People can not live without water. We value it to drink, to cook, to wash with and to swim in, for livestock and gardens, for its appearance, sounds, coolness and distinctive touch.Natural water systems provide key services to the functioning of the planet, such asmoving energy (heat moving within oceans drives the weather patterns), spreading nutrients, dispersing pollutants and clearing rain-floods. Flowing, fresh water supports plant life, fish and provides home to many creatures, disperses plant seeds and animal young (e.g. insect larvae and young fish).
Water from these different sources should not be mixed, and there are cultural traditions and practices (tikanga and matauranga) focussed on keeping water clean and protecting its mauri. MÄori traditions avoid release of human wastes to water, even if treated, preferring land disposal. From their perspective some of the greatest dangers to water quality are from harmful agricultural and urban activities, and water shortages created by seasonal over-use below minimum flows, which threatens aquatic life and thus food gathering potential.[1]
The more water used, the more expensive it gets to supply, and the less remains in the rivers, and the harder it is for the reduced-flow in stream to support animal and plant life.
Once we have used this water in our homes, most of it goes back into rivers or estuaries, and eventually the sea. The largest part of liquid wastes from toilets, washing, bathing, etc. goes through a wastewater treatment plant, while some surface flows go directly into the rivers through the storm water system, without any treatment. The water going through the wastewater treatment plant again causes costs and the release of treated water into a river or estuary increases the load of contaminants such as nitrates and phosphates it has to cope with.
Conserving water by reducing domestic demand will not only help protect our natural ecosystems, but will result in reduced water supply energy cost.
The water cycle
Drinking-quality water is a scarce resource globally (only 1% of the total), but nature steadily renews the supply through rainfall, particularly on mountains that catch the prevailing ocean winds. The diagram below illustrates the water cycle.
In New Zealand, about two thirds of our community-piped water supplies are taken from lakes and rivers, and a third from groundwater ‘aquifers’. Both surface and underground waters can easily be polluted by human activity. Pollution sources include pastoral and crop farm nitrogen fertilisers, herbicide sprays and animal manures (in New Zealand, farm animals in total produce 40 times more urine and faeces than the human population, mostly onto land but some washes into waterways). Soil erosion into rivers is common in deforested pastoral hill-country, especially after storms and cyclones. Waste water discharges from abattoirs and dairy factories; household chemicals such as moss-killers, herbicides, detergents, oil and paints; wood preservative chemicals, mine drainage and spoil heaps, as well as other industrial activities can affect groundwater and streams. Impacts can last, sometimes for years after a mine or industry closes. Also, in populated areas, oily and metal-polluted run-off in the ‘storm water’, gathered from roads and urban hard surfaces after rain, reduces stream quality.
In some areas treated wastewater is discharged into estuaries or the sea. Check out how the wastewater is disposed of in your area.
What happens upstream will affect downstream …… inevitably
All the land area supplying a particular stream is known as the watercatchment of the stream. Rain falling on healthy soils is absorbed and usually remains clean as it flows downhill. Sediments are trapped or filtered out by natural wetlands (metaphorically like the kidneys of the land), but few wetlands have survived pressures for land development near urban areas.It is very important, therefore to be aware of where our liquid waste materials flow, as they can easily pollute water catchments, especially through surface storm-water.Road side drains are only intended for rain!
Here is a little of the science relating to urban water pollution and stress on its natural life:
If dissolved oxygen in the stream or river falls below 60% of saturation, fish will die, and below 40% most everything else. Materials that are decaying, such as sewage effluent, soil and plant debris (including algae), will use up oxygen fastest;
Phosphate levels, from detergents and sewage, can be raised to ten times above natural levels in urban streams.It feeds fast algae growth in warm weather, which can suddenly use up oxygen (a process called eutrophication, which kills animal life in that water).
Nitrogen compounds from fertiliser run-off, sewage and decaying organic matter, at 100 times higher than in nature in some urban streams, also feed algae and can be toxic to stream animals.
Low flow and un-shaded streams can more easily overheat, killing aquatic life, starting with the native fish (over 17o Centigrade) and invertebrates (over 21oC).
Sediment reduces water clarity, reduces food production efficiency of plants and clogs the gills of fish.
Oil films and paints are visible by colour sheens when they enter streams.However, the invisible pollutants are often the most deadly: for example, dissolved metals such as zinc and copper, acids, detergents, herbicides and pesticides.
N.B. If you see a pollution incident, or abandoned chemical containers in Far North water, contact the Northland Regional Council 24/7 Environmental Hotline: 0800 504 639.
Waste water
Waste water from toilets is known as ‘black water’, or ‘foul water’. It contains bacteria that are naturally found in all people’s digestive systems, but capable of multiplying rapidly in numbers to become a health hazard. It needs to be treated, to make it less hazardous, before the water carrying it is released, whether to land, river or sea. Therefore if you have a septic tank in use at home, rather than a sewer pipe connection, it is important to have the tank pumped out at no more than two-year intervals, or as your Regional Council specifies, to reduce the risk of overflow and stream pollution by ‘raw’ sewage. Another important issue is keeping stormwater down pipes (from the roof) out of the gulley traps beside the house that collect water from sinks, baths, and washing machine and send it to the sewers. Not every DIY house-renovation and extension project gets this right, and the impact is overloaded public sewer pipes after heavy rain. They should feed into the stormwater drains. Building inspectors look out for this construction error.
Wastewater from baths, showers and laundry contain some bacteria, plus water softeners and detergents, but are less hazardous than sewage and are known as ‘grey water’. Grey water should therefore not be stored, or the bacteria in it will multiply. There are, however, systems which can filter and store the water for reuse in the toilet and garden. (See: www.ecoplus.co.nz, www.newwater.co.nz as examples)
