Det geografiska område som utgör den mellanvästra delen av USA i allmänhet eller då ingen specifik stat anges. De stater som vanligtvis anses tillhöra området är Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, Ohio, Oklahoma, Nord-Dakota, Syd-Dakota och Wisconsin.

The water cycle, also known as the hydrologic cycle, is a continuous process by which water circulates between the Earth's oceans, atmosphere, and land, driven by solar energy and gravity. This process includes evaporation, transpiration, condensation, precipitation, runoff, and infiltration.