Water Catchments
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energy from the sun drives the water cycle
condensation precipitation evaporation
(rain, snow)
transpiration from plants
Absorption
surface runoff
into the ground
groundwater movement
Water is always being recycled. Water begins as rain or snow (‘precipitation’). It falls onto the land, where some evaporates or is used by plants which then release it back into the air (‘transpiration’). Some of it is absorbed by the ground and travel to rivers, lakes and the ocean as groundwater. Some of it travels directly to rivers, lakes and the ocean as surface runoff. Water then evaporates off these waterways and rises into the atmosphere, where it condenses into clouds. Every area of land on the planet is part of a catchment. As water moves over the land, it finds its way into streams and down into the soil, eventually feeding the river. Some water remains underground (‘groundwater’) and this slowly recharges the river even when there is no rainfall. Every river catchment in every part of the world forms part of a larger system called the water cycle. Diagram credit: http://commons.wikimedia.org/wiki/File:Watercycle_no_text.jpg (text added)
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What’s a catchment?
What’s a catchment? The catchment of a river is the area of land that water falls on to feed that river. In the picture, the rain that falls inside the white line will flow into the rivers and eventually into the Firth of Tay. The rain that falls on the other side of the mountains will flow down the other side, to feed other rivers. Every area of land on the planet is part of a catchment. As water moves over the land, it finds its way into streams and down into the soil, eventually feeding the river. Some water remains underground and this slowly recharges the river even when there is no rainfall. Catchments range greatly in size and use, from small urban catchments to massive catchments spanning three states, such as the Murray Darling.
Image credit: http://commons.wikimedia.org/wiki/File:Tay.catchment.jpg
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Melbourne’s water catchments
Image copyright Melbourne Water
[You may want to zoom in to show students different catchments] Melbourne has protected catchment areas that capture and store our drinking water. The areas around these dams are protected from contamination and are often off-limits to people for recreation. Water travels from the mountain dams down to smaller reservoirs in pipes, where it is treated and purified before being released into our taps. These dams hold Melbourne’s water. They are well below storage capacity (at about 35%*) because we are using more water than is being replenished by rain. This is because of population growth and wasteful consumption. *as at November 2009: check www.melbournewater.com.au/content/water_storages/water_report/water_report. asp for Melbourne’s water storage levels. Image credit: copyright Melbourne Water
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Melbourne’s Yarra • Pristine mountain beginnings of the Upper Yarra
• Final journey to the sea
Rain that falls outside of the catchments feeding our reservoirs flows through other rivers and creeks toward the sea. Melbourne’s famous Yarra River is an example of how rivers in the upper mountainous region of a catchment and are joined by other rivers and flows to the sea. The Yarra is part of Melbourne’s storm water system and is not used for drinking water due to contamination. Photo credits: Ferns on banks of Yarra River at Warburton: http://www.flickr.com/photos/splatt/316943901/ Yarra in Melbourne (Princes Bridge): Environment Victoria
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• Unfortunately our rivers pay the price when we don’t take care in the catchment.
Photo credit: http://commons.wikimedia.org/wiki/File:Litter_trap.jpg
River health in Melbourne’s water catchment
Image copyright Melbourne Water
In 2002, an assessment was made of the overall health of Australia’s more intensively used catchments. The assessment looked at land, water and biodiversity in each catchment, including problems such as salinity, erosion, sedimentation, pesticide use, pollution, roads, native tree-cover, human population and pests. The survey, done by the National Land and Water Resources Audit, found: 5% of catchments are in the poorest condition 15% are in low range condition 50% are in mid-range condition, and 30% are in better condition. These stats suggest that the condition of 70% of Australia’s most populated catchments is merely average or worse than average. This map shows the health of the river catchments around Melbourne. Image credit: copyright Melbourne Water
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Sources of water pollution
Litter from households, shopping centres, etc.
Toxic waste from industrial sites Road runoff oil & petrol
Paint and detergent from houses
Animal droppings
Image credits Rubbish photo: Environment Victoria Toxic waste: http://commons.wikimedia.org/wiki/File:55gallondrum.sandia.jpg Detergent: http://commons.wikimedia.org/wiki/File:Barf_soap.jpg Paint can: http://commons.wikimedia.org/wiki/File:EWM_paint_2007.jpg Dog poo: http://commons.wikimedia.org/wiki/File:Dog_feces.jpg Freeway picture: Environment Victoria
Research a River Catchment
River Research Melbourne • Melbourne and the surrounding region are part of the Port Phillip and Western Port catchment management area. Melbourne Water has an interactive website where you can investigate the health of your own river system. An interactive map of river conditions can be found at: www.melbournewater.com.au/content/rivers_and_creeks/riv er_health/index_of_river_condition.asp • To find details of local Friends, Landcare or other community groups, contact the Port Philip and Western Port Catchment Management Authorities, www.ppwcma.vic.gov.au, the local council or Melbourne Water.
River Research Regional Victoria • Each of the ten regional Victorian catchment areas have a website where students can begin to investigate some of the activities of their local catchment management authorities (CMA). – – – – – – – – – –
Corangamite CMA ‐ ccma.vic.gov.au East Gippsland CMA www.egcma.com.au Glenelg Hopkins www.glenelg‐hopkins.vic.gov.au Golbourn Broken CMA www.gbcma.vic.gov.au Mallee CMA www.malleecma.vic.gov.au North Central CMA www.nccma.vic.gov.au North East CMA necma.vic.gov.au Port Phillip and Western Port CMA ppwcma.vic.gov.au West Gippsland CMA www.wgcma.vic.gov.au Wimmera CMA www.wcma.vic.gov.au