Natural Perspectives: Winter snows crucial to our water supply

One of the most dramatic portions of McBride's talk, and of the book, covered the last section of the river. A hundred years ago, the Colorado River flowed free and unfettered all the way to the Sea of Cortez.

No more.

The river stopped running to the sea in the late 1990s. We've used up all of the water in the river and it no longer ends its run at the ocean. It dries up miles before it reaches the sea.

Before the river soaks into the soil and disappears, it changes from a free-running torrent to a sluggish, trash-filled trickle. The surface is coated with a thick layer of foamy mousse, the result of pollution at its worst.

Waterman made the mistake of putting his feet in the water when the river became too shallow to paddle, and was hobbled with infected feet for the last 60 miles of his journey.

The Imperial Valley is one of the many areas that uses Colorado River water for irrigation. Farmers there have installed drainage tiles under the soil to prevent salt buildup. By the time the river reaches the Imperial Valley, it has been used over and over, and has collected a load of salts and minerals.

There are two series of canals or ditches throughout the Imperial Valley. One series brings in water from the Colorado River to irrigate the agricultural fields. The other collects water that has soaked through the soil of the farmers' fields and dumps it into the Salton Sea.

In 2003, during the George W. Bush administration, a pact between the Imperial Valley Irrigation District and the County of San Diego transferred water from the farmers to urban dwellers in San Diego. The agreement was touted as the largest transfer in the nation of water from agriculture to cities.

The loss of water to the farmers meant not only that fields would lie fallow, but also that the used irrigation water would no longer be flowing into Salton Sea. Even though that water was polluted with pesticides and salts, it kept the water level of the sea at a steady level. Now, that the sea is receiving less runoff, water is receding further and further from the shoreline.

Vic and I were at Salton Sea this past weekend, where Vic led a Sea and Sage Audubon birding trip. We saw that the shoreline at Red Hill Marina has receded many hundreds of feet since last year, and almost an equal amount the year before that.

The dried lake bed is now covered with a salty crust just like at Owens Lake below the Eastern Sierras. The desiccation of Owens Lake has resulted in clouds of toxic dust when winds blow.