Originally Posted by vid
Hydro-electric isn't a green solution, especially if you have displaced a significant amount of trees (which release methane as they rot in the reservoir for the first few years, probably polluting more per MW than a coal plant would for a time) and converted a wetland into farmland (wetlands filter water, farmland, unless it's just organic, tends to pollute waterways and watertables.) To power those 70,000,000 people, that hydro-electric dam has to be considerably larger than Three Gorges. It would be extremely expensive, unless your city is sitting on a lot of oil or a cheap labour pool.
I actually had this idea for the political evolution of the "super city-state" that I am developing. It would also help explain why the nation relied of hydroelectric power. In the valley were the reservoir would be built as part of the dam, there would be a major conflict zone were much of the forest would be destroyed by either deliberate fire bombings or accidental fires. As a result of the war with this adversary who I haven't really elaborated on yet, the city-state entered a alliance with a much larger super-power who in turn constructed the massive hydroelectric dam to both supply power to its ally (the city state) and to literally flood some of the adversaries hardened defensive positions in the valley. This eliminates the rotting tree problems and the environmental issues of the valley...seeing as the valley was obliterated in the war.
I don't know what to do about the farming issue. I kinda of want this city to be both great and yet have a few flaws to make it believable.
Well 15 years later and the war is over, the entire region belongs to the city state and the hydroelectric dam is turned over to the city much like how the panama canal was handed over to the Panamanians by the US. With a massive electricity monopoly in the region, the nation starts to accumulate wealth both from a large existing treasury, energy deals, large reserves of silver in the surrounding mountains and the end of a long hard war. The nation constructs a second, larger dam and builds smaller dams up in the surrounding mountains.
So with a recent modernization and upgrades, the first dam produces 20 gigawatts. The second dam produces around 25 gigawatts and the smaller dams in the surrounding mountains produce a combined 18 gigawatts of power. Perhaps if the required power-per million people was lowered by privately owned rooftop solar power, power for 70 million could be achieved.
I was also wondering about another idea. Is there a sort of dam that doesn't actually block the rivers flow, but still produces energy? Kind of like how a water wheel doesn't have to block the river, but produces energy. Is there a name for what I am describing?