Water conservation in Doha

Sadly, the post title is a bit of an oxymoron. I regularly see people washing the street in front of their house with a hose, or washing their car with a hose that they leave running as they scrub, or just plain leaving a hose running for no apparent reason. Considering that it's illegal to use potable water for any purpose other than drinking, bathing, or washing indoors, and it's rumored to take the energy of 7 gallons of oil to produce one gallon of desalinated water, these are pretty blatant abuses of the system and the environment. But one of the most irritating ones that hit really close to home for me is our neighborhood's automatic water tank cleaning system.
Once a month, each villa in our compound gets a waterfall off its roof as a pump (at least partially) empties its rooftop water tank of between 100 and 200 gallons of potable water. Supposedly this is to prevent buildup of sediment in the tank, which is believable--but also wasteful. So I went on my roof one day while we had our monthly waterfall and found the hose out of which the water was spraying. I put a 30-gallon storage tub under it, and then another, and then another, and I'm sure if I had gotten there just as it started, I could have filled four of them easily. As it was, I still caught some water as it flowed off our roof, and that's when my neighbor drove by and got this shot:

So then I bought 10 meters of hose, a hose connector, and two hose clamps, and now we have the drain hose leading down our house into these tubs, and we can water our garden and wash our car all month with this saved water!