There is a network of feedback sensors which give real time information from both the natural environment, as well as from within the city. Also, all cities would be providing each other witjh the necessry feedback. It is like cybernated global neural network (kind of like internet extended with environmental sensors). All information is gathered and processed by computers with help of AI and then resources are allocated intelligently and as most sustainable as possible, accordingly to the feedback from the environment. You have real time data about the quality of air, solar energy, wind power, amount of water and it's quality, population, weather changes, intensity of manufacturing, efficiency of recycling, quality of soil, speed of construction, amount of products, amount of natural resources, speed of agricultural growth, and so on.
It all works out automatically with no need for human intervention. People just supervise. Also, evey part within the city has it's backup system in case some part of the system malfunctions.

You are likely to find answers in FAQ. There are answers to most common questions, people have asked within years. There is an answer to your question too.
If you don't find it, then I would recommend reading the book. It's all explained there.