IRAN-WATER RESOURCES RESEARCH
Year:2018 | Volume:14 | Issue:2 |Papers Count:30

In this study, the effect of ENSO was evaluated on groundwater table changes using 22 piezometers wells located in Isfahan and Hormozgan Provinces. The results showed that among 10 ENSO indexes, the Pacific North American Index (NOI) and the Multivariable Enso Index (MEI) presented the maximum correlation of groundwater table in Isfahan and Hormozgan provinces, correspondingly. In Isfahan the percent of wells that had significant correlation between groundwater table and MEI was 26%. In Hormozgan the correlation for NOI was 55%. The comparison of correlation values of groundwater table in each province with El Niño and La Niña phases indicated that the effect of El Niño phase on groundwater table in both provinces was more than La Niña phase; as in each province, the number of stations with significant correlation in El Niño phase was more than La Niña phase. In Isfahan province, the effect of El Niño phase on groundwater table changes was more than Hormozgan province (64% compared to 36%). The results of percent of groundwater table changes in each province in La Niña to El Niño phases illustrated that there was no similarity and matching behavior in the studied stations.

In the recent decade, the occurrence of regional dust storm which is partly originated from drying Mesopotamia Wetlands (especially Hawizeh Wetland) had significantly increased in west of Iran and caused a lot of problems in impacted areas. Dust storm is a cross-border phenomenon so an international solution is required to assess and control it. The aim of this study is to evaluate the use of cooperative (partial bankruptcy) and non-cooperative (Nash method) game theory in allocating Hawizeh Wetland environmental water right in different water allocation scenarios for Iran, Iraq and Turkey. The results indicated that the best option to encourage Turkey to release more water from the Tigris to provide environmental water rights of Hawizeh Wetland is Iran-Iraq coalition to reach an integrated political and economic agreement with Turkey. By comparing cooperative and non-cooperative methods, it was revealed that the non-cooperative method allocates larger shares of water to Iran compared to cooperative method. The proposed method of this paper can be used to evaluate supply of environmental water rights for trans-boundary waters.

In groundwater modeling, an array of factors are the cause of deviation between estimated results and the observed data which demonstrate uncertainty in groundwater resources system. In this study, with the aim of investigating the uncertainty of groundwater flow model in Ali Abad plain of Qom with the area of 1712 km2, the parameter of hydraulic conductivity, as the most important source of uncertainty, was used to analyze the parametric uncertainty. For this purpose, in order to simulate ground water level, different uncertainty ranges in 90% of confidence interval of hydraulic conductivity was investigated by Monte Carlo method and the uncertainty assessment criteria were used to quantify the uncertainty. Eventually, the most appropriate uncertainty range was defined. The Rosenblueth’s Point Estimation Method (RPEM) was used to reduce the calculation process and time and then its performance for analyzing the parametric uncertainty was compared to Monte Carlo method using assessment criteria. Results showed that the most appropriate uncertainty range with RPEM and Monte Carlo method for hydraulic conductivity was obtained by increase of 40% and reduction of 30% of this parameter. RPEM method showed a better performance of 43% compared to Monte Carlo method.

Building non-core rock-fill dams is amongst the most effective methods of controlling floods. In flood events the input-flow of such dams typically contains a considerable amount of sediments. This underscores the need to study the flow behavior and sediment concentrations so that one could identify the amount of passing and depositing sediments and decide on the management practices all of which have been taken into account in the present research. First, on the basis of numerical solution of Saint-Venant equations, the flow characteristics (e.g. depth and velocity) were calculated using finite volume method with a completely implicit method. Then the concentration of the sediments at different points of the reservoir was determined using discretization of the convection diffusion equation. The results of the experiments conducted on reservoirs of rock-fill dams in the hydraulic laboratory of Bu Ali Sina University, Hamedan, were then employed to assess the functioning and validation of the mathematical model of flow simulator and sediment concentration. Comparing measurement data of the sediment concentration and the calculations conducted in eight sections and three height layers of 5, 10 and 15 cm in the reservoir of rock-fill dam, the mean value of the relative error of sediment concentration was found to be 9.17 percent, indication a good enough correspondence between the output of the mathematical simulator and the value measured in the experimental model.

Optimization and modeling of the pressurized irrigation systems in other to reduce their construction costs has attracted many scientists up to the present time. Optimization of these irrigation systems has often been conducted by using available commercial codes or toolboxes of conventional evolutionary algorithms combined with hydraulic models. The code developed in the present research which is based on one of the powerful methods of optimization, e.g. genetic algorithm, assigns an integer numeric value to each available diameter. Then, to determine the optimum diameters in the pipe network, the cross-over, mutation and reinsertion with elitism approach is applied on set of chromosomes and an integer numeric for each pipe diameter is then selected. Obtained data from optimization subroutine is then sent to another subroutine that has been developed to simulate the water hammer pressure. Maximum pressure due to the water hammer phenomenon in each network pipe is calculated in this subroutine. Calculated maximum pressures are sent back to the optimization subroutine where constrains of the working pressure are substituted by the bursting pressure constrains. Exchange of information between the optimization model and the hammer model continues so that the calculated optimal diameters do not change anymore. The results showed that compared to the existing design conditions, optimized design by the present model reduces cost of implementation of pipelines in Ismail Abad irrigation network from $825935.28 to $730958.37 which is equivalent to 11.5% of the total cost of pipeline implementation. Also the results showed that by changing the diameter of 3 pipes out of 16 existing pipes the excess pressure of the water hammer due to the rapid closing of all valve at the end of pipelines in less than 1 second can be controlled. In this case the cost of implementing the pipelines increases by 6.1% e.g. from $730958.37 to $775511.5.

Nowadays, evapotranspiration, which is an important component of water balance calculations, can be estimated using the technology of remote sensing. MOD16 actual evapotranspiration data are produced using the MODIS sensor imageries and have a spatial resolution of 1 Km. In the present study, MOD16 actual evapotranspiration data are compared with the actual evapotranspiration estimated using SWAP model. SWAP model was calibrated using the measured soil moisture content data during the growing season in two 38.9 and 45.6 ha corn fields located in Qazvin Province. The average RMSE values in the two fields under study were, respectively, 0.026 and 0.025. Considering the actual evapotranspiration estimated by the SWAP model as the evaluation basis, the MOD16 data were assessed. Accordingly, the RMSE values were obtained respectively 1.46 and 1.94 mm/day in the first and second field. Also, the r2 values were calculated as 0.86 and 0.87. The results of the present study suggest that MOD16 product can be effectively used when the measured data of evapotranspiration are not available.

The main purpose of this study was to implement, evaluate and modify the Dynamic Water Balance model (DWB) considering the proportional coefficients, like hydrological reality-based constraints, and implement the withdrawal of groundwater and surface water resources along with calibration and uncertainty analysis of its parameter. Based on the results and principal of equifinality, it is clear that a unique best set of optimal parameters of SDDWB and DWB modelscannot be achieved in general, and often the models’ parameters in the selected study areas to test (Neyshabur and Rokh watersheds) had similar effect on the simulated water balance. The average total amount of surface water balance error in DWB model for Neyshabur and Rokh watersheds were respectively -9.74 and -69.63 m3 which represented the poor performance of the model. There was a significant difference between the simulated and observed aquifer volume changes for which the main reason was that the effects of groundwater withdrawals were not employed in the model. Reviewing the performance results showed that the relative PRMSE index of the SDDWB model for both study areas were less than 10 percent, indicating the acceptable accuracy of the SDDWB model. In general, the results depicted that the overall error rate of surface and groundwater discharge equation components in SDDWB model were much lower than the DWB model which indicated the positive effects of its modification and development versus its original structure, DWB model.

One of the primary needs of planning for the management of water resources is to predict the amount of water necessary for agricultural practices, industrial usage and municipal consumption. Accordingly, it is necessary to determine the potential of water supply in different time scales for efficient plans by appropriate and reliable methods. The probability analysis is useful methods for prediction of components such as precipitation. The Markov chain is among these methods. Markov chain models are a special case of models in which the current state of a system depends on its previous state. In the present study, using available records of daily rainfall for 22 years (1995-2016) of the Lamerd weather station (in Fars Province), frequencies and durations of rainy days were studied by using Markov chain model. In this study, the period of May to October was disregarded due to the insignificant number of daily precipitation events. The daily rainfall data were arranged based on the transition matrix of occurrence of dry and wet days, while the transition matrix was calculated based on the maximum likelihood method. In previous studies done in Iran, only the first order of the Markov chain was used to forecast precipitation by using the Markov chain, which may not be in good agreement with the data and may resulted in incorrect results. But in this study, by using an accurate statistical method, the appropriate order of the Markov chain was diagnosed to be used. Matrixes of stationary probability and the return periods of rainy days for 2 to 5-day precipitations were determined for the studied months in this research. The results showed that the probability of precipitation per day is 0.126, and the probability of absence of precipitation is 0.874. It was also found that the highest probability of having rainy days occur in the months of January and March, and that precipitation in Lamerd city does not exhibit temporally homogenous distribution.

Currently, adaptation to water resources changes is one of the priorities in integrated water resources management. The capability of learning from past experiences is one of the main characteristics of such an adaptive structure which is crucial in dealing with changes. Adopting a social learning framework, this study aims to assess the water institution (both formal and informal) in the Tashk-Bakhtegan Basin. The social learning loops, orientation and direction features were adopted to assess the formal institution. To assess the informal institution, the drought of 2008 was considered as the change that affected the water resources system of Tashk-Bakhtegan Basin. The responses of informal water institution to that change were then assessed. Formal institutions were assessed by using qualitative content analysis of water law and project's documents. Informal institutions were detected by using snowball sampling and were assessed by using semi-structured interview and qualitative content analysis. For formal institutions, the results showed that this structure relies on the national authorities and has low level of learning capacity. In the informal sector, the components of social learning process were generally found low in the upstream (because there is still enough water resources), but those components were found at much better levels in the downstream. The assessment of social learning outputs components showed that the downstream sub-regions were at a higher level of social learning capacity comparing with the upstream (double and triple loops of learning are active), and the responses were oriented towards better conservation of water resources. Furthermore, the width of those responses went beyond individual levels to collective and participating levels. Therefore, those sub-regions showed to have higher level of adaptation capacity. For the water institution of the Tashk-Bakhtegan Basin, this paper suggests that implied mechanisms of water laws need to be modified, national and centralized governance requires to be transformed to participatory and cooperative structures, private and public institutions need to be initiated, and finally the components of social learning process, that were found at a low level, require to be improved.

Population growth and economic developing programs have increased the pressures on water resources and put serious challenges on the balance of water resources and especially groundwater systems. In recent years, green water has been considered as one of fresh water sources while various acts have taken for its scientific and practical management. Green water management acts affect both surface and ground water resources and can be effective in aquifer restoration plans. In this research, the effects of these acts in the study area of Namdan located in the Tashk-Bakhtegan basin in Fars province of Iran have been evaluated using MODFLOW model. The model was calibrated for a seven year period (2006-2013) and validated for a three year period (2013-2016) in both steady and unsteady conditions. Then, the effects of mulch, stone lines, terraces, and contour acts on the balance and the water level of the aquifer were investigated. The results showed that the mulch with the average of an annual increase of 4.2% in storage and terrace with an increase of 4% of stored water in the aquifer have had the greatest impact on the aquifer, which can be suitable acts for the aquifer restoration under plans such as Iran Aquifer Restoration Plan but results are not enough to cover for the restoration objectives.

The main goal of this paper is to explor of the effective parameters on behavior of the water supervision agents (decision makers and farmers) and to simulate them under rules and policies of water. To follow this goal, the framework ofagents’ behavioral rules on Lenjanat sub-basin was formed and then the behaviors were addressed with simulation using agent-based model. Agent-based model can be used for modeling of different agents, defining behavioral characteristics, showing links and interactions between agents. In this research the AnyLogic software has been applied. For evaluating the effects of parameters such as “Meeting with other organisations by regional water company” two scenarios (efficient and inefficient) were developed. The results showed that changing the behavior and the interaction of regional water company with other organisations are extremely effective. For example, having “Meeting with other organisations by regional water company” increases violation control by 36% in the first scenario (inefficient) while the absence of this parameter decreases violation control by 72% in the second scenario (efficient). Also, the results of scenarios showed that linking and suitable interaction by the regional water company can change the control of illegal withdrawals from 12.8 to 70.3 million cubic meters in 5 years.

Rivers have an important role to play in providing most of the water needed for agriculture, industry and domestic consumptions. They also are amongst the important economic and social arteries of various human societies rooted in the lives of people in every land. Most of surface water contaminations are non-point source pollutants which generally contain various forms of nitrogen and phosphorus. In this study, the amount of nitrate input from agricultural lands to Zanjanrood River has been simulated using the SWAT model. In order to calibrate and validate the results, SWAT-CUP software and measured mean monthly average flow rate at Sarcham hydrometric station (1996-2013) were used and 26 sensitive parameters were selected for sensitivity analysis. Three scenarios for irrigation practices, three scenarios for fertilizer rates and two integrated scenarios were defined. The p-factor and r-factor indices were used for uncertainty analysis and two statistical indices, i.e. determination coefficient (R2) and Nash-Sutcliff (NS) coefficient, were used for quality analysis of the results, . In the monthly runoff calibration, at the basin outlet, the coefficients r-factor, p-factor, R2, and NS were 0.27, 0.11, 0.83, and 0.53, respectively. At the validation stage, they were respectively estimated as 0.6, 0.18, 0.73 and 0.53. The results showed that by increasing the pressurized irrigation, the nitrate pollution in the basin was not significantly affected. With regard to fertilizer levels, by reducing consumption of urea fertilizers up to 50%, the amount of nitrate input into the Zanjanrood River reduced by up to about 16.7%. On the other hand, an increase of 50% in fertilizer use has increased nitrate input into the river by 17.2%. The study suggests that changing the surface irrigation method does not lead to a significant change in the average nitrate output from the basin. Also, reducing the amount of fertilization and preventing unnecessary fertilizations by farmers, can greatly prevent the pollution of water resources.

Faults are among very important factors that makes the groundwater flow systems complicated. Doroud Fault in Doroud-Borujerd plain, as a segment of the main Zagros thrust, is an active and strike-slip fault with NW-SE trend. The aim of this study was to evaluate the Doroud Fault impact on alluvium aquifer after the earthquake event of March 2006 using the groundwater iso-potential map, hydrographs of observation wells, electrical conductivity of the groundwater, and the water table fluctuations in relation to the earthquake. Results showed that the abrupt changes in the lithology and thickness of the aquifer as well as the groundwater salinity areprobably associated with Doroud Fault’s movement. In addition, lagoonal fine grained sediments and the low quality of groundwater observed in the eastern fault block and moreover, the groundwater channelized in the western block of the fault are among the hydrogeological effects of this fault. This study suggests that in one month the earthquake caused up to an approximate two meter rise in water table in the areas adjacent to the fault comparing to 0.5 meter water table rise in other areas. Unexpectedly, the electrical conductivity of groundwater has a decreasing trend in the flow line direction, but with some local increasing anomalies along the fault zone.

Land subsidence is often triggered by over abstraction of groundwater due to increased agriculture, industry and domestic demands. This problem is investigated in Shabestar plain formulating a framework to estimate subsidence potentials and the outcome is compared with measured values with the lowest subsidence threshold value of 30 cm. The research put together seven hydrogeological and geological factors affecting land subsidence, which comprised groundwater level decline, aquifer media, recharge, groundwater withdrawal, land use, aquifer thickness, and distance to faults. The resulting maps for vulnerability to subsidence were then validated with results from satellite images. Although the primary results were also acceptable, the Genetic Algorithm (GA) was used to optimize weights and to improve the correlation between calculated indices and their corresponding measured subsidence values. Results confirmed the improvement and further showed that the southern and southeastern areas in Shabestar plain have the most subsidence potentials. As such management plans are essential to meet the local demands and yet to protect the land against subsidence and other adverse impacts.

Passive defense measures are used to preserve equipment and vital installations of a country from the financial damages and prevent or minimize human loss. In this study, a risk analysis model was prepared and applied to Salman Farsi treatment plant as the case study, in order to select and rank the considerations of passive defense in water treatment plants. In other words, risks of all threatening factors to water treatment plants were designated separately, based on Fuzzy AHP method. Then, the contribution of each unit of Salman Farsi water treatment plant in total risk was determined. Obtained results of the proposed model indicates that the factor of earthquake has a threatening risk of 13.7% in Salman Farsi water treatment system which is the highest risk percent. Also, the chlorine gas storage tanks have the highest contribution in total risk of Salman Farsi water treatment plant system.

In the last decades, various methods have been proposed for stochastic operation optimization of reservoirs out of which one is the Stochastic Dual Dynamic Programming (SDDP). Reviewing the literature shows that in most previous studies the inflow uncertainties have been mostly modeled by auto-regressive AR (1) or seasonal aut-regressive PAR (2) models when using SDDP. Another approach toward inflow uncertainty modeling by SDDP uses Markov Chain which has received less attention. Furthermore, applicability of SDDP in developing long-term operation policies has not been tested before. In this study, MSDDP model has been developed which uses Markov chain concept. Also, after presenting an algorithm for using SDDP and MSDDP for formulating long-term operation policies, their performances have been compared in Karoun multi-reservoir hydropower system. The results have shown absolute superiority of MSDDP in formulating long-term operation policies. Furthermore, operation policies obtained from SDDP have shown highest compatibility with the best possible operation policy when there is no uncertainty (deterministic conditions).

Digital elevation models (DEMs) are one the most important inputs of hydraulic and hydrological models. Due to lack of high resolution maps, especially in regions where data is scarce, hydraulic modeling is a difficult and challenging task. In recent years, remote-sensing based DEMs are extensively used in several studies particularly hydraulic modeling due to ease of access and being free of charge. One of the most important questions in application of hydraulic models is the efficiency of these DEMs in flood simulation. This research focused on application of remote-sensing based DEMs, such as SRTM-30 and 90m, ASTER-30m and ALOS-30m DEMs, on the performance of HEC-RAS-1D model in two different rivers of Iran. The results showed that the accuracy of ALOS-30m DEMs in deriving geometric model and subsequently flood simulation was higher and more considerable than other DEM sources. For instance, the average relative error (RE) of using this valuable dataset in simulating inundated extents in Sarbaz and SojasRood rivers was lower than 13 and 9 %, respectively. In contrast, the results of ASTER-30m DEMs in both rivers was not satisfactory and the average RE of inundated extents was more than 38%. As an overall conclusion, one can deduce that ALOS-30m and ASTER-30m DEMs are the best and the worst datasets for deriving geometric model, flood inundation mapping and flood simulation. Hence, in areas with data scarcity or for underfunding projects, using ALOS-30m DEM especially in early design stages can be useful and more beneficial.

In many countries, especially developing countries, due to data shortage and costly environmental studies, simple hydrologic methods, such as the Tenant and Q95 methods, are main methods for determining environmental flow requirements. In this study, it was shown that employing these methods could lead to results which do not comply with ecological conditions of rivers. For illustrating difficulties in providing required data for running physical habitat simulation models the River2D as a 2D hydraulic model was used. The ecological regime of the studied river resulted from River2D was completely different from the outcomes of the two aforementioned hydrologic methods. The RVA method was investigated based on the assumption that the method is as simple as the other hydrologic methods while it is capable of giving results as precise as habitat simulation models. In the case study, the situation of the river based on the suggested EF by the Tenant and Q95 methods was shown and it was illustrated that the monthly ecological flow determined via River2D was captured by the upper and lower limits of the RVA method. Moreover, it was concluded that using monthly median flow instead of mean monthly flow is preferable in the presence of skewness. Finally, it was determined that the discharges prescribed by River2D could not be supplied in all months, while the RVA minimum monthly environmental flows could satisfy all the necessary conditions for conserving biotic and abiotic habitat in the study river.

Hydrochemical analyzes of 35 water samples during a dry and a wet seasons (July 2016 and April 2017) have been used to identify, extract the main factors of the hydrochemical changes, and investigate the geochemical processes controlling the surface water and groundwater resources of Bostan plain. In this research, two multivariate statistical methods of hierarchical cluster analysis (HCA) and principal components analysis (PCA) were used to classify water quality samples of the region. According to HCA, there are three main hydrochemical facies in Bostan plains; facies with higher salinity (group 1: Na-Cl), lower salinity facies (group 2: Ca-Na-SO4-Cl), intermediate facies (group 3: Na-Mg-Cl). In the analysis of the PCA, the first factor of the three factors showed 68.2% of the change. The second and third factors exhibited 14.45% and 9.25% of the change, respectively. The results of this study clearly demonstrated the usefulness and benefits of multivariate statistical techniques in assessing the hydrochemical characteristics of surface and groundwater.

Estimation of actual evapotranspiration (ETa) at the scales of basin and field is one of the essential information for water resources allocation. Although estimating actual evapotranspiration encounters spatial, temporal and cost restrictions, but data from satellite images can usually overcome these limitations in various extents. In this regard, the objectives of the present study were; a) evaluation and validation of WaPOR ETa product using Scintillometer instrument and, b) estimation of ETa over several land use regions in Zayanderoud basin. Based on the obtained results, MAE, RMSE, MAPE and R were equal to 2.14 mm for 10 days, 2.55 mm for 10 days, 5.50 and 0.97, respectively, which represented the appropriateness of WaPOR ETa data compared to Scintillometer. Also, the analysis of WaPOR product in different land-use showed that the maximum amount of actual ETa in 2016 has occurred in dual crops (513 mm), orchards (387 mm), spring crops (272 mm), autumnal crops (271 mm), dry farming (112 mm) and rangelands (83 mm). Also the results in rice fields showed that 992 mm of fresh water was lost in the form of ETa which is considered a dramatic value due to the climate and water resources of the selected basin and its relevance challenges.

In this paper, firstly, the 3D model of the Urmia Lake was obtained using SURFER software. Then the volume-area diagrams were drawn in different elevations. Afterwards, hydrological balance of Urmia Lake was simulated considering the evaporation volume, inflow surface volume, recharging groundwater volume, precipitation and other influencing parameters by using the System Dynamics. The main advantage of using System Dynamics was its ability to consider the feedbacks of elements within a system. The simulation was performed using VENSIM and after reviewing the results of the lake balance it could be seen that due to the particular situation of the basin, evaporation from the lake, is the most important factor in losing water from the basin. So the construction of dikes could have a significant impact on reducing the evaporation rate from the lake. In this context, various locations for constructing the proposed dikes were recommended. The effects of each dike on evaporation level and hydrological balance were examined in three location scenarios. The results indicated that by construction of dikes in the first scenario, the lake level rises to 1, 274 masl (the Ecological Level) after 65 months. This level was achieved in the second scenario after 120 months. In the third scenario in 10 years the lake level did not exceed 1272 masl.

In recent decades, metaheuristic algorithms have been applied successfully in various water resource engineering and management issues especially in optimal operation of reservoirs. In this paper, a model has been developed based on Symbiotic Organisms Search (SOS) algorithm for modeling optimal operation of complex multi-reservoirs systems. In the first step, the performance of the method was successfully assessed through several benchmark functions. Then SOS algorithm was used to derive the optimal operation of four- and ten-reservoir systems. The results of SOS were compared with other developed evolutionary algorithms including Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). The results showed that for cases of four- and ten-reservoir systems the best solutions achieved by the SOS were 308·8114 and 1190·0227, respectively. The results revealed that the SOS algorithm was the superior algorithm in optimal operation of multi-reservoirs systems.

Modern horseshoe spillways are combinations of external and internal weirs. In this study, by constructing a physical model of a modern horseshoe spillway including three different internal weir scales, some hydraulic parameters of these spillways; like discharge coefficient of the internal weir (CO) and discharge rate through the internal weirs, were investigated. Accordingly the effect of changing internal weir’s scale on the CO was examined in the research. The results showed that by increasing the internal weir’s scale from 1: 10 to 1: 5 and 1: 2.5, the head above the modern horseshoe spillway at the same total discharge, respectively declined to 44, 48 and 56% compared to the head in rectangular weir with the same width. Also by increasing the scale of internal weir, the ratio of the discharge to external weir discharge (Q1/Q2) decreased while the CO increased. To investigate the effect of varying internal weir’s area on CO, the ratio of the area to multiply of weirs length (A0/L0×Lw) was used and it was found that in the spillway with scale of 1: 2.5, the CO increased by increasing the ratio of A0/L0×Lw. Based on the results it can be claimed that the modern horseshoe spillways with internal weir with scales of 1: 2.5 has the best hydraulic performance.

In order to investigate the frequency of snowfall in Iran over the past decades, the data of present hourly weather were used at 304 synoptic stations during the period of 1951-2010. First, 6 snowfall parameters were extracted and the time series of temperature, dew point, and percentage of snow codes were calculated. Also the temperature conditions of the dew point and the temperature of the dew point were considered in time of snowfall. The results showed that snowfall in Iran is a low frequency phenomenon and includes less than 2% of the present weather. On the other hand, shower snowfall and extreme snow are not common, and most of the snowfall is mild to moderate.In terms of time, snowing is possible in Iran from November to the beginning of April, but most snow events occur in months of January and February. There is a possibility of snow falling throughout the day and night, but the highest frequency of snow associates to the early hours of the day, especially between 6 to 10 am. The frequency distribution of snowfall has a negative skewness and its axis of symmetry is around zero degrees. So that the best temperature conditions in ground surface for snowfall is around zero degrees Celsius, especially in the temperature range of 1 to -5 degrees Celsius.

In this research, the goal of evaluating the accuracy of interpolation methods is the prediction of spatial distribution of some of the quality indices of groundwater in Urmia plain. At first, the water quality data of 20 wells in the years of 2001-2014 were analyzed. The Kolmogorov-Smirnov test showed that the data were not normal and therefore the conversion of the box-cox was used to normalize them. Then, using the GIS software, the best semivariogram model was fitted to the spatial structure of the data. The results showed that for water quality parameters, circular, spherical, and exponential models are the best models for semivariogram. Then, the spatial variations of parameters were studies using different interpolation methods such as Kriging and Inverse Distance Weight with power of one to three. Then, the zoning maps of qualitative parameters were drawing with the most appropriate method in the ArcGIS software. Plain aquifer was also examined considering Wilcox and Schoeller standards for agricultural and drinking purposes. The results of the Wilecox and Schoeller standard showed that 40% of the wells in the plain have brine water to use for agriculture. Also the wells above are of good quality and acceptable for drinking.