In last week’s blog post, I wrote about #DamOrNot, a weekly game I host on Twitter, and shared definitions and imagery of different infrastructure we commonly encounter in the game. This week I’ll work to address a few questions that came through on Twitter.

A few of these questions came from Michiel Jorisson, an active #DamOrNot participant who asked, “We have seen hundreds of dams [on Dam Or Not] now, and seen their impacts (positive and negative), but how widespread are dams? How many people/countries/areas are impacted by the presence of dams? And is it increasing or decreasing?”

The first is a relatively easy question to answer. Built infrastructure, like dams, weirs, and roads, occur the world over, even Antarctica has small, unpaved roads. As one detailed example, we found one built infrastructure, be it a dam, weir, or road-stream crossing (likely culverts or bridges), every two river kilometres in the Great Lakes Basin in North American (nearly 300,000 in total!). When speaking of dams specifically, these large structures intersecting our waterways that are most commonly used for water storage or hydropower, occur on every continent except for Antarctica. There is an ever-changing list of the world’s largest dams on Wikipedia. One of the largest dams in the world, the Oroville Dam, was in the news in the United States a few years ago because of challenges faced with managing the dam and water flows under some of northern California’s heaviest rainfall in over 100 years.

YouTube video: California Dam Crisis: Racing to Avoid Environmental Disaster | National Geographic

Now come the trickier questions. It is not easy to quantify how many people, countries, or areas are impacted by dam presence. Why so? First, we have limited data on the existence of many dams and weirs, let alone information about the height, width, or reservoir size of these infrastructure, which would allow us to begin exploring this question in greater detail. Many of these infrastructure were constructed decades, some over a century ago, and several without detailed planning (‘off the books’, as it were). Second, a few databases exist at the global scale, see here and here, but these are heavily focused on larger built infrastructure, like the Oroville Dam above, which require maintenance and observation to ensure human safety and to mitigate potential disasters. Some countries like France, have more complete data sets that include tens of thousands of dams and weirs. However, overall, we are very far from a comprehensive understanding of where different infrastructure occur across the globe, and are even farther from understanding their characteristics and what impacts individual or collective dams, weirs, and road infrastructure have on rivers, the species that live in them, or the people that depend on them. While we can bring together different cases and studies to better understand impacts of individual, and increasingly multiple, built infrastructure, we are still challenged by the short cycle of research funding to fill in these data gaps more generally, and are constrained in our ability to address these questions for more than a limited number of infrastructure or areas across the globe.

I’ll take this opportunity to make a small plug for a research project that FIRE Lab and #DamOrNot contributors are helping to advance. With collaborators in the United States, we are working to overcome the data challenges using Google Earth Engine and many human-hours to map built infrastructure along rivers across the globe. We anticipate more updates about this work in 2019, and you can anticipate a blog post from Sayali, and possibly a few #DamOrNot contributors like Michiel, sharing more about the project, their contributions, and the first peer-reviewed publication from that work.

In terms of knowing if there is a net increase or decrease in dam numbers across the globe, this is also complicated to address. Why so? First, what is the baseline? When there were no dams? If so, we’d have to dig to find out when the first dam was built, or from another particular time, perhaps since the beginning of the Industrial Revolution, and work forward from there. Other options include focusing on expansion based on existing databases, but this can come with some challenges because of bias in data from certain regions. In that vein, a few months ago I came across a cool graphic produced by Penny Beams (@_peripatetic_ on Twitter) that showed the expansion of dams across space and time based on data in the global GRanD database, but the hyperlink doesn’t work anymore. Penny, if you are reading this, we’d love to see that graphic back in action! Anyway, I digress. The additional challenge with determining if dam numbers have increased or decreased over time (x) is knowing when dams have been removed, and these data are even spottier than dam data. I think this would make for a really interesting article in The Conversation, or even a peer-reviewed letter, with a few worked examples using different approaches to quantifying and addressing this question more broadly; thank you Michiel for asking about this!

Finally, a question from FIRE Lab collaborator, Dani Rabaiotti, “Is there like a ‘best dam’ – how does dam efficiency compare with like, letting fish through and the helpful ways dams can be designed to help the natural environment?”

First, in my opinion there is no ‘best’ dam. All dams negatively affect our aquatic ecosystems and the people who depend on them. It is more about what political powers have decided is acceptable in terms of economic benefit returned more than it is about any other consideration. A few interesting books on this topic are Silenced Rivers and Large Dams: Long Term Impacts on River Communities and Free Flowing Rivers; I have not read them in full, but I have started reading Silenced Rivers, and it offers diverse perspectives on the challenges faced with large dams, and the level of destruction and displacement that comes to communities and the ecosystem. Many of these social and ecological impacts are difficult to trade-off with perceived economic benefits, because we can’t easily qualify or quantify them.

To my knowledge dam ‘efficiency’ is not impacted by fish passages per se, but I have not explored this topic comprehensively. Fish passage devices are often a secondary consideration, and sometimes are added onto existing dams. I am personally more interested in knowing how efficient different fish passage structures are for different fish species. In terms of helpful ways dams can be designed, or rather, potentially retrofitted, to help the natural environment, I’ll share a story about a group of students in Wisconsin who worked to address a related question a few years ago for a Lego First League challenge (check out their short video (also below), song, art, and poetry, of their project). The students worked to develop different solutions for fish passage, and noticed some challenges based on the different fish species habitat preferences and swimming abilities. With this in mind, the students considered widening the river to return a more nature meander and to allow for water to flow around the dam so that fishes could more easily swim upstream. While there are still challenges to be faced with that design idea, in terms of how to keep fish from swimming or drifting into the dam and getting stuck or killed, the idea is one that I thought would likely benefit a wider diversity of fish species than most commonly used fish.

Additionally, a team of us are working to address such questions through a systematic review lead by Canadian Centre for Evidence-based Conservation and Environmental Management. I’ll end with a paper by my colleague, Virgilio Hermoso, which questions the impact of the Paris Agreement on freshwater ecosystems, and questions whether hydropower is a renewable or green energy source. He highlights that given uncertain climate futures and water resource availability, investment in hydropower infrastructure is extremely risky, and that we are not doing a good job of quantifying related considerations to evaluate these risks.

As I indicated above myriad different factors should and must be considered before dam projects are implemented, but the trend has and continues to be that we build these infrastructures, particularly the larger dams, with little data or explicit consideration of trade-offs. This trend is most likely because it takes a lot of time and effort to qualify and quantify the different factors that should be considered before building infrastructure that can heavily modify an aquatic system, not only at the site, but for 10s to 100s of kilometres downstream, as well as displace and affect communities that live along the waters. I think there is a lot to unpack about the use of dams for energy production, and the books and papers that I highlighted above give more time to specific cases and considerations. I hope to continue to have time to write about these topics and to dig deeper into topics about dams, weirs, and roads, and their effects on our freshwater ecosystems over the next few years with the FIRE Lab team.

Thank you for reading this entry, I hope my responses were interesting and useful! If you have additional questions related to #DamOrNot please be in touch with us on @FireLabTweets or with me on @ConnectedWaters. We are back with another #FishInThePost next Friday! See you in 2019!

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