Why are dams bad?

Answer 1

Dams are not just bad. They are disastrous. The reasons are multiple and complex. It really begins by saying that a river flows to its delta before reaching the ocean for a reason. The reasons for this flow to be unheeded are vastly important and concern all of us. Dams actually threaten the integrity of land mass because river deltas accumulate enormous quantities of silt. In the case of the Colorado; this would have been from erosion in the rocky mountains and all those famous canyons. This silt and sediment carried by the river is more precious than gold because so much life depended upon it. It might seem to us on a muddy river that it looks lifeless but that silt and mud are maintaining the health of the planet. To take the example of the Colorado River.

The hoover dam was completed in the 1930s and for 6 years almost no flow reached the enormous river delta. At this point the river would have deposited enormous quantities of silt and sediment. The delta itself was vast and acted (as all deltas do); like an enormous sponge. It absorbed and purified the river sediments and created vast wetlands were the river flow branched into countless lagoons. In the case of the Colorado river there were woodlands full of native cottonwood and willow. Deer and jaguar were part of the ecosystem as well as brackish water species of fish which only existed in the Colorado delta. Spring floods naturally cleansed the wetlands of salt and enabled native trees to take root.

For 70 years now the river delta has slowly dried to a caked desert in many places. IT is difficult to imagine the suffering caused in the 1930s when lake mead slowly filled and the river delta lost its vital nutrients and fresh water flows from the Colorado. It is difficult to comprehend what happened at that time as the ecosystem went into decay and decline. A simple look at the Colorado river delta today from Google earth is testament enough to the death of the once vibrant jewel of life.

Lake mead behind hoover dam is an incongruous body of water. Where the Colorado enters lake mead silt has now accumulated to a depth of 80 metres. Why is this important?

The silt that washes down from the mountains and canyons contains natural concentrations of heavy metals such as selenium. These would have been washed down into the delta were they would have been naturally broken down by unique biological processes that only occur in river deltas. This increasing concentration of heavy metals behind the dams of rivers that once flowed naturally is a growing problem. Many people and cities that wouldn't have existed without the river being dammed rely on the water in the reservoirs for drinking. The increasing sediment from the rivers entering vast bodies of water being deposited is a subject that seems to have no voice. An ever growing level of sediment in the catchment lake is an issue that dam engineers and governments who give the go ahead for these massive projects - seem to be in denial about. But just how much sediment does a river deposit?

The numbers are impressive. It seems that the pivotal role of a flowing river is the release of nutrients along its course and within its delta. The sediment and silt contain these minerals and organic elements that natural flooding would have enriched the land with. Often far above the river's natural flow in times of high flooding. Flooding is often an excuse for building a dam but the greatest irony is that flooding itself is often the reason why people have been able to live at the river's edge. The fertility of the soil on flood plains is without precedence for the simple reason that it floods and the river deposits life sustaining nutrients during that brief time. So where does all this sediment and wealth of nutrients end up in a river like the Colorado? It is dumped and settles to the bottom of lake mead far behind hoover dam and there it stays.

Answer 2

Because they can ruin the environment easily with in a few years.