Investigating the effect of land use change on base flow index, case study: Taleghan watershed

Base flows and related indicator is an important factor in water resource management. Several factors have contributed in the base flow values and its changes. From which, land use and vegetation cover are affected directly and indirectly by human intervention. In this research, land use changes in the Taleghan watershed are investigated, using aerial photos interpretation, satellite imagery and land use map in three periods of 1970, 1987, and 2002. Also, base flow index was extracted by using daily discharge and Lynie and Hollick algorithm. Then, mean annual value was used as an overall index and its change trend was investigated with the land use change trend. Results showed an increasing trend of land use change from dry and irrigated lands to rangelands. Also, both dry and irrigated areas, showed a decrease of 73.23 and 60.87 percent, respectively, while, in the rangelands, there was a rising of 20.6% compared to year 1970. The influence of land use change in the amount of base flow index, showed a negative trend with the dry land changes. This index was also negatively correlated with the percentage of irrigated land changes. The positive trend of base flow index with the change of rangeland, indicates their positive role in increasing the base flow index. The results also demonstrated that the mean base flow index increased from 0.778 to 0.795, during the period of research.