Historical Rainfall and Stream Flow
(Hydrodata Web) 

Frequently Asked Questions 

What data are available from this site? 
How do I download data? 
What Official Reports are available?  
About Variable Numbers and Data Types
 
About Quality Codes 
About Station Numbering Sequence  
Special Precipitation Types/Classes
About USGS Stream Gage Data   
About NON-VCWPD Data  
About High-Resolution Discharge Data 
About Stage Data that is Included with Peak Flows and Uncertainty of Peak Flows
What is a Water Year?  How is it defined?
About Certified or Non-Standard Data Request 
About Daylight Saving Time  
About Preliminary Rainfall Frequency Reports


What data are available from this site?

The information available from this site includes rainfall, stream flow and pan evaporation data from gages operated by Ventura County Watershed Protection District (VCWPD). Limited other data from public agency gages or gages co-operated with VCWPD are also provided.


How do I download data?

  1. Select the type of data you want from the 'Dataset' Menu.  You can sort by station name or station id by changing the 'Sort by' drop-down.

  2. Select station from list by clicking on the station name or id.

  3. The station page will appear and display all datasets and reports that are available.  When graphs appear, you can also display data tables or download files.  The data available through the 'Download' option are not official data and are subject to change.  Select a report or file from the ‘Official Data’ menu for the official published data.

  4. Individual water year reports and datasets are available by selecting the options under each dataset.  These reports and datasets contain official, preliminary, and/or unverified data.


What Official Reports are available?

Report Name File Type Description
Daily Discharge Data CSV Average daily discharge data in a comma separated file that can be used with Excel or Access.  Contains entire available average daily flow for this station.
Daily Discharge Summary TXT Average daily discharge data in report format for each water year.  Each page represents a separate water year.
Event Peak Data CSV Peak flow data in a comma separated file that can be used with Excel or Access.  Contains all peak events (if available) with peak discharge and associated stage elevation for that peak flow.
Daily Rainfall Data CSV Daily rainfall data in a comma separated file that can be used with Excel or Access.  Contains entire available daily rainfall for this station.
Daily Rainfall Summary TXT Daily rainfall data in report format for each water year.  Each page represents a separate water year.
Monthly Rainfall Summary TXT Monthly rainfall totals for entire period of record in report format.  May be multiple pages.
Monthly Evaporation Data CSV Monthly pan evaporation data in a comma separated file that can be used with Excel or Access.
Monthly Evaporation Summary TXT Monthly pan evaporation totals for entire period of record in report format.  May be multiple pages.
Seasonal Storage Precip Summary TXT Seasonal rainfall totals for remote storage rain gages for entire period of record in report format
Station Information (available for some stations) HTML List station history and movement.  Links to all stations and gives information about data not collected by VCWPD.  Links to these other agencies for available data.
Rainfall Frequency Short Term (Preliminary) PDF Lists the frequency return intervals for rainfall intensities for time periods of 5 minutes to 24 hours.
Rainfall Frequency Long Term (Preliminary) PDF Lists the frequency return intervals for rainfall intensities for time periods of 1 day to 1 water year.
Flood Flow Frequency PDF Currently these reports are not available due to the complexity of the analyses, please submit a data request to hydrodata@ventura.org.

About Variable Numbers and Data Types

The official reports use a VARIABLE NUMBER to describe different data types.  You will see these different VARIABLE NUMBERS in the following reports:

Report Name First Variable First Variable Description Second Variable Second Variable Description
Daily Discharge Data 262.01 Average Daily Discharge (cfs)
Daily Discharge Summary 262.01 Average Daily Discharge (cfs)
Event Peak Data 232.04 Event Peak Gage Height (feet) 262.01 Event Peak Discharge (cfs)
Daily Rainfall Data 11.01 Daily Rainfall (inches)
Daily Rainfall Summary 11.01 Daily Rainfall (inches)
Monthly Rainfall Summary 11.01 Monthly rainfall (inches) - calculated from daily
Monthly Evaporation Data 492.02 Monthly Pan Evaporation (inches)
Monthly Evaporation Summary 492.02 Monthly Pan Evaporation (inches)
Seasonal Storage Precip Summary 11.03 Annual or bi-annual precipitation measurements (inches)


About Quality Codes

Quality Codes are used to signify the quality of the data.  They are also used to identify periods with trace rainfall, snowfall in precipitation total, estimated, and pro-rated data.  The following quality codes are used for all data types:

Quality Code Code Letter Description
201 M No data exist for this time period.
151, 255 M Data currently missing in an electronic form.  Data may exist in hardcopy but would need extensive processing before being available in electronic form.
1,2,3,4,5 Good continuous data.

The following reports contain the Quality Codes that are used with a particular dataset

Daily/Monthly Rainfall Quality Codes
High-Resolution (Hourly) Rainfall Quality Codes
Storage Gage Rainfall Quality Codes

Daily Stream Quality Codes
High-Resolution Quality Codes
Peak Streamflow Quality Codes

Pan Evaporation Quality Codes


About Station Numbering Sequence
Ventura County Watershed Protection District uses a numerical numbering system to identify station locations.  Rainfall stations range between 1 and 599.  Stream stations range between 600 and 900.  When a station was moved within the same general area, the same number is used but a letter is attached to the end.  For hydrologic purposes, stations with the same numerical number  but different ending letters may be combined to provide a continuous hydrology record for analysis.  Station History Reports are available for some stations and can be found under the 'Official Reports' drop-down menu.
 
Special Precipitation Types/Classes
VCWPD uses a mix of different gages in the network of official rain gages.  Generally these gages meet the standards set by the National Weather Service for standard heights, resolution, and collection area.  Gages marked with the following classifications in the station name differ in the following ways:

Type B - These sites are non-standard Official recording rain gages.  These sites are automated gages that do not have as many maintenance checks as our other Official gages.  These sites may have collectors that are higher above the ground and contain larger measuring buckets such as 1 mm (0.04 in) compared to the 0.01 inch buckets that are installed with our standard recording gages.  Historic data may not have gone through the same QA/QC process as the standard recorder datasets.

Type C - These are non-standard recording gages similar to Type B gages except they are located at elevations where snow regularly falls.  These gages are not designed to record precipitation in the form of snow accurately.  As a result, daily and seasonal totals may not be accurate.  For Type C sites that have storage gages located next to the recording gage, use the storage gage total for seasonal totals as the storage gage measures total precipitation for the year including snow.  Historic data for these gages may not have gone through the same QA/QC process as the standard recorders.

 
About USGS Stream Gage Data
Some District stream gages have been operated  or co-operated by the USGS for various periods.  The USGS also currently either operates and/or reviews and publishes data from a number of other stream gages in the County.  The gages are identified as such in the Station History files provided under the 'Official Data' tab.  The USGS-published data are provided through this website for completeness, but the user should check the USGS website and download their data for use in design studies.  In particular, the USGS annual peak flow data set may not always match the annual peak flow values available from this website because the District has filled in some data gaps using available ALERT gage data that may not have been quality checked.  USGS daily discharge and annual peak values can be downloaded from their website at http://waterdata.usgs.gov.  USGS 15-min stream flow data can be requested from their Sacramento office.

About NON-VCWPD Data
The District has used a number of sources to obtain weather, stream, rain, and evaporation data for their planning studies.  These data are made available on this website for convenience.  The data sources are listed in the Station History files available under the Official Data tab.  The sources include CIMIS, DWR, NWS, UWCD, CMWD, VCAPCD, and USGS.  If you plan to use these data for design studies, you should obtain the data directly from the original source.   Links are provided to many of the original sources in the Station History files provided under the 'Official Data' tab.

About High-Resolution Discharge Data
High-Resolution discharge data are either 5 minute or 15 minute discharges.  Because quality checking of these data sets is a time-consuming to process, data for periods other than shown on this website may not be available without possible lengthy delays. Labor costs for the processing will be charged to the data requestor following the Ventura County Board of Supervisor's specified data request charges.  Date ranges shown on this website do not reflect any gaps of non-quality checked data that are within that range and data that are not currently not available in electronic format.
About Stage Data that is Included with Peak Flows and Uncertainty of Peak Flows
The stage data in the peak flow files provide rough estimates of the water surface elevations and/or flow depths for comparison purposes and should not be used to estimate flows.  A number of factors may affect the stage data from year to year, including possible channel reconstruction and a change to the elevation datum of the gage.  Therefore, the only way to calculate a flow value associated with a given stage height is to obtain the appropriate gage rating table from the Hydrology Section and calculate the flow value using the table.  Any other use of the stage data to estimate flows may provide inaccurate results that should not be used for design purposes. 

Peak flow values are calculated from either direct measurements of stage such as recorded stage or high water marks or indirect methods that include slope area surveys. Slope area surveys can have an uncertainty up to 30%. Peaks from stable channels with direct measurements will have the least amount of uncertainty.

What is a Water Year?  How is it defined?
A Water Year (WY) is defined as October 1 of the previous year through September 30, for example Water Year 2003 is from October 1, 2002 through September 30, 2003.

About Certified or Non-Standard Data Request
If you need certified data or other hydrologic information that are not available on this site, please fill out the Data Request Form and e-mail it to HydroData@ventura.org.  The data request form outlines the request procedures and any associated costs.

About Daylight Saving Time
All Ventura County Watershed Protection District's datasets are in Pacific Standard Time (PST) for the entire year. These datasets do not reflect any time changes to or from Daylight Saving Time.  Some historical observer daily totals may have reported some daily totals in daylight savings time.  These are corrected when possible.
 
About Preliminary Rainfall Frequency Reports
The VCWPD Hydrology Section has recently made available the short duration (5 min to 24 hours) and long duration (1 day to water year) precipitation frequency reports for current active precipitation stations. These reports are available through the "Official Reports" dropdown menu. These reports may contain historical data that are different than depths computed using the currently available high resolution digital data. These data are made available for the convenience of the user only. If these results are needed for design or other critical studies, the user should contact VCWPD for certified rainfall data to use in their own analysis.