75% of the earth is covered by water but only about 1.5% is fresh. However, most of it is locked in ice caps and only a tiny 0.003% is available.
Our water usage: The average household discharges around 500 litres of water per day, each person around 200 litres.
Flushing the loo can use 11 litres of water alone
A top loading washing machine uses 200 litres per load
A dishwasher uses 200 litres per load
A garden hose or sprinkler uses 15 litres of water every 15 minutes
A running tap uses 10 litres per minute - a dripping tap can waste 90 litres of water per week
Urban storm water contains a mixture of water from housing, surfaces and road run off and is collected by drains or soak holes which lead into creeks, waterways, the ground and eventually the sea. Run off from urban areas is higher due to the impervious surfaces (ie: concreted and tarsealed areas).Storm water contains litter, sediments, organics, detergents, and bacteria such as faecal coliforms, viruses, and other toxins. Bacteria have the ability to lower oxygen levels in the water, which is detrimental to fish and other aquatic organisms. Dissolved Oxygen is important as it supports aquatic life in the water. Storm water also contains heavy metals such as lead, zinc, chromium and cadmium. Zinc and copper comes from road run off (tyres and braking systems in cars). Heavy metals can accumulate in sediments and shellfish and are then passed on to humans when eaten (bioaccumulation).
Stock and farming can also compromise water quality. Cattle poohing in the water can cause bacteria Faecal coliforms to lower oxygen levels dramatically. Eutrophication can also occur in waterways where excess nitrogen and phosphorous causes aquatic plant growth.
A 2001 study looking into the spread of Campylobacter found the bacteria in 75% of shallow ground water and in 60% of N.Z's river water.
Sewage (dirty water from toilets etc) is normally taken to a treatment plant or discharged far out into the ocean. Problems arise when pipes flood or leak and the sewage gets into our waterways. That's when you see signs up at beaches saying ‘do not swim or collect shellfish'.
Remediation measures:
Riparian planting (planting of stream banks to slow erosion).
Fencing off stock from waterways.
Washing vehicles on the grass.
Minimising earth disturbance.
Lessening impermeable surfaces.
Ensuring piping is connected correctly.
Paints and hazardous substances not tipped into drains.
Soaps and detergents with low phosphates and nitrates.
