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The Hydrology Section has responsibility for a number of activities, including the following:

1.      Perform modeling studies to provide the peak flows and hydrographs used in District facility design projects.

2.      Monitor storm rainfall and runoff, do forecast modeling, and advise the Sheriff’s Office of Emergency Services on the potential for flood damages in the County.

3.      Install and maintain a hydrographic gage network to provide real-time data during storms and collect data for use in design studies.  The data collected from our gages are made available to the public for their use through our website.

4.      Perform sediment yield calculations, especially after fires.

5.      Maintain and update manuals and reports describing our design procedures and hydrology programs.

6.      Review Hydrology Studies submitted with permit applications and CEQA review packages.



Hydrology Data Available to the Public

The Historical Rainfall and Streamflow Data site contains finalized reports and preliminary data for the rain and stream gages operated by VCWPD or in conjuction with the USGS. Please read our The Frequently Asked Questions file included on the data home page for detailed information about the data website and the data it provides.  The Current Rainfall Information page privides snapshots of data collected over the past 2 days.  These data provide current rainfall totals and weather information.

Historical Rainfall and Streamflow Data - WISKI Web (rainfall, stream flow, stream peaks, and evaporation data)Historical Rainfall and Streamflow Data - WISKI Web (rainfall, stream flow, stream peaks, and evaporation data)

Additional Information

Hydrology Frequently Asked QuestionsHydrology Frequently Asked Questions
Hydrology Data Request Form (PDF, 176 KB)Hydrology Data Request Form (PDF, 176 KB)


Design Hydrology Methodology

Please see the 2006 update of the VCWPD Hydrology Manual (downloadable on this site) for information on our design hydrology methods.  In general, peak flows from urban and small undeveloped watersheds for use in channel design can be evaluated using our modified rational method and programs (VCRat2.6, Tc Calculator- available on this website, including training materials).  Peak flows and hydrographs for regional facility design can be evaluated using the calibrated S-Graph developed from 2005 storm data.  Other peak flow design methods that have been used to evaluate floodplains include the results from flow frequency analyses (for gaged watersheds) and inserting design storm rainfall in continuous models (HSPF).  For information on these advanced methods, please contact the Hydrology Section at (805) 654-2069 or email your request to HydroData@ventura.org.


Notice: VCRat 2.6 Program UPDATE!!!

On December 2, 2008, the design hydrology program VCRat2.5 was updated to version 2.6.  The Tc Calculator program was also updated at the same time. You can download and install the updated programs following the instructions provided below.


WARNING: VCRat 2.6 was tested successfully on a computer with the Windows Vista Operating System. VCRat 2.6 and the TC Calculator have not been verified to run on all versions and configurations of the Vista Operating System. We have also received reports that the programs WILL NOT run on 64-bit computers as of December 2010.


VCRat2.6 Program Enhancement Description (PDF, 0.5 mb)VCRat2.6 Program Enhancement Description (PDF, 0.5 mb)
Document with a list of upgrades made to VCRat2.5 program, resulting in the VCRat2.6 program,

Hydrology Manual and VCRat Program Downloads

The VCWPD has developed the Hydrology Manual and the Hydrology Manual Appendix E files as a resource for computing design hydrology. Although it is anticipated that the overall approach described in this manual will not significantly change, any hydrologic process should be considered a dynamic process and subject to periodic refinement as additional input data become available. Techniques described in this manual will be continuously reviewed and updated, as necessary, to provide a thorough and complete package for hydrologic design. The VCRat 2.6.2008.11 and Tc Calculator Programs are available for download as of December 2, 2008. You may also need the Tc Calculator Manual and the VCRat 2.6 and Tc Calculator Training Materials to help you in understanding the applications.


2006 Hydrology Manual (PDF, 10.8 MB superseded by 2010 Manual Below)2006 Hydrology Manual (PDF, 10.8 MB superseded by 2010 Manual Below)
Hydrology Manual Appendix E files (ZIP, 63.7 MB)
Tc Calculator Manual (PDF, 579 KB)Tc Calculator Manual (PDF, 579 KB)
VCRat 2.5.2007.2 and Tc Calculator Programs (ZIP, 35.8 MB)
VCRat2.6 and Tc Calculator Training Materials (zip, 3.5 mb)VCRat2.6 and Tc Calculator Training Materials (zip, 3.5 mb)
Training materials for VCRat2.6 and Tc Calculator Programs developed for December, 2008 Training Classes.


Board-Accepted 2010 Design Hydrology Manual!

Updated hydrology manual with additional design methods such as HSPF, HEC-HMS, and Bulletin 17B Flow Frequency Analysis information. Accepted by the Ventura County Board of Supervisors on December 7, 2010.  Please email comments and feedback to HydroData@Ventura.org. For questions and additional information email Bruce.Rindahl@ventura.org or Mark.Bandurraga@ventura.org.

December 2010 Design Hydrology Manual with Errata Page (18 mb-pdf)December 2010 Design Hydrology Manual with Errata Page (18 mb-pdf)

The final manual was updated in response to consultant comments received as of December, 2010.  It includes more examples of design hydrology techniques used by the District. It was accepted by the Ventura County Board of Supervisors on December 7, 2010.  Appendix E files provided for use in design hydrology work are available for download below. Several figures and some text were revised as shown on the Errata Pages provided below in June, 2011.


Appendix Files E-1-9 Rainfall and Soils Maps and Shapefiles (79mb, zip)Appendix Files E-1-9 Rainfall and Soils Maps and Shapefiles (79mb, zip)
Or download individual files in the following links:
Appendix File E-26 VCRAT2.2 Executable (zip)Appendix File E-26 VCRAT2.2 Executable (zip)
Provided for use in Areal Reduction calculations.
2010 Manual Errata Pages (PDF, 0.5 mb)
Report pages to replace 2010 Manual pages from files downloaded before June 16, 2011.


NEW NOVEMBER 2013- Proposed Hydrology Manual Update Report!

PDF Report, 11 mb
Report summarizing work done to evaluate proposed design hydrology update items. If approved, will be incorporated into planned 2014 update of Hydrology Manual. Any stakeholders wishing to comment on the proposals, please submit written comments to mark.bandurraga@ventura.org by December 31, 2013. Watch this space for schedule of proposed stakeholder meetings after report is distributed.



Design Hydrology Training - VCRat and Tc Calculator Programs

Basic training classes were offered on February 18 and 25, 2009.  An Advanced Training Class may be offered soon to interested individuals that provide their name to HydroData@ventura.org. Individual training is available at $75.00/hour and can be scheduled by sending an email request to HydroData@ventura.org.

Manual Hard Copies and Additional Assistance

Because of the numerous color figures included in the 2006 update to the Hydrology Manual, no hardcopies are available from the District.  For questions about the data and methods described in the Hydrology Manual, email your question to  HydroData@ventura.org or call the Hydrology Section at (805) 654-2069.
For questions about the data and methods described in the Hydraulic Design Manual, contact the VCWPD Design and Construction Division, or call them at (805) 654-2007.

Other Hydrology Reports and Manuals

Available below are additional reports and manuals from the Hydrology Section.


Gage Network ReportGage Network Report
Consultant report done in 2007 to evaluate gage network and resources and make recommendations to enhance network to meet District data and floodwarning goals.
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