A water separation system includes a production control valve fluidly connected to a production tubing and positioned at an uphole end of the production tubing at a well head of a well site, a production fluid pathway between the production control valve and a water separator, an injection control valve fluidly connected to an injection tubing and positioned at an uphole end of the injection tubing at the well head, and an injection fluid pathway between the injection control valve and the water separator. The water separator is positioned at the well site and is fluidly connected to the production fluid pathway and the injection fluid pathway. The water separator separates water from the production fluid and directs the separated water to the injection fluid pathway. An output fluid pathway fluidly connects to the water separator to direct the production fluid out of the water separator.