Quantify karstic aquifer potential recharge zones by integrated hydrogeology and GIS approaches, Northern Iran

One of the main challenges facing the sustainable development of the Kalaleh region is the need for better management of this limited karstic fresh water resources. Kalaleh mountainous region in the north of Iran is drained by several karstic springs such as Zaw, Aghsoo and Yal-cheshme, having discharge rate of 20 to 2500 lit/s. The springs are mainly discharged from Lar, Tirgan, Mozduran karstic formations. In this research, the potential recharge mapping and catchment area of the major karstic springs have been investigated based on the groundwater balance and a GIS approach considering geological factors. In another part of the study, the determined primary catchment area by hydrogeological budget method was reconfirmed with geological method and the results were acceptable. Eight potential recharge contributing factors were evaluated using the GIS including drainage and slope, karstic features, lithology, land cover, precipitation and lineaments. The weights and the score of the factors were assigned based on aerial photos, geological maps, land use database and field verification. The different prepared layers were overlaid in GIS environment, and finally, the mean annual recharge rate of the karstic springs was determined which are in the range of 39-44% of the precipitation. Understanding the groundwater potential recharge zone of the Kalaleh watershed is important for management, proper utilization and future planning of water resources for sustainable management. The Lar formation has higher potential for karst development and infiltration than others. The effective karstic formations in recharging process in order of significance are Lar, Mozduran and Tirgan.