There's a new (March 2018) report out about stormwater infrastructure in Los Angeles. Among the many tidbits (well sourced) are:
-In a typical year in Southern California, rainfall harvested from a 1,200 square foot roof can save 10,000 gallons of water.
-By reducing water imports, L.A. County could save enough energy to power 20,000–65,000 households annually.
-The City of Santa Monica generates over four million dollars annually through two different storm water fees.
Read the entire report here.