Technological advances have made efficient resource allocation an easier task nowadays. In the case of crop irrigation, sensing has improved in a way that it is possible to measure the amount of water needed to be provided in a certain area and to present this information in a single an image. Measurements of this type include Crop Water Stress Index (CWSI) and Normalized difference Vegetation Index (NDVI). Using these tools, we propose a method that designs paths for agricultural Unmanned Aerial Vehicles (UAVs), reducing the amount of water and energy consumed during the irrigation process, depending on the conditions of the crop. The proposed method takes a CWSI or NDVI image and generates a path that determines the UAV velocity and direction, assuming a constant discharge of water from the UAV. This method is based on a reformulation of the Traveler Salesman Problem that incorporates a dynamical model of a UAV and water stress indicators. We show through simulations that the proposed method allows for an important reduction of spent water and energy resources during the irrigation process.