Dams get a bad rap. They destroy natural heritage and native lands. They kill fish. Sometimes they break, devastating communities downstream. Sometimes they almost break, causing widespread panic (Oroville). All of these things make for exiting news stories. Of course, we do build dams for very good reasons, but try to find a newspaper headline that reads “another huge flood averted thanks to dams”. As a result, I think many people have a warped view on the costs and benefits of dams. No one has taken the time to rigorously quantify the benefits that dams have provided.
A new study by Gang Zhao, Paul Bates, and Jeffrey Neal (Bristol University) addresses this imbalance.
Compared with Federal Emergency Management Agency flood hazard maps, there was an obvious overestimation of flood extent downstream of each dam when reservoir operations are ignored. These overestimations can be significantly corrected using the proposed coupled model framework.
About half of dams (47%) have high flood attenuation effects (FAI < 0.4) and 36% dams have a low flood attenuation effect (FAI > 0.6).
The paper is published in Water Resources Research. Link here.
I actually need to read the paper more carefully to understand the method employed. Regardless, I think we should be doing much more to quantify the benefits of dams, including droughts and floods mitigated, energy and flexibility supplied to the power grid, irrigated croplands supported, navigation enabled, etc, etc. This work is an important contribution, and I hope these authors and the wider community follow up with more along the same lines.
Shout out to Ollie Wing, whose twitter thread alerted me to this paper.