The sequencing and scheduling aspects of some important capacity expansion problems encountered in water resources development are studied. Dynamic programing algorithms are developed for both project timing problems and combined project selection and timing problems involving durable high cost water supply projects, which in the aggregate are subject to continuous time demand requirements. The structure of the problems is successfully exploited to produce computationally efficient algorithms to solve problems of the dimension encountered in water resources systems. The computational superiority of these algorithms over conventional dynamic programing algorithms is discussed and illustrated by a numerical example.