Iranian Water Research Journal

Abstract Measuring soil evaporation is a difficult task and this can only be estimated either by using empirical methods or by water balance calculation from a lysimeter. An adjustment of soil evaporation estimation is required since farm condition is different from the standard condition set by FAO (56). In field conditions, the evaporation is decreased by soil salinity. The main objective of this study was to calibrate Aydin-Oiger model for a saline soil under three schemes of saline water irrigation in an arid and semi-arid region. Three conjunction strategy of fresh (1 dS m-1) and saline water (14 dS m-1) (blending, one-alternate and half-alternate) in three replications were applied in a completely randomized design in nine lysimeters. Soil samples were taken in 11 dates and 11 data series were collected. Soil evaporation was calculated for the internal between the two consequent samplings. Eight series of data were used for calibration of a new model and the other three were used for validation of the calibrated model. ANOVA, EF and CRM indexes were used for determination of significant levels of the calibrated model and its evaluation. The results indicate that the calibrated model predicates soil evaporation better than the original Aydin-Oiger model.

Abstract Flooding is a hazardous phenomenon that causes a great damage and loss to inland and coastal areas. Flood protection schems are employed to decrease the impacts of flood damage. The aim of this study is to measure the rate of flood hazard for all the flood plains located in Golestan province from discharges with different return period. After digitizing the maps and obtaining the digital elevation model (DEM), the characteristics of catchments and sub- catchments such as area, slope and the length of the main canal were obtained by using ArcView GIS software. Then, permeability specifications and the Land use of the watershed were obtained by using land use and permeability maps. Next, HEC-GeoHMS model was used using the prepared maps and data as described to obtain the CN of the basin. HEC-HMS model was simulated to obtain flood hydrographs with different return periods. From this, flood zonings for the threatened area at risk were specified. The results indicate that the Dough River sub-basin is more susceptible to flooding and has the highest flood rate. Using HEC-RAS Model and based on flood zoning maps, the scales of collateral and infrastructural damages to towns and villages including roads and building were estimated.

Abstract There are several methods for measuring and monitoring the status of soil moisture. One of the cheap methods compared with methods using more expensive devices, is determination of soil moisture status with the aid of a gypsum block. In this method, soil moisture status is determined by measuring the electric resistance of two electrodes embedded in the device. 5 brands of gypsum blocks with different structures were applied. The electrodes comprise of three omocentric cylindrical steal nets. The radiuses of these nets were 25, 15 and 10 millimeters. Gypsum Blocks were classified based on their types (dead, half dead, alive), composition (cement ratios) and the weight of gypsum used in their construction. By careful monitoring of their behaviors in air and soil, the most appropriate kind of gypsum block was selected according to their construction technique, type and ratio of their composites (gypsum and cement), electrode's space, characteristics of initial calibration and validation in the air and its equilibrium status in the soil. The blocks which use cement in structures have uniformity with soil moisture curve. In this study an ELE model 5910A soil moisture meter was used for reading the blocks. And as a result of the comparison of these devices functionality, the ELE soil moisture meter was recognized as a precise devise for the irrigation management program range. It was also determined that having the initial calibration curve of gypsum block in the air which is derived from the dimensionless relative moisture versus readings of the ELE, it is possible to measure the soil moisture without calibrating the gypsum block in soil.

Abstract This paper investigates the impact of inter basin water transfer from North Karun such as Koohrang number1&2 tunnels(under operation), Koohrang number 3 tunnel (under construction) and Behesht Abad tunnel (under Study), on the status of water resource in Behesht Abad and Koohrang basins using Water Evaluation and Panning System (WEAP) water balance model. The model was calibrated for a ten year period (1995-2004) and validated for a 30 years period respectively. .Results show that after the completion of all the proposed water resources development projects, river flows at both Behesht-Abad and Kohrang rivers will decrease by an average of 27 %. Also, considering the minimal environmental flow requirement for the downstream river, a total of 220 MMC of excess water can be transferred to the central plateau with a 95% confidence. By considering available regulated water resource, this figure can be increased to 470 MMC. Therefore, the maximum reservoir storage volume required is in Behesh-Abad dam is about 500 MMC. This is significantly lower than the suggested design storage of 1800 MMC; indicating that the proposed dam is over-designed by the consulting engineer.

Abstract Annual low flows are defined as the lowest average flows for consecutive days such as 7, 15,30 and 60 days (or d-days) period; in which d-days low flows are the minimum d-day moving average for a year. L-moment method was used for obtaining regional low flow frequency analysis in Halilrud, Jiroft. The stations in the area were found to be homogeneous by using two different homogeneity tests of Hosking and Wallis methods. Using goodness-of-fit-test, the best on site flow frequency distribution was found. Then for 3-parameter distributions was calculated from ZDIST period using a FORTRAN program. Pearson type III distribution was found to be the best regional low flow distribution. Finally, it was shown that catchments area is the best parameter for estimating low flows at different return periods for ungauged watersheds.

Abstract There are two important parameters in determining the suitability of land for crop production or amount of required water for leaching in saline soils: (1) the spatial distribution of salinity (ECe); and (2) pH in different depth of soil. Collecting sufficient soil samples and analyzing them are both time consuming and expensive. Therefore, it is essential to find alternative methods to easily estimate such parameters and with lower costs. Given that salinity and pH values are known for a particular depth, the same can be calculated for other depths since they are spatially correlated. There are two methods to estimate and prepare ECe and pH distribution map for different soil depths: Kriging and Cokriging methods. The aim of this study was to compare the results of these methods by determining the spatial distribution of salinity and pH in three soil depths 0-30, 30-60 and 60-90 cm in Boukan region; and to find out the spatial correlation among them. The results show that there is no significant difference between the two methods. Therefore, Kriging method is suggested, especially in the case of equal numbers of data and similar fitted models.

Abstract Water scarcity and soil salinity are two important limiting factors for agricultural production. Canola crop, with high resistance to soil salinity and adaptation to different climatic conditions of Iran, has great ability for satisfying the main part of the country’s requirements for edible oil. This research was carried out in 2006 on winter canola (Brassica napus L., cv. Zarfam) under greenhouse condition at the Agriculture and Natural Resources Research Center, Yazd. The experiment was performed as a complete randomized block design with three replications that contained salinity and irrigation water factors. Salinity factor had four levels of S1=3-4, S2=6-7, S3=9-10 and S4=12-13 dS/m and irrigation water factor had three levels of irrigation after W1=30, W2=50 and W3=80 percent of management allowed moisture depletion. Soil texture was sandy loam. The results showed that salinity and deficit irrigation were significantly effective on dry matter production (p

Abstract Ilam catchment was chosen for a study to examine the performance of MPSIAC model and its efficiency in estimating erosion and sedimentation (R). Initially, according basin maps such as topography map, slope map, direction map, elevation levels map, geology and etc. were prepared by using a GIS software. The first two primary maps were prepared by overlaying elevation levels on direction map and geological map on slope map respectively. The primary maps were overlaid to obtain the basic map with 132 working unit and 4 specific features including elevation, direction, geology and slope. Using the basic map and other available information and maps and controlling working units using GPS system in nature, MPSIAC model determined cumulative scores of 9 effective parameters for each working unit which make up the R value in each working unit corresponding to their total area in the catchment. The value of sediment was determined by substituting the value of R in the equation of the above model. Results of this research showed that sediment delivery ratio (R) in this catchment was 58.333 and sediment yield score and sediment yield weight were 303.981 m3/km2/year and 18234.327 Tons per year respectively. Based on the results in the study and the table provided by MPSIAC model, it can be concluded that Ilam catchment can be considered as medium class with regards to erosion and sediment yield and its sediment delivery intensity is between 50 and 75. Also, it was observed that estimated sediment yield can be categorized in terms of erosion classification and quality of erosion as class 3 and medium level respectively.

Abstract Because of difficulties in the field monitoring of overhanging riverbanks, it is not possible to monitor its deformations before failure, and therefore it is sometimes admittedly difficult to discriminate between shear versus toppling failures in the field. In This paper evaluated the extent to which uncertainties in the parameterisation of controlling factors feed through to influence the reliability of the resulting overhanging stability estimate.  Thus, the impacts of variations in each individual parameter on the factor of safety are investigated, while keeping all other parameter values constant. In estimating the magnitude of the uncertainty typically associated with each of the parameters, discriminating between (i) measurement errors and (ii) uncertainties associated with the inherent natural variability of each parameter is helpful. The results showed that the care should be taken when estimating the values of cantilever block height, block width, tension crack depth, block material cohesion, and the block material unit weight as the safety factor is more sensitive to the variation of these factors. Since parameter uncertainties are derived primarily from the inherent variability of the parameters, rather than measurement errors, much more careful attention should be paid to field sampling techniques.