A new mixed-integer linear programming model for location problem is developed in this work in order to find the optimal co-ordinates of the desalination plants. The model takes into account the given locations and capacities of the water incomes, the demands, and the costs of plants and pipelining. Feasible and infeasible plant regions are distinguished for locating the plants. The model has been developed in two consecutive phases. First, a basic model is developed that provides a solution within short time but does not take into account the possibility of pipeline branching. Application of this model gives rise to redundant pipelines to some connections, involving extra costs. Pipeline branching is dealt with an improved model developed in the second phase. This improved model provides realistic solution but with much longer computation time. The results of applying the different models on motivated examples of different sizes are detailed. (C) 2007 American Institute of Chemical Engineers.