What happens to water after facking is complete?

Most of the water used to fracture the shale remains trapped thousands of feet underground after it is injected. However, internal pressure in the geologic formation forces some of the water (around 15-20%) back to the surface through the well bore.
Most of this "flowback" water comes back to the surface within seven days to ten days after it is injected. Flowback water is stored temporarily in lagoons or tanks before being sent off-site for disposal. It is usually transported off-site by truck, although some companies are exploring rail transportation as an option.
Drilling companies send brine and flowback water to disposal facilities that have permits to inject fluids thousands of feet underground into deep injection wells (called class II wells).

How is natural gas extracted from a shale formation?

Natural gas is extracted from the shale through a two-step process of drilling and fracturing. To start, a production well is drilled thousands of feet downward and then gradually angled out horizontally through the shale deposit. The well is drilled horizontally to maximize the ability to capture gas once the shale is hydraulically fractured.
After the well is drilled, a mixture of water, sand, and chemical additives is injected at very high pressure to fracture the shale. This part of the process, called hydraulic fracturing (fracking), is a technique used in the oil and gas industry since the 1950s. The sand keeps the fractured shale open and serves as a conduit for extracting the natural gas.
The chemical additives reduce potential problems during drilling and gas production, since bacterial build-up and the formation of scale, mineral deposits and rust. It can take up to four million gallons of fresh water to fracture a single well. The water used in the fracturing process usually comes from a stream, river, reservoir or lake near the drill site, or in some cases, from a local municipal water plant.