Ars Science: The largest US dam-removal effort to date has begun



There's an analogy for software system migration and decommissioning here:

Across the US, dams are being removed for various reasons. Many are simply old. “They're in rivers beyond their designated life span,” said Lucy Andrews, a doctoral student at the University of California, Berkeley, who studies water resource management. “They have a high potential of failure, particularly when climate change is considered.” In other words, these dams weren't designed for today's capricious precipitation regimes. Other dams no longer function in the way they were designed, said Jonathan Warrick, a coastal geomorphologist with the US Geological Survey.

— Ars

These… data processing systems… “weren't designed for today's capricious precipitation regimes.” They will require careful, intentional planning and execution to upgrade, replace, or shut down.

Like dams, software systems come in many sizes, serve many functions, and have complex effects on human and ecological systems around them.

Removal can also reverse ecological damage that, in the western US, often harms migratory fish but can also cause problems for other sensitive species and ecosystems. In addition, dams “have displaced tribal nations from their lands and severed connections to culturally important waterways and species,” Andrews said, speaking specifically about California. “In these contexts, dam removal can actually be an important step toward repair.”

Dams, both large and small, serve various purposes, said Andrews (large dams are mostly those taller than 15 meters—roughly the height of a four-story building).

“Many dams were constructed in the eastern states for mills and power generation,” said Warrick. Most of these dams were relatively small, but after World War II, large dams proliferated across the West. Today, US dams control floods, generate hydroelectric power, and store water for municipal or agricultural use, he explained. “Most dams are built to do a little bit of each.” Recreation also factors into cost-benefit analyses for existing dams, Warrick said.

The metaphor breaks down in that dams stockpile and control not only water flow, but also sediment flow. In theory, you could turn off most software systems and the data they've collected would cease to exist in the form in which it was stored. With a dams, the physical sediment must be dealt with. The article elaborates on this and other systemic effects of dams and the engineering challenges in removing them.

I'll leave a couple more interesting quotes.

When dams are in place, few logs, sticks, and trees flow downstream, instead ending up stuck in a reservoir. “Large wood pieces are really important in terms of habitat,” Warrick said. Fish and birds along riparian corridors prefer complex settings. “Birds like to sit on nooks, and fish like to be in little holes, and trees and wood make those habitats richer.” When dams are removed, more wood enters the river corridor, and ecosystems become better for it.

Tribe members, including Thompson, are collecting native seeds and will be propagating these plants. “If we do not do native seed replanting, it will 100 percent get taken over by invasive species,” she said. “With the drawdown, it's such a great opportunity to be able to give these native species a chance.”