Frequently Asked Questions (FAQ)
Historical Rainfall and Stream Flow(Hydrodata) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
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 Public Works Agency - Watershed Protection (VCWPD). Limited other data from public agency gages or gages co-operated with VCWPD are also provided. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The official reports use a VARIABLE NUMBER to describe different data types. You will see these different VARIABLE NUMBERS in the following reports: |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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: |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
The following reports contain the Quality Codes that are used with a particular dataset Daily/Monthly Rainfall Quality Codes Daily Stream 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 may be available for more recent years for some sites. For older periods for USGS gages may be available and 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. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|