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RIVER AND WATER (FLOWS (OR TRANSFERS) (evaporation (we might say that…

- - - - instead it may be returned directly back to atmosphere from land by transpiration of plants and evaporation from both soil and water bodies
- - - - drainage basin cycle involves stores and flows
      - drainage basin cycle
        
        tributary drainage basin not shown here as most of the flows and stores are broadly same as hydrological cycle
      - important difference between drainage basin and hydrological cycle is that former is open system
        
        drainage basin has external inputs and outputs
        
        amount of water is system varies over time but amount of water remains exactly same in hydrological cycle
        
        most of flows and stores are broadly same as hydrological cycle
      - inputs of drainage basin
        
        energy from sun
        
        precipitation formed from moisture picked up outside basin
        
        possibly water from tributary drainage basins
      - outputs of drainage basin
        
        river's discharge
        
        water in its basin from which evaporation and transpiration take place which eventually falls as precipitation in another drainage basin
  - - - follows top of hill and it called watershed
        
        main river has its source to higher parts of basin close to watershed
        
        this is where most precipitation falls
        
        smaller streams of tributaries enter main river channel at locations known as confluences
        
        mouth or estuary of river is where it flows out into sea
    - - basin a's network is less dense (has fewer channels) than b's, though main channel is shorter
        
        channel networks can be mapped and their lengths and densities (number of channels per unit area) measured
        
        this network can change over short periods of time, eg during flooding drainage basins often have many more and longer channels than they do in periods of low or normal rainfall
        
        each drainage basin is unique in combination in range of features. these include size, shape, rock type, relief and land use
        
        these features become factors that determine how quickly or slowly water moves through basin
        
        factors affecting run off
        
        shows how some of these features can affect overland flow or run off
        
        rock type and relief are physical factors over which people have little control
        
        however, land use can be easily changed by people
        
        woodland can hold water and slow overland flow
        
        however, once cleared for cultivation, run off speed will speed up
        
        built up areas of towns and cities can speed up run off even more
        
        rainwater hits solid surfaces such as roofs, pavements and roads
        
        1 more item...
  - - - eg, basin of river negro in brazil is tributary or part of huge drainage basin of river amazon. the water it collects is conveyed to amazon then eventually to sea
- - - - means that there is a fixed amount of water in system because water neither enters nor leaves earth and its atmosphere
- - - - water exists as water vapour or as minute droplets in clouds
    - - water stored on surface in rivers, lakes and reservoirs
      - water is also taken in by plants and temporarily stored in vegetation. also stored below ground in soil or bedrock. known as groundwater store
      - water exists in three stores in liquid form, generally speaking
        
        however, can exist as solid form as snow and ice, as for example in ice sheets, glaciers and snowfields
    - - estimated that over 95% of earth's water is stored in sea
        
        overwhelmingly held in liquid form (water), but also in form of ice, for eg icebergs in high latitude seas
- - - - essential to life
      - vital to process of economic development
      - unevenly distributed with some areas 'water-rich' and 'water poor'
      - needed for
        
        domestic use
        
        industrial use
        
        agricultural use
        
        leisure use
      - all forms of water use involve 2 key elements
        
        demand
        
        need for water for range of uses
        
        often referred to as consumption
        
        amount of water consumed=level of demand
        
        supply
        
        demand for water by tapping carious sources, such as groundwater, lakes and rivers
        
        for any country or area within it, it is possible to compare water demand and water supply
        
        this comparison known as water balance