San Francisco is surrounded by water on three sides. But even in these dry days, it's also oozing water from within. Dozens of springs and streams are hidden within the city, and a new map plots these freshwater sources, many of which lie buried underneath the city's streets.

The map is the product of decades of research by writer and natural history educator Joel Pomerantz. In a recent Kickstarter campaign, Pomerantz raised more than $10,000 to produce the map and a companion book, due out later this summer, that documents his research and provides directions for urban hikers interested in tracking down historical and current waterways. Both will be sold at local stores and on the website for the project, which Pomerantz calls Seep City.

The Seep City map hints at how water (or the lack of it) has shaped the city's past and present. It sketches the city's original shoreline, rounded out with landfill during the Gold Rush and subsequent booms. That past came calling in 1989 when the Loma Prieta earthquake stuck, liquefying the filled in ground under parts of the Marina District, causing millions in damages.

Joel Pomerantz/Seep City

The most surprising thing about the map is the freshwater springs and streams. At one time, they supplied water to residents and businesses. A bottling company in the Mission drew groundwater from beneath its property to support its operations; so too did a nearby laundry, Pomerantz wrote in a historical essay a few years ago.

The Wiggle, a popular bike route that zig zags around several hills so cyclists can get from the Mission or downtown to Golden Gate Park without breaking a sweat, follows a waterway of sorts. Native Americans apparently used the same route as a footpath, and Pomerantz traced its course, in part, from a mid-1800s photograph showing a line of willow trees lining what must have then been a creek flowing on the surface.

Joel Pomerantz/Seep City (top); San Francisco Bicycle Coalition (bottom)

The area is mostly sand dunes, and rainwater filters through the sand down to an underlying bedrock canyon, that drains at a spot near what's now a corner of Duboce Park, Pomerantz says. The area is almost entirely paved and built up now, but several months ago a new brewery hit underground water along The Wiggle during seismic renovations. They say they hope to use it for cleaning, or maybe eventually for brewing.

Groundwater was more plentiful in the early days of San Francisco than it is today, Pomerantz says. It's been diminished by the construction of hard surfaces and the diversion of creeks and springs into sewers as the city developed. Since 1934 the city has gotten nearly all its drinking water from the Hetch Hetchy reservoir, 160 miles away in the Sierra Nevada mountains.

But the groundwater isn't entirely gone, and there may be renewed interest in tapping into it during the drought, Pomerantz says. "Recent changes in Water Department policy allows for a few percent of SF's tap water to be from the Westside Basin aquifer, mixed in to the rest of the supply," he said. "Also, Golden Gate Park and the Presidio (including its tap water) are mostly from groundwater sources now."

Pomerantz hopes the map and book will spark some curiosity and get people thinking about the relationships we have with our natural environment. He also hopes it will motivate people to get out and explore. "San Francisco is still a place where you can see water seeping up from the sidewalk or coming out of a hillside, but people don't even know it's there."