Multiple use of water is the practice of using water from the same natural or man-made system or infrastructure for variety of uses and functions. During the acute emergency phase, the focus is on providing a sufficient quantity of safe drinking water, as this is critical for maintaining good health. The demands of climate (e.g. dry climates) or health status (e.g. nursing mothers) may require additional water. Likewise, health-related emergencies must be prioritised for access to water to assure sufficient quantities for clinical use (i.e. hand washing, cleaning, equipment washing, medical care or oral medication). Additional water may be necessary depending on the population and situation. In any situation, water users, not water providers, will choose how they allocate water, so it is important for water providers to understand user priorities and identify where the priorities of users and providers do not align (i.e. users may prioritise watering livestock over handwashing). In these cases, providers should aim at providing enough water for both users and other priorities, although not necessarily from the same source or of the same quality.
During the post-emergency phase (stabilisation and recovery), additional water is required at the household level for small-scale productive uses, such as backyard gardens, livestock, or micro-enterprises. Wherever possible, emergency water systems should be designed to consider possible future applications to sustain multiple community water-use needs in the post-emergency phase. For example, spillage water from tank overflows or tap stands can be led to nearby run-off gardens or animal troughs. Rainwater harvesting systems can have a portion of harvested water treated for drinking purposes, and the remaining quantities can be used for productive use or livestock. In water scarce areas, communities often do not differentiate between water for domestic and non-domestic uses, so the water supply systems should be designed with multiple water uses in mind to achieve the desired impact and avoid competition within the community. Emergencies also affect commercial, agricultural, institutional and industrial users who will also see their water needs as essential. Although not a key priority in the acute phase, these additional water use requirements need to be considered (and balanced) during the stabilisation and recovery phases.
To successfully operate multiple-use water systems, an advanced level of organisational management and a stable communal context is needed. Proper assessments should assure that the water use requirements of different user groups are considered so that all are willing to fully collaborate with the operational and maintenance aspects of the water system. For this reason, it is essential that the assessment is conducted inclusively and considers social norms and habits to assure that multiple-use and reuse water are applied in a way that is acceptable for the community.Water from liquid precipitation.
Water reuse is the use of (treated) wastewater for alleviating water shortages and increasing a community’s available water supply. This is particularly important to counter the decline in available water resources for agriculture, domestic, livelihoods and industrial uses due to climate change, population growth or droughts. Water might be used directly without treatment (e.g. for flushing toilets) or be treated to the level required for the reuse purpose (reclaimed water).
Water reuse can be divided into potable and non-potable purposes. Design considerations for potable water reuse are complex and beyond the scope of acute emergency interventions if such technologies are not already applied in the affected area. Municipal water reclamation is therefore not often available in the acute phase, though could be useful for longer-term situations, particularly in areas with limited water access. Water reuse for non-potable purposes, (e.g. watering gardens, cleaning) is feasible in a post-emergency context after careful consideration and management of the contamination risks. Spillage water from tap stands can be used to water animals or, along with un-treated water and reclaimed water from bathing, handwashing and cleaning can be used for agriculture. Water that has been biologically contaminated should only be considered for non-drinking purposes (e.g. irrigation).
Greywater (water from bathing, cooking and cleaning dishes or clothes) offers a lot of opportunities for reuse in gardening and agriculture, as it is less contaminated than wastewater. Rainwater can be reused for artificial recharge to replenish groundwater basins in areas that depend on groundwater extraction for drinking water supplies. Necessary precautions (e.g. filter systems) may be needed to avoid groundwater contamination.Water generated from showers, bathtubs, washing clothes, handwashing and sinks.Water from liquid precipitation.