فصلنامه علوم و مهندسی آبیاری
سال سی و چهارم شماره 1 (بهار 1390)

Runoff is one of the important parameters in hydrologic cycle and water resources management of basins. In this research, Remote Sensing (RS) and Geographic Information System (GIS) techniques were used for runoff potential estimation in Khosro-Abad watershed, located in the Hamedan region. In this regard, first, the various thematic maps layers such as Digital Elevation Model (DEM), land use and land cover, slope, soil hydrologic groups and sub-basins location were prepared. Then, based on the prepared thematic layers, a weighting method was developed to runoff potential estimation of the area. To spatial runoff variability investigating, the classifieds estimated runoff potential (low, medium, high and extreme classes) was evaluated using the SCS method. The SCS method was estimated based on three previous soil moisture conditions (dry, normal and wet). The results showed that the weighting method is enable to runoff potential estimation. This method can be proposed for runoff potential estimation especially in the cases that the needed data were missed. The results also
showed that with the previous soil moisture increasing (from dry to wet conditions), the CN increase about 30%.

Salt and drought stress is one of the main problems of Agricultural production in many parts of the world, especially in arid and semi-arid area. Therefore, this study was conducted to investigate the effect of both stresses (individually and simultaneously) on yield and yield component of tomato (Super Strain B) in order to program irrigation management in Karaj. The experiment was carried out as Factorial on base of complete randomized design with three replicates including two factors: Salinity and irrigation water. Salinity and irrigation water factors consisted of four levels (S1=0.7, S2=4, S3=8 and S4=12 dS/m) and three levels (W1=100, W2=75 and W3=50 percent of water requirement), respectively. The soil texture was sandy loam. The results of this study showed that the yield production reduced by increasing salinity and drought stresses. The maximum yield (240.7 g) was corresponded to W1S1 treatment and the minimum yield (48.58 g) was corresponded to W3S4 treatment. Salinity, deficit irrigation and their interaction had significant effect (p

The amount of daily rainfall for a solitary wet day (Class 0) is normally less than the rainfall for a wet day that is enclosed by wet days on either side (Class 2). The same characteristics hold true for the case of the first or last day of wet spells (Class 1) and there fore the rainfall here is found to be smaller than the Class 2 rainfall. In many regions, there exist large differences between these rainfall classes. In this study, the daily rainfall data from 5 rain gauge stations in the north and northwest of Iran are classified to classes 0, 1 and 2 according to the number of adjoining wet days. To examine the impact of adjoining wet days on the distribution of rainfall amounts, different distributions were tested with 3 different data sets: (1) all rainfall classes grouped together, (2) solitary wet days fitted separately from other wet days, and finally (3) all rainfall classes separately. The results showed that the models which treat the rainfall classes separately are a better fit for all the 5 stations. The Akaike Information Criterion (AIC) values are significantly reduced as the rainfall data are split into rainfall classes. Also, among 4 different distributions considered (Gamma, Lognormal, Mixed Exponential and Weibul), mixed exponential distribution in most cases and lognormal distribution in one case showed better performances.

Vertical and horizontal extension of cities and growing trend of industrial activities in them has resulted in wide changes on ground physical properties, released energy, air pollution, temperature and as a result change of local climate in metropolises. Cities are often warmer than their environment. This phenomenon is determined by the difference between cities’ energy and their environment’s energy. Synoptic climatology data of Ahvaz and Dezfool in a 44- year period was surveyed and studied to specify these changes in Ahvaz metropolis. The results showed that annual average minimum temperature of Ahwaz in this period has a total increasing trend of 3.375 °C and (0.077 °C/1yr) yearly, whereas the corresponding parameter was without any changes in Dezfool. Temperature increasing trend in Ahwaz in comparison with Dezfool as indicated by the results which is resulted by the heat island effect in Ahwaz and the lack of development of Dezfool with time. The greatest increase rate of Ahwaz average minimum temperature is 4.14 °C and (0.094 °C/1yr) yearly in Azar monthly in this period and the smallest is 2.07 °C and (0/047 °C/1yr) yearly in Esfand monthly. Usually the extent and extension of the city are known as the most important factors in the severity of heat island effect, and population growth is among the serious factors which cause the increase of its severity and finally result in the change of local climate of metropolis. Population is considered as
parameter which is explanatory of city’s size. In this study, a relationship has been developed for the average intensity of heat island effect in Ahwaz and the logarithm of population.