From Cut-in to Qanats - Ancient Groundwater Extraction Techniques

Abstract

Where a hillside stratified aquifer intersects the earth surface, springs and outseeping are observed. Cutting into this zone, thus opening it by digging, allows to increase and capture water outflow. As a matter of principle this classical method for water extraction without pumping, which is still found in hilly rural regions today, was already used 3600 years ago by the Hittites to fill the ponds of their capital Hattuşa in Central Anatolia. The today sedimented reservoirs were dug downhill of groundwater bearing zones. Rising in winter, groundwater discharged into the ponds through alongside cuts. The Hittites avoided the risks of strongly varying surface flows by opening near-surface groundwater and stratum aquifers. Although hydraulic investigation based on in-situ measurement of groundwater level supports the short-term efficiency of the ponds in supplying water to the ancient city, at the long-term, the decline of the Empire was probably triggered by severe droughts expanded over years. This seems plausible as severe droughts are still being experienced. For a higher and more reliable water yield, the further development went from ’cutting’ in to ’penetrating’ into the aquifer with tunnel-like drain conduits which collected the water and conveyed it to settlements and irrigation schemes. The improved water extraction system, named qanats, appeared in Eastern Anatolia and Persia about 500 years after the abandon of Hattuşa. An example of a qanat system in western Iran is presented in this study with less emphasis compared to the cut-in yet representative enough to demonstrate its role in supplying water sustainably. We conclude that the ancient time thinking is the same as that of modern engineering, and the ancient time hydraulic works are fundamental for today's civil structures.