Water resources: Difference between revisions

[[File:Total Renewable Freshwater Resources in mm per year By WaterGAP Average 1961-1990.jpg|thumb|Total renewable freshwater resources of the world, in mm/year (1 mm is equivalent to 1 L of water per m²) (long-term average for the years 1961–1990). Resolution is 0.5° longitude x 0.5° latitude (equivalent to 55 km x 55 km at the equator). Computed by the global freshwater model [[WaterGAP]].]]The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many [[farm]]s require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a [[power plant]] that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when average stream flow is below the power plant's need. Nevertheless, overOver the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.