This blog post was written in response to the question "Should we build more large dams" as part of a series of responses for World Water Day 2014.
“Should we build more large dams?” It's probably the wrong question.
The question we should be asking decision-makers, governments and ourselves is: What do societies and economies reasonably require in terms of water resources and energy production? This, of course, leads to follow-up questions. What are the options to meet such demands sustainably and in a world of changing climate and hydrology? What is a reasonable price to pay, economically, socially and environmentally for these services? Are there other options to provide such services, and what is the price tag attached to those options?
Water storage and hydropower dams can make a lot of sense and be the right choices for water, food and energy security – but only when done right in the right places. Put in the wrong place, a dam can have devastating consequences. How does anyone make that critical distinction? There are clear sustainability criteria, as outlined by the World Commission on Dams in 2001, under which such projects can be designed. The Hydropower Sustainability Assessment Protocol (2011) operationalizes these guiding principles for early stage planning, preparation, implementation and operation of hydropower projects.
However, dams always come with impacts and costs. And the equation “small dams equal small impact” does not hold. Why? Small dams have the habit of coming in large numbers, thus the resulting cumulative impact of small dams may be massively damaging – fragmenting a river and cutting fish migration routes. It has been shown that the overall “impact-per-dam footprint” of small dams can be very unfavorable compared to their bigger brothers, especially when compared to their delivery of the same service (for example, impact per kWh production).
So, the crucial questions are whether a dam is the right choice to deliver a reasonable and justified service (water storage, energy, transportation, flood protection), and where the dam is located within a river system. These are questions that should not to be answered dam-by-dam, but by strategic master-planning exercises, usually at the scale of an entire river basin.
(You didn’t really think it would be a simple “yes” or “no,” did you?)