Dams in rivers not only obstruct fish migration but can also have substantial ecological effects upstream and downstream of the dam. Conservation Magazine writes about a new study on how hydropeaking affects macroinvertebrate communities downstream of the regulating dams:

“A massive new study led by the U.S. Geological Survey lays much of the blame on hydropeaking, the practice of varying river flows below a dam depending on electricity demand. Because of hydropeaking, the amount of water released from a dam can vary by as much as ten-fold throughout the day, creating an artificial intertidal zone that propagates for hundreds of kilometers downstream.

The hour-by-hour variation in water levels is a major problem for aquatic insects, which are a key element of river food webs and important prey for fish, birds, bats, and other wildlife, researchers reported last week in the journal BioScience. But lowering river flows during times of peak egg-laying and low electricity demand could give those insects a boost.

Consulting a database of insect life-history traits, the researchers determined that more than three-quarters of aquatic insects lay their eggs in shallow water at the river’s edge or by cementing eggs to the undersides of partially submerged rocks. These species could be vulnerable to hydropeaking, they reasoned, because eggs laid during high river flows are likely to be exposed to the air once the hydropeaking tide passes.” 

Read the article from Conservation Magazine here: A hydropeak tweak could make dams less damaging. The orginal paper is titled “Flow management for hydropower extirpates aquatic insects, undermining river food webs” and available here.

Part of the study was conducted in the Colorado River by young citizen scientist organized by the Grand Canyon Youth. The groups data collection and broader activities feature in this short film by Freshwater Illustrated:

National Geographics presents the film and credits the filmmakers here: Deeper Grand Canyon, More Communal Colorado River Revealed in New Online Film. 

“The Lost Fish – The Struggle to Save Pacific Lamprey” is a short film about the Pacific lamprey, its cultural importance, and conservation by Freshwater Illustrated. It’s available online at Vimeo: 

Earth Day är en dag då stödet för och behovet av naturvård uppmärksammas världen över. Dagen organiseras den 22:e April varje år sedan 1970. Samorganiserationen presenterar årets Earth Day så här: “Earth Day’s 45th anniversary – could be the most exciting year in environmental history. The year in which economic growth and sustainability join hands. The year in which world leaders finally pass a binding climate change treaty. The year in which citizens and organizations divest from fossil fuels and put their money into renewable energy solutions. These are tough issues but we know what’s at stake is the future of our planet and the survival of life on earth. On Earth Day we need you to take a stand so that together, we can show the world a new direction. It’s our turn to lead. So our world leaders can follow by example.

Vi uppmärksammar dagen modest med tre kortfilmer från Freshwater Illustrated om naturvård och behov av den i rinnande vatten. En film om att Oregon Chub (Oregonichthys crameri) tagits bort från Endangered Species List, en film om återintroduktionen av Bäckröding (Salvelinus fontinalis) i Appalacherna och en film om stillahavsnejonögon (Entosphenus tridentatus) i Columbia River.

Bevarande av Oregon chub

Återintroducering av Bäckröding

Stillahavsnejonöga i Columbia River

Här följer tre korta men vackra feel-good filmer från Freshwater Illustrated om livet i rinnande vatten. Trevlig helg!

Diversitet och entusiasm i Appalacherna:

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Död ved och habitat restaurering i McKenzie River, västra USA:

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Migrerande mountain whitefish i Colorado River