نشریه پژوهش های حفاظت آب و خاک
سال بیست و دوم شماره 4 (مهر و آبان 1394)

Climate condition is one of the most important factors which affect agricultural production. Amongst climate parameters, rainfall variability is one of the most crucial factors which has important role on agricultural productions because of its effect on available water for plants. The amount of water available to plants strongly depends on the rainy seasons onset, length and rainfall temporal distribution, hence can determine a success or failure of a growth season. One of the most important areas for crops production in Golestan province is the Aq-Qalla township. Most of the areas are used for rainfed farming, such as wheat and barely. In general, agriculture in Aq-Qalla township is dependent on rainfall. Determination of the precipitation spatial variability in these agricultural lands is particularly very importance. Therefore, the objectives of this research were the investigation of different interpolation methods for estimation and zoning of precipitation variables in agricultural lands of Aq Qalla township for rainfed cropping of autumn cereals. Also, this research provides information at local level that could be used by farmers to increase of yield in rainfed condition.
In this research, the spatial distribution of precipitation on agricultural lands of Aq-Qalla township evaluated using 18 method-models from deterministic and geostatistic interpolation such as, Inverse Distance Weighted (IDW), Universal Kriging (UK), Ordinary Kriging (OK), Radial Basis Function (RBF) and Local Polynomial Interpolation (LPI). The performance criteria for evaluation were Root Mean Square Error (RMSE) and General Standard Deviation (GSD) with the Cross Validation methods.
The results showed that Local Polynomial Interpolation (1 and 2 degree) was the best method to estimate precipitation parameters except spring and June precipitation. Because, it had the highest accuracy and the lowest error for estimating of these parameters. Semivariograms analysis indicated that annual and June precipitation were best fitted to Exponential model, also, autumn, spring and May precipitation by Spherical model. Results of final maps showed that amount of annual, autumn and June rainfall were lower in north than south regions. Moreover, the results of this research showed that about 65.62 percentage of agricultural lands of Aq-Qalla had suitable level of annual rainfall (300-400 mm). Also, in this area amount autumn rainfall was 101.11 to 166.08 mm.
The results indicated that same as temperature requirements, the annual and autumn rainfall requirements of current crops such as wheat and barley are provided in this township. But, amount of spring and June rainfall are non-suitable in this area. Wide area in Aq-Qalla township were under 10 mm rainfall in June. This amount is not enough for grain filling.

Climate change and its impacts on water recourses is known as one of the most important challenges which human would be faced with it in the future century. Although different studies are performed to consider the effects of climate change on the metrological and hydrological variables using climatic scenarios and General Circulation Models, but its effects on agricultural sectors such as water requirement are less investigated. The main objective of this study is to asses the effect of climate change on the net irrigation requirement changes of main crops in Hamadan-Bahar plain (winter wheat, barley, potato, sugar beet, maize (grain), maize (grass), peas and onion) in three next decades according to different scenarios using LARS-WG5 model compared with baseline period.
In this study daily metrological variables including precipitation, minimum and maximum temperature and relative humidity were collected from the Islamic Republic of Iran Meteorological Organization for 1981-2010. For main purpose, first of all, the capability of LARS-WG5 model was investigated and verified to simulate meteorological variables including minimum and maximum temperature, solar radiation and precipitation at Hamadan synoptic station in the baseline period (1981-2010). In the next step, meteorological variable values were stimulated by HadCM3 model based on A1B, A2 and B1 emission scenarios in the period of 2011-2040. Finally, the net irrigation requirement values of main crops were estimated for baseline and three future decades.
Based on the simulated results of LARS-WG5 model, the average values of air temperature and precipitation will increase by 0.77, 0.88 and 0.78 oC and 2.1, 5.9 and 10.2% for A1B, A2 and B1 scenarios, respectively.The results showed that average monthly precipitation will increase in October, December and February for three scenarios and decrease in March, April and May for A2 and B1 scenarios. Also, the total amount of net irrigation requirement of examined crops will increase between 2.6 to 28.2 mm for three future decades compared with baseline period. According to A2 scenario, the net irrigation requirements of wheat and barley have the lowest values of increasing change and sugar beet and potato have the highest increasing changes.
According to the A2 as a plausible scenario, the total net irrigation requirement of sugar beet, wheat, barley, potato, maize (grain), maize (grass), peas and onion in 30 next years will increase 267, 75, 57, 275, 250, 153, 145 and 224 cubic meters per hectares, respectively compared with baseline period. In general, considering increasing changes of the net irrigation requirements of different examined crops, the selection of appropriate cropping patterns consistent with climate change is required.

Clay minerals have significant impacts on all physical, chemical and biological properties of soils. Weathering of clay minerals in soil could be affected by several factors such as redox status, dehydration, hydrolysis, dissolution, chelation (bond a metal ion with an organic capsule) and release of aluminum hydroxide into juicy clays structure through exchange position. Limited information is available about the influence of organic acids on dissolution of fibrous clay minerals especially in saline conditions. This study was carried out to identify the influence of studied parameters on release of magnesium, silicon and aluminum from sepiolite and palygorskite minerals.
A laboratory experiment was set up with a completely randomized design and factorial arrangement in three replications. Treatments included two types of mineral (sepiolite and palygorskite in size of 25-53 μm), two organic acids (0.01 M citric and oxalic) and a control and four salinity levels (0, 6, 12 and 24 dS/m). The sepiolite and palygorskite minerals were taken from a mine in Fariman city (northeastern Iran) and Tolsa Co. (Spain), respectively. Then their elemental composition and X-ray diffraction patterns were measured using Bruker Pioneer S4 and Bruker D8 machines, respectively. The concentrations of released elements were also measured by GBC atomic absorption spectrometer.
The results obtained from determination of elemental composition of sepiolite and palygorskite minerals showed that sepiolite has higher concentration of MgO than palygorskite which is compatible with those reported in literature. The presence of minor concentration of CaO in elemental composition of the both minerals suggests that both minerals have minor amounts of carbonates as the accompanying phase. This was further supported by the results of XRD analysis of the samples. The results also illustrated that the amount of released elements is highly affected by the type of organic acids, salinity and type of mineral. Among the organic acids, the amount of Mg and Al released from sepiolite and palygorskite in citric acid treated samples were greater than those from oxalic acid samples. However, oxalic acid was found to be more effective for extraction of Si from the minerals. With increasing salinity, the release of all elements was increased, however; in presence of organic acids the amount of released elements was reduced comparing with non-saline conditions. Moreover, the results illustrated that the ratio of released Si/ (Al) in sepiolite samples was higher than palygroskite.
The results of this study suggest that sepiolite is less stable than palygorskite and is much more weathered under the conditions studied.

In the world, groundwater resources are counted the second freshwater resources after polar glaciers. Investigating changes in groundwater levels in any region has an important role in planning and sustainable water resources management. Continuous decline of groundwater level has been observed in many places of the world in the past half-century. It has indicated the depletion of groundwater reserve in large scale. This reserve depletion has been caused either by over-exploitation or reduction of groundwater recharge. In the recent years, groundwater use has continuously increased to meet demand for expanding industrial, agricultural and urban water supply. Meteorological parameters changes exert extra pressure on further reduction of groundwater level. Since, until now, the comprehensive studies about trend changes of ground water level have not accomplished in Urmia region therefore the main goal of the present research is to investigate the changed trend of Urmia ground water level using Mann-Kendal non-parametric method.
The study area has located at 55° 10´ 26" longitude and 37° 4´ 12" latitude in northwest of Iran. For studied region, the mean annual precipitation is 304 mm and its climate is dry and cold. This plain located in west part of Urmia lake in west Azarbayjan. In the present research, trend analysis was conducted on groundwater level of 31 piezometeric stations in the monthly and annually scales in the period of 2002-2011 using Mann-Kendall non-parametric test. Data Analyze was carried out using the boxplot software in SPSS. Trend line slope was estimated by using Sen’s estimator for each time series. Homogeneity of trend was tested using the Van Belle and Hughes method.
The results showed that the trend of groundwater level for all stations was negative and the negative trend in 1% probability level was significant for 56 percent of the stations. The investigation of trend line slopes revealed that in average, the groundwater level of Urmia plain has been decreased about 19.9 cm/year. Also, the results of homogeneity test of trend in 5% probability level showed that the trend was non-homogeneous for different months and heterogeneous for various stations.
According to the obtained results from the present research, the changes trend of the region ground water level is negative. If the exploitation from ground water resources continues in the present form, social and economic crisis can be formed. According to the results of this research, it is necessary to control the ground water exploitation and ground water level will be increased by increasing agricultural water efficiency and artificial recharge.

Agricultural and industrial development, degradation of surface water resources, groundwater levels drop are among the major factor causing water scarcity. The integrated management of groundwater and surface waters serves as a solution to cope with such issues.
In the present study, using a water resources simulation model WEAP and its adjunction to the groundwater simulation model MODFLOW, consumption for Dashte Bojnord basin was evaluated. Calibration and validation of both models were undertaken based on 6 years (from 2005-06 to 2010-11) and 2 years (from 2011-12 to 2012-13) respectively. Then different management scenarios, including keeping acreage and cultivation area as constant against increasing number of industries, increasing irrigation efficiency in agriculture were considered combinations of the above scenarios alleviate reduce water demand. Under this scenario, projections for a period of 28 years (from 2013-14 to 2040-41) and its effects on water resources of the basin were studied.
The results showed that simultaneous applying multiple water management strategies seems to be better than any of its individual states, reducing water withdrawing on various resources. Reliability of water supply in the whole complex scenario, for urban drinking water, rural, agriculture and industry purposes was estimated to be 100, 100, 60.4 and 71.5 percent. To adopt above scenario alluvial aquifer by drop about 0.47 million cubic meters per year could be the relative balance between aquifers exploitation and recharge but limestone aquifer by drop about 6.02 million cubic meters per year need more management actions to have no problems.
With simultaneous use of groundwater and surface models in management of water resources, reliable results would be achieved.

Rill erosion is causes soil degradation, loss of rangeland potential and unfavorable conditions for plant establishment. So understanding, modeling and predicting this type of erosion on rangeland and natural resource management is important. One of the major challenges in planning and management of natural ecosystems such as rangelandsis lack of understanding the complexities and dynamics of these ecosystemsinconventional models. That based on basic idea of fuzzy theory, this limit can be entered in the model. The main aim of this study is to design and evaluate the performance of rill erosion prediction model using fuzzy inference systems on a part of Ahmadabad- Mashhad rangelands.
In this study by establishing 50-m transects in each different slope length, the number of rills and effective parameters in shaping rills, including canopy cover, ground cover, gravel, sand, silt, clay, slope and mutual effects between length and degree of slope have been measured. By measuring, width and depth of any rill and their geometric section, cross-section of rills have been calculated. Then by using Gamma test, the optimal combination of variables "percentage of gravel surface", "mutual effects between length and degree of slope" and "amount of silt available in soil" as inputs factors and "cross-section of rills per unit length" as variable Output (Function) were chosen for the fuzzy modeling. Some (9) different combinations of membership functions to fuzzification of input and output variables with 5 defuzzification approach combined maximum - minimum of fuzzy were trial and error. Model is chosen so that the addition of small amounts of IPE, the generalizability also is appropriate.
Results showed that the defuzzification of smallest maximum (SOM) has the lowest IPE compared with the other methods and then the mean of maximum method (MOM) with the lowest IPE was used in second priority. In all methods of defuzzification (except the mean of maximum method), models such as “Gaussian – trapezoidal” “Gaussian 2 – trapezoidal” and “Gaussian 2” selected models are known. According to the results obtained, in the erosion modeling using the softer functions such as Gaussian, will lead to better results than the sharp and simple functions such as trapezoidal and triangular. The combination of two trapezoids and triangles will have better results than using each alone, if only the simplicity of the model has to be considered.
Gaussian membership function with the defuzzification of smallest maximum is the optimal model for predicting rill erosion in Ahmad-Abad area of Mashhad.

Global warming, due to greenhouse gas increase in the earth atmosphere, caused an increase of about 0.8 oC in global mean air temperature since the early 20th century. The long-term heat energy deposition, both in atmosphere and in soil depths, affect physical and biological processes. Climate change detection statistically is a process which could reveal significant changes that might not be related to natural variations. Long-term thermal energy deposition in soil depths could play an important role in detecting climate change. Thus, the aims of this study were to fill the gaps in soil temperature data and determination of the effect of global warming on long term soil temperature trend.
Kerman synoptic station was chosen to collect data for 1951-200 interval. This station is located at 30o 15’ north latitude and 56o58’ east longitude with 1754 m above Sea level. The long-term annual mean temperature and mean annual total precipitation are 15.8 oC and 150 mm, respectively. For detection of climate change the long-term annual rainfall and cloudiness, daily air temperatures for 1951-2009 interval and daily soil temperatures at 3, 9 and 15 GMT at different depths (5, 10, 20, 30, 50 and 100 cm) for 1992-2009 interval were collected. The parametric methods of Pearson and regression techniques, along with nonparametric techniques of Spearman and Mann-Kendall were employed to detect temperature trends.
The results of these study indicated that Mann-Kendall test could reveal soil and air temperature trends more accurately. The mean annual, spring and summer air temperature trends significantly increased (P≤0.01). The mean annual, summer and autumn soil temperatures also had increasing and significant trends (P≤0.01). These findings also show significant negative trends in both cloudiness and rainfall (P≤0.05).
It is concluded that there is a pronounced similarity in Kerman air and soil temperature trends with global temperature trend and soil temperature could be used to detect climate change.

Presently, evaluation of soil erosion and sediment yield is one of the challenging issues in watershed management. It is considered to be a concerning issue in the developing countries and thus access to accurate data is essential for the measurement of soil erosion and sediment in watersheds for proper designing of soil conservation programs and determine ways to against erosion and reduce sediment. The natural resources degradation and soil erosion are the major problems in Golestan Province. The aim of this study was the investigation of sediment and runoff in experimental plots by using of natural rainfall in three land uses of forest, afforested and disturbed forest in Shastkalate watershed.
Nine erosion experimental plots with 2×2 (m) size were installed in all three land uses.
The results showed that in 1.7 to 14.4 (mm) of precipitation, the amount of sediment were 0.007 to 19.95 (g) in natural forest, 0.13 to 11.87 (g) in afforested and 0.26 to 43.94 (g) in disturbed forest land uses. The amount of runoff varied from 0.23 to 25(l) in forest, 0.1 to 16.1 (l) in afforested and 0.27 to 25 (l) in disturbed forest land uses.
Results showed that the forest degradation increased erosion and runoff at rate of 63.4 and 32%, respectively. Whilst, the amount of erosion and runoff decreased in afforested land use by 46.6 and 50.7%.

Water collection systems and disposal of superficial rain runoff are of the important components of urban planning and development, and any negligence in the system design could be problematic for human societies. In the superficial water collection networks design, design errors increase with the increment and extension the network. To reduce the error, the network design should be accurate. Computer models have greatly contributed to the accurate design and played a very useful role in achieving economical plan.
A study was done to determine the optimum dimensions of Gorgan city drainage network using hydrologic-hydraulic model SWMM. In this study, to calibrate the model, four rainfall events in dates 22/11/1390, 30/11/1390, 12/01/1390, 12/02/1390, were used and the speed of the corresponding runoffs in the chosen sub basin were recorded. In this study, Nash-Sutcliff, square root of error and bias error were used as model performance indices in the estimating peak discharge and flow volume.
The model calibration results showed that the simulated peak discharge and flow volume are in good correspondence with the observed values (BIAS%=11.44, RMSE 0.006 and NS=0.70) and the calibration results were used for the optimum values of parameters. To evaluate and test model validation, two rainfall events in dates 2/02/1391, 16/02/1391, were used. The evaluation results were confirmed the efficiency and accuracy of the model, so that the model performance indices were acceptable in both cases (BIAS%=8.01, RMSE 0.00043 and NS=0.69). After evaluating model performance, design rainfall with return period was calculated and model with design return period was performed in respect to the optimal parameters and dimensions of the drainage network. Peak discharge passing through the channels was identified based on design rainfall intensities. The adequacy of existing network to carry runoff with design return period was assessed with regard to model results based on presence or absence of added load and flood conditions at the nodes and channels. According to the model results, 40.11, 58.30 and 48.12 percent of drainage network channels possess critical and flood conditions in 2, 5 and 10 return periods respectively. Finally, the optimal dimensions of flood channels were determined by the model through trial and error test according to the type of optimal dimensions for each design return period.
The results of the study indicate that the model has the accuracy required for urban runoff simulation and it can be used for urban runoff management plans and designing superficial water collection and disposal networks.

Water resources limitation in the Neishaboor Plain, in addition to a significant increase in water demand in urban, agricultural and industrial sectors, has caused researchers to investigate and provide the basic information necessary for development of a sustainable water management program. In this study the temporal changes in groundwater quality and the possible causes of these fluctuations were studied.
The water quality data used in this investigation included a 9 year (2001-2009) periodically measurements of TDS, total hardness, Na, Ca2, Mg2, Cl- and SO4 2- concentrations.
The results, as were shown by the changes in parameters such as TDS, SAR and hardness indicated a significant degradation of groundwater quality over the period included in this study. The TDS concentration in 77% of the investigated wells increased substantially over this period, with mean increase of 19.63 mg/lit.yr. In regard to possible causes of groundwater deterioration, the decline in groundwater level, geological formations and agricultural activities were considered to be the most important factors. The results showed that for every 0.81m mean annual decline in groundwater level, the TDS concentration increased by a value of 19.63 mg/lit. The geological tertiary formations (Miocene) and volcanic rocks could also be included among the factors affecting the spatial quality changes observed in some parts of the Nayshaboor's aquifer.
The result of this study clearly indicated that there is a strong correlation between the groundwater level decline and the increase in salt concentration of the aquifer. However, due to the lack of adequate data and information, definitive statements on the relative contribution of agricultural activities and geological formation on groundwater quality changes could not be made.

Pan Evaporation data used to estimate crop water requirements, but in some cases due to lack of accurate data on measurements or defective equipments failure and lost data as referred in missing data. Since data integration is important for irrigation planning, it is necessary to correct the statistical errors. Many methods were used for finding missing data, In the meantime, neural network and tree models have high degree of accuracy, however these models were not compared and evaluated. The aim of this study is to compare the model tree and neural network for reconstructing missing daily evaporation data for four stations in Khuzestan province.
In this study, the required data from four stations include Aghajari, Bandar Mahshahr, Izeh and Bostan located in Khuzestan province were collected. On the basis of the Koppen climate classification, the climate of these stations is arid. The data related to the years 1997 to 2008 that include daily values of pan evaporation, wind speed, maximum and minimum air temperature, relative humidity, sunshine and the extraterrestrial radiation. The data were divided to two four-year period (2005 to 2008) and 12 years (1997 to 2008) and at any period after intentional removal of 5%, 10% and 20% of the measured data, their values were estimated with the use of tree and neural network models. The results of the model were compared using Statistical indices.
In tree model coefficient of determination for four years period were: 85%, 75% and 85% and for 12 years period were: 90%, 83% and 84% respectively. In neural network model coefficient of determination for 4years period were: 85%, 75% and 85% and for 12years period were: 90%, 82% and 85% respectively. A higher coefficient value for 12 years period showed that models are more accurate to estimate missing data for longer term statistical data. By increasing missing data from 5% to 20%, accuracy of models was diminished. This research also indicated that both models have similar accuracy in the estimation of missing data.
According to the results of this study, when more than 10 years of data are available, both neural network and tree models will have relatively good results. Also, when the number of missing data are less or missed in shorter periods, estimated values will be closer to the actual values. In order to improve and complete results, it is suggested that statistical estimates of missing data for different periods, such as 8 or 15 years are repeated and the best period to determine for best practice models.

Limitation of water resources has led to unusual waters applications and the use of high-efficiency irrigation systems such as drip irrigation in some areas. The mismanagement of water resources has caused increases the accumulation of salts in the soil. Due to the executive limitations of field experiments such as high cost and timeconsuming, using of simulator models for studying different management scenarios is recommended. Purpose of this research is evaluation of the salt transport in heterogeneous heavy soil and unsteady conditions with estimating hydraulic and solute transport parameters using inverse solution with the HYDRUS-2D model.
Drip irrigation system was applied as a line source and was done with water salinity of 1.279, 2.5 and 5 dS/m. Soil profiles were drilled to 40cm depth and networking with dimensions of 10 × 10 cm was performed. 48 hours after irrigation. In order to check the status of solute, sampling from beneath the tape and horizontal distance of 20 cm from the tape was used to determine the salinity of the soil saturation extract. ECe observed values of field experiments were compared with ECe simulated values using statistical indices i.e. nRMSE and CRM.
Simulated soil salinity values were slightly lower than the observed values. Also it was observed that the maximum amount of salinity was in the surface layer of soil, this could indicate the need for salt leaching in cases such as the early stages of plant growth which is more sensitive to salinity. According to HYDRUS model estimations, ranges of longitude dispersion coefficient (DL) and transverse dispersion coefficient (DT) were between 24.57-39.56 (cm) and 0.1298-5.2680 (cm), respectively; These differences in coefficients of different may be due to the soil heterogeneity and the high spatial variability in soil transformation parameters. Ranges of nRMSE for beneath the tape and the horizontal distance were between 2.79-18.49% and 3.084-20%, respectively. Simulations placed in good to excellent category. Ranges of CRM for beneath the tape were between -0.049 and 0.097 and the horizontal distance were between -0.065 and 0.081.
Despite heavy soil texture and soil heterogeneity in the study area andaccording to statistical indices i.e. nRMSE and CRM, HYDRUS-2D model could estimate satisfactorily the hydraulic and the solute transport parameters using inverse solution and simulated salinity with good quality; Thus, this model can be used as a suitable tool for the design and management of drip irrigation with saline and brackish water.

Generally, a moment that sediment particles start moving in stream is called incipient motion. A lot of research has been recently done to determine the conditions of incipient motion velocity of uniform and non-cohesive sediment in open channels and many Relationships or graphs are presented. But studies on non-cohesive and non uniform sediments are very little. With regard to the channel sediments are mostly non-uniform, Determination of the flow rate for prevent of sediment deposition can be an effective role in increasing of transmission efficiency and which reduced costs.
In this study, incipient motion of non-cohesive and non-uniform sediment was investigated by Laboratory modeling and dimensional analysis. In this study 9 non-cohesive and non-uniform sediment has been tested with different dimensions and uniformity coefficient in 0.0005, 0.001 and 0.002 slopes.
Results showed that increasing channel slopes from 0.0005 to 0.002 for sediments with different size, stability parameter on average decreases 45 percent. Also increasing particle size parameter from 0.12 to 0.35 for different slope, stability parameter on average decreases 15 percent. Results showed that with increasing uniformity coefficient from 4.5 to 7.5 for different size of sediment and channel slope, stability parameter on average increases 6 percent.
With increasing the slope and particle size parameters, decrease stability parameter and stability parameter, will increase with increasing uniformity coefficient.

Hydraulic jump is one of the common methods for dissipation of the kinetic energy of the flow in downstream of the hydraulic structures in stilling basins. Length of the stilling basin, depth ratio and the energy loss are some of the important parameters that should be taken into account for designing an economically efficient structure. Historically, Bidone was the pioneer to conduct investigations on the hydraulic jump in 1818.There after characteristics of this phenomenon have been investigated by many researches using cubic, rhombus and trapezoidal baffle blocks with and without curved upstream edges, sinusoidal bed, trapezoidal corrugation, sills and rectangular corrugations. Despite of the comprehensive researches performed during the last two centuries, there are still unknown issues that warrant more research on this subject. The perpose of this research is investigation of the effects of block inclinations on the hydraulic jump characteristics in the stilling basin USBR III.
Experiments were conducted in a flume with glass walls and smooth bed with a rectangular cross section 1m wide, 85 cm deep and 15m long. The model consisted of a head tank, a slice gate with constant opening of 3 cm and a tail gate to obtain various flow depth and a flowmeter to measure the discharge. Part of beginning of flume immediately after the gate of the head tank, was used as stilling basin and baffle blocks and end sill were installed according to the criterion of a type ΙΙΙ USBR stilling basin. In this study, baffle blocks were installed in two cases of diverge and converge position relative to the central axis of the flume and in each position 8 placement angle of 10, 20, 30, 40, 50, 60, 70 and 80 degrees were considered for blocks. For each flow discharge, the tailgate was adjusted to establish a non-submerged hydraulic jump so that toe of the jump was formed at the beginning of the flume under upstream gate, then the length of jump, initial and secondary flow depth were measured and burst photos were taken from profile of the jump. Froude numbers and discharges ranged from 4.44 to 8.56 and 39 to 81.7 l/s respectively. In total, 180 tests were carried out for classic, USBRΙΙΙ and diverge and converge position jumps.
In diverge position, increase in the placement angle of blocks up to 30° on convergent position caused significant decrease in jump length and further increase in placement angle resulted in separation of jump front from walls of flume and inclination to the central axis of flume and in turn increase of jump length. Also in diverge position, for all placement angles of blocks increase in jump lengths were observed.
The results showed that, increase in the placement angle of blocks up to 30° on convergent position caused 40 percent decrease in jump length and 10 percent decrease in depth ratio and also increase in relative energy loss to 75 percent. It is believed that the main reason of decreasing the jump length was raising the rate of secondary flows due to inclination of blocks in angle of 30 degrees.

Desertification is a phenomenon that has been impacted by the natural, social and financial factors and vice versa. The first step in desertification and desertification combat plan should be based on the identification and studying phenomena which are responsible for the changes in areas and induce desertification. Also, the intensification of desert conditions is considered as a trend which leads to biological reduction of ecosystems and desertification of environmental condition.
In this research, by using GIS 8 indices are selected and evaluated in Atrak Watershed of Golestan province: soil, vegetation, climate, management, Runoff, Land use and composite Indicators. The model of DIS4ME is applied in this research. Each of factors is estimated one by one and for each of them, data was collected.
The result showed that 5.5% of study area was found to be in critica (c1), 25% in critica (c2) and about 69% in critica (c3) class of desertification. Also soil, vegetation cover and climate criteria with a geometric average of 1.67, 1.62 and 1.58 show high class desertification.
According to the results of desertification in the region is intense. Measures of soil and vegetation have the greatest impact on desertification. The impact of climate measures with regard to changes in recent decades, such as reduced rainfall and persistent drought is remarkable.

Dust is an atmosphere catastrophe that its occurrence cause many damages in every aspect. Because of placing in dry and semi-dry region of the world, Iran is permanently subject to local dust and various synoptic system. In this study, some available dusty day's data were analyzed to identify the trend of dusty day by synoptic stations in the Sistan and Baluchistan Province. It was identified that all selected weather stations have the complete, long-enough recorded data.
It was determined that inside of the study area, the occurrence of days with dust are not homogeneous and such phenomena increases from the south to the north. To review the trend of occurrence of dusty day's non-parametric statistical methods of Mann-Kendall was accordingly introduced to the data.
Primary results showed that this method could be adapted for signifying of the existing trend types. Result showed that all stations have positive trend in monthly and yearly periods. But in warm months (May, June, July and August) positive trend are larger than other months.
Results of analyzing rate and orientation for different seasons showed that province level is not only significant in eastern part (Khash and Saravan Stations), but also in the other parts of the province.

Improving techniques of regional flood frequency estimation at ungauged sites is one of the foremost goals of contemporary hydrology. The evaluation of the frequency of flood events in ungauged catchments are usually approached by deriving suitable statistical relationships (models) between flood statistics and basins characteristics. In this study, regional flood frequency was carried out between flood as a dependent factor and physical characteristics as independent factors using inverse method in the catchments of Ardabil province.
Study area is located in the central region of Ardabil province which consists 9 gauging stations. Seven gauging stations for calibration and 2 gauging stations for validation were used. To yield a single model, return period was taken into account as the independent factor. Four types of models including Area, Area-slope, Area-slope-channels length models and Fuller model were studied.
Fuller model did not show suitable estimation of flood. Area model with RMSE equal to 25.30 and 23.51 (m3/s) showed lowest accuracy and Area-slope-channels length model with RMSE equal to 9.51 and 6.32 (m3/s) highest accuracy for estimation of flood in the validation gauging stations.
Area-slope-channels length model estimated flood with good accuracy for return period less than 50 year. It can be concluded that this model can be used for the frequency of flood events in the study area. Accuracy of all models decreased with increasing return period.