摘要：Saudi Arabia (SA) is facing a severe scarcity of its water sources. The gap between sustainable irrigation water sources (SIWS) and irrigation water requirements (IWR) in SA is in a continuous increase. Groundwater is considered the primary source of irrigation water in SA and a huge part of which (non-renewable groundwater) is used to bridge this gap leading to a continuous depletion of this vital source. In the current study, present and future IWRs have been estimated and predicted. IWRs for principal crops in SA has been calculated based on available climate data for the period from 1985 to 2011 in Najran Region (NR), in the southwestern part, as a case study. IWR for the main perennial crops (dates, citrus, and alfalfa) has been calculated as an average for the 13th regions contributing to agriculture in SA. These regions include Riyadh, Makkah, Madinah, Qaseem, Eastern, Aseer, Tabuk, Hail, Northen, Jazan, Najran, Baha, and Jouf. Reference evapotranspiration (ETo) has been calculated using FAO56 Penman-Monteith equation. Five reform scenarios for the future use of agricultural areas have been proposed hoping to reach sustainable irrigation water requirement (SIWR). The results proved the opportunity of SA to reach SIWR in the coming twenty years by: phasing out the cultivation of forage crops by the year 2036, and keeping current rate of growth (or decline) trend in the agricultural land areas of both fruits and vegetables. Supporting farmers to shift 1% annually of the current planted area of each crop from the traditional to the modern irrigation system is also a must
关键词：crop water requirement; FAO56 Penman-Monteith; reference evapotranspiration; Crop evapotranspiration; irrigation water requirement; sustainable irrigation water source
