For such time as is specified in the contract, and not to exceed 10 years from the date thereof, the control and management of the reclamation works shall be vested in the person having contract with the state. At the expiration of such time the clear and unencumbered title to the reclamation works and all franchises thereunto belonging, also the control and management thereof, shall pass to the purchasers of water rights from the reclamation works in the manner to be prescribed in the contract, the contractor retaining an interest in the works proportional to the amount of water right unsold.