(a) A court having jurisdiction over a suit described in § 11.401 of this code may appoint a watermaster with power to allocate and distribute, under the supervision of the court, the water taken into judicial custody.
(b) The court may not appoint a watermaster with authority to act both upstream and downstream from an existing reservoir on any surface stream of the state. However, once a watermaster is appointed, the construction of a new reservoir does not invalidate his appointment or restrict his authority over that portion of the stream contemplated by the original order of appointment.

(c) Under terms and conditions prescribed by the court, the watermaster may incur necessary expenses, appoint necessary deputies and assistants, and perform duties and assume responsibilities delegated to him by the court.