Paul,
Success in an arid climate is about predictability. Average precipitation numbers are just that -- averages. If you average 10" of rain a year, that could be considered as a lot of
water, but it depends on if you can count on getting about 10" of water each year and when in the year you get it. Most successful agriculture in arid climates is based on irrigation using surface water resources whose drainage covers areas many times larger than the area being irrigated, and/or groundwater.
If you have no access to, or cannot afford, either conventional surface water or groundwater, you are stuck with making the most of the water that falls on your property -- in most cases, without impounding it. This is usually done by using dry farming techniques, which can be combined with runoff agriculture for greater success.
There are varieties of plants that have been selected over the millennia to thrive under dry farming. Varieties from the American Southwest, the Middle East and Central Asia would be a good start.
Whether dry farming or irrigating, soil amendments, such as organic
compost, charcoal and/or expanded clay/shale will help with retaining water in the soil. Mulch is also very useful in keeping the evaporation rate down. If organic matter is in short supply, which is likely in an arid climate, you can use gravel or rocks (Lift with your legs. Keep your stomach tight and your back straight. Don't twist.) If you are irrigating, plan on investing in drip irrigation and/or greenhouses to extend your productivity.
Anticipate drought. Wet years are not normal years in arid climates. Make the most of them when they come, but don't get fooled into thinking it will last. The West is filled with ghost towns built during wet cycles.
Anticipate flooding. Build permanent structures assuming that natural drainage systems are full of water, because they may be some day -- or night. The West also has its share of ghost towns that fell victim to flash floods.
If you plan on keeping livestock, remember that it takes a lot more
land to support an animal in an arid zone. You will be unlikely to have
enough land to support many animals, maybe none. Make sure you have access to grazing permits on near, or adjacent, public land. Land managers are much more restrictive these days and grazing permits have become much more costly and difficult to obtain, so study up before you invest.
Whether farming or ranching for
profit or subsistence, doing it in an arid climate is far more challenging, but certainly doable and rewarding, with planning, hard work, stubbornness and a lot of luck.
