Napa River headed for another tipping point

Letter to the Editor, Napa Register


In June, Napa County voters will be asked to consider Measure C -- the Watershed and Oak Woodland Protection Initiative. This measure will protect some of the last intact uplands from development for viewshed considerations, increased recreational access, and protection of biodiversity and clean drinking water sources.

I am a consulting fisheries and watershed scientist, and I offer my perspective on the benefits, if Measure C passes, and a note of caution about potentially irreversible impacts to domestic water supplies, should Measure C fail.

The Napa River was the largest salmon and steelhead producing tributary of San Francisco Bay and had robust, fishable populations of steelhead trout and Chinook and coho salmon into the 1950s. Today these fish species have gone extinct or have been reduced to remnant populations. The change in the aquatic habitat over the last 70 years is profound, and the loss of these iconic species is due to the wholesale change in the aquatic environment. We have passed an ecological “tipping point” and the Napa River has almost no functional coldwater habitat that these species require.

The cumulative effects of water development for municipal and agricultural supply have caused tributaries to become dewatered. The main Napa River was once fed by groundwater on the valley floor, but pumps installed to water the vineyards have reduced or eliminated coldwater contributions to the lower Napa River in summer. The result is that the main Napa River is now a warmwater habitat where exotic fish species, washed down from reservoirs, proliferate and Pacific salmon species cannot survive. Studies by the University of California and Stillwater Sciences documented that most tributaries of the Napa River lost surface flow in 2001 and that steelhead juveniles were extremely rare.

Steelhead are amazing animals. They can live as resident rainbow trout in headwater streams, such as Bell Creek, upper Conn Creek and Milliken Creek, but they can also adopt an anadromous life history, if they are washed downstream to the bay. Steelhead adults that have been to the ocean can leap more than 15 feet, which allows them to reach the headwaters in wet years and replenish some trout populations.

Upland development of Milliken Creek, near the Walt Ranch Project, and the Le Colline project in upper Conn Creek, would impact water-bearing areas that support rare native trout populations. Desiccation associated with these projects would drive these populations further towards extinction, which should be sufficient reason for blocking such developments.

However, there is another even more important concern – to protect the water supply for the City of Napa and for other domestic water users.

Water storage reservoirs were constructed in the eastern portion of the Napa River watershed to provide drinking water. When first constructed, they were clear and cold and excellent trout habitat year-round. Steelhead confined to these artificial impoundments began to use them as their feeding grounds, and subsequently spawned in headwaters when they were only few inches in length.

Historically, headwater streams had robust, cold, perennial flows into these impoundments, until upland vineyard and rural residential development proliferated. As flows have diminished, the quality of water in Napa River reservoirs has deteriorated, and they may be on the verge yet another tipping point, developing toxic cyanotoxin blooms that would compromise domestic water supplies.

In summer, cold creeks flowing into reservoirs create a cold water lens at depths that trout can inhabit. Without this cold water input, surface waters heat up, creating ideal conditions for the formation of cyanobacteria, some of which are toxic. Nutrient run-off from leaky septic tanks or agricultural activity can further fuel cyanobacteria growth.

Cyanobacteria, also known as blue-green algae, are photosynthetic bacteria that have inhabited the earth for a billion years. Not all species are capable of producing toxins and those that can, don’t produce them at all times. Proliferation in water bodies around the world is likely being caused, in part, by global warming. However, the greatest influence is land management in areas upstream of reservoirs and lakes. Lake Chaohu in China is now dominated by the toxic cyanobacteria Microcystis, and 20 million people are drinking bottled water as a result. Closer to home, Pacific Northwest and California reservoirs are experiencing toxic cyanotoxin proliferation, including some operated by the East Bay Municipal Utility District.

Passage of Measure C will help protect oak woodlands, biodiversity, aquatic habitat, endangered steelhead trout, and the community’s water supply. Development pressures and the influence of big money have made protection of Napa Valley uplands challenging.

It is time the people spoke through the initiative process, before it is too late.

Patrick Higgins

McKinleyville, California