The Lake Berryessa Watershed

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The Lake Berryessa Watershed

by Paige Norberg, Lake Berryessa Watershed Partnership

Did you know that Lake Berryessa is a reservoir and that its water is used for recreation, habitat for fish and wildlife, irrigation for farming, AND as a drinking water source for Solano County? Many people are surprised to learn that the water that they boat on has such a wide array of uses and that they personally are affected by the water quality, either directly when they drink it, or indirectly as it is used on local farms. As the water in the lake is delivered across a network of creeks, canals and pipes to the surrounding community, this watershed is critical for our region.


A watershed is an area where water is carried in the form of rain and snow through groundwater and runoff on roads to a network of storm drains, creeks and rivers that eventually converge into one water source. Lake Berryesssa naturally drains into Putah Creek and travels through Davis and into the Sacramento River and eventually into the ocean. The constructed watershed brings water from Lake Berryessa to the Putah South Canal and into Solano County.

The water supply for Lake Berryessa is derived from the 568 square mile drainage basin above the dam. (See map on Page 6.) There is no connection to the snowmelt from the Sierras. The elevation of the basin ranges from 182 feet at the dam to 4,722 feet at the upper end of Putah Creek with most of the basin lying below 1,500 feet. There are four principal creeks that flow into Lake Berryessa: Capell Creek, Pope Creek, Eticuera Creek, and Putah Creek, the main drainage of the basin.

The lake is 23 miles long, 3 miles wide, with 165 miles of shoreline and is fed by the headwaters to the 576 square mile Putah Creek watershed. Rainfall levels vary significantly by location. Moskowite Corners is usually about 10% - 20% higher in rain totals than the nearby (7 miles) Berryessa Highlands. Calistoga, Angwin, and Napa provide an interesting precipitation comparison, but they are not within the Putah Creek Watershed. Middletown rainfall is a better comparison since it is really the headwaters to Putah Creek and flows directly into the lake

The water cycle plays a crucial part in a watershed as the evaporation from the bodies of water eventually make it back into the entire ecosystem in the form of rain or snow. As John Wesley Powell, a geologist, said, a watershed is “that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community."

It is this connection to all living things that is so important to remember when thinking about Lake Berryessa as a watershed. Trash, oil, or other chemicals dumped in the surrounding areas will eventually make their way into the storm drains that connect to the creeks that flow into Berryessa. From there the water will either be consumed by humans, used for irrigation, or make its way to the Pacific Ocean. Marine debris, or trash, can then be consumed by life at sea or end up in the North Pacific Gyre, also known as the Great Pacific Garbage Patch. This swirling mass collects trash from all over the world.

This is why the Lake Berryessa Watershed Partnership is working so hard to educate boaters and recreationists about keeping the lake clean. Our watershed and our entire region will benefit if each one of us do our part by not polluting and picking up litter. Remember, if you wouldn’t want to drink it, don’t put it in the lake! 

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pKilkus@gmail.com                       © Peter Kilkus 2020