Depletion of Fresh Water Resources

The demand for fresh water resources is accelarating, and competition for fresh water is increasingly of conncern to planners and policy makers. At present 70% of the world's fresh water withdrawal is used by agriculture, while 20% is used in industry and only 10% is used for municipal consumption. | Increased Use of Irrigation Use of Fresh Water in Industrial Animal Production and Processing Systems Environmental Assessment: Pressure State Response Indicators Policy Pressures and Policy Options Technology Options

The projected growth of urban populations will increase localised pressure on water resources for urban consumption, while increasing the demand for feed production in distant ares to support urban linked industrial animal production systems. The demand for water resources has exceeded population growth by a factor of two or more over the last hundred years.

Increased Use of Irrigation

Approximately 20% of the worlds arable land is used for the production of livestock feed, with over 30% of the world's cereal production going to livestock. The current global expansion of cropland is very small, at around 0.1% annually, while production is increasing at around 1.9%. This increase in production is a result of intensification, and a key component in intensification is irrigation.

Already some 40% of the worlds food supply is grown under irrigation, and there is increasing pressure to increase irrigation despite recognised problems with management and failure of irrigation systems, often associated with salinisation and/or waterlogging (affecting some 20% of the irrigated land).

The problem is compounded by inefficient use of water, with an estimated 60% loss through seepage and evaporation from delivery channels and bare soil between crop rows.

The impact of increased use of water for irrigation is a decrease in the quality and quantity of downstream water, with implications on both ecosystem functioning and on downstream use for agriculture, industry and muncipal supplies. However, as the demand area, the farmland, is often distant from the critical urban/industrial demand areas, these linkages are often overlooked.

Use of Fresh Water in Industrial Animal Production and Processing Systems

The demand for fresh water for consumption by livestock in industrial units, and for maintaining clean and hygenic production sites is considerable. Given that production sites are almost invariably near urban/industrial centres, this demand is in direct competition with demand for industry and municipal supplies.

In many cases, even where lower quality water would be suitable, the only supply is from treated mains water, treated to domestic standards.

The demand on fresh water has a direct impact, a reduction in the overall availability of fresh water among competing users. It also has an indirect impact through decreasing the water available for diluting effluents, and hence increasing the levels of pollution in downstream systems.

Discharged wastewater is generally loaded with nutrients (N and P) and organic compounds. When discharged directly onto surface water, the large quantities of wastewater easily exceed the natural cleaning capacity of the system, causing pollution and increasing biological oxygen demand.

The potential for reducing water demand includes:

- Collecting solid wastes instead of flushing with cleaning water;
- Increasing efficiency of water use through "good housekeeping"; and
- Reuse of purified waste water for some of the cleaning operations

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