final Report 5/16/05 and 2002-03 Contents Introduction Purpose.............................................................................................1 History..............................................................................................1 Setting ..............................................................................................2 Presentation......................................................................................3 Water Year.......................................................................................5 Summary of 2002 and 2003 Water Years........................................5 Precipitation Background......................................................................................7 Data Collection ................................................................................8 Evaporation Background....................................................................................43 Data Collection ..............................................................................43 Stream Flow Background....................................................................................55 Data Collected................................................................................56 Data Reported ................................................................................57 Groundwater Overview........................................................................................76 Data Reported ................................................................................77 Discussion......................................................................................77 Basin Descriptions .........................................................................79 Reservoirs Background..................................................................................106 Reservoir Descriptions.................................................................106 Data Reported ..............................................................................109 Appendix A. References..............................................................................119 B. Glossary..................................................................................120 C. Abbreviations .........................................................................122 Tables and Graphs Active Volunteer Rainfall Stations Tables .............................. 11-14 Precipitation Tables and Graphs .............................................. 15-42 San Luis Obispo County Water Years 2001-02 Hydrologic Report Final Report 5/16/05 and 2002-03 Evaporation Tables and Graphs............................................... 45-54 Stream Gage Stations Table...........................................................61 Stream Flow Tables and Graphs.............................................. 62-75 Groundwater Well Table................................................................86 Groundwater Well Elevation Graphs..................................... 88-105 Reservoir Description Table ........................................................110 Reservoir Operational Charts............................................... 112-117 Maps and Figures 1. Water Planning Areas .................................................................4 2. Precipitation Gage Location Map .............................................10 3. Evaporation Station Location Map ...........................................44 4. Stream Gage Locations Map (County-Wide) ...........................58 5. Stream Gage Locations Map (Zone 9)......................................59 6. Stream Gage Locations Map (USGS).......................................60 7. Groundwater Basins in SLO County ........................................78 8. Paso Robles Basin - Well Vicinity Map ...................................87 9. Santa Maria Basin - Well Vicinity Map ...................................93 10. San Luis Obispo Basin - Well Vicinity Map ..........................99 11. Los Osos Basin - Well Vicinity Map....................................102 12. Reservoir Location Map .......................................................111 San Luis Obispo County Water Years 2001-02 Hydrologic Report Final Report 5/16/05 and 2002-03 Introduction The Hydrologic Cycle Purpose This report presents hydrologic data collected for the County of San Luis Obispo for the period beginning October 1, 2001 and ending September 30, 2003. The data and report are divided into five sections: o Precipitation o Evaporation o Stream flow o Groundwater levels o Reservoirs This report provides a general overview of the hydrologic conditions measured by the County during the water year ending in September 30, 2003, but is not intended to evaluate the quantity or quality of water resources within the County. History Hydrologic data for San Luis Obispo County has been collected by various Federal, State and local agencies, including the County Public Works Department, for decades. Rainfall and temperature records