There are many pathways the water may take in its continuous cycle of falling as rainfall or snowfall and returning to the atmosphere. It may be captured for millions of years in polar ice caps. It may flow to rivers and finally to the sea. It may soak into the soil to be evaporated directly from the soil surface as it dries or be transpired by growing plants. The cycle for water may be short, or it may take millions of years.
People tap the water cycle for their own uses.
Water is diverted temporarily from one part of the cycle by pumping it from the ground or drawing it from a river or lake. Used water normally is lower in quality, even after treatment, which often poses a problem for downstream users. The engineering hydrologist, or water resources engineer, is involved in the planning, analysis, design, construction and operation of projects for the control, utilization, and management of water resources. Water resources problems are also the concern of meteorologists, oceanographers, geologists, chemists, physicists, biologists, economists, political scientists, specialists in applied mathematics and computer science, and engineers in several fields. They may be concerned with finding water supplies for cities or irrigated farms, or controlling river flooding or soil erosion.