The water resource, energy and economy aspects of rainwater collection are assessed to evaluate rainfall collection as an alternative option for sustainable water supply. A maximum of 229 million m3/year of rainwater can be collected from Danish roofs, provided that all possible surfaces are used and all rain falling on the surfaces is collected. This is equivalent to 24% of the total present production of drinking water, which is mainly based on groundwater. From household roofs 64.5 million m3/year can be collected if used for toilet flushing and washing of clothes. This is 68% of the actual demand for toilet flushing and washing of clothes in households and 22% of the total water consumption in households, but only 7% of the total present drinking water production in Denmark. From the society point of view there is neither an environmental nor an economic reason to systematically promote rainfall collection on a larger scale in Denmark. Thus it is important to see rainfall collection in a local context, and in each case to evaluate whether there are cheaper alternative water sources or options for minimising the water consumption.
Collected rainfall as a water source in Danish households - what is the potential and what are the costs?
P. S. Mikkelsen, O. F. Adeler, H.-J. Albrechtsen, M. Henze; Collected rainfall as a water source in Danish households - what is the potential and what are the costs?. Water Sci Technol 1 March 1999; 39 (5): 49–56. doi: https://doi.org/10.2166/wst.1999.0221
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