Frequently Asked Questions
Question: What is DBHYDRO?
Answer: DBHYDRO is the South Florida Water Management District corporate environmental database which stores hydrologic, meteorologic, hydrogeologic, and water quality data. This corporate database is a one-stop source for all historical and up-to-date environmental data for the region covered by the District. The database includes the not only data from South Florida Water Management District but also data from other agencies such as United States Geologic Survey, National Oceanic and Atmospheric Administration, and Everglades National Park.
Question: What kind of data is in DBHYDRO?
Answer: Not only does DBHYDRO contain environmental data, but is also stores additional information about sites, water control structures, and stations where data are collected. Accurate descriptions are available for most of the sites, giving the user information on the hydrologic basin, latitude, longitude, state plane coordinates, county, section, township, range, and many other useful attributes.
Question: How big is DBHYDRO?
Answer: To give an idea of the amount of data in DBHYDRO we offer the following: DBHYDRO contains more than 5 million water quality results, more than 30 million daily hydrologic values, and hydrogeologic data from more than 3000 boreholes.
Question: Is the data up-to-date?
Answer: The data on DBHYDRO is up-to-date. That is, as data is posted (or revised from provisional to approved), it is immediately available to the public.
Question: What is DBHYDRO Browser?
Answer: DBHYDRO Browser is a web-based application that allows users to browse DBHYDRO using one or more criteria to generate a summary listing of time series. The user can then select one or more time series of interest and have the time series data dynamically displayed on their screen in tables or graphs. Alternatively, the data may be saved to a file and post-processed by the user.
Question: Who can use the system?
Answer: Any one with internet access can use the system.
Question: Do I need to get a user id and password from the District to access the data?
Answer: No, the data is available immediately.
Question: I want the data sent to me in a file rather that displayed on the screen. What kind of file downloads are available?
Answer: You can always get a fixed format file and, in some cases, a comma separated (.csv) file or an Adobe Acrobat (.pdf) file is available.
Question: What is a DBKEY?
Answer: A DBKEY is a the DBHYDRO system assigned unique identifier for a data set (or time series). A DBKEY is to a data set what a social security number is to a person. Each unique combination of station, data type, frequency, statistic type, recorder, operation number, and agency results in a unique dbkey. A dbkey cannot be decoded to imply any attributes of the data set.
Question: Do I have to know the DBKEY in order to access the desired data?
Answer: No, you may access the data in a variety of methods. Access can be by site name (general location), station name (more specific location at a site), project name (for water quality data), data type (flow, rainfall, water level, etc.), agency (SFWMD, USGS, etc.), hydrologic basin, county, etc... Criteria may be applied in combination to be as general or as specific as you like.
Question: Is the data safeguarded?
Answer: Yes. If you are an internet user you are accessing a read-only version of the database that is further protected by password and other means.
Question: Is there a training class for DBHYDRO?
Answer: Yes. The District offers an in-house class; course number is 50015360 and the course name is "DBHYDRO Users". Sign up through your training coordinator. Public classes are scheduled regularly. Public requests for training are accepted at http://xportal.sfwmd.gov/dbhydroplsql/show_dbkey_info.training. Registration and confirmation are required.
Question: Can I get large amounts of data?
Answer: Yes. Large batch retrieval capability is available. Because web browser technology can "time out" during long queries batch retrievals are suggested for retrieval of long periods of instantaneous values. The user is notified by email when results are ready for download. Typical turnaround time is under 15 minutes. Large data requests can take up to 2-3 hours. Experience has shown that approximately 10 years of breakpoint data for a single dbkey might be considered at the upper limit of what the batch process can handle. The daily values limit is orders of magnitude larger.
Question: Where is the map-based interface?
Answer: Map-based access is available from the main menu. Just click on the map icon. Also, each station, on its individual station information page, has a link to a map.
Question: What is "preferred" data?
Answer: Some hydrologic data has a recorder type of PREF. These specific data sets have undergone an additional level of QA/QC by the SFWMD and should be used when available.
Question: What coordinate system and projection is used for X-Y coordinates?
Answer: X-Y coordinates are NAD83 HARN Florida State Plane East Zone coordinates in units of feet.
Question: Which vertical datum is used?
Answer: NGVD29 is the official vertical datum for the South Florida Water Management District and DBHYDRO data. The South Florida Water Management District is executing its NGVD29 to NAVD88 migration plan. Some data may be in NAVD88 and is explicitly labeled as such. Information on the Vertical Datum Upgrade Program is at www.sfwmd.gov under the "Technical Data and Documents" section.
Question: Is water quality data only for surface water samples?
Answer: No. The results of analyses on other media such as groundwater and animal and plant tissue are analyzed are present in the database.
Question: What is OLECAS?
Answer: OLECAS is the On-Line Environmental Chemist Analysis System, a tool to assist in the quality assurance process for the SFWMD water quality laboratory. If you are part of the routine monitoring program you may contact Michael Wright at mwright@sfwmd.gov to get on the distribution list for the daily laboratory "outlier" report.
Question: What does a negative value for a water quality analytical test result mean?
Answer: A negative value indicates the value was below detection limits. This fact is verified by a U in the remark code for the result in question. Always review the remark code and sample/result comments for water quality data. In DBHYDRO reports, results of sample analyses below the MDL are displayed as -1*MDL and, for purposes of computing statistics, are treated as 1/2 the absolute value of the MDL. A less than sign (<) also prefixes the reported statistic if any of the values contributing to it were below MDL. The exception to this rule is for results from test numbers 65, 256, 258, 319, 978 which can be negative.
Question: What is a water quality sonde?
Answer: A sonde is a water quality logging system for in situ monitoring and profiling. Typical parameters may include turbidity, dissolved oxygen, conductivity, pH, and temperature.
Question: Is all SFWMD environmental data available through DBHYDRO Browser?
Answer: Requests for related data categorized as research or regulatory may be made via public records request.
Question: Is all the data usable?
Answer: Data usability depends on the needs of the individual user. Most data are collected to meet stated data quality objectives for some primary purpose. However, these objectives may or may not be sufficient for secondary uses of data. When in doubt contact the agency to whom the data is attributed.
Question: What is a "flag" in water quality data?
Answer: The water quality remark code consists of zero, one, or more qualifiers. Certain qualifiers in the remark code indicate potentially more serious quality issues. Such data are considered flagged and are excluded from certain SFWMD reports. The mere presence of such qualifiers does not necessarily exclude it for all intended purposes.
Question: What is a DCVP Station ID?
Answer: A DCVP Station ID is an identifier for a single time series in the District's internal hydrometeorologic data processing system. Most data stored in DCVP are instantaneous readings. These readings are identified in DBHYDRO Browser as those having a frequency code of "BK". The SFWMD computes mean daily values for these instantaneous readings (where meaningful) and stores the daily values with a frequency code of "DA".
Question: What is "strata"?
Answer: A vertical distance relative to the local ground elevation for most cases. For surface water samples the reference is the water surface. For monitoring locations a fixed distance from the bottom of a water body, the water body bottom is the reference. For groundwater wells, strata is equal to the distance, in feet, from land surface to the bottom of the monitored interval (i.e. bottom of screen depth or open hole) and is a positive number. Ultimately, and most conveniently strata is a relative z coordinate. We try to make it meaningful. The station description or detailed metadata usually elaborates.
Question: How do I cite DBHYDRO in my works-cited list?
Answer: A generic web reference to DBHYDRO Browser following the Modern Language Association style: DBHYDRO Browser, South Florida Water Management District, accessed date_site_accessed, at URL www.sfwmd.gov/science-data/dbhydro. Information regarding citing web sources in MLA style may be found at: http://www.mla.org/
Question: What does it mean when a report indicates my data has been QA'ed?
Answer: QA'ed data is that which has undergone routine Quality Assurance procedures. Other data which has not undergone such procedures may be labeled as Provisional.
Question: What is the difference between salinity, conductivity, and specific conductance and what are the correct units of measure?
Answer: Since 1978, the Practical Salinity Scale, adopted by oceanographers and the UN, is the conductivity ratio of a sea water sample to a standard KCl (potassium chloride) solution. It just so happens that 35 ppt = 35 psu (practical salinity units). The reason for the adoption of this new scale is that ppt, or parts per thousand, refers to a gravimetric measurement of salinity by weighing out 1000 g (1 kg) of seawater, evaporating the water, and weighing the residue. Typically, for every 1000 g of seawater, approximately 35 g of salt would remain. Hence the units of parts per thousands. However, this method of determining salinity is cumbersome. Thanks to the Law of Constant Proportions (Marcet's Principle) of ions in seawater, a titrametric method (Mohr-Knudsen titration) was developed using chloride as an indicator of salinity. Based on this chloride content or chlorinity, salinity can be calculated: Salinity = 1.80655*Chlorinity (in ppt) Since most salinity measurements have shifted from an analytical method to direct measurement using conductivity, the new salinity scale is therefore more appropriate. There is a difference between conductance and conductivity: Conductance is the reciprocal of resistance and therefore its unit is 1/(ohms) or mhos or S (for Siemens) Conductivity is the reciprocal of resistivity. Its unit is expressed as 1/(ohm m) or mhos/m or S/m Members of the scienitific community have sometimes confused these measurements and have used them interchangeably. Even the Class III water quality standards refer to specific conductance expressed as micromhos/cm rather than to specific conductivity.
Question: What is SHEF .E Format?
Answer: The Standard Hydrometeorological Exchange Format (SHEF) is a documented set of rules for coding of data in a form for both visual and computer recognition. It is designed specifically for real-time use and is not designed for historical or archival data transfer. All the critical elements for identification of data are covered. Station identifiers, parameter descriptors, time encoding conventions, unit and scale conventions, and comment fields are all part of the code. SHEF was designed for inter- and intra-agency sharing of data,visual and machine readability, and compatibility with anticipated receiving databases. The widespread implementation of SHEF allows the same decoding software to process data from various agencies. New data sources can easily be added as they become available. The visual nature of SHEF allows users quickly to become familiar with it. SHEF fully qualifies the data so that receiving databases have all the necessary information to describe the data. http://www.nws.noaa.gov/oh/hrl/shef/shefcode.htm
Question: How do I determine which direction is positive for flow data?
Answer: South Florida Water Management District flow data is considered positive when flowing from the headwater station to tailwater station. Headwater and tailwater stations typically are named with _H and _T suffixes respectively. The map interface shows relative locations of headwater and tailwater stations and is therefore helpful in determining the compass direction for which flow is considered positive. Positive flow direction for data from other agencies may need to be confirmed with the respective agencies. For instance, the USGS NWIS database may have more complete USGS station descriptions than what is carried in DBHYDRO.
Question: How are daily rainfall data reported?
Answer: For continuous recording gages daily values are the sum from 00:00 to 24:00 for the given day. For daily (once per day) observations the sum is for the 24 hours preceding the time of observation on the given day. These once per day data are identified by recorder OMD.
Question: In what time zone are data reported?
Answer: Continuous recording gages are reported in EST (GMT-5). Manual readings from field visits and sample collection are in DST (GMT-4) during Daylight Saving Time and EST (GMT-5) otherwise.
Question: How do I view down-hole video attachments for wells?
Answer: The down-hole videos are stored in a compressed .zip file format. The original files typically were in DVD-Video format. Therefore, the unzipped files need to be 1) copied to a DVD preserving the folder hierarchy and played in a DVD player or 2) played using computer software such as VLC Media Player or similar. Zip file size ranges from 200 Mb to 50Gb and may take from one minute to two hours to download depending on file size and quality of internet connection.
Question: Why are some USGS data available in DBHYDRO and not on the USGS NWIS Web web site?
Answer: Through the 1990's the data transfer from the USGS to SFWMD's DBHYDRO was based on a USGS-internal program called ADAPS. Since then most of the USGS data has been made available via NWIS Web and SFWMD uses USGS NWIS Web Services to fetch most data. Records that are not available on NWIS Web may be requested by contacting the USGS directly.
Question: What is the limit to the number of pixels I can download at once with the NEXRAD Viewer application?
Answer: The NEXRAD viewer application is limited to approximately 55 pixels at once when the user specifies a list of pixel_ids separated by a "/" character.
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