The Impact of Building Dams on River Ecosystems and Electricity Generation

Everything comes with a price. The masses must realize this. It turns a river into a reservoir, which sounds like a win for human infrastructure but often at the expense of the natural river flow and the rich ecosystems that depend on it.

"Wow! Fishing, boating, camping, swimming ... What a wise and thoughtful thing is to find the most suitable place, that doesn't kill towns or 85 endangered species."

Green is only green on the user end. The downsides to all things must be considered, and all things, not just agenda cherries picked by a few. Let's delve into the details of how building a dam on a river to generate electricity affects the natural flow of the river.

How Dams Alter River Flow

When a dam is built, it stops the natural flow of the river above it, forming a reservoir. The water flow is reduced below the dam as the lake is forming. This has significant downstream benefits, such as flood control, by holding back surges that might cause flooding, while still releasing enough water to prevent overwhelming downstream dykes or containment banks.

Dams are designed to mitigate big flooding during wet times and provide water for commerce in dry times. The purpose of dam storage is to manage water conservation and water discharge regulation. For example, the Indus River in Pakistan at the Tarbela Dam has a winter flow restricted to about 6000 cusecs, whereas during summers it increases to 100 times that amount. This requires a dam with a live storage capacity of 11.1 MAF, leading to a 50-mile-long reservoir upstream.

Seasonal Flow and River Activity

Depending on the dam, seasonality of the flow, and the substrate of the river's bed, the intersection of water flow and sediment is different. For instance, hydroelectric dams must discharge sufficient water to meet consumer demands, altering life along the river around the reservoir and below. Large reservoirs evaporate water, and muddy rivers carry a lot of silt during floods, which can lead to the silt filling up the reservoir over time.

Water Management and Drought

Water management through dams also includes conserving water during drought periods and diminishing downstream flow. The recent prolonged Southwestern drought in the United States, from 2000 to 2017, exemplifies the impact, with Lake Meade's water levels drawn down significantly. The U.S. Drought Monitor reported that 11 of the past 14 years have been drought years in the American Southwest, with the biggest headlines being in California.

Impact on Aquatic Life

Dams obstruct fish migration upstream, impacting freshwater spawning areas for species like salmon, alewife, trout, or shad. As the U.S. Southwest and Central Plains face unprecedented 21st-century drought risk, the impact of dams on downstream erosions, especially in shrinking river deltas like the Nile or Yangtze, becomes crucial. For instance, the impact of dams on sediment supply to the sea and deltaic regions is significant.

Expert Insights and Research

Research on the impacts of dams on riparian ecosystems is extensive. For example, the Journal of Hydrology published Analyzing the impacts of dams on riparian ecosystems: a review of research strategies and their relevance to the Snake River through Hells Canyon in 2008. This article discusses how dams affect hyporheic exchange in the riparian zone and the impact on sediment supply to the sea and deltaic regions.

Moreover, Impact of dam operations on hyporheic exchange in the riparian zone of a regulated river discusses how stage fluctuations caused by dam operations persist for long distances downstream, affecting river water infiltration into the banks.

Conclusion

In conclusion, building a dam on a river to generate electricity has profound effects on the natural flow and aquatic life, as well as on water management and conservation. While dams provide essential benefits, they also pose significant challenges that must be carefully managed and studied. The scientific community and policymakers should continue to explore the impacts of dams to find sustainable solutions that balance human needs with environmental preservation.