Khettara: What a water adduction model from the heritage holds for the future

In arid and semi-arid climate areas throughout the world, aerial photos might present interesting lines of equidistant craters. These are called, depending on the geographic area in question, Khettara, Qanat, Karez, Falaj, Qanat Romani, Fouggara, Galeria, Puquio…, an ancient underground water tapping system, born in Persia (Iran) around 3000 years ago and spread to multiple continents following trade routes, conquests, religious propagation, to reach as far as the Americas. Khettara, as called in Morocco, is an ingenious and sustainable water adduction and irrigation technic, part of our immaterial heritage. The system consists of an underground gallery that can extend to several kilometres, dotted with maintenance and ventilation shafts. It taps the water table through a main well, drains and conducts water by gravity to the surface, in order to rationally manage it for domestic use and irrigation. Many cities and settlements depended on Qanats for centuries, and in some cases until recently. This paper is a multidisciplinary review to understand the engineering behind Khettaras and their complex implementation, the causes of its decline and abandonment, and the potential it offers in terms of reviving or repurposing perennial and dead ones. Navigating studies from different countries, this paper investigates whether Khettaras can be revived for their original function, reworked as hybrid hydraulic systems, repurposed for ventilation, heating or cooling, integrated in urban planning or touristic promotion, many possibilities to perpetuate this ancient heritage.