a. fakheri fard

A hydrological parameter affecting the management of water resource systems is changes in the amount and occurrence time of extreme precipitation (OTEP). In this research, the seasonality of precipitation in the Lake Urmia (LU) basin was analyzed using the daily extreme precipitation data of 30 rain gauges in the statistical period of 1991-2018. The uniformity of OTEP was tested by Rayleigh and Kuiper’s tests at 0.1, 0.05, and 0.01 levels. The slope of the trend line for OTEP was estimated using the modified Sen slope estimator. The uniformity of OTEP was rejected at each level. The results revealed two strong seasons: late winter and early spring (S1) and autumn (S2) for OTEP. The results showed a general median seasonality index of 0.3, which changed to 0.82 and 0.9 for S1 and S2, respectively, after dividing the whole year into two seasons. The seasonal strength of S1 was similar in both the western and eastern parts of LU, but the west of the lake was stronger than the eastern part in S2. In S1, negative and positive trends in the OTEP were observed on average in 40% and 60% of the stations, respectively, with corresponding values of 77% and 27% for S2, respectively.

Determining the actual evapotranspiration value and analyzing its temporal trend is essential for optimal water resources management in a basin. In the present paper, the actual evapotranspiration time series is simulated and its trend is analyzed according to the trend of climatic variables and land use in the Ajichi basin during the period of 2015-1987. The comprehensive SWAT model was set up, calibrated, and validated for the Ajichi basin. Also, the average of simulated actual evapotranspiration of crops (in wet years) was compared with similar values in the National Water Document. The results of the Mann-Kendall trend test showed that the annual rainfall in most meteorological stations had a decreasing trend and the rainfall trend in the ten stations decreased significantly. While the annual maximum temperature at all stations and the annual minimum temperature in most of them have significantly increased. Investigation of land use maps illustrated that the irrigated land area of the basin has increased by a 39% during the study period. According the study's results, the potential evapotranspiration of the basin has had a significant increasing trend with a rate of 2.54 mm per year. The results indicated that despite the increasing trend of potential evapotranspiration and irrigated land area, the actual evapotranspiration of the basin had a significant decreasing trend with a rate of 2.2 mm per year due to the decrease in rainfall.

In drought risk management, the regional analysis of drought is significant. In this paper, this important issue is investigated by presenting the new hydrological regional drought index (RDI). For this purpose, the Ajichai basin was selected as the study area. First, the time series of the streamflow drought index (SDI) was calculated for each of the hydrometric stations in the basin f regional analysis of hydrological drought. Then, to determine the homogeneous regions in terms of hydrological drought, the k-means method was used for clustering analysis. Based on the clustering results, 6 Homogeneous regions were identified in the basin. For each of these regions, the time series of the RDI index was calculated from 1365 to 1393. The results showed that during the study period in each of the regions 1, 2, 3, 4, 5, and 6, mild Wet and mild drought has occurred at 82.1, 80.1, 78.9, 83.3, and 84.3 percent of regions, respectively. Also, the total percentage of drought events (moderate and high) is higher than the total percentage of wet events (moderate and high) in all regions. So, during the study period, the total percentage of drought events (moderate and high) is more than twice the total percentage of wet events (moderate and high) in regions 2 and 3.

Characterizing soil infiltration parameters is time consuming and costly. We carried out the current research to predict different parameters of soil infiltration using field/laboratory measured and remotely-sensed data. The investigated parameters included infiltration rates at different time intervals and the parameters of the three well-known infiltration models. We employed soil sampling and field measurements on late spring 2012 and acquired ETM+ data for the correspondent dates. We measured several soil properties as well as infiltration. Then, we developed several pedo-transfer functions (PTFs) from the collected field/laboratory measured and remotely sensed data to predict the intended infiltration parameters. Results showed that field/laboratory measured data were able to predict soil infiltration rates and parameters of the investigated models with reasonably high accuracies (E value up to 0.961). The results also revealed that, although there was no significant and robust relationship between soil surface reflectance and the investigated parameters, the developed PTFs had reasonable accuracies (E value up to 0.634) in estimating the intended infiltration parameters using soil characteristics (moisture content, soil separates, and organic carbon) which are predictable from remotely sensed data.

Prediction of water table oscillation, especially in arid and semiarid areas is essential for better planning. In this study, monthly data of water table elevation, during the period of 1380 to 1390 for Ajabshir plain with an area of 130 km2 were used by application of two methods to estimate and predict the water table elevation. The date of 1380 to 1390 were used for estimating and the water table elevations were predicted for the three years of 1391 to 1393. The first method is solving partial differential equation for consecutive time steps and the second one is time series model. The GMS software was used for numerical solution of the differential equation by finite difference method. The correlation coefficient value of 0.9 and RMSE value of 0.41 between the estimated and observed amonts of groundwater levels were obtained using this method. The best fitted model for the water table elevation data using time series was ARMA (3, 2), correlation coefficient and RMSE values of this method were 0.85 and 0.49 respectively. According to the evaluation criteria, the partial differential equation method was more accurate than the time series method.

One of the experts' suggestions for restoring Lake Urmia is to convert irrigated lands in to rainfed farming in the Urmia lake basin. Rainfed wheat farming might be considered as one of the effective alternatives to the irrigated areas. So, evaluating the soil available moisture as the most important limiting factor of the rainfed wheat farming is necessary. Since the field experiments are costly and time-consuming, application of the crop yield simulating models, e.g. AquaCrop which can estimate the crop yield based on soil water content with high accuracy, would be desirable. In this study, after calibration and validation of the mentioned model for simulating rainfed wheat yield in Tabriz plain during a period of 35-years (1360- 1395 HJ), the meteorological variables of the studied region were predicted for a 5-years ahead prediction interval using Thomas- Fering method. The rainfed wheat yield was then estimated using Aquacrop model for the period between 1396 and 1400 (HJ). Finally, management scenario for increasing the potential of rainfed wheat was proposed. The results of this study confirmed the ability of the conjunctive crop model and time series technique for simulating crop yield and meteorological variables in the studied region. Results showed that despite no significant change will be occurred in rainfall amount, ascending trend of the air-temperatures will cause an increase of about 13% in rainfed wheat yield during the next five years. Also, due to precipitation insufficiency for rainfed wheat farming, predicted supplemental irrigation is recommended equal to 40 mm, to increase the potential yield production.

Reduction of rivers inflow which discharge to reservoirs of the country such as Lake Urmia is the most important present problem of water industry. so the role of runoff coefficient to determine the runoff arising from precipitation in order to anticipate and manage the stream flow is of great importance.Soil moisture, especially surface soil moisture, plays an important role in the natural water cycle in nature particularly in the distribution of rainfall and its turn into runoff and infiltration. On the other hand, stream flow always affects the level of the groundwater table. Therefore, the relationship between the runoff coefficient with surface soil moisture and water table level in order to determine the volume of runoff arising from precipitation can be one of the most important issues in the field of water resources management. In this study, MODIS satellite images were used to estimate the spatial and temporal variations of soil moisture and relationship between instantaneous runoff coefficient (events) and daily groundwater table level, as well as its relation with daily surface soil moisture extracted from the atellite images for the two hydrometric stations located at the beginning and end of the Ghaleh _Chay river discharging into the Lake Urmia were investigateResults of this research confirmed the existence of a direct relationship between the runoff coefficients and water table at the Shishavan and Yengejeh stations with a correlation coefficient 0.9 and 0.84 respectively.Also direct connection between the runoff coefficient and daily surface soil moisture was registered with correlation coefficient of 0.792 and 0.815 at the stations of Shishavan and Yengejeh, respectively.

For reducing the destruction of water resources and for resolving the future populations, needs for food, the replacement of rainfed farming instead of water farming will be inevitable. According to the importance of the agricultural sector, determining indices to identify the fertile lands for cultivation of rainfed wheat is essential. For this purpose, to evaluate the yield of rainfed crop at the East part of Lake Urmia, two indices Interval Ratio and Partial Interval Ratio, for identification of the eligible areas for rainfed farming, were introduced using irrigation depth, irrigationintervals, and daily rainfall in corresponding with the time intervals. Clustering of the indices and yield of rainfed area were done with a K-means method. Regionalization of the obtained clusters for the yield and indices were done in GIS environment. Results of the regionalization showed that between the two introduced indices the Partial Interval Ratio index has the more compatibility to region reality, So the Partial Interval Ratio index selected for evaluating the rainfed regions. To identify the fertile rainfed regions of crop yield, the isoline of the yield of rainfed and index (Partial Interval Ratio index) was used. The results showed that in the northwest and central parts of the studied area the yield and Partial Interval Ratio index were increased, which indicated the good potential of rainfed farming in these areas. Therefor the fertile regions based on the introduced index were at the central and northwest parts of the studied area.

Imperfect knowledge due to unpredictable climatic conditions leads to uncertainty in decision making in agriculture. Therefore, a probabilistic analysis of the various possibilities besides increasing flexibility in decision-making can also enhance the reliability of decisions. Using Tabriz Synoptic station’s data, the values ofthe crop (TriticumAestivum L.) evapotranspiration and effective rainfall in mid to late season in the study area (Tabriz plain) were estimated. Analyzing the effective rainfall and crop evapotranspiration as probabilistic variables, a reliable method for estimating the irrigation water requirement was described using the “probability distributionfunctions”.By examining 12 different probability distribution function, it was found that the log normal distribution function achieves the best results for the monthly precipitation data with values greater than 30 mm, but there is no unique probability distribution function for evapotranspiration data.This method can also provide a general formula for calculations of irrigation water requirement with different probability levelsduringthe growing season. Results showed thatthe reported values of irrigation requirement in the NETWAT program that is atthe 50 % probability level andused in most of irrigation projects in Iran, were different the calculated values in this study.According to similar reports in different researches, the represented method is recommended for more precise estimation of irrigation water requirements (with different probabilities) especially in critical situations (with high evapotranspiration and low rainfall values) or for crops that are sensitive to water stress in 80% probabilitylevelor higher.

Local scour around bridge pier is one of the most important destruction factors of bridges. Many researchers have investigated scour around bridge pier; however, there is still not available single solution for this issue due to complexity of the problem and multiplicity of the effective factors. Different methods have been proposed to prevent or reduce scouring around bridge piers such as Riprap, collar, slot, submerge sheet and so on. According to researches, installing a collar around the base to delay the onset of scour in some cases significantly reduced the depth of scour around the base. In this study, by using the rectangular collar around the cylindrical pier, the effect of the collar thickness on scour reduction around bridge pier was investigated. The results of the experiments showed with installation of the collar not only velocity of scour is reduced but the depth of scour hole around the pier especially in downstream of the pier is also decreased. Also, with increasing collar thickness, the performance of the collar is reduced. Based on the results, the collar thickness was equal to 5 percent of the pier diameter and less than that had negligible reduction in the performance of the collar. However, the performance of the collar decreased when the collar thickness was more than 5 percent. Therefore, the appropriate thickness of the collar is proposed 5 percent of the pier diameter.

Drought monitoring systems are efficient factors in providing methods for drought mitigation and its logic management. These systems are designed by using of drought indices and their goals are presenting a simple and quantitative evaluation of drought characteristics. From the many of drought indices، the standardized precipitation index is used vastly for drought monitoring. For this purpose in the present study، meta-heuristic methods such as genetic algorithm and simulated annealing algorithm were used for accurate estimation of this index in Tabriz station for 1965 to 2004. The results showed that genetic algorithm and then simulated annealing algorithm had better results، respectively، in analyzing standardized precipitation index in comparison with maximum likelihood method which was conducted to precisely monitor drought events.

In the present research the transformation of rainfall into runoff was simulated using twodimensional Saint-Venant equations in the Kamanaj watershed, a subwatershed of Ajichay, located in East Azarbaijan Province, Iran. Rainfall-runoff was simulated based on diffusive model by consideration of momentary infiltration rate for temporal and spatial analysis. Saint-Venant equations were solved using explicit method of finite difference numerical technique as the initial and boundary conditions were defined. For this purpose, the watershed area was divided into 250×250 meters cell size grid by the tools of GIS, then digital elevation model was prepared. Kostiokov infiltration model, as the best fitted model to measured infiltration data was selected for expression of infiltration in Saint-Venant equations. Three hydrographs were used to verify the model. In the calibration of the model, lower relative average error of discharge was equal to %9.4. Comparing the simulated hydrographs to those observed, verificated the capability of model in simulation of rainfall-runoff. The presented model can be used for determination of runoff from momentary rainfall with consideration of temporal and spatial variation of infiltration over the watersheds. This model can also be used to forecast the peak discharge and time to peak in the watershed outlet.