Variable spatio-temporal source contributions during storm hydrographs revealed by composite fingerprinting

The Kasilian watershed with an area of 67.22 km 2 is located in the eastern part of Mazandaran province. This study investigated the spatio-temporal variations in sediment sources during rainfall events. For this purpose, source samples were collected from various land uses, including rangeland, natural forest, hand-planted forest, and agriculture, as well as from the river bed. Suspended sediment sampling was conducted at 60-minute intervals during three rainfall events at two monitoring stations: MS1 (mid-watershed) and MS2 (watershed outlet). The concentration of 59 geochemical elements in source and sediment samples was measured, and composite fingerprints were selected using statistical tests in the FingerPro package in R software. The study found that the contributions of rangelands, natural forests, hand-planted forests, and the river bed at MS1 were 46 %, 24 %, 19 %, and 11 %, respectively, while at MS2, the contributions were 72 %, 7 %, 4 %, 14 %, and 3 % for agricultural lands. Additionally, intra-event variations showed that at MS1, rangelands contributed the most at the hydrograph peak, whereas during the rising and falling limbs, both rangelands and natural forests were dominant. At MS2, rangelands had the highest contribution throughout all hydrograph phases. These findings provide valuable information for managers in developing management programs. • Soils from different land uses and suspended sediments at two monitoring stations were sampled • Spatio-temporal variation in sediment source contributions were investigated at hourly intervals during rainfall events • Rangeland was identified as the dominant sediment source, with significant variability between monitoring stations • The intra-event contribution of sediment sources was analyzed based on the location and erosional condition of the sources