Welcome to California Data Exchange Center

CDEC Support Help

General Help

Abbreviations/Acronyms

Search/Query

Data Definition

Data Quality

Downloading

Alternative Access/Format

Miscellaneous


General Help

There's a problem with your site/page/application. Something is missing, broken, or not working correctly.
We are proud of our work so if you encounter a problem, do let us know. Since we have a small staff on a lean budget, we ask that you do the following before contacting us:
  1. Check these Frequently Asked Questions below to see if the problem can be resolved with one of the answers. Use Ctrl+F in your browser to look for a keyword in this page that might fit the situation at hand.
  2. Make sure your browser hasn't cached an old copy of the page that is presenting the problem. To clear your cache of the current page, be sure to hold down the Ctrl button when you Refresh (using Internet Explorer) or the Shift button when you Reload (using a Mozilla-based browser) the page. For more information on clearing your browser cache, see this Wikipedia article.
  3. Wait several minutes and then try the site again. Sometimes the problem is only intermittent due to an unusual spike in traffic to our site.
  4. Make sure the page in question is actually part of our site. Many questions come to us about pages that we don't maintain. Check the web address in your browser to make sure the address contains the CDEC acronym and is followed by the water.ca.gov domain.
If none of these resolve the issue, then
  • Copy the web address of the page into your message to us.
  • Copy any error messages displayed.
  • Be patient. Our main focus will be on resolving any problems with our site. You may not receive a reply immediately but we will do our best to reply.

The station that I normally check has stopped reporting data. Do I need to report this?
If you have verified that the outage has not been previously reported by checking the station metadata information through the Station Information page, the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page, then go ahead and email us. Please be aware though that most of the stations in our database are not maintained by us, and thus we would merely forward your message to our contact if one is available. We will also verify that the communication links are still working for the site in question, but have no control over when or if such a site will be fixed.

I'm having problems with the dynamically generated graphs. How can I change the look of them? I want to graph a large amount of data and the x-axis is unreadable.
The graphing application is a very rudimentary tool meant only to give an overall impression of the trend for a particular data stream. There are no parameters to adjust the display of the graphs, other than width and height. The graphing application has a limit of 8,192 data points. If you attempt to exceed this limit, the application will not return a graph. We recommend that you consider plotting daily data, where available, for long time periods, rather than hourly or event data. To get better graphs, one method is to download the data using the Download CSV Data tool available through the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page, then save the data and load it into a spreadsheet program such as MS Excel, and generate graphs using MS Excel.

Why are you releasing/not releasing water? The river is too high/too low. The reservoir is too low.
The electronic records maintained on our website are used primarily to monitor current weather and hydrologic conditions in support of flood forecasting. We provide data to those agencies making operational decisions, but in most cases they are outside of our organization and in all cases we have no control on those decisions. Many factors are taken into consideration when decisions are made to release water including existing water rights; regulatory mandates for flood control, water quality, or fish habitat; contractual agreements for water deliveries, or power generation; anticipated inflows; and public safety. If you wish to contact a specific operator directly, please check the station metadata information for the operator on record through the Station Information page, the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page. Then go to the Other Data Sources page available through the CDEC home page and follow the link to the appropriate organization.

I would like to add my data to your database. How do I go about this?
Generally, the data we add to CDEC is due to requests from our immediate cooperators, that is, government and municipal agencies we work with in order to monitor and forecast flood conditions. If you are a representative of a government or municipal agency, and your data is available through an established network such as ALERT or RAWS or through GOES satellite, please contact us. If a data stream would need to be established in order to obtain your data, we will consider it on a case-by-case basis. If you are a private individual, we suggest you look into joining the NWS Cooperative Observer Program.

How do I find out if stations in your database are the same as ones I've used through other data sources?
Many of our stations are also available through the U.S. Geological Survey (USGS), the National Weather Service (NWS), or other federal participants of the National Environmental Satellite, Data and Information Service (NESDIS) including the Fire Weather RAWS network. To check if a station ID from one of these other data sources is available through CDEC, see the CDEC ID Crosstab. Please be aware that not all IDs from these other data sources are available in the crosstab -- it is a good idea to compare the latitude and longitude values listed to those found at the other data sources. A more comprehensive crosstab showing NWS, USGS, and NESDIS GOES IDs is available from the National Weather Service at http://www.weather.gov/oh/hads/USGS/CA_USGS-HADS_SITES.txt.


Abbreviations/Acronyms

Can you please explain/translate the abbreviations used in the column headings of the data query results page?
For a complete list of sensor definitions, see definitions of sensor types available through the Station Information page. Our sensor types are based on those defined by the Standard Hydrologic Exchange Format (SHEF) Manual developed by NOAA. Many Federal agencies (such as NOAA/NWS, USACE, or USFS) and State agencies use the same standard. For more information, use the first 2 letters of the PE column from the Sensor Definitions page and reference Appendix G of the SHEF manual.

Some of the data is missing, and in the place of a numerical value there is either "ART","BRT", or "--". What do they stand for?
"ART" stands for Above Rating Table, "BRT" stands for Below Rating Table, and "--" stands for missing value. The acronyms, ART and BRT are used for flow data only. River flow data for stations with river stage data are computed using a specific rating table/rating curve for each particular station. When the river stage is above or below the available rating table, a flow cannot be computed. An explanation is provided at the bottom of the query results page when such rating conditions are present.

When downloading data in CSV format, there is either -9998, -9997, or "m". What do they stand for?
"-9998" stands for Below Rating Table, "-9997" stands for Above Rating Table, and "m" stands for missing value. Both values, -9998 and -9997, are used for flow data only. River flow data for stations with river stage data are computed using a specific rating table/rating curve for each particular station. When the river stage is above or below the available rating table, a flow cannot be computed.

I love the weather discussions, but would get more from it if I had a list of the acronyms you use. Where can I get one?
We get the weather products from the National Weather Service (NWS). They also provide a glossary.


Search/Query

How can I find stations near my location?
You can search for stations either with the CDEC Station Search tool or with the CDEC GeoAtlas, both available through the Station Information page, the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page.

The CDEC site does not seem to have data for the stations and times I'm interested in. Is that correct?
You can check the station metadata information through the Station Information page, the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page among various locations on our site to verify the availability of data for each station of interest.

I'm trying to retrieve historical data, but I can't seem to find the sensor number. The sensor id's for the gauges all seem to contain four digits. However, the web page only allows me to type in three digits. Can you tell me how to resolve this problem?
If you leave the sensor number text box blank, you will receive a list of what sensor numbers are available for the station you are querying. The query page uses a sensor number which is a category of sensor types. This is the 3 digit number. The application will then determine the individual sensor id that has been assigned to the specific instrumentation/data stream. This is the 4 digit number.

Is there an easier way to query past records? Currently, I have to click on "Earlier " over and over again to reach a past date.
There are various ways to quickly go to past records:

  1. Edit/change the date in the Web Address text box of your browser; or
  2. Use the Real-time Data navigation link at the bottom of the query results page, which provides a form with a date text box; or
  3. Use the Historical Data tool available through the navigation links at the bottom of the query results page, the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page; or
  4. For a larger quantity of data, use the Download CSV Data tool available through the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page.


Data Definition

I regularly look at the snow information for the Sierras. I know that the information you are gathering is geared toward water, but how do the figures you gather equate to snow depth?
The most important characteristic of snow to water managers and hydrologists is its water content. However, depth is of interest to many people also. Our data collection equipment measures the weight of the snowpack, and therefore its water content. However, generally depth can be approximated by multiplying the snow water content values by a factor. For more information, see this discussion from our snow surveys staff on the relationship of snow depth and density.

Is the stage data actually showing river surface elevation or from sea level?
Stage is defined as the height of a water surface above an established "zero" plane, or datum. It may or may not be the river surface elevation as a datum can be set below the natural bottom of the channel so all stage height readings will be greater than zero. Each location may use a different zero datum.

What is the datum for a particular station? How do I convert datums from USED to NGVD or vice versa?
If the datum is known, it will be listed on the station metadata information page and on the real-time data query results, among various locations on our CDEC site. If the datum is not known, a datum of 3.0 feet USED is used.

Can you please explain how unimpaired flows are calculated and how they can result in negative numbers?
A Full Natural Flow (FNF) equation, or unimpaired flow equation is an adjustment to the measured flow in the river. The adjustments are made due to alterations to the natural flow such as upstream diversions, reservoir storage changes, and accretions. For some rivers, the equation may not include ALL of the un-natural additions and subtractions from the natural flow. For this reason, some equation results may be negative. If, for example, there is a diversion that is not accounted for, the FNF value will be erroneously lower than had the diversion been included in the calculation. Therefore, the equation value might be negative because the value of the diversion is not added. Because data is not always perfect, inaccurate data can create negative FNF values also. The negative FNF values become more common with low flows because small errors in data can have a larger impact on the final FNF value than when flows are heavy.

I often see stations with "Battery Voltage" readings. What does this refer to?
The battery voltage sensor is used to monitor the health of the battery that is powering the station.

I was wondering which time zone the data is recorded in. Will I need to account for daylight saving time when looking at the data?
If you are looking at the data on one of the web display pages, it's in local Pacific time. (PST during the winter, PDT during the summer). On the text download pages such as queryCSV or querySHEF, it's in PST only. Also, please be aware that due to architectural issues, the data during the change from PST to PDT and from PDT to PST may not be correct.

What projection are the latitude and longitude values in?
The latitude and longitude coordinates were gathered thru various methods, many of the methods for particular stations are unknown to us. As you may know, our hydrologic database is fed from various agency sources. Geospatial precision, including horizontal datum and projection, was not part of the original scope nor intent for this database. However, for sites maintained by the Department of Water Resources this is what one of the technicians has to say:

The basic coordinates are arrived at by pinpointing the location on a 15-minute USGS quad and then calculating the Lat/Longs. This means the coordinates are NAD-27. In recent years we have been gathering coordinates using handheld GPS with the added antenna to give us +/- 20 feet accuracy and we use the WGS-84 datum. We also have been using UTMs and then converting the UTMs using the Jeep website converter. I'm sure the converted GPS coordinates are good for your needs, but the problem is I can't tell you precisely which sites have been corrected. We gather the GPS coordinates, but we have not been rigorous about comparing them with the database coordinates or making the corrections. ... Your request is not the first time this issue has been raised, so we will need to discuss internally if or how we can flag our coordinates by their respective datums.


Data Quality

We had a thunderstorm here Sunday night but your database indicates no rainfall.
According to our hydrology staff, thunderstorms can be very localized so it's possible that one area receives rain while a nearby spot received nothing.

The rainfall total for a specific station appears to be incorrect. The accumulated total is too high/too low for the season.
The rainfall total should be primarily used as a relative number. The accumulated rainfall may not truly reflect the total for the season because of various issues that include field technicians resetting the number at the site due to maintenance issues, not being able to reset the number at the beginning of the "season", data transmission errors, or physical limitations of the precipitation gage equipment.

We experienced a series of significant snowfalls during a several day period but the total precipitation reading hardly changed at all during the storm. Is there a malfunction?
At some precipitation sites, there is a lag between snowfall and the recording of precipitation. It's common to gages that are located in exceptionally cold areas where there is a good deal of shade. During significant snowfall events, snow often accumulates in the top of the device. Eventually after temperatures have warmed and/or direct sun warms the device, the frozen precipitation slips into the bucket/basin. It may take several days of warm temperatures or sunny weather before all the buildup has melted.

Two nearby gauges recorded widely different amounts of precipitation for the same storm.
Precipitation gages are prone to under-measurement of precipitation when it falls as snow and there is much wind. Snow measurements are subject to snow drifting in these same conditions. All of these effects vary from storm to storm and from year to year. Thus, it is common for less precipitation to be measured at a windy, high mountain precipitation gage than at a nearby snow sensor or snow course.

I follow hourly reservoir information on a regular basis but I don't understand what a negative inflow means.
According to our water supply staff, inflows into large reservoirs are usually not directly measured and are generally back-calculated using pool elevations, outflows, estimated evaporation, and other parameters. Sometimes, especially on windy days, the "bounce" in the gage readings can result in negative calculated inflows. Other reservoirs also have this same problem, especially when inflows are low. Running averages should probably be used to avoid the negative inflows.

How much quality control do you perform on your data? Is there routine checking of the data for such things as "extremes", missing, or obviously "bad" data?
Limits are checked post-process, though there are some checks done at the instrumentation level. We do flag data that is out of limits. The flagging varies depending on the type of data. Be aware though that much of this real-time data has not been reviewed, and it should be checked against nearby stations. We emphasize that our data is preliminary and is used to primarily monitor current weather and hydrologic conditions as it relates to river forecasting and water supply. Since we are a real-time operation, our data is provisional and should not be considered data of record and is not an official source of historic climate data. For data of record, we refer you to the Western Region Climate Center.

Sometimes there are intermittent missing data values. Why is that?
Intermittent outages are not unusual for some satellite transmissions. It is a limitation of random channel assignment, a method of sharing the limited satellite bandwidth. Short of the operator getting their own satellite, there's not much that can be done to alleviate this.


Downloading

We are analyzing precipitation data and your site has been suggested for use in our study.
Our website is used primarily to monitor current weather and hydrologic conditions. We are not the official source for climate data. The official source for historical climate data is the Western Region Climate Center. If you still would rather use our archived data, you should check the data retrieved against data from nearby stations. You should also confirm that the cumulative hourly precipitation data was reset to zero on October 1 and that there are no sudden offsets (caused by equipment problems, maintenance visits, or a snow 'cap' falling into the gage suddenly) before using the preliminary raw data. We recommend that you use the Download CSV Data tool available through the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page. For best performance, retrieve a maximum of no more than 8,192 data points per query.

I tried to download historic event data using the Historical Data tool, and got the following error message: "exceeded session limit on CPU usage, you are being logged off"
The tool you tried to use is not guaranteed to work for large data sets. Please use the Download CSV Data tool available through the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page. Even though the Download CSV Data tool can handle more data than the Historical Data tool, it is recommended that you retrieve a maximum of no more than 8,192 data points per query for best performance.

I'm having problems with the "Download Data Now" feature. It downloads a file of unknown file type.
You can change the file name if you wish. In the file name, specify an extension. If you want it to open directly in MS Excel, use the extension .xls For Save As Type, be sure to change it to All Files, then click Save.

Is it possible to download data straight from the web to my computer in text or any other readable format, not html?
For text in comma-separated values format, use the Download CSV Data page available through the Query Tools page or from the CDEC Quick Search menu on the CDEC home page.

I'm trying to put the CSV formatted data into a MS Excel spreadsheet, but am having difficulty changing the date and/or time format.
To format text into a date in MS Excel, do the following:

  1. Insert another column in your spreadsheet. For this example, I will assume inserting a column ahead of column A.
  2. Use text formula in new Column A to manipulate text in column B where date text is now. Assuming first row of data starts on row 4; this is the case if you're using the CSV file. Start with cell A4.
    =CONCATENATE(MID(B4,5,2),"-",MID(B4,7,2),"-",MID(B4,1,4))
  3. After applying formula to cell A4, use fill handle (+) to apply to all cells in column A.
  4. Highlight all applied cells in column A.
  5. Select Edit/Copy menu item.
  6. Select Edit/Paste Special menu item.
  7. Select Values button.
  8. Click OK.
Now you can format the new column as date using the Format menu, Cells option, and remove the old column.

To format text into a time in MS Excel, do the following   (assuming conversion of date column is already done):

  1. Insert another column in your spreadsheet. For this example, I will assume inserting a column ahead of column B.
  2. Use text formula in new Column B to manipulate text in column C where time text is now. Assuming first row of data starts on row 4; this is the case if you're using the CSV file. Start with cell B4.
    =IF(LEN(C4)=4,CONCATENATE(MID(C4,1,2),":",MID(C4,3,2)),
    IF(LEN(C4)=3,CONCATENATE("0",MID(C4,1,1),":",MID(C4,2,2)),
    IF(LEN(C4)=2,CONCATENATE("00:",C4),
    CONCATENATE("00:0",C4))))
  3. After applying formula to cell B4, use fill handle (+) to apply to all cells in column B.
  4. Highlight all applied cells in column B.
  5. Select Edit/Copy menu item.
  6. Select Edit/Paste Special menu item.
  7. Select Values button.
  8. Click OK.
Now you can format the new column as time using the Format menu, Cells option, and remove the old column.


Alternative Access/Format

Could you please send me via e-mail or make available as FTP twenty or more years of stream flow data?
Sorry, we don't have a public FTP site and our email system won't allow large files to be mailed. Our web site is the access point to our data. We recommend that you use the Download CSV Data tool available through the Query Tools page, or from the CDEC Quick Search menu on the CDEC home page. For best performance, retrieve a maximum of no more than 8,192 data points per query.

Is the data available in another format besides CSV?
Data can be downloaded as SHEF, Standard Hydrologic Exchange Format or in web format. To download in web format, click the Download Data Now link. The web format will allow you to not have to format the date in MS Excel or other spreadsheet program but the file will be larger due to the web formatting so you will not be able to get as many data points per download.

Is your data available in a GIS-compatible format?
Unfortunately, we don't have our data in a spatial format. However, you can download a comma-separated file of all CDEC stations from the Station Information page to import into your GIS application. Please note that any number 99.999 or 999.999 is a placeholder and its value is undefined. Also, the longitude will need to be converted to negative.

Can I get your data thru my cell phone?
If you have a web-enabled mobile phone, you can get real-time data using this web address -- http://cdec.water.ca.gov/cgi-progs/wmlData. This application directly outputs WML so there is no need for a WAP gateway. All other tools and products available on our CDEC site will require a WAP gateway to translate the web pages into a format viewable on your cell phone screen.

I work for a government agency/public utility/reclamation district. How can I get CDEC data without competing with traffic from general users?
If you are a member of a government or cooperating agency, you are eligible for access to the CDEC Intranet Web site. With CDEC Intranet access, you have dedicated and direct access to all data and products maintained by the California Data Exchange Center. And you won't have to compete with public users during peak times who are also accessing CDEC data and products. All data and products available on the public CDEC Web site are available through the CDEC Intranet site.

To obtain CDEC Intranet access, please send us a request. In order to process your request for CDEC Intranet access, you will then be asked to provide certain information.

In addition to CDEC Intranet access, sign up now for a CDEC dial-up account. A dial-up account will allow you to connect directly with our computers should there be any problems getting connected to the Internet via your network or through your Internet service. CDEC dial-up accounts are provided FREE of charge. However, you will only be able to retrieve CDEC data and products, not items on other Internet Web sites.


Miscellaneous

Do I need to have flood insurance?
The National Flood Insurance Program (NFIP) is based on Federal Emergency Mgmt Agency (FEMA) flood maps. The FEMA maps are what's used by your lender to determine whether flood insurance is mandatory. The 100-year flood is also known as the "base flood" and is the standard used on the maps. The 100-year flood means there is a one percent chance per year of a flood or equivalently a 1 in 4 chance of a flood occurring over a life of a 30-year mortgage. The 100-year floodplain is also known as the Special Flood Hazard Area (SFHA). 10-year, 50-year, 75-year floods will also fall into this area. To avoid flood insurance, you will need to purchase in an area beyond the 100-year floodplain or SFHA.

Are maps available showing areas of potential flooding?
In addition to FEMA maps, our sister organization provides Awareness Maps which indicate potential flood hazards (100-year) currently not mapped as a regulated floodplain in addition to the FEMA SFHA. The additional areas in the Awareness Maps may be incorporated into the FEMA maps at a later date if further study deems necessary. To view rudimentary FEMA maps, check out National Geographic's MapMachine and use their Quick Map Search feature.

Am I in the floodplain?
Please check the FEMA Region IX Community Status List for your local government office that is responsible for floodplain management administration in your community. If the property is in an incorporated area, you will need the name of the city; if the property is in an unincorporated area, you will need the name of the county. Find the name and phone number of the appropriate floodplain management administration office. The parcel number of the property is needed when you call. Parcel numbers appear on county tax bills.

Is there a way I can compare water rates for all of the districts in California?
We do not have water rate information on our CDEC site. You may be able to obtain rate information from individual water districts directly. The Association of California Water Agencies (ACWA) has a list of over 300 public water agencies in California with links to those that have web sites. This list however does not include private water agencies. If you are interested in a particular region of California, ACWA provides a map of water agencies by county.

 





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