Analysis of Check-dam effects on flow duration curve alteration of the Zarcheshmeh River- Hoonejan watershed, Isfahan Province

The damming can cause changes in the hydrological regime of the river. There is a crucial need to understand the potential impacts of water structures on river hydrologic regimes in order to set managed environmental flows. In this study, the statistics of Tang Esferjan hydrometric station at the outlet of Hoonejan watershed (Isfahan province) were used to investigate the monthly average discharge and flow duration curve alteration using IHA software (version 7.1). The amount of monthly flow has decreased in the post impact compared to the pre impact period. The flow duration curve is higher in all seasons before the construction of check-dams than after construction. The interpretation of flow duration curves shows the reducing effect of correction clauses in all types of flow. The hydrological indicators of the stream (normal discharge index in the high flow condition, normal discharge index in the low flow condition and normal discharge index) have decreased in the post-impact period compared to the pre-impact period. In all months of the year, except for February, March and April, the rate of decrease of the normal discharge index in the low flow condition (Q75) was higher than the normal discharge index in the high flow condition (Q25). The normal discharge index in the high flow condition has decreased more in the spring season than in other seasons after damming. The normal discharge index in the low flow condition in winter, autumn (91%) and summer (90%) has decreased more than in spring.