WATER: it forms two thirds of the weight of the human body and covers 70% of the Earth. Most water is salty. Only about 2.5% of all water is fresh, but three quarters of this is frozen in ice caps at the poles and most of the remaining one quarter is found underground. Only 0.5% of all freshwater is easily accessible. The amount of water we have on earth does not change. No 'new' water is imported from an extraterrestrial source and only a very small amount is lost from the atmosphere.

THE WATER CYCLE: when water evaporates it forms clouds and returns to Earth as rain. The amount of water that evaporates each year and the amount falls to the ground is virtually constant. If we have a drought it is not because the world's rainfall for the year is less but because the rain is falling somewhere else and not on us. All water found in nature contains some substances from soils, from plants and animals and from the air through which it falls as rain. We interact with the water cycle in many ways. We extract groundwater, build dams and weirs and use water for a variety of domestic, industrial and agricultural purposes.

SUSTAINABLE MANAGEMENT OF THE URBAN WATER CYCLE: the management of the urban water cycle is complex. In order to deliver sustainable water services it is important to consider all available options for the supply of water and the management of wastewater – including recycling. The options should be evaluated from triple bottom line aspects:

  • Environment – greenhouse gas emissions, energy requirements, impact on receiving water, management of solids and waste concentrates
  • Society – public health, acceptance
  • Economics – total life-cycle costs.

They should be considered in the context of the total water cycle and their evaluation based on science, not perceptions. Information regarding the scientific and technical aspects of water management must be provided before the community is asked how they would prefer their water to be managed.

water treatment plant
ground water surface water water at work
recycling treatment_plant wastewater
purification effluent discharge