It’s a sweltering summer day, no rain for months, but Nichols Canyon Creek is gurgling merrily on its two-mile journey from a rocky outcrop high in the Santa Monica Mountains to the white-hot sidewalk of Hollywood Boulevard. As California languishes in drought, the spring-fed creek is cool and shaded by sycamore, oak, sumac, and laurel. Houses overlook its banks. Birds and insects flit above the water. Frogs croak. Deer, coyotes, and other animals quench their thirst.