288
J.e. Ritchie and P.R. Schiebe
countries that recognize the water quality parameters that affect the aquatic food chain
and human usage. If standards are met, a healthy aquatic habitat usually results.
Reduction in the quality of water in streams, lakes, reselVoirs, estuaries, and oceans
is a major concern around the world (Brown 1984; LaI1994). The knowledge base
describing the effects of pollutants, the development of management techniques to
control pollutants, and the education to transfer this knowledge to the end user
continues to expand.
Monitoring and assessing the quality of waters in streams, reselVoirs, lakes, estuaries, and oceans are critical for managing and improving the quality of the environment. Classical techniques for measuring indicators of water quality involve in situ
measurements and/or the collection of water samples for subsequent laboratory
analyses. Although these technologies give accurate measurements for a point in time
and space, they are time consuming, expensive, and do not give either the spatial or
temporal view of water quality needed for accurate monitoring, assessing, or managing water quality for an individual water body or for multiple water bodies across the
landscape. Remote sensing of indicators of water quality offers the potential of
relatively inexpensive, frequent, and synoptic measurements using sensors aboard
aircraft and/or spacecraft (see Colour Plate 13.A).
13.2 Basis for using Remote Sensing
Major factors affecting water quality in fresh waters estuaries and oceans are suspended sediments, turbidity, chlorophylls (algae), chemicals, dissolved organic matter
(DOM), nutrients, pesticides, thermal releases, and oils. Suspended sediments
(turbidity), chlorophylls, DOM, and oils produce visible and/or thermal changes in
surface waters that can change the energy spectra of reflected solar and/or emitted
thermal radiation from surface waters. Such changes in the spectral signals from
surface waters are measurable by remote sensing techniques from many platforms.
Substances can also change the thermal properties of water thus affecting the heat
content and thus water temperature that can be measured in surface water temperature
remotely with thermal sensors. Most chemicals do not directly affect or change the
spectral or thermal properties of surface waters. Measuring water properties affected
by chemicals can only be inferred indirectly from remotely sensed measurements of
other water quality parameters affected by these chemicals. Measurement of these
surrogate properties may then be used in mathematical modelling and analyses to
indirectly infer chemicals in water.
The strength of remote sensing techniques lies in their ability to provide both spatial
and temporal views of surface water quality parameters that is typically not possible
from in situ measurements. Remote sensing makes it possible to monitor the landscape effectively and efficiently, identifying water bodies with significant water
quality problems. These water quality parameters, often, can be quantified using
remote sensing techniques allowing management plans to be formulated to reduce
movement of substances from catchments (see Chap. 12) to water bodies thus
reducing the effects of the pollutant on water quality.
J.e. Ritchie and P.R. Schiebe
countries that recognize the water quality parameters that affect the aquatic food chain
and human usage. If standards are met, a healthy aquatic habitat usually results.
Reduction in the quality of water in streams, lakes, reselVoirs, estuaries, and oceans
is a major concern around the world (Brown 1984; LaI1994). The knowledge base
describing the effects of pollutants, the development of management techniques to
control pollutants, and the education to transfer this knowledge to the end user
continues to expand.
Monitoring and assessing the quality of waters in streams, reselVoirs, lakes, estuaries, and oceans are critical for managing and improving the quality of the environment. Classical techniques for measuring indicators of water quality involve in situ
measurements and/or the collection of water samples for subsequent laboratory
analyses. Although these technologies give accurate measurements for a point in time
and space, they are time consuming, expensive, and do not give either the spatial or
temporal view of water quality needed for accurate monitoring, assessing, or managing water quality for an individual water body or for multiple water bodies across the
landscape. Remote sensing of indicators of water quality offers the potential of
relatively inexpensive, frequent, and synoptic measurements using sensors aboard
aircraft and/or spacecraft (see Colour Plate 13.A).
13.2 Basis for using Remote Sensing
Major factors affecting water quality in fresh waters estuaries and oceans are suspended sediments, turbidity, chlorophylls (algae), chemicals, dissolved organic matter
(DOM), nutrients, pesticides, thermal releases, and oils. Suspended sediments
(turbidity), chlorophylls, DOM, and oils produce visible and/or thermal changes in
surface waters that can change the energy spectra of reflected solar and/or emitted
thermal radiation from surface waters. Such changes in the spectral signals from
surface waters are measurable by remote sensing techniques from many platforms.
Substances can also change the thermal properties of water thus affecting the heat
content and thus water temperature that can be measured in surface water temperature
remotely with thermal sensors. Most chemicals do not directly affect or change the
spectral or thermal properties of surface waters. Measuring water properties affected
by chemicals can only be inferred indirectly from remotely sensed measurements of
other water quality parameters affected by these chemicals. Measurement of these
surrogate properties may then be used in mathematical modelling and analyses to
indirectly infer chemicals in water.
The strength of remote sensing techniques lies in their ability to provide both spatial
and temporal views of surface water quality parameters that is typically not possible
from in situ measurements. Remote sensing makes it possible to monitor the landscape effectively and efficiently, identifying water bodies with significant water
quality problems. These water quality parameters, often, can be quantified using
remote sensing techniques allowing management plans to be formulated to reduce
movement of substances from catchments (see Chap. 12) to water bodies thus
reducing the effects of the pollutant on water quality.