8.2 Water for Living

Sources of contamination

Water pollution includes a range of adverse effects upon rivers, lakes, streams, oceans and groundwater usually caused by human activities. Of course there are a number of naturally occurring pollutants throughout the world such as volcanoes, storms and earthquakes which can have a major effect on water quality but these effects are usually very localised and short lived. This type of pollution is not considered to be pollution as it occurs naturally and the systems can usually recover within a reasonable length of time.

The type of water pollution being discussed here is the type caused by human impacts which include but are not limited to:

  • Increased nutrient loading which causes eutrophication (the fertilisation of surface water by nutrients that were previously scarce)
  • Organic wastes such as sewerage which inflict high oxygen demands on water which causes oxygen within the water to become depleted
  • Heavy metals, organic toxins, oils, nutrients and solids are discharged in large amounts with wastewater from industry
  • The run-off from construction sites into stormwater drains, rivers and creeks can have high silt loads
  • Deforestation
  • Agricultural effects including pesticides and fertilisers

The effects of water pollution can range from increased sediment loads and decreased oxygen and nutrient availability which can kill off many aquatic species to waterborne diseases caused by pathogens in the water which can hurt and often kill humans and animals.

The pie chart below is a rough indication of the percentages of major pollutants which enter the world’s oceans annually. As you can see the three main contributors to water pollution are air pollution, farm run-off and sewerage; most of which come from major industry and primary production.
  
Figure 1: Pollutants Overview
(Source: http://www.informaction.org/cgibin/gPage.pl?menu=menua.txt&main=waterpol_gen.txt&s=Water+sewage)

Australia spends more than $1 billion on herbicides, fungicides, insecticides and pesticides which are applied each year. The CSIRO with support from Land and Water Australia now offer a free software package online called The Pesticide Impact Rating Index (PIRI) which can be used to measure the effects of particular pesticides on the aquatic environment. It is a risk indicator for different pesticides and cropping systems. This software can be downloaded from the CSIRO website.

Outcomes
9.4.5 Students learn to describe possible sources of contamination that may enter catchments