Posted Thursday, March 2, 2006

By Tom Valliere Organizing Committee

     At our organization meeting Friday, there was much interest in a proposed dam that would divert San Bernard River Water near Boling. Here are a few general facts about dams

     Few man-made things are as majestic or provoke as much emotion as dams. Dams like bridges are classified as societal structures. A societal structure is one whose performance - including catastrophic failure - has a large impact on a significant population. Dams can be classified by construction and usage. Four of the more common construction types are: Arch, Buttress, Gravity and Embankment. Hoover Dam pictured above is an excellent example of an Arch dam. Classification by usage would include: Flood control, Irrigation; Recreation; and Power Generation. Most dams are multi-use and serve several of these purposes. The proposed dam on the San Bernard would most likely be an embankment type of structure and its usage would be primarily irrigation with secondary usage as a recreation facility.

Impact on Environment

     Dams and their impoundments always have a significant impact on their surroundings. When the mighty Columbia River in the northwest was transformed from a raging torrent into a series of slackwater lakes, thousands of acres of former desert suddenly became fertile farmland. While anthropologists and environmentalists were lamenting the decline of the salmon fisheries and the demise of the indigent culture that relied on them, a huge aluminum industry was created using abundant and cheap hydroelectric power giving rise to multiple industries in cities such as Spokane. Such is the nature of dams, some good effects some bad with the weighting hopefully on the beneficial side.

Irrigation Dams

     The dam proposed for the San Bernard would be primarily a water storage facility for irrigation usage. It is important to note the differences between an irrigation dam and a flood control dam. Irrigation dams are kept as full as possible at all times as a hedge against unpredictable precipitation. As such, there is usually very little available capacity to impound flood waters which are generally discharged through a spillway. In fact, such a dam may even exacerbate flooding if the flood gates are opened to lower the lake level during an event.

     A flood control dam keeps the impoundment as low as possible at all times to insure maximum capacity to buffer downstream flows. This is a fundamental and critical differences. As an irrigation structure, the proposed dam could not guarantee that it would alleviate downstream flooding and might actually worsen these events. Think how the lower Trinity is affected when the dam on Lake Livingston is opened during heavy rains. It is therefore imperative that all residents of the lower San Bernard River area, stay informed about this proposed dam and use our new organization to speak with a collective voice to insure our interests are considered and protected with this or any other upstream activity that might affect us.

     There will be follow-up articles on this topic. Please check the web daily!

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