Water quality can be assessed by examining the
physical, chemical and biological characteristics of a
particular body of water. Samplers allow water to be
collected from various specific locations, depths or
simple grab samples for analyzing in the lab or for
on-site analysis. Often water quality parameters can be
evaluated at a gaging station continuously and recorded
with a data logger.
Common water quality parameters to be measured and
recorded by hydrologists include temperature (° C),
conductivity or specific conductance, dissolved oxygen
(µg/L), pH, turbidity (suspended matter), salinity,
biochemical oxygen demand (BOD) as well as total dissolved
solids (TDS) and its specific components such as sulfates,
nitrates, calcium, etc.
Physical and chemical characteristics can be evaluated
by instruments that continuously monitor and record these
properties or by spot checks when the hydrologist is on
site making measurements. Three basic types of water
quality meters are used for on-site measurements. We have
selected the best available and commonly used instruments
by the USGS, USEPA, and other major state and federal
- Single parameter water quality meters allow the
hydrologist to take quick, accurate measurements in the
field. These meters can have a probe with cable from the
water into the stream or lake or have a cup in the meter
to hold a sample which is poured into the analyzer. Also
these can be used with a flow through chamber for
multiple meters to analyze a sample pumped through it.
- Multi-parameter water quality meters offer the
advantage of one meter which can simultaneously monitor
several parameters at once from a hand-held meter with
probe suspended by cable from the meter. A Sonde type
multi-parameter meter is deployed in the river or lake
for short or long term recording.
- A multi-channel data logger at the gaging station
can be equipped with water quality sensors that can be
deployed in the river with cable running to the
datalogger in the gage house. Often a flow-through
chamber is installed in the gage house and the probes
mounted in the chamber and connected to the data logger.