Aflaj Systems: History and Factors Affecting Recharge and Discharge

Abstract

“Aflaj” systems are man-made tunnels or channels that intercept groundwater or base flow at the foothills of high mountains and channel it to land surfaces at a lower altitude, without any mechanical means, mainly for irrigation purposes. The objective of this chapter is to discuss the history of aflaj systems and the factors affecting their recharge, discharge and water quality.

Aflaj systems are part of the agricultural heritage: aflaj tunnels receive water from mother wells that intercept shallow aquifers; they were designed and have been used in the UAE since the beginning of the Iron Age in Al Ain, Bida bint Saud, Nahil and Al Jabeeb areas. Aflaj construction, maintenance and management are part of water history in the UAE.

Aflaj recharge depends on their water source, including rainfall, groundwater or natural springs. The mother well location, tunnel gradient, aquifer type and amount of recharge are the main factors affecting aflaj discharge. Aflaj systems were classified based on source of recharge and discharge into Al Gheli, Al Daudi and Al Hadouri. During the last three decades, several aflaj systems faced challenges such as excessive groundwater pumping and a sharp decline of groundwater levels in their recharge areas. For this reason, several aflaj systems, particularly in the Al Ain area, became dry. The discharge of active aflaj systems measured by the authors varies between 0.08 and 89.7 L/s and averages 17 L/s.

The factors affecting water quality and water use of aflaj systems are climate, geologic setting and human activities. The salinity of aflaj water ranged from 293 mg/L in Fujairah to 7111 mg/L in the Al Ain area. The relationship between the Sodium Adsorption Ratio (SAR) and electrical conductivity (EC) showed that most of aflaj water in the UAE is good to fair for irrigating conventional crops.