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Water use of Al Ghaf (Prosopis cineraria) and Al Sidr (Ziziphus spina-christi) forests irrigated with saline groundwater in the hyper-arid deserts of Abu Dhabi

The arid forests of Abu Dhabi provide a variety of valuable provisioning, regulating and cultural ecosystem services.‎ They require irrigating.‎ And groundwater is the source.‎ About 95% of groundwater consumption is for agriculture and forestry.‎ Over-extraction threatens groundwater resources.‎ The Government of Abu Dhabi recently passed Law 5 to restrict groundwater abstraction.‎ We have determined the minimum allocation required for the irrigation of two tree species.‎ We carried out experiments at Madinat Zayed in the western desert on two arid-forest species: Al Ghaf (Prosopis cineraria) and Al Sidr (Ziziphus spina-christi), both planted on a 7m×7m grid.‎ We measured the actual evapotranspiration (ETc) using heat-pulse equipment in the trees.‎ Saline groundwater with an electrical conductivity of about 8–10 dSm−۱ was used for irrigation.‎ Current practice is to drip irrigate with 60 L d‐۱. Both species displayed distinct, and different, summer ‘deciduous behaviours’ that determine their seasonal pattern of ETc.‎ A single crop-factor approach, using ETc predicted from Kc.ETo, where Kc is the crop factor and ETo is the reference evaporation, would not provide appropriate irrigation allocations.‎ From our hourly measurements of ETc, made over 3 years, we quantified the seasonal pattern in Kc.‎ For Al Ghaf, Kc ranged from 0.‎1 during February–July, to 0.‎15 in November–December;‎ for the Sidr, Kc was at a minimum of 0.‎06 in May, and rose to 0.‎16 in December.‎ Daily irrigation requirements were provided for Law 5.‎ With a 25% factor-of-safety, and a 25% salt-leaching requirement, irrigation requirements for Al Ghaf ranged from 24.‎4 L d−۱ in January to 52.‎8 L d−۱ in July.‎ For Al Sidr the range was from 33.‎8 L d−۱ in April to 53.‎5 L d−۱ in September.‎ These are a 40% saving on current practice.‎

Authors: 
Wafa Al Yamani, Steve Green, Rommel Pangilinan, Steve Dixon, Shabbir A.‎ Shahid, Peter Kemp, Brent Clothier
Year: 
۲۰۱۸
Publication type: 
Scientific Paper
Publication Source: 
Agricultural Water Management
Volume/Chapter/Issue: 
۲۰۳
Page Number: 
۱۰۵ - ۱۱٤