Regional Air Quality Plans -- San Joaquin Valley Unified APCD

This page updated June 27, 2003.

Graphic: San Joaquin Valley Regional MapThe San Joaquin Valley Unified Air Pollution Control District occupies the southern two-thirds of California's Central Valley. The eight-county area comprises Fresno, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare counties and the western portion of Kern County.

The Valley spreads across nearly 25,000 square miles. With very few exceptions, the San Joaquin Valley is flat and unbroken, with most of the area below 400 feet elevation. The Valley floor slopes downward from east to west, and the San Joaquin River winds its way along the western side from south to north. Similar to other inland areas, the San Joaquin Valley has cool, wet winters and hot, dry summers. Generally, the temperature increases and rainfall decreases from north to south.

About nine percent of California’s population, or 3 million people, live in the San Joaquin Valley, while pollution sources in the region account for about 14 percent of the total statewide criteria pollutant emissions.

In contrast to other California areas, air quality in the San Joaquin Valley is not dominated by emissions from one large urban area. Instead, there are a number of moderately sized urban areas spread along the main axis of the Valley; chief among them are Fresno, Bakersfield, Stockton and Modesto. This wide distribution of emissions complicates the challenge faced by air quality control agencies.

Regional Air Quality Plans