<p>When people think of San Diego, they don't necessarily think of rivers. That's partly because many of the region's waterways are ephemeral, and they run underground for the majority of the year.</p><p>Yet, San Diego is part of an important, and increasingly threatened, watershed. There are hints of the water's power when local streams and rivers breach their banks during storm events. The overflowing water can close roadways and access to homes and businesses. The problem&nbsp; has gotten worse thanks to development encroaching onto floodplains.</p><p>(Related: "<a href="http://greenliving.nationalgeographic.com/deforestation-effects-global-scale-2214.html">Deforestation and Its Effects on a Global Scale</a>")</p><p>Let's take a brief tour of the San Diego area's unique watershed, and visit recent efforts to better protect it.</p><p><em>—Shannon Switzer</em></p><p class="MsoNormal"><em>This story is part of <a href="http://news.nationalgeographic.com/news/clean_water_crisis.html">a special National Geographic News series</a> on global water issues.</em></p>

Over the Bank

When people think of San Diego, they don't necessarily think of rivers. That's partly because many of the region's waterways are ephemeral, and they run underground for the majority of the year.

Yet, San Diego is part of an important, and increasingly threatened, watershed. There are hints of the water's power when local streams and rivers breach their banks during storm events. The overflowing water can close roadways and access to homes and businesses. The problem  has gotten worse thanks to development encroaching onto floodplains.

(Related: "Deforestation and Its Effects on a Global Scale")

Let's take a brief tour of the San Diego area's unique watershed, and visit recent efforts to better protect it.

—Shannon Switzer

This story is part of a special National Geographic News series on global water issues.

Photograph by Shannon Switzer, National Geographic

Pictures: Reclaiming San Diego's Vital Rivers

Surrounded by desert and ocean, San Diego is watered by several rivers. They face threats from mining, pollution and overuse, but they also support important species, and occasionally still flood.

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