SAN DIEGO -- New restrictions on when and and how often San Diego residents can water their lawns will go into effect Sunday.

Sprinklers can run seven minutes at a time, down from 10 minutes, and residents can water lawns before 10 a.m. or after 4 p.m. The afternoon restriction had been 6 p.m.

Unchanged is the three-days-per-week limit on watering. Homes with odd-numbered addresses will be permitted to water on Sunday, Tuesday and Thursday. For homes with even-numbered addresses, watering is allowed on Saturday, Monday and Wednesday. Apartments, condominiums and businesses can water only on Monday, Wednesday and Friday.

The regulations are outlined in a 15-second "No Time To Waste -- No Water To Waste" public service announcement to begin airing locally. According to Mayor Jerry Sanders, San Diego residents have reduced their overall water usage by about 13 percent since mandatory restrictions were enacted in May.

San Diego's water supplies are threatened by years of drought which, combined with restrictions on the amount of water that can be pumped from the Sacramento-San Joaquin River Delta, has led to shortages in Southern California.