Farmers in the Central Valley and San Joaquin Valley in California have been abandoning the growing of cotton and lettuce and planting almond orchards over the last 15 years because almonds are more lucrative and do not need to be replanted after each harvest. California's almond orchards now produce 80% of the world's almonds.
The problem is that almond orchards require lots of water, but there is severe drought in the areas most populated with almond orchards. As a result, growers of almonds have been getting the water necessary for their orchards from groundwater. However, there are other claimants to the available ground water, including other farmers, communities, and the fishing industry, which needs the water diverted to waterways that support salmon. There is no guarantee that those who grow almonds will be able to get sufficient water to maintain their orchards.
Farmers to the north, who have not experienced drought, have taken notice and have started converting parts of their land to almonds. They realize that limited availability of water in the areas most populated with almond trees will constrain the growth of orchards and drive prices up. Some also see almond growing as a sound business decision which will make their farms more secure because of the diversity that almond growing will bring.
At this time California is the only state that produces almonds commercially. That can change.