Use of historic Persian water system data in groundwater models: Examples from Afghanistan and Emirates

Abstract

Obtaining calibration data for models depicting conditions during pre-development periods can be challenging as such periods are characteristically data poor. This study presents two examples where simulation of historic water conveyance structures were used to help characterize historic, or pre-modern, conditions in calibration of groundwater flow models. Persian water conveyance structures, called ‘aflaj’ (or singular ‘falaj’) in the Emirates, ‘karezes’ in Afghanistan, or ‘qanats’ in some other regions, consists of a hand dug tunnels, hundreds to thousands of meters long, that intersect upgradient water table surfaces and convey water downgradient for domestic use and irrigation of small farms. These structures can be identified, using remote imagery, by the presence of regularly spaced access holes that were used to create and maintain these tunnel systems. This type of water-supply system was commonly used throughout North Africa, the Middle East, and Asia for centuries. They are generally not used today having largely been supplanted by modern groundwater wells, and, in many areas these structures have failed because of water-table declines caused by groundwater development and/or climate change. Evidence of these systems from satellite imagery provides an indication of pre-modern water levels and this information was used in the calibration of two contrasting pre-development models in Afghanistan and the Emirates.