If you’re ready to head to a sunnier climate this winter to do some desert prospecting, understanding the weather and topography can add to your success. Before loading up and heading to the Southwest, only to be disappointed by bad weather, first check out the weather patterns for the last 60 days and the predicted weather for the next 30-60 days. Why is that important? Well, it mostly comes down to rainfall— how much and how fast. For example, if there will be a lot of rainfall over an extended time, soils will be loosened and gravity will do its job and cause deeper, and sometimes more concentrated, pay streaks. In general, cool season precipitation (October through April) is the most extensive source of rain in the desert regions. Rainfall is more widespread and of relatively long duration during the cool season. On the other hand, warm season precipitation (May through September) results largely from convective precipitation in the form of short monsoon-type thunderstorms.
There are three major desert areas that make up the American Southwest:
The roughly 200,000-square-mile Chihuahuan Desert stretches from the southeastern corner of Arizona across southern New Mexico and west Texas to the Edwards Plateau. It runs deep into central Mexico,The Chihuahuan Desert is the most moderate of the three deserts, made up of low and high desert regions and grasslands. It sees the most rain on a regular basis throughout the year with anywhere between 8-12 inches, and areas in New Mexico receive up to 17 inches per year. Unfortunately, because of the Chihuahuan Desert’s higher altitude in southern New Mexico, and the rain patterns there, winter prospecting is a real challenge, especially dry washing. October - March averages 2 inches of rainfall per month, with an average daytime temperature of 55 degrees, making it hard for the ground to dry throughout the season. The pay layer in the Chihuahuan Desert is most likely going to be deeper and more evenly distributed and more highly concentrated than in the Sonoran Desert, but there will be a lot of effort needed to stay on track sampling to find the richest pay layer.
The Sonoran Desert occurs primarily in Mexico. In the USA, most of it can be found in the southern third of Arizona, with small areas in southeastern California.The Sonoran Desert region of Arizona receives between 3-20 inches per year, but these numbers are skewed for the actual low desert gold-bearing region of the state. The Sonoran Desert encompasses a large section of high desert area, ending a few miles south of Prescott, Arizona, following a higher elevation line to the east and west. The normal rainfall in the lower elevation gold-bearing areas of Arizona averages 6 inches annually, all of which falls in about 30 days and includes the monsoons. Yuma is considered the driest area of the state with only 3 inches of rain on average.
The Mojave Desert is primarily in southeastern California and southwestern Nevada, with small portions extending into Arizona and Utah. It has a large amount of high desert elevations and has skewed numbers for the majority of the gold-bearing areas. Lowland areas at less than 1,000 feet elevation average 3.7 inches per year of rain, while Granite Mountain at 4,200 feet above sea level averages 8.5 inches annually. Rich pay layers have been found northwest of Barstow, California by testing and eliminating low to no pay overburden. This area is known for seismic activity with several earthquakes and aftershocks occurring west of the 117 degree meridian, which helps in concentrating gold.
When prospecting in the desert, it’s a good idea to test larger areas in compass headings— testing every few feet north to south to find highest values, then east to west of that spot. Doing so provides you with a line in the desert for further testing. Because of the extended days of rainfall in the Chihuahuan and most of the Mojave compared to the Sonoran Desert, you’ll likely discover a shallow and slightly more compacted layer of good material that is worth processing. However, this “pocket gold” layer can be directly above the really good pay layer you want. Finding gold and digging straight down without continued testing and sampling is not taking advantage of the forces of nature, especially that of water following the path of least resistance and taking the heavies along for the ride. In other words, don’t settle for just any pay layer— follow and use the over burden to get to the BEST pay layer!
If you are planning a desert prospecting trip far in advance, it’s a good idea to start checking weather patterns in April, which is when desert prospecting begins to wind down. That way you will be very prepared when the following fall and winter rolls around. That also gives you time to form a Plan B if the weather is not conducive to your Plan A. If you are a member of Gold Prospectors Association of America (GPAA), there are hundreds of opportunities across the Southwestern states to get on the gold at a GPAA claim. Knowing a little about desert geology is a great start to understanding more about the “why” and “how” gold deposits are formed. And weather is a key factor in knowing “where” gold settles after it breaks from the lode and residuals. Get out there and get your share! Good luck getting the GOLD!