rivers out of balance
TRANSCRIPT
RIVERS OUT OF BALANCEL.O. to be able to explain fully the impact of clearing vegetation in river catchments
Starter: unscramble the following key terms…
GALAL MOLOB TRUECAPOONITHI TINSALIY
NOTGARIRII UNDERGRAWTO NAILIFTRANIT
CHANGES TO RIVER SYSTEM
PURPOSE OF ACTIVITY (1 mark each)
IMPACTS ON RIVER SYSTEM (2 marks each)
DAMS To control water flow/ regulate water supply
Changes to natural seasonal flow can disturb fish migration & spawning patterns. E.g. Murray Cod usually migrate when river is in high flow & return downstream in low flow
IRRIGATION To provide water for farming (watering crops)
Excess water drains into groundwater, raising water table to salt table & increasing salinity of soils. This can cause plants to die and the salt contaminates freshwater through runoff into river
CLEARING VEGETATION
To allow room for development (agriculture or urbanisation)
Reduced inputs such as leaf litter & insects into system. Increased soil erosion due to exposure & therefore more sediment washed into river. This can clog fish gills & reduce light for photosynthesis.
AGRICULTURE To provide food for national supply or trade
Algal blooms occur due to eutrophication. Runoff containing fertilisers allow algae to grow, which then starve fish & plants of oxygen & light vital for survival.
FISHING To provide food for national supply or trade and recreational purposes
Reduced numbers of fish stock, may lead to extinction of certain species.
http://assets.panda.org/img/original/rivers_at_risk_big.gifhttp://www.ldeo.columbia.edu/users/menke/ENERGY/HYDRO/img20.jpg
CHANGES TO RIVER SYSTEM
PURPOSE OF ACTIVITY (1 mark each)
IMPACTS ON RIVER SYSTEM (2 marks each)
DAMS To control water flow/ regulate water supply
Changes to natural seasonal flow can disturb fish migration & spawning patterns. E.g. Murray Cod usually migrate when river is in high flow & return downstream in low flow
IRRIGATION To provide water for farming (watering crops)
Excess water drains into groundwater, raising water table to salt table & increasing salinity of soils. This can cause plants to die and the salt contaminates freshwater through runoff into river
CLEARING VEGETATION
To allow room for development (agriculture or urbanisation)
Reduced inputs such as leaf litter & insects into system. Increased soil erosion due to exposure & therefore more sediment washed into river. This can clog fish gills & reduce light for photosynthesis.
AGRICULTURE To provide food for national supply or trade
Algal blooms occur due to eutrophication. Runoff containing fertilisers allow algae to grow, which then starve fish & plants of oxygen & light vital for survival.
FISHING To provide food for national supply or trade and recreational purposes
Reduced numbers of fish stock, may lead to extinction of certain species.
http://www.supergreenme.com/data/images/33/Irrigation-salinity-httpwww.napswq.gov.aupublicationsbrochuressalinity.html.gif
CHANGES TO RIVER SYSTEM
PURPOSE OF ACTIVITY (1 mark each)
IMPACTS ON RIVER SYSTEM (2 marks each)
DAMS To control water flow/ regulate water supply
Changes to natural seasonal flow can disturb fish migration & spawning patterns. E.g. Murray Cod usually migrate when river is in high flow & return downstream in low flow
IRRIGATION To provide water for farming (watering crops)
Excess water drains into groundwater, raising water table to salt table & increasing salinity of soils. This can cause plants to die and the salt contaminates freshwater through runoff into river
CLEARING VEGETATION
To allow room for development (agriculture or urbanisation)
Reduced inputs such as leaf litter & insects into system. Increased soil erosion due to exposure & therefore more sediment washed into river. This can clog fish gills & reduce light for photosynthesis.
AGRICULTURE To provide food for national supply or trade
Algal blooms occur due to eutrophication. Runoff containing fertilisers allow algae to grow, which then starve fish & plants of oxygen & light vital for survival.
FISHING To provide food for national supply or trade and recreational purposes
Reduced numbers of fish stock, may lead to extinction of certain species.
http://www.anra.gov.au/topics/water/pubs/estuary_assessment/images/fig_034.gif
CHANGES TO RIVER SYSTEM
PURPOSE OF ACTIVITY (1 mark each)
IMPACTS ON RIVER SYSTEM (2 marks each)
DAMS To control water flow/ regulate water supply
Changes to natural seasonal flow can disturb fish migration & spawning patterns. E.g. Murray Cod usually migrate when river is in high flow & return downstream in low flow
IRRIGATION To provide water for farming (watering crops)
Excess water drains into groundwater, raising water table to salt table & increasing salinity of soils. This can cause plants to die and the salt contaminates freshwater through runoff into river
CLEARING VEGETATION
To allow room for development (agriculture or urbanisation)
Reduced inputs such as leaf litter & insects into system. Increased soil erosion due to exposure & therefore more sediment washed into river. This can clog fish gills & reduce light for photosynthesis.
AGRICULTURE To provide food for national supply or trade
Algal blooms occur due to eutrophication. Runoff containing fertilisers allow algae to grow, which then starve fish & plants of oxygen & light vital for survival.
FISHING To provide food for national supply or trade and recreational purposes
Reduced numbers of fish stock, may lead to extinction of certain species.
http://library.thinkquest.org/04oct/01590/pollution/culturaleutroph.jpg
http://www.thirteen.org/edonline/studentstake/water/schoolwater/Phosphorous/Images/image44.gif
CHANGES TO RIVER SYSTEM
PURPOSE OF ACTIVITY (1 mark each)
IMPACTS ON RIVER SYSTEM (2 marks each)
DAMS To control water flow/ regulate water supply
Changes to natural seasonal flow can disturb fish migration & spawning patterns. E.g. Murray Cod usually migrate when river is in high flow & return downstream in low flow
IRRIGATION To provide water for farming (watering crops)
Excess water drains into groundwater, raising water table to salt table & increasing salinity of soils. This can cause plants to die and the salt contaminates freshwater through runoff into river
CLEARING VEGETATION
To allow room for development (agriculture or urbanisation)
Reduced inputs such as leaf litter & insects into system. Increased soil erosion due to exposure & therefore more sediment washed into river. This can clog fish gills & reduce light for photosynthesis.
AGRICULTURE To provide food for national supply or trade
Algal blooms occur due to eutrophication. Runoff containing fertilisers allow algae to grow, which then starve fish & plants of oxygen & light vital for survival.
FISHING To provide food for national supply or trade and recreational purposes
Reduced numbers of fish stock, may lead to extinction of certain species.
Focus: Clearing Vegetation• Think about the what you’ve learned in the last few lessons. • Have a go at filling in the flow chart to show effects of
vegetation clearance in river catchments. (USE PENCIL!)
• Extension: Read p.46-47, answer q.1-7
Focus: Clearing Vegetation
Trees cleared
Decreased transpiration & interceptions
Increased infiltration
Increased runoff
Soil erosion
Land less suitable for agriculture
River silting
Increased turbidity
flooding
River species reduction
Soil erosion
Land unsuitable for agricultureWater table
rises salinity
Vegetation unable to survive
Streams & rivers become saline Threat to
rural & urban water supplies
Runoff & seepage carry salt into waterways