Madera County

Geological Influences

Volcanic activity has been the primary, long-term generator of soils in Madera County. Whether the loam is gravelly, sandy, silty, or even clay, the origin material is substantially granite. The granite was created millions of years ago by underground lava flow. Slow but epic tectonic shift then uplifted the granite to form the Sierra-Nevada Mountain Range.

Mountains/River/other key influences

The slopes of the Sierra Nevada mountain range have been influential as a source of soil and for the water that runs off them. But the mountains don’t have an important effect on the climate of western Madera County, where the grapes grow. Likewise, the county is 100 miles (161 km) from the Pacific Ocean and separated by at least two mountain ranges, so the ocean is not an influence.

More important is the San Joaquin River. It runs roughly southwest from the Sierras through Millerton Lake and then meanders into the valley where it eventually splits, heading north as a river and south into the Fresno Slough. While on its westward path, the San Joaquin River forms a dividing line between Madera and Fresno Counties.

Soil Diversity

As with most counties, there are many soil series. However, in the main growing areas of Madera County, just two pairs of series are both widespread and considered good for grapes. Both the Hanford-Tujunga and Dinuba-El Peco pairs are alluvial soils. 

The associations are paired like this because they are very similar, but distinct from each other in a minor, but meaningful way. For example, Hanford is well-draining, whereas Tujunga is excessively draining.

Hanford-Tujunga are both deep, good-to-excessive draining soils of moderate to coarse grain, sometimes atop a layer of silt. The origin material is primarily granite. The water table is very low due to many years of pump extraction. 

Dinuba-El Peco are older alluvial soils with more clay and silt than Hanford-Tujunga. In many areas, those layers have been compressed into impenetrable clay hardpan. These two series are moderately to poorly draining. They can both contain levels of salts and akali unsuitable for grape growing, so planting needs to be selective or the soils must be amended.

In the eastern foothills, there is Vista Sandy Loam. That’s a soil common to the lower foothills within many counties of the Sierras that have low to moderate rainfall. The terrain is gently sloping and drainage is good. The water table is low. Alkali isn’t a problem though. The primary origin material for the sandy loam is granite eroded from the mountains. In actively used areas, the most typical application is range land. But grapes and fruit trees do well too.

Climate

The Madera County climate is hot and dry. Technically, the designation is steppe. Steppe climates get a little too much precipitation to be categorized as desert. However, given the high heat, rainfall is still low enough that evaporation is often at least equal to rainfall. So, if aquifers are to be replenished, the water must come from rivers or canals.

Madera County winegrowers often refer to the San Joaquin River, detailed above, as a moderating influence on the climate. However, that effect is both minimal and localized, because the river is at the very southern and western edges of the county.

Madera AVA

Location/Geography

230,000 acres (93 ha) in Madera and northern Fresno Counties, within the San Joaquin Valley

Name Background

The AVA was named for the county and city of Madera. The county was also named for the city, which was given its name when the area became a distribution point for the California Lumber Company in 1876. Madera means “timber” in Spanish.

Topography/Elevation/Water Sources/Geographic Features

Low altitude and primarily flat, though a small portion extends into the Madera foothills. Irrigation is required. The main water source is wells tapping underground aquifers. Due to high use and climate change, dry wells are becoming a serious problem for farms and residences.

Geology/Soil Composition

Most of the AVA has deep, alluvial soils. The Madera foothills feature Vista Sandy Loam of shallow, granitic schist

Climate

Steppe with heat summation indicating Winkler-Amerine Region V (hot)

Main Grape Varieties

• French Colombard
• Chardonnay
• Cabernet Sauvignon
• Merlot
• Zinfandel