JWSS - Journal of Water and Soil Science

Trees crown can be regarded as main factor contributing to the conservation and support of soil in many ecosystems including semiarid forests in Zagross. The aim of this study was to find out the effect of tree crown of pictachio (Pistacia atlantica Desf) on N, OC, P, pH, EC and the texture of the soil. Soil samples were collected in and outside the crown of 5 single pistachio trees on four directions of each tree in a northern slope from the 0-5 cm depth of soil in the Sarvabad region, Kurdistan. The results of this study showed that the amount of the soil organic carbon was decreased from 6.71% in the soil inside tree crowns to 4.73% in the soils outside the tree canopies. The soil inside trees had a higher concentration of soil nitrogen (0.406%) than the one outside (0.224%) the tree crown; the concentration of phosphorus was measured to be 32.7 mg/kg in the soil inside canopy, while it was 21.1 mg/kg in the soil of outside the tree canopy. EC under the tree crowns was more than that outside the canopy. The results, therefore, showed that soil texture was lighter inside the canopy, as compared to outside; however, the acidity of the soil was not affected by tree crowns and no significant differences were observed in different areas of the crown. Therefore, Persian turpentine trees have positive impacts on the soil properties in Zagros forests and eliminating them will lead to the significant loss of soil fertility and greater soil erosion.

Understanding the distribution of different P forms in soil aggregate fractions is important in evaluating the risk of P run-off and leaching in the agricultural soils. The objective of the present research was to determine the effect of aggregate size on soil phosphorus availability and fractionation in 10 calcareous soils. Micro aggregate (< 0.25 mm), macro aggregate (> 0.25 mm) and whole soil were separated by dry sieving. Olsen P, total P, organic P, and inorganic P fractions in micro aggregate, macro aggregate, and whole soil were determined. Soil inorganic P fraction was  determined by a sequential extraction procedure including: dicalcium phosphate (Ca₂-P), octa calcium phosphate (Ca₈-P), apatite (Ca₁₀-P), P absorbed by Al oxide (Al-P), P absorbed by Fe oxide (Fe-P) and P incorporated in to Fe oxide (O-P). The results showed that the amounts of (Olsen P), (Ca2-P), (Ca8-P), (Ca10-P), (Organic P), (Al-P), (Fe-P), (O-P) and (Total P) in 70, 60, 40, 40, 60, 70, 60, 50 and 70 percent of soils, respectively, in the micro aggregates were significantly higher than those of the macro ones. Finally, by increasing the P content, particularly the smaller sized aggregates, it was likely that the eroded material would favor greater P loss.

Determining the cultivation crops area is important for properly supplying crops. The aim of this study was mapping the cultivation area crops in Chadian city for spring and summer during 2015 by using the time series data of the Landsat 8 satellite of OLI imagery. At first, the under cultivation area was determined by setting a low threshold in the marginal pixels of the agricultural rain fed in the spring image NDVI index. The area cultivated with wheat and alfalfa was prepared by subtracting spring and summer NDVI values. Cultivation maps, which were cultivated with potatoes, corn and orchards, were prepared using the supervised classification with the FISHER method in a step by step manner. Spring and summer cultivation maps were combined; finally, the major cultivation crops maps were produced by the hybrid classification method. Map accuracy assessment was done by producing error matrix and calculating kappa coefficient, total accuracy, commission and omission error, producer, and use accuracy; in all indices, they had an acceptable value, showing the capability of OLI and the used methods in separating each cultivation.

To determine the potential for groundwater contamination, vulnerability should be evaluated in different areas susceptible to contamination should be investigated. Aquifer (carbonate) karst or part of it is karst aquifer in the western region of Iran; due to the natural conditions of the region and human activities, they are susceptible to contamination by carbonate aquifer through holes devourer and feeding point leading to pollution. The aim of this study was to analyze aquifer vulnerability zoning map karst plain elster by using COP. This model uses three parameters including lining (O) the concentra flow(C) and precipitation regime (P) to assess the vulnerability of groundwater against pollution GIS software. The results showed that the plain with an area 7.8 km² was dominated in terms of vulnerability, being in the middle class. Other classes, respectively, were low with the area 18.69 km², high with the  area 0.65 km² as part of the northeast plain, and much less with the  area of  0.6 km^{2 ,} The results of the sensitivity analysis  also showed that at the factorization (P) due to appropriate rainfall area, the  maximum impact was in determining the vulnerability  of the area. And the factor (C) minimum has impact on determining the vulnerability of the area. Due to the small size of the mature karst area, the wide extent of non-karst region was shown for the verification of results related to electrical conductivity data (EC) against discharge wells in the region with the high vulnerability and moderate. A comparison was made too.

Many studies have been done on various properties of dust and one of the most important characteristics of dust is the ability to carry different microorganisms from the source points. The aim of this study was to investigate the bacterial and fungal community of dust and to identify its dominance species in a single event of intense dust storm, in the northern regions of Sistan and Blauchestan Province (Sistan plain). Dust samples were accordingly collected by Siphon dust samplers after one of the most intense dust storms in 28-31 August, 2015, from 5 cities in the northern regions of Sistan and Blauchestan Province; after that, the microbial community of dust was determined by culturing in petri dish and its dominant bacterial and fungal species were identified. The results showed maximum aerobic and anaerobic bacteria population was observed in the Hirmand city dust (1875000 CFU/g and 156667 CFU/gr, respectively). The maximum aerobic fungi population was observed in the Zabol city (833 CFU/g) and the maximum anaerobic fungus population was observed in Zahak city (2167 CFU/g). The most frequent type of bacteria was Bacillus sp, which was followed by Streptomyces pactum. The most frequent type of fungi in this research was Penicillium sp and the second one was Aspergillus. The results showed the high and variated microbial community, especially pathogenic fungi associated with dust in this region.

Assessment of soil quality helps to make a balance between soil function and soil resources, improving soil quality and achieving the sustainable agriculture. For the quantitative evaluation of soil quality in the Shahrekord plain, Chaharmahal va Bakhtiari province, 106 compound surficial soil samples (0-25 cm) were collected. After the pre-treatments of soil samples, 11 physico-chemical soil characteristics/indicators as the total data set (TDS) were measured using the standard methods. Statistical analysis showed the usefulness of Principle Component Analysis (PCA) transformation. The minimum data set (MDS) was selected using PCA. Analytical Hierarchy Process (AHP) was carried out for the quantitative determination of indicator priorities and weights. Soil quality of the samples was calculated by introducing TDS and MDS into Integrate Quality Index (IQI) and Nemero Quality Index (NQI). The results showed the soil quality of the land uses was as Rangelands> Drylands<Irrigated croplands. The correlation coefficient between IQI-TDS and IQI-MDS was 0.97, while this value for NQI-TDS and NQI-MDS was 0.98. The correlation coefficient between IQI-TDS and NQI-TDS was 0.87 and that between IQI-MDS and NQI-MDS was 0.91. Classification of the resulted soil quality map IQI-TDS revealed that 12.5 % and 15.5 % of the plain were in very high and low quality conditions, respectively.

Nonlinear weirs are regarded as important hydraulic structures for water level adjustment and flow control in channels, rivers and dam reservoirs. One example of non-linear weirs is shaped as curved-zigzag. The crest axis of these weirs is non-linear. At a given width, the crest length is greater than that of the conventional linear weirs. Thus, they achieve a higher flow rate for an identical hydraulic load. This research experimentally focused on the discharge coefficient and flow rate of curved weirs with three different curve radii in two triangular linear and zigzag shapes. The discharge coefficients of these weirs were comparatively explored in terms of the hydraulic performance as a function of the total hydraulic load to weir crest height ratio (hd/P) and curvature angle (θ) (or curve radius). The results indicated that for the same hydraulic load, the increase of θ (the decrease in curve radius) led to a lower discharge coefficient; this was first because of the increased topical rise of water level, and then the more indirect path with a greater curvature through which the flow had to transport. Both factors could negatively affect the water discharge coefficient. In practice, the runoff coefficient at a weir with a curve radius of R/w=1.25 was approximately 8.5% greater than that of a weir with a curve radius of R/w=0.75 under a hydraulic load of 0.2.

Rivers are one of the most important source of water supply for drinking and farming purposes. Zard River is one of the surface water resources of Khuzestan province. The purpose of this study is to evaluate the quality of the river water and to observe the trend of changes in the water quality of this river in the Mashin station during the period of 1997-2015 by using the Man-Kendal, Spearman, variance analysis statistical methods and the least significant difference (LSD) and cluster analysis. LSD test shows SAR, Na, Cl, pH parameters up to 2010 (before Jare dam construction) were significant at 95% confidence level compared to 2015 (year of control). No changes were made after dam construction. According to Mann-Kendal non-parametric test, pH, Ca and SO₄ have a significant upward trend to the 0.037, 0.393 and 0.376 respectively, the variables Cl, SAR, Na and temperature have a significant decreasing trend to the -0.387, -0.417, -0.386 and -0.1 respectively. Also Spearman test shows that the dam improved the quality of river water regarding to salinity. Variance analysis show that pH, SAR, Na, Cl, Ca and SO₄ have significant difference. Cluster analysis classified the qualitative data before the construction of the dam in three clusters and after the construction of the dam were divided into two clusters where TDS variable was less distant than other variables. As a result, the quality of the irrigation water is changed downward and the TDS is more similar to the other variables compared.

Droughts are natural events and could lead to declining surface water quality of regional basin. Understanding the complex impacts of drought may help authorities to monitor changes in different regional basin and to make appropriate decision on development of a river basin management plan. In this study 20 years annual precipitation time series from 1994-2013 from 7 synoptic weather stations located in the Halil-Rood basin were analysed using both Standard Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) and then dry (-1.35 to -1.75) and wet years (1/7 to 2.45) were determined by model simulation studies. Several climate based drought indices and remotely sensed based drought indices were used for monitoring and evaluating of drought. The impact of drought on the water quality parameters in the study area was evaluated. Results showed that there was significant relationship between most of the examined water quality parameters (Ca²⁺, Mg²⁺, HCO^3-, SO4²⁺, Na⁺, total dissolved solids TDS, SAR) and drought, however there was no significant relationship between water pH and drought. The study indicated that focus on the drought indices might be helpful as a tool in improving surface water resources management under drought condition and may promote sustainable water resources utilization and management in the study area. Also, dividing the Halil-Rood basin into several homogeneous regions is recommended for future studies to prepare a better ground for studying the effect of drought on the quality of water at a regional scale.

Nowadays, water supply for the sectors of household consumption, agriculture, green spaces and industry is currently one of the most important challenges for governments in many parts of the world, especially in arid and semi-arid climate regions such as Iran. The aim of this study was to simulate the amount of run-off from the daily precipitation for Sarpol-e Zahab city, for the purpose of estimating the required amount of water for the irrigation of the green spaces of the city. In this study. After providing information and using the Digital Elevation Model (DEM) map of city, all individual sub-basins of the basin were produced. All data related to creating and overlaying hydrologic, climatologic and physiographic layers were used according to the HEC-HMS hydrologic model. The run-off depth and flood volume of each sub-basin were obtained through the SCS method. Then the required amount of water for the green areas of Sarpol-e Zahab city was calculated. The efficient rainfall was estimated using four methods including SCS, 80 percentage, reliability, and USDA for each month, separately. Finally, the amount of needed water for the green area was obtained using these four mentioned methods. The results indicated that the role of curve number in the infiltration rate was more than other variants. Impermeability of urban basins and changes was created due to the growth and development of the city such as removal of vegetation, soil compaction, creation of the water collection and leading surface waters, decreasing the amount of water penetrating to soil significantly. The amount of surface water for sub-basins was estimated to be 266000 cubic meters. Besides, the results showed the amount of required water for 5 months of the year (from early May to September late) using four methods of SCS, 80percentage, reliability  and USDA was  equal to 243525, 238062, 267865 and 236458 cubic meters, respectively. The amount of the estimated runoff volume was 266,000 cubic meters. Regarding the area of green spaces in Sarpol-e Zahab city and its daily need of water, this volume of water could  supply the required amount of water to irrigate the green area of the city for five months (From May to September).

The use of free launch jets in flip bucket structures with associated submerged ponds, in the appropriate geological, and topographic and hydraulic conditions, could have significant economic and safety benefits. In this research, the downstream scour phenomenon of a flip bucket jet was investigated in free conditions, as well as in the presence of a trapezoidal and triangular slot in the coastal manner with different layout intervals at flow rate of 9, with a total of 45 experiments. The results of this study showed that the presence of the slot had significant effects on the depth and range of scour, so that the fit bucket jet with alternate triangular slots reduced the scour by about 12.7%, as compared to the no slot mode. Moreover, the maximum scour depth occurred in the bucket mode with the alternate trapezoidal slots in the more favorable interval than the rest of the models. Then, the results were compared with several empirical formulas and Veronese A relation showed closer results to the actual values.

Expert aquatic designers face many problems; among these, in hydrology, defective occurrences in time-series can cause errors in the ultimate results of the study. This more often happens in the regions where the number of hydrometric and rain gauge stations is limited. In addition, assessing, developing and maintaining the use of water resources require accessible long-term and high-quality quality hydrological time-series. Thus, this necessitates correcting the statistical flaws and magnifies the importance of how to deal with the problems in the hydrological analyses. Statistical methods are, currently, used to infill data and statistical gaps. In this study, in order to introduce a multivariate method for estimating the missing data on rainfall and runoff, in a hydrologic homogeneous region in the Mazandaran province, self-organizing map methods were examined under two scenarios and some reliable estimates were obtained. In this regard, the correlation coefficients between the observational data and the model output were calculated for the precipitation data up to 0.92 and up to 0.95 for the runoff data. Therefore, to avoid the reduction of uncertainty caused by the inadequate data in water resource management, this method could be used.

In this study, to evaluate the rain- fed land capability in the west of Gavkhooni basin and Plasjn sub- basin, a multi- criteria evaluation method was used. First, by reviewing the literature and expert knowledge, proper data were determined. Criteria and constraint were standardized by Fuzzy and Boolean methods repeatedly and the criteria weights were determined using the analytic hierarchy process. Calculated weights showed that soil and climate criteria with 0.27 and 0.26 had the highest weights among other criteria. Criteria and constraints were combined by considering criteria weights and using the weighted linear combination method; then the rain- fed land capability model was prepared. By re- classing the prepared model, the rain- fed land capability map was produced in 6 capability classes. The results showed that 178430 hectares of the study area was related to very high and high rain- fed capability classes. To determine the rain-fed agriculture sustainability, rain- fed agriculture locations were determined in each land rain- fed capability map. The results showed that 19686 hectares of rain- fed areas were located in high and very high capability and 5999 hectares were the in lower classes.

The purpose of this study was to investigate the relationship between time and spatial features of meteorological, hydrological and agricultural droughts in Karoon 1 Dam basin. Meteorological and statistical data were accordingly selected to evaluate the drought situation between 1993 and 2016. The results showed that hydrological droughts occurred in the meteorological drought and had a very high correlation with this year's meteorological drought. The most severe droughts occurred between 2006 and 2011. Studies also showed that every three years, the basin was accompanied by a meteorological drought and then a hydrological drought. The results also showed that the highest correlation was observed with the 12-month meteorological index, with a delay of 3 months, and the 6-month meteorological and hydrological index with a delay of 3 months and a three-month hydrological drought index with a delay of two months. Therefore, it could be concluded that hydrological droughts showed a delay of almost two to three months in the entire catchment area; since this period was 4 months or more, the correlation between these two indicators was eliminated and decreased. Also, due to drought zones, during the period from 1993 to 2009, most of the droughts were caused by rainfall reduction in the southwest of the province, and this was associated with a reduction in runoff in its hydrometric stations. Of course, in 2009-2012, the runoff status had been temporarily improved, and from 2012 to 2017, the drought situation had again returned spatially to the previous routine.

In determining the allocation of water resources, the probable conditions of water resources and water demands are considered as the water allocation scenarios in the basin scale. Then, these scenarios are evaluated in the context of integrated water resources management and from the perspective of sustainable development indicators. The best scenario is selected in order to determine the water allocations. In these evaluations, there are spatial distributions and their interactions are simultaneously the key charaterictics in the decision matrix. These features are not often considered in the evaluation process. In the present study, distributed indicators and simple and integrated multi-criteria evaluation models, including ANP and CP methods, were used to evaluate the water allocation scenarios in the Aras Basin. The results showed that modeling of the spatial distribution and interactions of water allocation impacts was not possible through any of the simple multi-criteria evaluation methods. Simplifying and discarding one or two key features in the evaluation process can lead to significant uncertainties on rankings with a Spearman coefficient of -0.1. By implementing the integrated spatial decision-making approach and applying two features simultaneously, the fourth scenario was ranked first. The proposed approach was compared with the individual models, showing more accurate, with the correlation coefficients of 0.5, 0.6 and 0.7.

Optimization of artificial intelligence (AI) models is a significant issue because it enhances the performance and flexibility of the numerical models. In this study, scour depth around bridge abutments with different shapes was estimated by means of ANFIS and ANFIS-Genetic Algorithm. In other words, the membership functions of the ANFIS model were optimized using the genetic algorithm, finding that the performance of ANFIS model was increased. Firstly, effective input parameters on the scour depth around bridge abutments were defined. Then, by using the input parameters, eleven ANFIS and ANFIS-GA models were produced. Next, the superior ANFIS and ANFIS-GA models were introduced by analyzing the numerical results. For example, the correlation coefficient and scatter index for ANFIS model were calculated to be 0.979 and 0.070; for ANFIS-GA, these were 0.986 and 0.056, respectively. In addition, the average discrepancy ratio (DR_ave) for ANFIS and ANFIS-GA models was 0.984 and 0.988, respectively. Also, it was shown that the ANFIS-GA models had more accuracy, as compared to the ANFIS models. Moreover, a sensitivity analysis showed that Froude number (Fr) and ratio of flow depth to radius of scour hole (h/L) were the most influential input parameters for simulating the scour depth around bridge abutments.

Iron (Fe) is an essential micronutrient for plants and its deficiency occurs in calcareous soils. However, a suitable extractant for the estimation of plant-available Fe and its critical level in calcareous soils depends on the type of soil and plant. The objective of the present study was to evaluate several chemical extractants to estimate available Fe and its critical level for corn growing in calcareous soils from Chaharmahal-Va-Bakhtiari Province. The amount of available Fe was measured by DTPA-TEA, AB-DTPA, 0.01 M calcium chloride, Mehlich IІ, and Mehlich ІІI extractants. At the end of the experiment, corn was harvested, and dry weight, Fe concentration in the plant, and the amount of Fe uptake by corn were determined. Extracted Fe had a significant correlation with all extractants used with maize indices. . The highest correlation coefficients were determined between the DTPA-TEA (0.32-0.94) and AB-DTPA (0.43–0.96) methods and the plant indices. The results of this research showed that the DTPA-TEA and AB-DTPA methods were the most suitable extractants for predicting available Fe content in these soils and the critical level of Fe extracted by these extractants was 2.81 and 3.67 mg kg^-1.

This study was conducted to investigate the temporal variations of runoff and rill erosion in various soil textures under different slope gradients. So, a laboratory experiment was set up in three soil textures (loam, clay loam, and sandy clay loam) and four slope gradients (5, 10, 15, and 20%) using the completely randomized design with three replications. Runoff production and rill erosion were measured at a flume with 4 m×0.32 m in dimensions using a simulated water flow with 0.5 lit min^-1 in discharge during 30 min. Results indicated that runoff and rill erosion and their interaction were significantly affected by soil texture and slope gradient (P < 0.001). Significant relations were found between rill erosion and runoff both in three soils and four slope gradients, and the strongest relations were in loam (R²= 0.86) and 15% slope gradient (R²= 0.94). Runoff and rill erosion varied considerably in the soil textures and slope gradients during the experiment. A 10-min pick time was found for runoff and rill erosion. In contrast to runoff, rill erosion appeared an irregular and gradual increasing pattern during the experiment which was associated with the frequency of transportable soil particles. Clay loam had more sensitive particles due to a higher percentage of fine particles and weaker structure, and most of them were washed in early times, and finally, rill erosion was reached to a constant pattern. This study revealed that temporal variation patterns of runoff and rill erosion are influenced by soil type (texture and structure) and slope gradient.

The study of annual damage statistics due to floods in Iran and the world shows the extent of flood damage to natural and human resources in different regions. Determining the flood zone of rivers in order to protect national resources and reduce flood damage provides the possibility of protecting the river from encroachment and the construction of any unauthorized facilities in it. Therefore, in the present study, the capability of numerical models in simulating the flood zone of rivers was evaluated in the range of Azarshahr Qushqura river and the two-dimensional hydraulic model HEC-RAS 5.0.7 and one-dimensional HEC-RAS model were compared. Changes in the hydraulic characteristics of the flood flow including depth and velocity of the flow at different cross sections of the models were evaluated. The results showed that the water surface level (flow depth) of the two-dimensional model HEC-RAS compared to the one-dimensional model had the lowest error as compared to other hydraulic parameters of flood flow. The two-dimensional HEC-RAS model showed the highest error rate in the flow velocity parameter in comparison to the one-dimensional model. The results indicated that two-dimensional HEC-RAS model V5.0.7 determined the surface of the flood zone 12.46 % more than the one-dimensional HEC-RAS model. The confirmation of the resulting zones on the current state of the river and comparison with the river aerial photo of 1346 indicated the higher accuracy of the two-dimensional HEC-RAS model in estimating the flood zone of the river.