If per chance you happen to mean the most complex structure known to man, often referred to as a hole in the ground. Can also be found on many roads, known as a pot hole. Well I think its to complicated for our politicians. In India the usually have a backup ground water bore in some areas to get water for cleaning etc. They also collect Rain water in most buildings and run it into a ground tank or roof tank for use. This water is the main source for cleaning water. Drinking water comes from metro pumps that if your lucky you may have in your home else one per building or street. They also have underground power lines. Our politicians cant cope with power lines and pot holes you think they are going to come up with a decent water solution.
A underground dam (i think thats what you ment to say
is not a bad idea, and could be built in every council area to collect water runoff from rain.
The amount of rain water we waste in this day an age is truely appalling. And I just dont understand why its allowed to happen. We have protest marches for many things in this nation, but I am yet to see any action about Water. Water is not a joke, its is the blood of society without it we perish. I am looking into puttin a tank at my place, but I feel useless watching and hearing the rain water run down roads and sewers into the sea.
Regards