Not knowing anything about geology, why aren’t we undertaking massive earthworks projects like the Romans apparently did: dig a giant deep hole and wait for it to fill up with rain?
We did. Look around a map of Southern California. Many dams created the reservoirs you are asking about.
Usually where it is needed it does not rain much?
- cost of the dig or dam
- loss of land use that goes underwater
- cost of transporting the water to where you need it
- if it is just a really deep & big hole, you have to pump it back up to then transport it or you could lump that in with ‘cost to transport.’
Y(?) MV
Most rain when gathering into substantial quantities flows into rivers and lakes; so basically, you are asking why wouldn’t we build giant reservoirs on some rivers?
First, along with run-off comes silt. a big problem with a lot of dams is they slowly fill up with silt, meaning they hold a lot less water.
Second, in any area where water is hard to get (California? Arizona? Anywhere in the west) the water rights in a river watershed are already spoken for. Virtually nothing leaves the Colorado river, it’s all sucked out along the way. Whatever you take, is stolen from someone else with a prior claim. I recall some article where the person mentioned that the water rights laws(Colorado? Arizona?) forbade them from putting a rain barrel to catch roof run-off.
Third, scale - there’s not that much rain and there’s too many people. The Romans usually had to worry about “cities” of around 100,000 people; that’s a small suburb in California. The Romans used water for drinking and cooking. Except for public baths, they didn’t have a lot of other uses - they didn’t each take a private bath and throw out the water, they didn’t water expansive lawns, wash cars, fill swimming pools, etc.
The cisterns at Masaada, for example, captured the occasional rainstorm - a few a year - and guided the runoff from the nearby hills into large caverns where the water was stored for the rest of the year (yum!) It only had to support Herod’s Palace or a small garrison. Larger cisterns, as are found in Pompeii or Constantinople, were fed by aqueducts from regular water sources uphill and were filled as fast as they were emptied - and this was not a dry climate. The city at Petra in Jordan relied on water fed through piping along the Sook (the narrow canyon leading into the location). When that feed was broken after an earthquake, the place became deserted for centuries.
What the American Midwest has been doing is almost the same as what you suggest - they’ve dug wells into the underground aquifers. What took millennia to fill up is close to being drained within a century.
And the reservoirs that exist can’t be filled by current sources. Which means there’s no point in building more reservoirs.
Agree. When the existing reservoirs are not filling then building more reservoirs will not give you more water.
Orange County is not only reclaiming sewer water, they are actively injecting the purified waste water back into the aquifer.
They are also removing silt from some reservoirs.
From 2009: It’s Now Legal to Catch a Raindrop in Colorado. The five-year-old article says it’s still illegal to catch rainwater in Utah.
Very well-written and informative. Thank you.