or forced draft. Detailed descriptions of these may be found elsewhere. Reference
section of this chapter has the authors’ suggested reading [25–44].
Regulations on thermal discharges are the responsibility of the various states. It is
impossible to cite regulations common to all states; however, some of the criteria for
evaluation should be useful.
The first criterion is the definition of a thermal discharge, usually as one that is at a
temperature above a set value such as 70
F (21
C) or if it causes a natural body of
water to rise above a recommended limit, such as 3–5
F (1.5–3
C). It should be
defined separately in terms of lakes, streams, and tidal waters. There is usually a
definition for trout and nontrout streams in which the requirements are more
stringent for trout streams. There may be greater temperature tolerances during the
summer. Summer and winter may be defined as periods when the temperatures reach
certain limits. Many criteria involve the degree of mixing in a stream with a
description such as at least 50% of the cross-sectional area and/or volume of the
stream, including a minimum of 1/2 of the surface, shall not be raised above a certain
minimum temperature. This is to allow fish to pass a heated section of the stream. In
a lake, frequently the regulations are to prevent a certain temperature rise in a circle
or a plume from the point of discharge into the lake. Here it is recommended that a
surface area be specified rather than a radius of a circle, which is frequently specified.
This will compensate for any distortions in the shape of the plume other than
circular. In a summer stratified lake, there should be no discharge of heated effluent
into the hypolimnion. Withdrawal of water for cooling may be from the hypolimnion
or the epilimnion, depending upon regulations. Discharging the heat to the epilimnion will help maintain the cool water in the bottom and maintain the thermocline
relatively constant. These are just some of the generalities to be observed in
regulations on thermal discharges.
It is most useful to find alternate uses for this excess heat. When homes or
factories may be located close to a source of heat, it may be used for heating or
industrial processes. However, during the summer there is less need for this heat
unless it can be converted to operating air-cooling systems. The heat has been used
for agricultural purposes. Here, again, this has benefit only during certain times of
the year. Some aquaculture systems have been put into operation in which the waste
heat is placed in ponds, lagoons, or bays to encourage the growth of fish or shellfish.
This has been shown to be very beneficial in reducing the reproduction time and the
time to reach maturity. However, again this has limited use and will not solve all the
problems of the utilization of excess heat. As energy becomes more and more
expensive, it is certain that more systems will be devised to utilize this excess heat.
12 Toxics in Water Resources
The concern for toxic materials in water supplies has created one of the greatest
controversies of recent time. The US Environmental Protection Agency issued a list
of 129 priority pollutants that are of concern and should be eliminated from water
6 Basic Hydrology, Water Resources, and DAF Boat Plant for Lake Restoration
287
section of this chapter has the authors’ suggested reading [25–44].
Regulations on thermal discharges are the responsibility of the various states. It is
impossible to cite regulations common to all states; however, some of the criteria for
evaluation should be useful.
The first criterion is the definition of a thermal discharge, usually as one that is at a
temperature above a set value such as 70
F (21
C) or if it causes a natural body of
water to rise above a recommended limit, such as 3–5
F (1.5–3
C). It should be
defined separately in terms of lakes, streams, and tidal waters. There is usually a
definition for trout and nontrout streams in which the requirements are more
stringent for trout streams. There may be greater temperature tolerances during the
summer. Summer and winter may be defined as periods when the temperatures reach
certain limits. Many criteria involve the degree of mixing in a stream with a
description such as at least 50% of the cross-sectional area and/or volume of the
stream, including a minimum of 1/2 of the surface, shall not be raised above a certain
minimum temperature. This is to allow fish to pass a heated section of the stream. In
a lake, frequently the regulations are to prevent a certain temperature rise in a circle
or a plume from the point of discharge into the lake. Here it is recommended that a
surface area be specified rather than a radius of a circle, which is frequently specified.
This will compensate for any distortions in the shape of the plume other than
circular. In a summer stratified lake, there should be no discharge of heated effluent
into the hypolimnion. Withdrawal of water for cooling may be from the hypolimnion
or the epilimnion, depending upon regulations. Discharging the heat to the epilimnion will help maintain the cool water in the bottom and maintain the thermocline
relatively constant. These are just some of the generalities to be observed in
regulations on thermal discharges.
It is most useful to find alternate uses for this excess heat. When homes or
factories may be located close to a source of heat, it may be used for heating or
industrial processes. However, during the summer there is less need for this heat
unless it can be converted to operating air-cooling systems. The heat has been used
for agricultural purposes. Here, again, this has benefit only during certain times of
the year. Some aquaculture systems have been put into operation in which the waste
heat is placed in ponds, lagoons, or bays to encourage the growth of fish or shellfish.
This has been shown to be very beneficial in reducing the reproduction time and the
time to reach maturity. However, again this has limited use and will not solve all the
problems of the utilization of excess heat. As energy becomes more and more
expensive, it is certain that more systems will be devised to utilize this excess heat.
12 Toxics in Water Resources
The concern for toxic materials in water supplies has created one of the greatest
controversies of recent time. The US Environmental Protection Agency issued a list
of 129 priority pollutants that are of concern and should be eliminated from water
6 Basic Hydrology, Water Resources, and DAF Boat Plant for Lake Restoration
287