Impacts of the Golestan and Voshmgir Dams on Indicators of Hydrologic Alterations in the Gorganroud River Using Range of Variability Approach

Dams construction as one of the methods in water resources management, are among the most important man-made structures along the river that can make major changes in the river regime and ultimately in the entire drainage basin and surface flow adjustment that hydrologic alterations are one of the most important alterations. Therefore, the quantity evaluations of hydrological changes and the deviation magnitude of natural flow regime affected by human activities such as dam construction need to be considered, that one of these methods is the indicators of hydrologic alterations (IHA). Therefore, the purpose of the present study is the statistical analysis of the IHA affected by the dam Bostan, Golestan and voshmgir (pre- and post-dam construction periods) and Without construction a dam using the IHA and RVA in the all stations Gorganroud Watershed. Toward this, the trend in the amounts of precipitation, temperature and evapotranspiration variables were evaluated using MATLAB software using Mann-Kendall test and Sen’s slope at a confidence level of one and five percent. Then, the 33 Indicators of hydrological indicators in five main groups (magnitude-duration-timing-frequency- rate of change) will be computed pre- and post-dam construction. After calculating the indicators values, IHA changes will be computed using the variability range approach (RVA). According to the results of trend analysis, change in climatic Variables In the form of significant increasing the precipitation and temperature the has been increased during the available time period.