1964. A dam is also under construction under the Upper Thames Authority's 

 agreement at St. Mary's (Wildwood). 



In addition to large dams and reservoirs, a number of Authorities have 

 undertaken projects involving the building of smaller dams. These dams 

 have such purposes as irrigation water supply, municipal water supply and 

 improvement of summer flow. Examples of such small dams include the 

 Ausable Authority's Morrison Dam and reservoir near the town of Exeter, 

 the Napanee Authority's Second Depot Lake Dam, Kelley Lake Dam con- 

 structed by the Junction Creek Conservation Authority, and the Kelso Dam 

 recently completed by the Halton Region Conservation Authority. 



Not all dams built by Authorities are new ones. A number of Authorities 

 have acquired existing dams and surrounding land. At one time, most streams 

 in Southern Ontario had numerous dams up and down their length. These 

 dams had been built for the purpose of providing power for mills. They also 

 had the incidental value of conserving water. Many of these old dams have 

 long since disappeared or fallen into disrepair. Authorities have acquired 

 control of a number of these dams and have carried out necessary repairs 

 on them. They now fulfill a valuable function of storing water for the im- 

 provement of summer flow and for recreation. Examples of such dam restora- 

 tion are the Belfountain Dam on the Credit River, repaired by the Credit Valley 

 Conservation Authority, and the Thornbury Dam on the Beaver River, restored 

 by the North Grey Region Conservation Authority. 



In some valleys, a significant measure of flood control can be obtained 

 through public ownership or public control of the flood plain lands. Such 

 control prevents encroachment of buildings on to flood-vulnerable lands adjacent 

 to the river. This control is necessary in conjunction with the building of dams 

 and channel improvements. Four Authorities had flood plain land acquisition 

 programs under way in 1963. Flood plain surveys and mapping, which is 

 the necessary preliminary to land acquisition, were carried out in three Authorities. 



HYDROMETEOROLOGY AND FLOOD WARNING 



Variations in weather conditions have a pronounced effect on the flow 

 pattern of the streams and rivers in Southern Ontario. Problems concerning 

 the relationship between meteorology and hydrology must be considered in 

 detail before control works can be established on a stream. Hydrometeorology 

 analyses are therefore an important part of the water studies carried out by 

 the Conservation Authorities Branch. 



An extensive network of precipitation and stream gauge stations has 

 been established on the watersheds in Southern Ontario. Data from these stations 

 are used to relate rainfall, snowmelt and soil moisture conditions to runoff. 

 Such studies establish the characteristics of a stream under a variety of meteoro- 

 logical conditions. The results are used to determine the capacity of reservoirs, 

 the size and type of dam structure or channel improvements and the availability 

 of water for urban use, pollution control, recreation and irrigation. 



The need for a flood warning system in Ontario was made clear following 

 Hurricane Hazel in 1954. In 1955, the Meteorological Branch of the Canada 

 Department of Transport seconded a hydrometeorologist to the Conservation 

 Authorities Branch to head a flood warning system, particularly for the more 

 heavily populated sections of the Province. He is responsible for maintaining 

 a watch of river conditions, issuing flood forecasts, supervising the operation 

 of flood control reservoirs and establishing meteorological design criteria for 



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