So why are some local drivers reporting active sprinklers on the side of San Diego highways during the day?Cellphone video obtained by 10News shows Caltrans sprinklers at 3:24 p.m. pumping out water earlier this month on state Route 163.Caltrans spokesman Edward Cartagena explained, "To reestablish those plants they have to water during the daytime."According to the city's water rules, renovation or repair of an irrigation system is exempt, which is what Caltrans said was happening that day.New public planting is another category that can be exempt from the daytime restriction. The restriction states watering is allowed before 10 a.m. and after 6 p.m. from June to October. For the rest of the year the hours are before 10 a.m. and after 4 p.m."The majority of the plants we put out there are hardier than the normal household plant. They're more drought resistant so they don't require as much maintenance, but they do still require maintenance," said Cartagena.But does Caltrans have to water even new plants during the day? Could they be watered in the morning and in the early evening?"In order to keep them alive, the schedules in which they're put on are set to give them the best chance of taking root and surviving," Cartagena said.Caltrans said it has invested $400 million in landscaping for more than 4,000 acres in San Diego County -- most of which is in the city of San Diego.The plants are not just cosmetic, as Caltrans said they help prevent erosion and mudslides and can act as firebreaks.Caltrans, however, admitted a mistake or malfunction could have them watering when they shouldn't be."We rely heavily on the motorists and the residents of San Diego to let us know when that occurs because we cannot be everywhere at all times," said Cartagena.To report any water waste in the city of San Diego, click here or call the city's water hotline at 619-515-3500.