CRBCZO -- Stream Water Chemistry, Stream Suspended Sediment, Stream Water Temperatures, Groundwater Depth -- USGS -- Christina River Basin -- (1985-2007)

OVERVIEW

Description/Abstract

The United States Geological Survey has collected continuous instantaneous time-series data, with intervals commonly ranging from 5-60 minutes. Historically, these instantaneous data have been processed into various daily values, such as the daily maximum, minimum and/or mean. This was done primarily to provide concise values for publication in paper reports. In more recent years, and particularly since the USGS began making real-time instantaneous data available on NWISWeb in 1994, more attention has been given to historical instantaneous data and USGS offices have received increasing requests for these data. Some challenges with meeting those requests are:

Most historical instantaneous data are paper based and were never stored on a computer or were deleted from computers after the computation of the daily values in order to save computer storage space. In most cases this data still exists as original field records, but it is a significant effort to create digital data from the paper-based records. Instantaneous data have not historically received the same level of quality control as the official published daily values. For example, periods of fouling may affect the calculation of daily values for a water-quality parameter. In these situations, daily values are typically not published but erroneous instantaneous data remain in the database.

For more info on accuracy codes etc, see comments/README

Creator/Author

US Geological Survey

CZOs

Christina

Contact

Pennsylvania Water Science Center 215 Limekiln Road New Cumberland, PA 17070 (717) 730-6900

Subtitle

USGS Instantaneous Data Archive -- water-quality unit values for selected stations in the Christina Basin.

SUBJECTS

Disciplines

Water Chemistry|Hydrology|Geomorphology

Topics

Stream Water Chemistry|Stream Suspended Sediment|Stream Water Temperatures|Groundwater Depth

Subtopic

USGS

Keywords

hydrology|stream temperature|stream chemistry|christina river

Variables

Oxygen_ dissolved|pH|Specific conductance|Turbidity|Temperature|Groundwater Depth

Variables ODM2

Water depth|Oxygen, dissolved|pH|Specific conductance|Temperature|Turbidity

TEMPORAL

Date Start

1985-10-01

Date End

2007-09-30

Date Range Comments

30 min to 1 hour intervals

SPATIAL

Field Areas

Christina River Basin

Location

Christina River Basin

North latitude

40.072778

South latitude

39.869721999999996

West longitude

-75.861111

East longitude

-75.593611

REFERENCE

Citation

USGS http://pa.water.usgs.gov/infodata/qw/czo_qw_uv/map.php

CZO ID

2506

External Links

Instantaneous Data Archive (water-quality unit values for selected stations in the Christina Basin) |

Award Grant Numbers

NSF - 0724971

NSF - 1052716

COMMENTS

Comments

Processing and quality control of this historical dataset was co-funded by an NSF supplement to the White Clay Creek LTREB project (NSF award 1052716) and by internal funds from the USGS PA Water Science Center. Coordination was supported by the CRB-CZO project (NSF award 0724971).

In developing a system to provide historical instantaneous data, the USGS has built a process that compares the available instantaneous data to the published daily values and assigns an accuracy code based on the result. Accuracy codes are as follows:

0 - The published daily mean* value for a water-quality parameter is zero.

1 - A daily mean value for a water-quality parameter, calculated from the instantaneous data on this day, matches the published daily mean within 1 percent.

2 - A daily mean value for a water-quality parameter, calculated from the instantaneous data on this day, matches the published daily mean from greater than 1 to 5 percent.

3 - A daily mean value for a water-quality parameter, calculated from the instantaneous values on this day, matches the published daily mean from greater than 5 to 10 percent.

*Subsequent to 1999 median is used as the comparative statistic for pH

If the daily mean (or median when appropriate) water-quality parameter calculated from the instantaneous values on a given day is greater than 10 percent different from the published daily mean or median, those instantaneous values are excluded from the archive. In addition, instantaneous data that corresponds to a daily mean or median value that was estimated are automatically excluded from the archive regardless of any comparison.

An additional classification is available at those limited sites where quality assurance of individual instantaneous data has been done. When this classification is used there is no comparison to the daily mean values.

9 - The instantaneous value is considered correct by the collecting USGS Water Science Center. A published daily mean value does not exist and/or no comparison was made.

It is important to note that, other than for classification code 9, the values available in the archive have not been individually reviewed and approved. They have been automatically compared against the published daily mean value and found to have no gross errors when used to compute a daily mean. Individual instantaneous values may still have significant error. For example a data spike might cause a given value to be off by several hundred percent, yet when combined with the other available values in the daily mean calculation the result might lead that spike to get added to the archive with an accuracy code of 2 or 3 because the impact on the daily mean is less than 5%. Users of the archive are thus strongly encouraged to review all data prior to use.

A cursory review of all processed water-quality data, the oldest of which date back to October 1985, took place prior to public distribution. Apparent erroneous data “spikes” were addressed in the following ways based on the best judgment of the reviewer:

a. Data were removed when determined to be an obvious error and the correct value could not be estimated based on adjacent data.

b. Data were corrected if adjacent data provided a reasonable degree of confidence as to what the correct value should be.

c. Data were left as is if the questionable value was at least minimally feasible, allowing the user of the data to make the final determination.