In this study, the spatial and temporal variability of water quality including monthly series of TDS, EC, So4, Cl, Ca and Na in common statistical period 1993-2014 was evaluated for the Karun River. This assessment is based on qualitative data stations including Susan in the upstream of Gotvand reservoir, Gotvand, Mollasani and Ahvaz in the downstream. To determine the parameters trend process, Mann-Kendall and Sen slope estimator tests were used. Also, Petit test was used to determine the breaking point. The results showed that in all quality parameters of the Susan station, a combination of increasing and decreasing trend is observed. Mainly downward trend is corresponding to the wet months and the upward trend is corresponding to the low water months. Susan, Mollasani and Ahvaz stations are located in downstream of Gotvand dam. The results of modified Mann-Kendall showed clear decrease in water quality after Gotvand dam. The upward trend for the quality parameters were observed in all months of the all stations. According to the results of Sen’s slope estimator, the most trend for the EC series was 108.83 micromhos per centimeter per year, for TDS is 76.07 ppm per year, and for Sulfate, Chlorine ,Calcium and Sodium, are respectively 0.52, 0.65, 0.41 and 0.75 ppm per year. In general it can be found that there are no significant changes in water quality for upstream Gotvand during the study period, however, after the dam, severe changes in water quality parameters have occurred. Based on Petit test, most of changes happened in 2006 and 2007 caused by dam constructing, diversion tunnels and coastal loss in these years. That changes the Karun river water quality in downstream of Gotvand dam. Indeed, water quality Variation before and after the dam construction was showed by hydrometric stations. پرونده مقاله

The intensity –duration –frequency (IDF) curves play most important role in watershed management, flood control and hydraulic design of structures. Conventional method for calculating the IDF curves needs hourly rainfall data in different durations which is not extensively available in many regions. Instead 24-hour precipitation statistics were measured in most rain-gauge stations. In this study, scaling properties of extreme rainfall are examined to derive scaling IDF curves over different durations. This new method in comparison with traditional method is less computational steps and has lower parameters numbers which causes increasing in reliability of IDF curves. Scaling method was used to extract the IDF curves in Ahwaz rain-gauge station and results proved the efficiency and robustness of the scaling method. The accuracy of scale model method for Determining precipitation intensity, with Duration 30 to 180 minuts in Ahwaz station, is quite acceptable and maximum error is about 11.5%. پرونده مقاله