Determination of Suitable Method for Estimating Suspended Sediments Discharge in Arazkoose Hydrometric Station (Gorganrood Basin)

Sediment transport and settling leads to some outcomes such as sedimentary island establishment in river stream and consequently, decrease in transfer capacity of flood water flows, decrease in useful life of dams and depots saving capacity, corrosion in river factor foundations, damaging the water buildings and farms, settling in the canal bed and many other problems. Also it is necessary correct estimation of the rivers sediment load in all hydraulics projects is necessary. One of the methods of sediment estimating is hydrological methods. Hydrological methods are divided to several categories, such as USBR, FAO, Median of groups, MVUE, QMLE, and Smearing. In this research estimating of sediment in Arazkoose hydrometric station which is located on Gorganrood watershed was carried out by these methods. Therefore, sediment and flow discharge data during years of 1973 to 2008 accumulated and analyzed. After determination of sediment rating curves in various methods, the best method was selected by comparison of the statistic parameters such as R, RMSE, r and GSD. After that, the daily sediment discharges in all statistic period were determined. At last estimating’s quintiles during 45 days period with the statistic indicator, relative mean of error. The results of this study showed that median of groups with R=0.79, RMSE=52148, r=0.68 and GSD=0.89 is the proper method for suspended load estimating in the Arazkoose station and based on this method the average of daily sediment discharge was estimated at this station as 11324 ton/day.