It has been two weeks and we can no longer put off our analysis of water engineering and policy in Frozen II. If SPOILERS would destroy your pristine viewing of Frozen II, now is the time to stop reading. The dam removal theme was unmistakable and much appreciated. Still, we can delve deeper.
This readership must have immediately noticed that the “gift” of the dam was suspect; it served no observable purpose. The recipients of the “gift” are herders who don’t visibly practice agriculture. The donors of the gift live in a far northern temperate climate and would likely practice rainfed agriculture, with no need to carry water over a dry season. I don’t see a powerhouse for hydropower, indeed, these are a pre-electrified societies.
The only possible use for the dam is flood control. In that case, it is clearly not a “gift” for the recipients, who live above the dam. It isn’t clear from the movie that it is needed for Arendelle. It is true that floodwaters after dambreak do threaten to inundate Arendelle, but that was a wall of water caused by the sudden release of several years of stored water. We cannot know without a look at their hydrology, but knowing that there is an undamaged upper watershed and that they receive quite a bit of precip as snow, I have to doubt that the river that got dammed was very flashy. On an annual basis, unimpaired flow probably never did flood enough to raise the bay that Arendelle sits on. So this alleged “gift” offers no benefit to the recipients and likely, no benefit to the donors. (We may further reflect that had the magically-connected Northuldran’s wanted a dam, perhaps they could have asked the earth spirits to raise one or even become a dam.)
What I find less plausible is that Queen Elsa didn’t recognize this immediately. It is canon that Queen Elsa has considerable water engineering expertise. In Anna and Elsa #1, All Hail the Queen, Queen Elsa is designing the city’s municipal water delivery system (at 1:25). In Anna and Elsa #9, Anna Takes Charge, it appears that Queen Elsa has gotten the system built and remains in charge of O&M (at 10:00). I have to believe that at some level, Queen Elsa must have wondered that her grandfather had built an entirely superfluous dam. She cannot have been entirely surprised by the later revelations, that he did it to destroy the balance and weaken the magic of the north.
In conclusion, I can only assume that the writers of Frozen II have read this article on the Elwa as many times as I have. People of the Klamath, hopefully your day is next.