Where would water come from in an underground colony?
A large solar flare event ignites the atmosphere of Earth, but luckily, humans have been preparing for an event like this for some time. We have a fairly large shelter around 2.2 kilometers underground.
Energy is no problem, as we have built heat wells where they bring up heat into a controlled area, and we then run water over a heated cathode to spin a steam turbine.
Assumptions about the environment and living conditions:
- No materials can be retrieved from surface.
- They are alone in their venture to survive: no divine intervention, no magic.
- They need a sizable amount of water for their needs, and for vertical hydroponic farming.
- The shelter accommodates up to 1000 people at a time. Assuming that each person drinks half a gallon a day, that will average out to 500 gallons for people, plus that for the farm.
I would prefer for the colonists to have a liberal amount: enough for baths or other luxuries.
How do I explain how these survivors get water?
This post was sourced from https://worldbuilding.stackexchange.com/q/30245. It is licensed under CC BY-SA 3.0.
1 answer
Given that they're 2.2 kilometers underground, it looks like they can take advantage of the water table, the place where rocks are saturated with stored groundwater. The water table often holds aquifers, which can be accessed with only a bit of drilling.
Is groundwater accessible 2.2 kilometers down? Well, they're certainly below the water table. I've found a map of the water table depth of Wisconsin (chosen at random), and it shows that the water table is seldom more than 50 feet below the surface:
It is important to note that the water table doesn't mark the area where the water is stored; it simple marks the highest point of stored groundwater.
We do have a problem, though: How deep does groundwater go? 2.2 kilometers is pretty far down, relative to some sources of groundwater. For a good survey on aquifer depth, I chose this report (Ashworth & Hopkins (1995)), a summary of various studies of aquifers in Texas. They identified nine major aquifers in the state. Here they are, along with the estimated water depth.
- Ogallala: 600 feet
- Gulf Coast: 3,200 feet
- Edwards: 600 feet
- Carrizo-Wilcox: 3,000 feet
- Trinity: 900 feet
- Edwards-Trinity: 800 feet
- Seymour: 360 feet
- Hueco-Mesilla Bolson: 9,000 feet (Hueco), 2,000 feet (Mesilla)
- Cenozoic Pecos Alluvium: 1,500 feet
2.2 kilometers is about 7,200 feet, so most of these aquifers wouldn't be deep enough. Even the lower depths of some of the large ones contain dissolved solid minerals, that could be hazardous to human health. The USGS National Water-Quality Assessment (NAWQA) Program has a variety of maps and data detailing water quality nationwide. Various sources of terror for groundwater include
- Nitrate
- Chloride
- Miscellaneous "dissolved solids"
- Mercury
- Phosphorous
- Atrazine
- More miscellaneous pesticides
The water quality can vary by region. For example, this map of nitrate concentration in the High Plains (from (Gurdak et al. (2009)) varies widely, do to agricultural use and other sources. Location is everything when it comes to water quality.
A nationwide map of aquifers can be found here.
There's one last thing we have to address: How will these people access the groundwater? I would wager that they have decent drilling equipment, if they're that far down, so digging a well system (vertical or horizontal) shouldn't be too hard.
0 comment threads
0 comment threads