Linking up Sustainable Sanitation, Water Management and Agriculture

Water resources are under increasing pressure. Population growth, urbanisation and a steep increase in water consumption for domestic uses, agriculture and industry have significantly heightened water consumption. Climate change exacerbates the problem. This development leads to water scarcity and conflicts worldwide and seriously undermines progress towards achieving the Millennium Development Goals.

Changing consumption patterns such as an increased demand for meat and dairy products, monoculture or the production of biofuels also require more water, and furthermore also more nutrient inputs in agriculture. In particular in development countries, where artificial fertiliser is expensive (as it is bound to world market prices), the nutrients that are taken from the soil by harvesting crops are often not replaced.  The area of degraded soil increases steadily - one quarter of the surface land of the earth are already degraded, putting the livelihoods of millions of people at risk (SCIENCE DAILY 2009). These problems are recognised, yet we do not recognise their interdependence. We now continue to deal with them in a sectoral manner:

• If there is not enough surface water, aquifers are tapped, also in areas where these aquifers are not recharged under current climatic conditions. The wastewater generate in such a way continues do be discharged in surface water, leading to decreasing water tables.
• Water is provided without taking into consideration wastewater management, leading to pollution of aquatic ecosystems.

Nutrients that are taken from the soil in the form or plants are consumed, excreted again and discharged with wastewater into watercourses. In the long term, if they are not replaced in agriculture, this leads to decreasing yields and soil degradation. To counteract this, artificial fertiliser is mined and applied — though artificial fertilisers are energy intensive and the availability of some of the constituent parts (e.g. phosphorus) are limited (see also the nutrient cycle).

These sectoral approaches ignore one crucial fact: The water cycle and the nutrient cycle are inherently linked. When using water, be it for agriculture, for use in households or industries, water is contaminated and wastewater produced. Parts of this “contamination” are valuable plant nutrients. Wastewater is considered a waste, because of the many negative consequences it has on health and the environment it discharged in an uncontrolled manner into the environment. Yet: they need not be. Wastewater is not a waste: It is simply a misplaced resource. If we deal with it properly, it is a highly valuable resource!

• It contains a lot of nutrients that can be used in agriculture or aquaculture and can replace mineral fertilisers.
• Wastewater contains energy: This energy can be in the form of heat, which can be reused using heat exchangers, or in the form of biogas produced from wastewater (which can also be transformed to electricity).
• Wastewater contains water: After treatment, this water can be reused for many purposes such as irrigation, washing etc.

The benefits of wastewater can only be used if we consider agriculture, water management and sanitation together: 

• Each local water cycle - here indicated with the blue arrows - is influenced by water uses upstream and again has impacts on water uses downstream. Each intervention in water management must consider these issues (see integrated water resources management).
• When water is used - for agriculture, industry or households - wastewater is produced. Different sanitation options treat it in such a way that the potentials of wastewater can be used. It is essential to recognise the potentials of this wastewater. Containing nutrients and water - both crucial resources for food production - it is essential to link water management with agriculture.
• This approach should be considered on a global level. Yet, its practical implementation starts at the local level: Farmers being aware of the benefits of wastewater and using it for fertigation, industries recycling their used waters, and families using rainwater for showering, or for watering their gardens. That is why this toolbox aims primarily at the local and practical implementation level.

Such an approach to water management — linking water management, sanitation, and agriculture — is a crucial step to sustainability: 

• It closes water cycle at a local level, recharges groundwater sources and provides valuable water for agriculture.
• It closes nutrient cycle, thus making expensive artificial fertilisers unnecessary and provides a much more balanced fertiliser.
• It improves food security, and even creates additional income.
• It applies solutions that are socially acceptable, economically viable and environmentally sustainable (see also sustainable sanitation).