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Water
All life depends on water for survival. Two goals of watershed protection efforts in Napa County are:
- protect water quality
- protect water quantity
Improving water quality means preventing water pollution. Non-point source pollution (pollution from diffuse or scattered sources) is the nation's leading cause of water degradation and is a concern in Napa County. As rainwater flows across streets, yards, construction sites and agricultural fields, it picks up sediment, oil, fertilizers, pet droppings, and other pollutants. These are carried into channels and storm drains that empty into our waterways. Understanding and managing non-point source pollution is a major strategy for protecting water quality in Napa County.
Improving water quantity means making better use of the water supplies that we have. Establishing long-term water budgets, monitoring groundwater and stream flows, minimizing water use, and increasing the use of recycled water are some of the practices being implemented throughout the county to make water use more efficient. Residential water conservation information is available through your local water provider, or visit www.wateruseitwisely.com
Weather
The Napa Valley has a Mediterranean climate characterized by warm, dry summers and cold, moist winters. The majority of annual precipitation occurs as rain that falls during the winter and early spring.
The highest rainfall occurs on the western side of the watershed. Rainfall gages also show a north-south trend of precipitation in the watershed.
The average annual precipitation is 35–40 inches in the western portion of the watershed, and 20–25 inches in the eastern portion of the watershed (1961-1990, Western Regional Climate Center 2002). Average annual precipitation is 38 inches at Calistoga and 25 inches at the Napa State Hospital (1961-1990, Western Regional Climate Center 2002).
The average daily maximum temperature is lower in the south (Western Regional Climate Center 2002), because coastal fog keeps the lower valley cooler.
