This ties in to many ideas that are floating around out there right now. BMP’s or Best Management Practices are regulating Civil Engineers and designers to keep stormwater on site at levels of runoff as if the development was never there. So when the development was a grassland, how much water would runoff? Take that minus what runs off after development, and that’s how much you need to store.
Additional impervious area like buildings, pavement, sidewalks all contribute to how much water need to be stored. Now that we’re storing it, what do we do with it? As it stands now, we release it slowly or choke back the flow to ensure the downstream riverbeds and channels are not flooding. There’s also a lot of encouragement to infiltrate water back into the ground. In some geographical areas, that’s fine. In others, it’s not due to saturation of the soils, and expansion/contraction. There’s also the whole mosquito and critters thing to worry about when storing water on site. Keep it on too long and it becomes a potentially dangerous breeding ground for bacteria and insects.
The next step is for onsite treatment of the water, and potential reuse. The system would need to use naturally available materials to purify the water, and pump it back into the landscaping or building for re-use. This technology seems like it could break any year now. It’s just waiting for the right catalyst. Which will likely be water pricing going up. And this could be a reality, especially in the southwest.