1. Moving the facilities such as crops, lawns, golf courses, and sewers etc would be unrealistic to change because many of the owners would not comprise (costs so much already), yet there are solutions. For example, the town can restrict farmers from poluting the rivers with pesticides as well as fining them and the house developments golf courses and land owners in which the money can be used towards the filteration cost. Another idea would to build cheaper wells to soak up water from different river locations or build barriers around settlements from the river. Another idea would to simply grow natural filters such as using the trees and soil they already had.
2. Of course their are limits such as costs, and figuring out the landscapes of where to build wells, add soil and trees (trees take time to grow) and more that would need plan of action from community leaders in which the people would need to speak with the advisors or the management of the buildings nearby. Without clean water people will get sick or die, and building managers need healthy people to live in their houses and work and grow crops so they'll have to make change.
If there is enough rainfall and little disease, then a population will increase in size because rain waters the plants of which the animals of that population eat and little disease is also a huge plus because the population will have a low chance of the disease wiping the population of animals. This will help the population of animals grow.
