GLOBE Water Quality Data After Three Years: An Emerging International Resource
R.C. Bales, C.J. Peters, M.H. Conklin.
Dept. of Hydrology and Water Resources
University of Arizona
Presented at the 1998 Spring Meeting of the American Geophysical Union
INTRODUCTION
Students involved in the GLOBE (Global Learning and Observations to Benefit the
Environment) program have collected water quality data from sites all over the world
since 1995. In the United States the GLOBE program provides what is currently the
most easily accessible nationwide data base of selected surface water quality
measurements. GLOBE data are readily accessible via the www, and the methods used
for data collection and quality control are documented on the www. Most data are
available within hours after being submitted by the K-12 schools doing the sampling and
analyses. Procedures are in place for data retrieval and display.
Volunteer water quality monitoring programs such as GLOBE provide scientists with
spatially distributed information on water quality at scales ranging from local to global.
However, the very nature of a distributed volunteer monitoring program such as
GLOBE often raises quality control questions.
The purpose of this comparison is to evaluate the quality of GLOBE data relative to
other water quality data sets, specifically the U.S. Geological Survey National Stream
Water-Quality Monitoring Network and the volunteer Rivers of Colorado Water Watch
Network.
DESCRIPTION OF DATA SETS
GLOBE
The GLOBE hydrology data consist of measurements taken at
nearly 1,200 sites throughout the world by K-12 students. The
data are reported via the Internet to a central data repository.
GLOBE data for any site can be downloaded by anyone with
an Internet connection. In addition to water quality
parameters, GLOBE schools measure air temperature, land
cover, soil moisture, biology, and more. The period of record
is 1995 to the present, with new locations constantly being
added.
United States Geological Survey
The USGS data are currently available on CD-ROM. Data are
available for over 600 monitoring stations throughout the
United States.
Rivers of Colorado Water Watch Network
This set consists of data from 260 sampling locations in the
state of Colorado. In addition to the water quality parameters
studied here, Colorado Riverwatch monitors discharge and
trace metals. The program began in 1990 and is administered
by the Colorado Division of Wildlife.
METHODS
Extreme Values
The mean, minimum, and maximum value
were determined for each water quality
parameter (water temperature, pH, dissolved
oxygen, alkalinity, and electrical conductivity) at
each GLOBE sampling location. The relative
frequency of each was plotted. Means and
standard deviations were calculated for each
parameter in each of the three data sets.
Distribution of Means
The relative frequency of the means for
each parameter at each site was plotted for
each monitoring program to assess how well
the distributions of mean values corresponded.
RESULTS
CONCLUSIONS
The GLOBE data set is comparable to volunteer monitoring
programs (such as Colorado Riverwatch) and governmental
programs (USGS) in terms of mean values and standard
deviations for common water quality parameters.
GLOBE dissolved oxygen measurements are generally lower,
which may be the result of sampling a wider variety of water
body types.
The quality control procedures established by GLOBE are at
least as good as those of other volunteer programs, although
some follow-up is needed to address alkalinity questions.
QA/QC problems are dealt with on a case-by-case basis.
GLOBE data are helping to fill a clear need for spatially
distributed, regular information on water quality at local to
continental scales for a variety of research, assessment,
planning and educational activities.
The wide distribution of study sites, long duration of
monitoring, readily accessible data base and overall
institutional support place GLOBE at the forefront of efforts to
bridge critical gaps in water quality data.
ACKNOWLEDGEMENTS
This project was supported by GLOBE. Thanks to Barbara Horn with the
Colorado Dept. of Natural Resources, Division of Wildlife for assistance in
obtaining data. Special thanks to Ray Brice for his computer skills and poster
preparation expertise. Thanks to Anne Kramer for help in preparing this poster.
Last updated 13 July 1998
Comments?roger@hwr.arizona.edu