AbstractRealizing the importance of Karez irrigation systems, field research was conducted in the district of Khwaja Omari of Ghazni (Afghanistan) to assess traditional water management practices in three selected Karez irrigation systems. In the Karez irrigation system, an informal water users’ association performs the function of water allocation, distribution, operation and maintenance of the physical infrastructure. Water is distributed on a rotational basis and each plot receives their due share of water once in the water distribution cycle that ranges from 6 to 12 days. The available flow discharges of three sampled Karez irrigation systems were measured that ranged from 6.30 to 9.28 l s−1 during the months of June to October and served cropped areas that varied from 12.53 to 24.15 ha. Conveyance losses measured in unlined irrigation canals varied from 21.9 to 32.7% km−1 with an overall average of 26.0% km−1. In general, crop water demands exceed available irrigation supplies particularly during the months of July and August. It may be concluded that water distribution is reasonable but can be improved further by considering the conveyance losses in these systems which will improve the overall productivity. Copyright © 2015 John Wiley & Sons, Ltd.