Irrigation Water Supply and Management in the Central High Plains: Can Agriculture Compete for a Limited Resource?.

The era of expanding irrigated agriculture in the central high plains has come to an end, and we are likely entering a period of contraction.  Contraction has begun in Colorado where the state estimates that current consumptive use exceeds sustainable supplies by about 10%.  Groundwater pumping has been curtailed or stopped entirely in several areas in Colorado due to depletion of downstream surface water rights.  Pumping is being curtailed in many areas overlying the High Plains aquifer due to unsustainable groundwater depletion.  Cities along the Rocky Mountain front range continue to  purchase agricultural land and take it out of production to secure the rights to the appropriated water.  Downstream states are demanding flows to meet interstate compact requirements.  There is little potential to gain supply through increased efficiency because most return flows already return to the river or groundwater and are reused.  Environmental restoration efforts in the Platte system will require increased river flows.  Impact of climate change on high plains water supplies is uncertain, but predicted temperature increases will likely reduce snow pack water storage.

The challenge for agriculture and rural communities will be to maximize productivity and economic return from a diminished water supply.  Maximum production per acre will cease to be the primary objective.  Several studies are underway to determine cropping, tillage, and irrigation management practices that can increase productivity and returns per unit of water.  Irrigated agriculture in the central high plains will continue and will help meet the food needs of a growing world population, but it will be carefully managed to maximize water productivity.