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Comment by esturk | Hacker News Reader

I've always wondered how sensible is it to dig temporary holes/ditches that will store excess amounts of water and then later fill it back up once we're done with it. This is similar to how an empty swimming pool may be used to store excess rainfall. Perhaps the work put into it isn't worth the effort?

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India's arid areas appear to have some experience with 'check dams' for precisely this purpose - turning monsoonal wet seasons into year-round wellwater.

http://lawschool.unm.edu/nrj/volumes/48/3/03_agoramoorthy_in...

http://www.researchgate.net/publication/247773763_A_review_o...

http://www.iwmi.cgiar.org/Publications/CABI_Publications/CA_...

Digging ditches is much less cost-effective for this purpose than building small dams, though they seem to have also worked with those, ditches filled with rocks under a cover and used as a storage tank.

I think that's what Stepwells are all about.

https://en.wikipedia.org/wiki/Stepwell

https://www.youtube.com/watch?v=ilWbowNv5PI <- This is a huge stepwell, to give you an idea of why these can be so amazing.

Is this not what reservoirs are?

Right. It is impractical to dig a ditch big enough to matter. That's why you damn up mountain canyons instead.

It's very worth it. I can't find the link now, but there was a great article about traditional wier/retention pond building in Africa that both provided water but also helped recharge the local wells. The system had fallen into disrepair, and one local evangelized rebuilding the structures. It really took the entire community to rebuild and maintain, but improved the quality of life massively.

https://en.wikipedia.org/wiki/Groundwater_recharge

> Groundwater is recharged naturally by rain and snow melt and to a smaller extent by surface water (rivers and lakes).

This doesn't work when you've collapsed your aquifers through excess pumping.

http://news.nationalgeographic.com/news/2014/08/140819-groun...

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