Rain water harvesting is an important topic in environmental controlling and internal optimisation of input and output of resources in operation systems. It could reduce the cost of water expenditures as well as it could be a burden if not well managed not to dilute with other substances/solutions/gases to provide contaminants. This reminds me of some consultants activities that i have carried out in some companies that i will provide two examples. A carrot farming /buying and processing firm (water intensive company) was about to close up because it was only breaking even. I did an environmental controlling assessment and recommended on rain water harvesting, and recycling of waste water and reuse. It was done and the profit margine rised drastically. On the other hand, while for a case of a maintenance operation that i was involved for a performance evaluation, i discovered that the rain water harvested for washing activities passes through many potential polutant sources (waste oil, gaseous and other liquids) that could mixed up to form contaminants and provide risk to workers and the open environment, eventhougth after the washing activities, the waste water is well drained. This may also provide huge cost for waste water handling, especially in regulation countries like Germany that has regulations on the continuous declaration on operations that lead to mixture of substances in waste water.

Rain water harvesting is part of the Green Infrastructure projects including, but not limited to so called "Blue Roofs" and other concepts. It may not be justified economically, while it finds its way as we are looking to save water.

Rain water harvesting is productive in area where water levels are low and hilly area by check dams which can be used as per requirement and even agricultural activities.

THE BLUE ROOF

A blue roof is a roof design that is explicitly intended to store water, typically rainfall. Blue roofs that are used for temporary rooftop storage can be classified as "active" or "passive" depending on the types of control devices used to regulate drainage of water from the roof.

A number of blue roof pilot projects have been implemented around the United States. Active blue roofs for storm water detention using forecast integration were first proposed in 2008. Active blue roofs are sometimes as automated roof runoff management systems.

Any thoughts?

If it takes 10,000 litres of water to produce one pair of jeans, we really need to capture every drop of rainwater (and out it to better use!).
It's still February in the UK and temperatures have been around 20 Centigrade (they are usually 5C). I'm having to water my garden as usually dormant plants are starting to grow. I have rainwater collection capacity of 2000 litres in my garden and still will run out during the Summer.