A district may make surveys, plans, investigations or studies for generating electric energy by water power, steam, or other methods, and for systems and facilities for the generation, transmission or distribution thereof, and for domestic and industrial water supply and irrigation, and for matters and purposes reasonably incidental thereto, within or without the district, and compile comprehensive maps and plans showing the territory that can be most economically served by the various resources and utilities, the natural order in which they should be developed, and how they may be joined and coordinated to make a complete and systematic whole.