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Abstract In this study, the data at Idenak hydrometric station were used to predict the inflow to Maroun Dam reservoir. For this purpose, different models such as artificial intelligence, Holt-Winters and hybrid models were used. Partial mutual information algorithm was used to determine the input parameters affecting modeling the monthly inflow by artificial intelligence models. According to the Hempel and Akaike information criterion, we introduced the monthly inflow with a 3-month lag, and the temperature with a 1-month lag, with respect to the lowest values of Akaike and the highest values of Hempel as input parameters of artificial intelligence models. The results showed the weak performance of the Holt-Winters model compared to other models and confirmed the superiority of the Holt-adaptive network-based fuzzy inference system (ANFIS) hybrid model with the root-mean-square error of 54 and the coefficient of determination (R 2) of 0.83 in the testing process compared to other mentioned models. In addition, the above hybrid models performed better than other models in the test process.

Abstract In this paper frequency analysis of annual extreme daily rainfall of 14 gauging stations located in an arid zone of Iran were performed using parametric and nonparametric approaches. The parametric methods include normal, two- and three-parameter log-normal, two-parameter gamma, Pearson and log-Pearson type III, extreme value type I (Gumbel), generalized extreme value and generalized logistic distributions. The nonparametric approach is Fourier series method. The data were fitted to all of above mentioned models and the results showed that the goodness of fit of the data to Fourier series is much better than other parametric methods. Thus the Fourier series can be used as an alternative approach for frequency analysis of extreme daily rainfall in an arid zone. In addition, the quantiles can be calculated by the Fourier series.

The prediction of stream-flow have incessantly attracted water engineer studies with due regard to its importance in the design of water structures, water intake from the rivers, planning and operation of reservoirs of dams, and erosion and sedimentation control measures in rivers. In this research, HEC-HMS model was used in prediction of daily stream-flow in the Maroun Basin, evaluating the ability and precision of this model in predicting stream-flow. For this purpose, continuous simulation of daily rainfall-runoff was performed before the prediction period using soil moisture accounting algorithm (SMA). In order to calibrate and verify the HEC-HMS model, daily stream-flow data from 1995 to 2006 and from 2007 to 2011 at the Idenak hydrometric Station were respectively used. Then, daily stream-flow at Idenak Station was predicted from 2011 to 2012. The results showed that the goodness of fit tests including Nash-Sutcliffe efficiency index, coefficient of determination and root mean square error in the runoff prediction process at Idenak station are equal to 0.56, 0.67 and 32.2 m3/s, respectively. Therefore, the HEC-HMS model has acceptable ability and precision in predicting runoff.

This paper studies the effect of different molarities of sodium bicarbonate on enhanced absorption capacity of rice husk to remove cadmium in low concentrations. Maximum absorption efficiency was achieved at a pH of 6 and absorption equilibrium time was 1.5 hours. Results of chemical experiments and photography by electronic microscope from improved rice husk revealed a good relationship to exist between number and average diameter of absorber pores, on the one hand, and absorption efficiency, on the other. Meanwhile maximum absorption efficiency of rice husk in cadmium removal was 99.1 percent which shows improvement due to 0.3 molar sodium bicarbonate. In this study, kinetic absorption models were also studied. Both Lagergrn (1898) and Ho et al. (1996) models satisfactorily described data with a confidence level of 95 percent; however, the latter model was found superior in this respect. Comparison of the coefficients calculated here with those reported in other models showed a faster cadmium absorption rate by improved rice husk due to 0.3 molar sodium bicarbonate.