Global water use - towards a sustainable future?

Agenda 21 of the UN conference on Environment and Development in Rio in 1992 specified the need to protect the quality and supply of freshwater resources by an integrated approach to protect the quality and supply of freshwater resources by an integrated approach to the development, management, and use of water in a sustainable way.

What means sustainability? One definition: 'a set of activities that ensures that the value of the services provided by a given water resource system will satisfy the objectives of future generations.' ('services' include maintenance of eco systems)

Major threats

Vegetation/land use change

trees and shrubs have been replaced by agricultural cops and grassland -> lower nterception and ET -> increased runoff -> erosion

negative feedback: less precipitation or retention of snow

sometimes vegetation is purposefully changed in order to increase yield, however surprises happen:

in Australia, Eucalyphtus trees have been removed near the Murray River in order to increase recharge; as a result, salty groundwater has been put into motion -> increased discharge into rivers -> incease of river salt content (Fig)

desertification

deserts cover about 37% of the land on the globe (= 4.5 billion ha), 30% are natural, 7% man-made
deserts increase at a rate of 6 million ha/y
factors contributing:

deforestation, overcultivation, poorly designed irrigation schemes
destabilization of the topsoil is key factor

by the year 2000, one third of all the land used by agriculture will have either been totally lost or become drought ridden
feedbacks on the desertification process

Hydropolitics

many countries in the world need to share river basins and groundwater resources
examples:

Jordan River (Fig)
River Nile (Fig)

redistribution of freshwater
rising sea levels
worldwide contamination of water resources
rapid population growth

One example: As in Bangladesh

Some ideas:

adjustment of cost of water to market value, reduction of subsidies
implemetation of water saving measures, reduction of leaks, water metering, new technology, recycling
integrated management of water resources
reduction of population growth
conserving ecosystems (wetlands, forests)
environmental audit, environmental impact assessments
hydropolitics; conflict, treaties, and international law

Jordan, Nile, Ganges-Brahmaputra, Rio Grande,....