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Climate change is bringing more incidences of heavy rains – not necessarily more precipitation overall, just more concentrated downpours. That’s a problem for dams built under the assumption that past rainfall patterns will continue.

I’ve got a story in today’s Monitor (read it here) about the dam that holds back Lake Penacook, which provides the water supply for Concord. It is one of 32 dams rated as “poor” – mostly not because the infrastructure is crumbling but because it’s unclear that existing spillways are big enough for anticipated heavy deluges. Spillways are the area next to the dam itself that handle overflow; if they can’t handle it water over go over the top of the dam, eating away at the structure – that’s a very common cause of dam failures.

Here’s the thing I learned that surprised me: The lake loses about 1 million gallons of water to evaporation on a sunny day. It’s the water cycle in action!

By the way, I wrote this a couple of weeks ago and it was finally printed on the same day that the state warned about possible drought. Such timing!

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