Yes - the water table does replenish
The water table in SimCity is replenished from the following sources;
- Rain
- Water from shorelines
- Sewage treatment plants
- Other cities
- Outflow pipes from industrial buildings
Rain is not a reliable source of replenishment but does contribute. Due to its random nature (it never rains when you want it to) you should never rely on your water table being replenished by rain. Water from the shorelines however does replenish the water table a lot faster than water from rain, but seemingly not fast enough to cater for a sudden explosion in population.
The outflow pipes from industrial buildings will put polluted water back into the ground. This doesn't show up as blue but even so, it is still water. It will need treating before it gets to your Sims but it is still present on the water table.
Sewage Treatment facilities will replenish the water table during their normal operation. Sure they're pretty expensive to place but if you're heading towards a high population city you will need to cater for replenishing the water table just as much as getting garbage off your streets or keeping everything powered.
Some tips for managing your water
- SimCity is not SimCity 4 - large cities are not supposed to be self sufficient. This is managed by the 'multi-city' game mechanic and if you want clean and efficient cities with large populations you are going to have to import some of your water
- See water management as a challenge you're going to have to overcome along the way through proper planning and preparation
- Slow down! The purpose of the game isn't to get a massive population in as little time as possible, the goal is to create a stable region consisting of multiple cities that compliment each other
- Some cities may be your population centers and some cities may be mining hubs, and these cities are going to be thirsty, but other cities in the region may have an abundance of coal or oil, and these smaller cities can provide the water to your population centers
The best advice for a perpetual water supply
Build a water pump next to a sewage treatment plant. The sewage treatment plant will replenish the water table as fast as the water pump is depleting it, thus providing the effect of infinite water. It's also a good way to pick up germs and make your population sick in the instance of a sewage overflow, so filtration pumps at your water pump may be the way to go with this.
OK, since nobody has an answer, I tried it out myself in a private region.
Turning off addons did not affect the other city in the region, although it could be due to the region propagation delay. I'll check again tomorrow and see if anything's changed. I would imagine it's by design so one city shutting down or bulldozing everything doesn't wreak havoc on the region.
Also, only some buildings are shut down when I turn off the prereq. For the Dept of Safety, the Hospital will stay open while Fire and Police stations shut down.
For Dept of Tourism, Landmarks were still unlocked but big parks were not.
Looks like all the specialization unlocks stay after you close the HQs too.
Don't know if these are bugs or not, but right now you can save some $ per hour while keeping the bonus services.
Also, unlocks do not go across the entire region in the 16-city maps. They only go as far as the 4-city subregion.
Wish I could test this from sandbox mode, but everything is unlocked there from the get go.
Best Answer
1) First of all there's no sewage return, I know that for sure. Second, the numbers of "regional resources" are slow to update (maybe once a month?) so snap testing is hard to do. I did turn off my water supply to see what would happen. I am sure Power works in the exact same way as Water as far as the Arcology is concerned, but I did not test Power independently. Also, note it seems the Arcology caps out at 1,000 power and 1,000 water in Regional Resources (meaning it only 'sees' up to that point).
The water or power required to run the Arcology MUST be "available to trade" and not in use. It isn't "sent" (or listed anywhere) to the Arcology but the region has have atleast 120 kgal/hr "available to trade" in order to keep Arcology running.
2) I know in order to get the Arcology "activated" and fully built I had to visit each city in my region, so they obviously have some sort of internal clock whether it's built or not AND whether it's functioning. However, switching between all my cities the "Regional Resources" of the Arcology remained the same.
Basically, while you are playing each city its that city's knowledge of available regional resources when its turned "on" and when its got enough resources to function.
As you can see my water producing city doesn't show any water being sent to the Great Work, but it has more than enough "available for sale".
Hope this cleared some stuff up for you!