Lesson 2 hydrology
Download as PPT, PDF1 like631 views
The document provides an overview of hydrology and the hydrological cycle. It discusses key topics like the significance of water, water availability globally, the stores and transfers of water through evaporation, transpiration, precipitation, runoff, and groundwater flow. It also describes key hydrological concepts such as drainage basins, patterns of drainage, and nested basins.
Lesson 2 hydrology
- 1. Access Geography Unit 3 Lesson 2 Hydrology
- 2. Today’s objectives Significance of water Water availability Hydrological system Stores and transfers
- 3. Why study physical systems? Human activities are frequently effected by physical systems on the planet. In groups, write at least 3 ways that each system (water, earth, air) can have an effect Examples Direct and indirect Water: river floods, rain on crops, rising sea levels, water supply, transport, power Earth: soil type for agriculture, natural hazards (earthquakes, volcanoes, mudslides), landforms for settlement (favourable or hindering) or tourism Air: tourism and leisure, agriculture (economic impact), travel, money spent on predicting the weather, power Life: food, resource for settlement and housing, transport, aesthetics, economic
- 4. Energy from the Sun The energy received from the sun radiated into space is known as insolation. This energy is sufficient to provide light and warmth for life on this planet plus the heat to drive atmospheric and oceanic movements There are thus two major systems powered by solar energy: the living system and the ocean-atmosphere system Both are closed systems in that there is no exchange of mass with the surrounding space system However, both systems are dependent on materials supplied by the solid Earth
- 6. The Hydrological System: Water on Earth The Earth is located in the habitable zone of the solar system 5% (8 Million km) either way and water would not be able to exist in its 3 states simultaneously Earth’s mass allows gravity to hold an atmosphere Water vapour and C02 in the atmosphere produce a greenhouse effect which has helped maintain a steady state over geologic time
- 7. 2. The Miracle of Water All forms of life depend on water. It is central to: Photosynthesis Respiration Enzyme function Within conditions on the Earth, it has unique properties: It is naturally occurring in all 3 states It is a very strong solvent (the universal solvent) It has a very high specific heat capacity (can buffer changes in temperature) It’s solid form floats on its liquid form
- 8. 3. Water Availability & Use 70% of the Earth’s surface is water Of this, 97% is in the oceans Of the available 3% freshwater, over 75% is locked in polar ice and glaciers Only 1% of freshwater is easily accessible in lakes, rivers and shallow soil moisture Globally the average amount of water available per person per year is 9000m3 By 2025 with the increase in population, this will drop to 5100m3 per person per year. This would be enough if it was distributed evenly
- 9. 4. Distribution: Water Stores
- 10. Hydrology The study of water and its properties including its distribution and movement through the land areas of the earth Principally concerned with the part of the cycle after the precipitation of water onto the land and before it’s return to the oceans Hydrologists study the cycle by measuring such variables as: Precipitation Ice and glacier stores Water flow in rivers Soil-water balance Amount and flow of groundwater
- 11. Before we can understand the Hydrological cycle we need to understand a little about weather
- 12. So it is hotter at the equator but why???
- 13. Where on earth receives the most year round sunshine to provide good growing conditions? 1) Distance the sun’s rays have to travel through the atmosphere Equator Sun Rays Longer Distance Shorter Distance
- 14. 2) The curvature of the earth
- 15. 3) The sun´s rays have to travel through thicker atmosphere at the poles Thinner atmosphere Thicker atmosphere
- 16. What causes it to rain? 1) The sun heats up the sea. This causes water to be evaporated (made into a gas called water vapour). 2) The warm air full of water vapour rises high into the sky. Because it is so warm it is very light, that’s why it rises. 3) The higher up the air gets, the colder it gets as well. This makes the water vapour condense (turn back to liquid) and form clouds. 4) These clouds eventually drop all of the water in them as rain. This type of rain is called CONVECTIONAL rain
- 17. The UK is affected by a number of different air masses. Air masses are huge blocks of air at different temperatures. Some of the air masses are warm and some of the air masses are cold .
- 18. But air masses at different temperatures DO NOT like one another so they won’t mix together. Birmingham is affected by cold air coming down from the north and warm air coming up from the south. The junction between these two different air masses is called a front so when they cause it to rain it is called FRONTAL RAIN .
- 19. But if they won’t mix, what happens when they meet?
- 20. Its fair to assume then, that the final type of rainfall will also follow the same process. But what is it that is causing the air to rise? A FEW CLUES Name: RELIEF rainfall
- 21. Meet Reggie, the RELIEF RAIN raindrop Reggie is a gas flying in the air (water vapour) but when he meets a hill he has to climb over it. It gets very cold near the top of the hill as he is so high and Reggie changes from a gas to a liquid and settles into some clouds (condensation). When lots of Reggie’s friends arrive in the cloud it is too cramped to stay so some of them fall back to earth as relief rainfall (precipitation).
- 23. Hydrological Cycle Matching Resurgence Overland Flow (surface runoff Ground water flow Infiltration Surface water storage Percolation Transpiration Isolation Precipitation Atmospheric Store Snowmelt Saturated zone (aquifer) evaporation Soil moisture Ocean store Base flow Atmospheric condensation Water table Volcanic water Ice cap storage Human activities Interception Stream runoff Impervious bedrock Reabsorbed by plants
- 24. The Drainage Basin This is the area of land drained by a single river and its tributaries Water drains downhill into a lake, river, dam, wetland, sea or estuary The boundary (or watershed) is the ridge of high land, hill or mountain beyond which any precipitation will drain into adjacent basins The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels
- 25. Drainage Patterns Dendritic – completely random like blood vessels Trellis – strong geology structure produces parallel forms with right-angled tributaries Deranged – highly irregular often as a result of repeated glaciations Rectangular – grid like pattern reflects tectonics faults or bedrock joints Parallel - often found in areas with steep relief or where flow is over non-cohesive materials.
- 26. Nested Basins This image shows the nested order of drainage basins. Rivers are in blue The red lines describe the watersheds for the drainage basins of first order streams The yellow lines define the watersheds for two drainage basins from locations further upstream Note that the first order basins are components of these much large drainage basins.