B. Ghahreman,
Volume 7, Issue 2 (summer 2003)
Abstract
An intense storm occurred on June 6, 1992 in Mashhad city and its suburb, which caused a flood in the residential areas of Najafi, Chahar-cheshmeh and Nodareh. As a consequence of the abnormally huge flood, 25 people lost their lives and many structures were destroyed. Three recording rain gages located in Mashhad city (airport, College of Agriculture, and Water Authority) and one in the suburbs (Toroq dam) recorded the temporal distribution of the storm. Twenty five other nearby rain gages in the region also recorded the event. The rainfall hyetographs and rainfall amounts were analyzed.
The results of this survey showed that: a) maximum rainfall intensity over a 15-minute duration in the College of Agriculture station, one of the centers of the storm, was 112 mm/hr, b) temporal distribution of rainfall for all recording stations were nearly the same, c) these patterns were in close agreement with all historic storms, and d) a return period of 380 years was implied via comparing the maximum rainfall intensity with relevant IDF curves. As a consequence, although an intense storm had happened, it was simply an outlier.
M. Ghahremannejad, S. Boroomandnasab, M. Behzad, A.a Naseri, A. Sheini Dashtgol,
Volume 18, Issue 70 (winter 2015)
Abstract
Infiltration is the most crucial process affecting surface irrigation uniformity and efficiency as it is the mechanism that transfers and distributes water from the surface to the soil profile. As a direct method of infiltration measurement, the volume balance method requires time, accuracy and high costs. Moreover, before the land preparation and at the research phase the use of this method is not feasible. The revised USDA- NRCS method is used to convert the infiltration parameters to different hydraulic conditions. In this study, the accuracy of the original and revised USDA-NRCS method in the estimation of furrow irrigation infiltration parameters in Amir Kabir Agro Industrial sugarcane fields of Ahvaz was evaluated. For this purpose, infiltration parameters and the cumulative 6 hour infiltration for furrow irrigation systems of this region were estimated using four methods of original USDA- NRCS, revised USDA- NRCS for border irrigation, revised USDA- NRCS for furrow irrigation and field measurement (inflow-outflow). For evaluation of the results, four indices including average prediction error of model (Er), distribution into 45° line (λ), determination coefficient (R2) and average relative error of model (Ea) were used. According to the results, the revised USDA- NRCS method for border irrigation with average values of λ, R2, Er and Ea equal to 0.95, 97, 6.5 and 7.6 percent, respectively was the best estimate of cumulative infiltration.
F. Farsadnia, B. Ghahreman, R. Modarres, A. Moghaddam Nia,
Volume 22, Issue 3 (Fall 2018)
Abstract
In recent years, the joint distribution properties of drought including severity and duration have been widely evaluated using copula. Few studies, however, have worked on drought modeling based on stream flow, especially in semi-arid regions such as the southern regions of Iran. This study followed two purposes. The first purpose was to find the appropriate marginal distribution function for hydrologic drought duration and severity, and the other one was to find appropriate copulas. First, the severity and duration of hydrological droughts in the hydrometery stations in the Karkhe basin were extracted by the run’s theorem, and the absence of trends was tested using the modified Mann-Kendall trend test. Appropriate marginal distribution functions for duration and severity drought were derived by using the linear moment's method. In addition, copula’s parameters for Frank, Clyton and Gumbel families were calculated by both direct and indirect methods. The best copulas were selected by the goodness of fit tests. Finally, the joint and conditional return periods for duration and severity drought were derived for each station. The results showed that drought severity and duration for all hydrometery stations in Karkhe basin followed both the generalized extreme value marginal distribution function and Gumbel copulas family, which could be used for regional copulas modeling.
