Karez (qanat) irrigation in the Helmand River Basin,Afghanistan: a vanishing indigenous legacy

A karez is a gently sloping tunnel into a hillside with a series of vertical shafts. At the upstream end, the karez depresses the water table such that groundwater enters the tunnel. Farmers all over Afghanistan have built and managed karezes for centuries using indigenous knowledge. This report focuses on karezes in the Helmand River Basin in southern Afghanistan, and describes the location of karezes in relation to geology, technological and managerial aspects of karez irrigation, and their current status. Karez irrigation has declined in recent decades due to the following: a prolonged reduction in precipitation, increase in number of boreholes that lower the water table below the karez tunnel, breakdown in community-based management, and reduced maintenance. Systematic field measurements are a challenge in the Helmand Basin due to security constraints. The current condition and management of the karezes have been assessed through short field visits and structured focus-group discussions with karez farmers and staff from provincial departments. The surveys indicate that over half of the karezes in the Helmand Basin have gone dry. Furthermore, the flow in karezes that are still operational has also declined significantly. The report demonstrates the value of using data from the US National Centres for Environmental Prediction (NCEP) Reanalysis 1 project, to estimate historic precipitation for various karez zones in this data-poor basin. Strategies for rehabilitating karezes are discussed. Rehabilitation is financially expensive in comparison to drilling new boreholes, but karezes are part of the national heritage of Afghanistan and can facilitate social cohesion.