All of the farm fields in the Mesilla Valley -- with crops such as alfalfa, cotton, onions, chiles, and pecan orchards -- are irrigated with water from the Rio Grande because rainfall (about 10" per year)
is too sparse to support agriculture. The water level is controlled by dams and reservoirs to the north of Las Cruces and the water is released downstream during the agricultural season (Spring to Fall) for irrigation.
When rainfall is insufficient (as 2011-2012) irrigation water from the Rio Grande may be seriously reduced and farmers are forced to rely on expensive pumps to bring up irrigation water from deep wells.