Watershed Grouping Based on Effective Parameters on Base Flow Using Different Clustering Algorithms in Ardabil Province

Grouping of similar watersheds using clustering methods helps to explain hydrological processes and regional water yields. In the present study, the daily discharge, base flow and Base Flow Index (BFI) and effective parameters including annual rainfall and physiographic characteristics (Area, Mean elevation, main stream length and drainage density) were analyzed using K-means and Hierarchical clustering algorithms over 22 sub-watersheds to determine the homogeneous groups in Ardabil Province. The Davies- Bouldin Index criterion was used to determine the optimal number of clusters over the study area. The base flow amount were separated from daily flow hydrographs by using One-Parameter algorithm through Excel programming. Then, the BFI values were calculated using the ratio of base flow and total amount of runoff. This K-means algorithm aims to find groups (clusters) of similar watersheds from a data set. Firstly, the watersheds were classified based on base flow and BFI and then other variables were used to cluster the studied watersheds. According to the results of K-Means clustering method considering base flow discharge the number of watersheds in first three groups were 4, 3 and 15, respectively. According to the results, the K-Means clustering methods detailed groups of watersheds compared with the Hierarchical method. Watershed grouping based on base flow and base flow index showed that the Arbabkandi and Gilandeh falls into a cluster, and Doostbeiglou, Pole-almas, Samian and Firozabad had similar characteristics. In general the Aladizgeh, Ahmadkandi and Baroogh watersheds had similar hydrologic response in terms of base flow, BFI and other physiographic and land-use related factors and classified into same group. Therefore, the homogeneous watersheds in terms of surface water and base flow variations had similar water yield and ecological flow behavior. Water resources planning and management of watersheds can be considered in homogeneous regions as planning unit.