Climate change has exposed the vulnerability of power utilities to low water availability for hydropower generation and to high river temperatures for thermoelectric power plants. In this study, we focus on a region whose power system is controlled by an operator that relies on a set of thermal power plants to generate electricity, and consider the conventional economic dispatch problem in the presence of cooling water scarcity and climate change constraints. Specifically, we consider water constraints on the amount of water that can be consumed by the power plants, and heat constraints on the amount of heat that be transferred to the environment by the thermoelectric power plants. We focus on a practical scenario in which the power plants are aligned on a river shared by all the power plants. We then propose a general optimal power flow (OPF) framework. The proposed economic dispatch problem is NP-hard. We have developed numerical techniques to compute sub-optimal solutions to the proposed problem. Finally, we show the impact of climate change (i.e., water availability and heat constraints) on electricity generation.