The primary purpose of Fanshawe Dam and Reservoir is
to assist in flood control efforts to reduce flood damage in the City of London.
Throughout most of the year, the amount of water released from the reservoir is the same
as the amount of water entering from upstream. During a flood, less water is released than
comes into the reservoir, which results in the reservoir gradually filling up as the extra
water is stored. After the flood passes, the stored water is gradually released. Although
some flooding may still occur, the flood peaks (the highest flood levels) downstream may
be reduced by up to 40% (see graph below).
Hydrology staff use information from several sources
to operate Fanshawe Dam and to integrate operations of the three dams on the Thames.
Computer models of floods, operating tables, weather data and water level information from
above and below the dam enable staff to assess and respond to flood potential and initiate
the municipalities’ flood warning systems, if necessary. Many factors affect the
severity of flooding, such as snow pack (depth and water content), soil conditions (may be
frozen or saturated), temperature (affects snow melt, evaporation and soil moisture) and
plant cover (may intercept rainfall). The amount of rain and where it falls is also
important. Although London may not receive much precipitation, snowmelt or rainfall in the
northern part of the watershed could cause flooding in the city.
Dam Statistics
- Constructed: 1950 - 1952
- Cost: $5 million (structure and land)
- Who paid: Federal government 37.5%, Provincial
government 37.5%, UTRCA 25%
(95% from City of London, 5% from London Township)
- Drainage area: 1,450 square km
- UTRCA property around reservoir: 7.3 square km
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