A rivulet (actually, many of them) runs through it

Here in Los Angeles, we've paved over almost all of the coastal sagebrush, bulldozed hillsides, channeled our rivers and streams, and filled in our creek beds.

Mother Nature has taken a real beating. But she hasn't given up the fight.

In the middle of August, weeks after the last serious rain, she is sending pure, cool water flowing through the city of Los Angeles and environs. The fresh water runs in a handful of places as it has for centuries, in the perennial streams and riverbeds that soothed the thirst of Spanish explorers and settlers almost 300 years ago, and before them, the Tongva Indians.

Underneath the Westside traffic on Wilshire Boulevard, a small creek flows south. It's filled with groundwater that's percolated, very slowly, down from the Santa Monica Mountains. Near the corner of Wilshire and Barrington Avenue, the stream makes a right turn, then surges upward through an earthquake fault on the campus of University High School in Sawtelle.

Last week, I watched the water bubble up at a spring next to a school science building. At the bottom of a pond about 12 inches deep, I could see the water pushing up through sand, oozing like some Hollywood special effect.

"Seeing this is like a religious experience," said Jessica Hall, who writes for the "L.A. Creek Freak" blog.

Indeed, there was something miraculous about reaching down into a pool of water in the middle of L.A.'s urban sprawl, and then cupping my hand to take a drink. I felt transported in time to the unspoiled Los Angeles that was a little village surrounded by rivers that ran rocky and free.

I also got a taste, perhaps, of the Los Angeles of the future.

Before it was developed in the 20th century, the western half of Los Angeles was covered with streams, most of them tributaries of Ballona Creek. Hall, 41, is one of a small band of activists who are documenting that old watershed and trying to bring stretches of it back to life.

She can tell you where streams like the Flower Garden River used to flow. Or the Sacatela, which ran south from Los Feliz -- underneath the current location of the famous Shakespeare Bridge -- all the way to the Mid-Wilshire district.

Beneath the asphalt and concrete, Los Angeles is a city crisscrossed with dormant streams. Hall tracks their paths using old U.S. Geological Survey maps, aerial photographs and what she finds during long walks through the city.