Class Visual Glossary Drainage Basin Key Terms Instructions: Use the information on pages 2 – 7 of the textbook to add the definition of each key term to the table, as well as an image or diagram that represents that key term. An example has been completed for you. Key Term 1. Drainage basin Definition A drainage basin is an area within which water supplied by precipitation is transferred to the ocean, lake, or a larger stream. It includes all of the area that is drained by a river and its tributaries. 2. Closed drainage basin (‘endorheic’) A closed drainage basin is where water supplied by precipitation but is not then transferred to the ocean, instead it is transferred inland to a lake 3. Hydrological Cycle Refers to the cycle of water between the biosphere, atmosphere, lithosphere, and the hydrosphere at a local scale Image/Diagram 4. Open System A system that allowed the movement of energy and matter across it’s boundaries in the deeper subsurface 5. Precipitation Precipitation includes all forms of rainfall, snow, frost, hail and dew, the conversion and transfer of moisture in the atmosphere to the land. 6. Evaporation The process by which a liquid or a solid is changed into a gas, the conversion of solid and liquid precipitation to water vapour in the atmosphere. 7. Transpiration The process by which water vapor escapes from living plants, mainly the leaves, and enters the atmosphere. 8. Evapotranspiration The combined effects of evaporation and transpiration are normally referred to as Evapotranspiration. (EVT) Represents the most important aspect of water loss accounting for the loss of nearly 100% of annual precipitation in arid areas and 75% in humid areas. 9. Potential evapotranspiration (P.EVT) The water loss that would occur if there was an unlimited supply of water in the soil for use by the vegetation. The distinction between EVT and P.EVT is moisture availability. ---------------------------------------------------------------------------------------------------------- 10. Infiltration Is the process by which water soaks into or is absorbed by the soil. The infiltration capacity is the maximum rate at which rain can be absorbed by a soil in a given condition 11. Infiltration capacity Infiltration capacity decreases with time during a period of rainfall, until a more or less constant value is reached. Vegetation also increases infiltration 12. Overland flow Overland flow is water that flows over the lands surface. It occurs in two main ways. 1. When precipitation exceeds the infiltration rate 2. When the soil is saturated (all the pore spaces are filled with water). 13. Through flow When Water flows within soil Through natural pipes . 14. Base flow Is when ground water discharge flows into a river it is constant except may increase during wet seasons or periods . 15. Discharge This is when ground water gets discharged into bodies of water such as rivers and lakes and the ocean. 16. Interception Water that is retained by plant surfaces and which is later evaporated away or absorbed by the plant. 17. Throughfall Water that either falls through gaps in the vegetation or which drops from leaves, twigs, or stems. Water that trickles along twigs and branches and finally down the main trunk. 18. Stemflow 19. Field Capacity Field capacity refers to the amount of water held in the soil after excess water drains away, that is, saturation or near saturation. 20. Wilting point Wilting point refers to the range of moisture content in which permanent wilting of plants occurs. The wilting point defines the approximate limits to plant growth 21. Groundwater What is groundwater? groundwater is water from either rain or melting snow that fills the empty spaces between the soil and the rocks below the earth, these small spaces are called pores. 22. Percolation Percolation is the process of water slowly passing through the soil. 23. Permeability The property of soil sample which permits the flow of water through it. 24. Water Table A water table is an underground boundary between the soil surface and the area where groundwater saturates spaces between sediments and within rocks. 25. Recharge Recharge refers to the refilling of water in pores where the water has dried up or been extracted by human activity. Hence in some places where recharge is not taking place, groundwater in conspired a non-renewable resource. Recharge is important as it continues the water cycle and helps certain places with their water supply. 26. Aquifer Aquifers are rocks that contain significant quantities of water and provide a great reservoir of water. Aquifers are permeable rocks such as sandstone and limestone. The water in aquifers moves very slowly and acts as a natural regulator in the hydrological cycle by absorbing rainfall that would otherwise reach streams rapidly. Aquifers also maintain stream flow during long dry periods. 27. Cryosphere Cryosphere refers to the ice and snow environment. 66 percent of the world’s freshwater is in the form of snow and ice. (over 97 per cent of the worlds water in salt so very little is available to humans). High latitude regions and high-altitude areas have many important stores of snow and ice.
