We obtained a database of water quality measurements
(storet_summary_[date].xls) from
EPA.
This database contains over 53,000 records from over 200
locations, showing mean value, median value, standard
deviation, number of observations, and start and end dates
of sampling for a large group of water quality parameters
(each database record is a single variable at one sample
station). We calculated and analyzed duration of sampling,
and analyzed number of observations for each parameter.
The following statistics are on a per-station basis (since
measurements made at different stations cannot be compared).
We found that 80% of parameters were measured less than
5 times during the entire period of record; 54% of parameters
were measured only once. The total duration of sampling
(from earliest sample to latest sample) was less than
1 year for 75% of parameters. Time (of day) of sample
collection was not recorded in the database.
An example is water temperature, one of the parameters
measured most frequently. The database contains 2000 observations
of water temperature. For these water temperature measurements,
median number of observations was 4, and median duration
of sampling was 8 months.
We could not use the STORET data for
prioritizing 6th fields (see below).
STORET data are scattered across a total
of about 320 stations throughout the study area (
STORET_m6stns.xls).
We could not use the STORET data for prioritizing
6th fields because the number of STORET stations
are unevenly distributed across the study area, the number
of observations per variable are low, and stations do not
generally have data on the same variable measured at the
same time.
Please address questions or comments
to:
Dr. Ralph Garono
Principal Investigator
Earth Design Consultants, Inc.
rgarono@earthdesign.com
Laura Brophy
Principal Investigator
Green Point Consulting
brophyl@peak.org |
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