THE WATER NEXUS IN SOUTHWESTERN IDAHO, USA: DEVELOPMENT VERSUS AGRICULTURE

Abstract

The Snake River Plain is a rapidly growing region in southwestern Idaho, USA. The Snake River Plainis arid and receives less than 300 mm of annual precipitation. Even though this is a desert biome, irrigationwater from the local mountains transforms the region into an agricultural oasis. However, there is afinite amount of available water. The region is rapidly growing as the population is annually increasingby 20,000 people. Thus, there is a rapid transformation from irrigated farmland to suburbs. The goals ofthis paper are to evaluate: (1) population growth, (2) public opinion about the pros and cons of populationgrowth, (3) current agricultural crops and water use, (4) if water is actually a limited commodityand (5) strategies to optimize the population growth-agriculture nexus in southwestern Idaho. Thisrapid population growth is displacing traditional irrigated agriculture and shifting a portion of the wateruse to the urban sector. The population of the six-county region that comprises the Snake River Plainin southwestern Idaho has grown from 202,400 in 1970 to 744,800 in 2019. Most of the growth is notnatural, but rather caused by in-migration from other states, especially California, Utah and Washington.The population growth rate is actually increasing. Consequently, up to 45% of the farmland in thevalley may be transformed into urban/suburban housing in the next 25 years. The purpose of this paperwas originally to determine the strategies needed to maintain sustainable water resources for both theurban and agricultural sectors. However, many planners are unsure of the impact of changing water usefrom agriculture to urban on the total amount of water that will be needed. Annual irrigation water useranges from 400 to 1,150 mm depending on the crop. Water use differences between crops may allowfor better water management as land use changes. It is unclear if the suburban/urban development of theirrigated farmland will result in an increased, decreased or unchanged demand for water use. Becauseof this uncertainty about water demand the proposed strategy to cope with changing land use is waterneutral. Irrigated agriculture in the six-county area will lose up to 45% of its land base by 2045. Toreduce the impact of the land base loss agriculture should focus on retaining or expanding its high valuecrops – vegetable seeds, onions, hops and mint. The agriculture industry should reduce the amount ofland devoted to cereals, alfalfa and hay pastures over the net 25 years. An implemented crop selectionstrategy could partially offset the economic loss to agriculture associated with a major reduction ofirrigated land. The best soils (capability classes 1 and 2) should be protected to continue to supportirrigated agriculture. Conversely, soils with capability classes of 4 or above are not as productive andshould be preferentially targeted for development.