Journal of Water and Soil Science
Year:2011 | Volume:15 | Issue:57|Papers Count:24

In this research, the effect of installing position of bridge pier on scouring depth was studied in a bend laboratory flume, which is made of Plexiglas with 180 bend and a relative radius of Rc/B=4.7. Tests were conducted using one pier 6 cm in diameter under four discharge conditions with constant depth of 12 cm and clear-water conditions. Flume bed was fully paved by uniform sand. It was found that maximum scouring depth occurred in bend when bridge pier was installed in the position of 60 degrees. Also, in all situations increased scouring depth occurred by increasing discharge.

The accuracy and precision of the input data in decision making is important. Error originates from data collection, data entry, storage, retrieval and analysis of the data which consequently result in model error. One of the errors in spatial analysis is interpolation error. The main objective of this research was the suitability assessment of some interpolation methods for estimation of groundwater level in Farsan-Joneghan and Sefiddasht aquifers, located in Beheshtabad catchment, Chaharmahl-Va-Bakhtiyari province, Iran. Cross-validation technique was employed for the determination of each method's error. The RMSE and MAE indices were used for the error comparison. The results show that the modified Shapard's method with an MAE=6 and RMSE=7 was the most accurate for interpolation of groundwtaer level in the Sefiddasht aquifer. The inverse distance power method with MAE=6 and RMSE=9 was the best interpolation method for Farsan-Jonaghan aquifer. The Kriging with MAE=7 and RMSE=12 is the second best method in these aquifers. The moving average, minimum curvature and polynomial regression procedures produce the maximum error in the aquifers (17<MAE< be should methods interpolation suitable the aquifer any for Therefore, aquifer. of levels topographic minimum and maximum between difference (3) points; measurement number total (2) centered, to relative points (1) upon depends recommendation specific as either in level groundwater recommended can method particular no that concluded was It 25< RMSE.

Submerged vanes are low aspect ratio flow-training structures mounted vertically on the river bed at an angle to the prevailing flow. The aim of application of vane is to generate a secondary circulation in the main flow, designed to modify the near-bed flow pattern and thus redistribute flow and sediment transport within the channel cross section. Collar is a flat sheet with low thickness fixed vertically on the pier at stream bed level or near it. Installation of a collar leads to protect the river bed against the direct impact of downflow produced at the upstream face of the pier and therefore reduces the scour depth. This research is a laboratory study that examines the effectiveness of submerged vanes and combination of submerged vanes and collar as a pier scour protection device. Experiments were conducted in an 8 m long and 0.8 m wide flume and a cylindrical pier used was 6 cm in diameter. Clear-water scour tests with u*/u*c = 0.9 were performed with a collar 3 times wider than the pier diameter at the stream bed level and submerged vanes 1.5 times longer than the pier diameter at the stream bed level (H=0). Different arrays of vanes with different angles to main flow direction were employed. The highest reduction in the depth of scour hole with four vanes and a collar showed 61% reduction in scour depth.

In diversion flows, a portion of stream flow which enters the intake is diverted from upstream of the intake denoted by a surface and is called dividing stream surface (DSS). The amount of flow and sediment discharge entering the intake as well as design of submerged vanes to control sediment depends on determination of dividing stream width. In this study, the experimental tests were carried out at a 30 degree water intake from a trapezoidal section. Three components of velocity data were obtained for different flow conditions. Then numerical SSIIM2 model was calibrated and verified using tests data. More flow conditions such as the main channel with rectangular section were run using SSIIM2 model to get enough hydraulic data. From analysis of these datas it was found that the dividing stream width in different distances from the bed depends directly upon the diversion flow ratio. It was found that in comparison to the rectangular section, in trapezoidal cross section, the DSS dimensions are modified in such a way that its width is increases at the surface and reduced at the bed for the same flow conditions. Relations for predicting the dividing stream width and diversion flow ratio have been presented in this paper for intake from both rectangular and trapezoidal cross sections.

Fertilizers in agriculture are potential sources of environmental pollution, especially in ground water quality and soil resources. Studying factors effective in water and nutrient transport through soil profile is helpful for nutrient management to minimize adverse impacts on environment and nitrate leaching below the root zone. In this study, the ground water level and nitrate leaching transportation below the root zone were measured in a paddy rice field and the data were simulated with the DRAINMOD-N model. For evaluating DRAINMOD-N software in a paddy rice field under surface drainage in Mazandaran, the ground water level and nitrate transportation were measured during four months (June, July, August and September) in 2008. The DRAINMOD-N model was calibrated by adjusting nitrification and denitrification rate constants to reach the best fit between measured and predicted data. Results indicate that predicted ground water level and nitrate concentration by model were significant at one percent level. The statistical comparison was done by model efficiency (EF) 0.84 for estimation of ground water level and 0.97 for estimation of nitrate concentration, respectively. The DRAINMOD-N model can be used as a tool to manage environmental pollution of nitrate in paddy rice fields.

Selecting an appropriate particle size distribution (PSD) model for a particular soil may be important for a precise estimation of soil hydraulic properties. Various models have been proposed for describing soil PSDs. The objective of this study was to compare the quality of fitting of eight PSD models (Fredlund, Gompertz, van Genuchten, Jaki, Logarithmic, Exponential, Logarithmic-Exponential and Fractal) in 71 soil samples collected from Lordegan and Saman in Charmahal-va-Bakhtiari province, Iran. Coefficient of determination ( ) and Akaike’s information criterion ( ) were used to compare the goodness-of-fit of the models to the experimental data. Results showed that Fredlund model is best for describing PSD of silt loam, silty clay loam, silty clay and sandy loam soil textures. While Fractal, Exponential and Logarithmic-Exponential models produced the poorest-fit in silt loam, silty clay loam and silty clay, they had the best performance in sandy loam texture. The performance of Fredlund and Gompertz models improved with an increase in clay and silt content from 25 and 40 percentage, respectively. The performance of Fractal, Exponential and Logarithmic-Exponential models improved by increasing the sand content. Reverse correlation was observed between silt content and the performance of the Fractal model.

Floodwater Spreading (FS) plays an effective role in improving soil fertility, ground water recharge, vegetation cover, and desertification control. The soil fertility might increase as a result of a suitable suspended sediment material transferred to the downstream by flood events. To define a relevant FS method which increases the efficiency of the FS projects, it is necessary to study the quality and quantity of transported sediment material, spatially and temporarily. In this research, this subject was investigated by taking soil samples throughout 13 FS stations for physical and chemical analysis over 5 years. Within each of the 13 selected stations in the three first flooded dikes, soil sampling was carried out using random-systematic method. The total Nitrogen, absorbed Phosphorous and Potassium, and Organic Carbon of each sample were analyzed. Because of the abnormality of data, nonparametric test was adopted to compare means. All stations were classified into three groups using cluster analysis method. Based on the results, the variations of fertility factors are irregular between the dikes and amongst years. This could have been affected by several factors such as the quality and quantity of diverted flood, the characteristic of FS sites, and irregularity of sediment material deposited on the sites. Despite the low quality of soil fertility prior to the construction of these stations, in general, FS has a considerable role in improving the soil fertility. However, desirable objectives may be achieved in long term through occurrence of diverse flood events and suitable maintenance of the stations.

Biological soil covers such as lichens have critical roles in soil stability and prevention of erosion. In order to study the effect of lichen biological covers on aggregate stability and soil conservation, loess hills covered with lichen and uncovered ones were selected in Northern Golestan Province. Five samples were taken from the depth 0 to 5 cm of both two areas for physico-chemical analyses. The undisturbed soil samples were taken for micromorphological studies, too. Analyses of soils revealed that soil organic carbon content increased markedly, compared to uncovered soils. Mean weight diameter also increased about three folds in soils covered with lichen. Fungal hyphae and polysaccharides excretions bind soil particles together and increase size of aggregates. Micromorphological study of thin sections showed that uncovered soils had a weak and massive structure, but soils covered with lichen had a crumb granular and also well -separated angular block and higher proportion of voids. Due to the effect of lichen on upward movement of calcium carbonate, crystallitic b-fabric appeared in the surface layer of covered soils and speckled b-fabric underneath. Excremental pedofeatures are the most common pedofeatures in the covered soils.

Soil characteristics are affected by climate. Available potassium is one of the most important soil fertility indices. This study was conducted to determine the availability of potassium using Quantity- Intensity (Q/I) relationships in Vertisols of Isfahan and Chaharmahal-Va-Bakhtiari provinces with aridic and xeric moisture regimes, respectively. Soil mineralogy showed that smectite was the dominant clay in Chaharmahal-Va-Bakhtiari soil. The results showed that the activity ratio of K (AReK) in the soil solution of the surface soil in Isfahan and Chaharmahal -Va -Bakhtiari soils, ranged from 0.019 to 0.11 and 0.0037 to 0.0078 mmol.L-1 respectively. The labile K (DK0) in Isfahan and Chaharmahal Va Bakhtiari soils ranged from 0.23 to 3.8 and 0.72 to 1.6 mmolkg-1, respectively. Potassium on specific sites (KX) in Isfahan and Chaharmahal-Va-Bakhtiari soils ranged from 2.8 to 7.1 and 2.6 to 3.7 mmolkg-1 respectively. The potential buffering capacity (PBCK) in Isfahan and Chaharmahal-Va-Bakhtiari soils ranged from 12 to 36 and 191 to 201 mmolkg-1/(mmolL-1)0.5 respectively. The results suggested that the Q/I parameters were affected by soil depth. In all of the soils studied, PBCK increased with soil depth.

Performance of proper deep tillage can reduce negative effects of soil compaction. The objectives of the research were to determine the effects of deep tillage application on soil physical properties and wheat yield. Therefore, in 2006-2007 an experiment was conducted at Tajarak Agricultural Research Station of Hamedan on a soil with clay loam texture. In this research, four tillage methods were used. These methods were: 1) subsoiling with 30cm soil depth + conventional tillage (moldboard plowing) 2) subsoiling with 50cm soil depth + conventional tillage, 3) plowing by combined plow (chisel plow + roller) with 30cm soil depth and 4) conventional tillage (plowing by moldboard plow to 25-30cm soil depth). Randomized complete block design with four treatments and replications was used to analyze data and compare the treatment means. Before and after the application of the tillage treatments, parameters of cone index, bulk density and infiltration rate were measured in soil. Also before yield harvesting, components of yield (grain number in panicle, panicle number in plant and 1000 grain weight) were measured. To measure grain yield in experimental plots, in each plot ten square meter area from the yield was harvested. Result indicated that effect of different tillage treatment on soil resistance was not significant. Effect of deep tillage methods on bulk density and infiltration rate was significant. Deep tillage methods increased water infiltration rate in the soil and decreased soil bulk density. Effect of different deep tillage methods on wheat yield was not significant. However, application of chisel plow increased the wheat yield by 25%. It may be concluded the subsoiling treatment does not affect the crop yield in intensive and fully irrigated field condition. The results of this study indicated that if there is a compacted layer at 30cm soil depth, and with the same climate and soil as those in the experimental site, the application of chisel plow due to economical consideration (low fuel consumption and high field efficiency) can be recommended for soil preparation and cultivation of irrigated wheat.

Effect of drought stress and mycorrhizal symbiosis on growth and phosphorus (P) uptake by two sorghum cultivars different in root morphology was studied in a pot experiment. A factorial experiment with a randomized complete block design was performed. In this study, sorghum speed feed cultivar with high root proliferation and branching and sorghum KFS2 cultivar with low root proliferation and branching were colonized by Glomus intraradices. All plants were watered equally in the first three weeks to establish them. Drought stress was applied from the week four and the plants were watered when 40% (T1), 60% (T2) and 80% (T3) of the available water was consumed. Results showed that in both sorghum cultivars, plant dry weight decreased as drought stress was increased. However, dry weight of mycorrhizal plants was higher than that of non-mycorrhizal plants at all levels of drought stress. This increase for speed feed cultivar was greater than for KFS2 cultivar. Phosphorus concentration and total P uptake in shoot of both mycorrhizal plants were greater than those of non-mycorrhizal plants. P accumulation in both cultivars decreased by increasing drought stress due to the decline in plant biomass. However, P accumulation per unit length of colonized root increased by increasing drought stress. The greater percentage of root colonization and the increased total length of external hyphae per unit length of colonized root of KFS2 cultivar led to an increase in mycorrhizal growth response and improved P nutrition of KFS2 cultivar compared to those of speed feed cultivar.

In order to assess the effect of drought stress and various levels of potassium on solutes accumulation and chlorophyll of canola and Indian mustard, a field experiment was conducted in a factorial design based on randomized complete block design with three replications including three irrigation regimes (I1=irrigation after 50% depletion of soil water(control), I2=irrigation after 70% water depletion and I3=irrigation after 90% water depletion), two species (Hyola 401 hybrid of canola and landrace cultivar of mustard) and three levels of potassium fertilizer (K1=0 ,K2=150 and K3=250 kg.ha-1 K2SO4 ) at Agricultural and Natural Resources Research Center of Sistan in 2008-2009 cropping season. Water stress increased proline and soluble carbohydrate accumulation in the leaves of Brassica sp. In non-stressed condition (control) in different growth stages, proline was lower than water-stressed plants and Leaf proline content decreased significantly after irrigation. Mustard landrace showed higher capability for accumulating assimilates such as proline, soluble carbohydrates and potassium than hybrid Hyola 401. Water stress decreased the amount of chlorophyll a, b and total leaf chlorophyll, but Potassium application caused an increase in the mentioned parameters. The highest content of chlorophyll pigments was observed at flowering stage. Potassium application caused a decrease in proline and an increase in soluble carbohydrates concentration in the leaf under water stress condition. There was a negative correlation between grain yield and proline content and soluble carbohydrates, but grain yield was positively correlated with chlorophyll, a, b. It was concluded that osmotic adjustment can be an important mechanism for Brassica species under water stress conditions and that organic and inorganic compounds such as proline, soluble carbohydrates and potassium play key roles in this regard.

The growth and fluorescence parameters of chlorophyll in four corn hybrids including two sweet (K.S.C. 403 and K.S.C. 404) and two grain hybrids (S.C. 500 and S.C. 700) were evaluated in response to Fe and Zn nutrition in a nutrient solution culture. This study was conducted in a randomized complete block design with a factorial arrangement with three replications at the Soilless Culture Research Center (SCRC). Corn hybrids were exposed to two Fe levels (5 and 50 µM Fe in the form of FeEDTA) and two Zn levels (0 and 2 mM Zn in the form of ZnSO4). Increasing Fe concentration in the nutrient solution increased F0, Fm, and Fv/Fm values by 48, 96, and 123%, respectively. The fluorescence parameters of chlorophyll were affected by corn hybrid and there were significant differences in F0 and Fv/Fm at 1% level and Fm at 5% probability level among the studied hybrids. Iron deficiency significantly (P<0.05) reduced the root dry weight of all the studied hybrids. Zinc deficiency resulted in a significant decrease in the root dry weight of H403 and H500 hybrids while no significant decrease was found in the root dry weight of the H404 and H700 hybrids under Zn condition. The results showed that corn hybrids varied significantly in their tolerance to Fe and Zn deficiency. Based on the results of plant growth and fluorescence parameters of chlorophyll, the studied grain corn hybrids were more tolerant to Fe and Zn deficiency conditions in comparison with sweet corn hybrids. It seems fluorescence parameters of chlorophyll might be suitable parameters to screen corn hybrids in their tolerance to Zn and particularly Fe deficiency condition.

Calcareous and gypsiferous soils are restricting factors for uptake of some plant nutrient elements and plant production. Most soils in Iran are calcareous and gypsiferous. Therefore, the aim of this study was the evaluation of calcium carbonate (Caco3) and gypsum effect on availability of some nutrients and corn growth. This study was conducted in a greenhouse at Vli-e-Asr University of Rafsanjan. Treatments were arranged in a factorial manner as a completely randomized design with three replications. Treatments were three levels of Caco3 (0, 20 and 40 g/100g soil), gypsum at three levels (0, 15 and 30 g/100g soil) and two soil textures (Sand and Silt clay loam). Results indicate that irrespective of soil texture, Caco3 application significantly decreased leaf area (by 80% and 15% for sand and silty clay loam texture, respectively), dry weight (by 80% and 15% respectively), plant height (regressed on Caco3 percentage by slopes -0.7 and -0.15 for sand and silty clay loam respectively), and shoot Fe (-9.67 and -11.3) and Zn (-0.24 and -1) uptake, but had no significant effect on shoot Cu uptake. In sandy soil, application of gypsum, significantly decreased leaf area (80%), dry weight (62%), and shoot Cu uptake (slope= -1.93), but had no significant effect on plant height and shoot Zn uptake. Gypsum application significantly reduced shoot Fe uptake (slope= -24.86) in fine textured soil, but it had no significant effect in coarse textured soil.

In this study, the transport of nalidixic acid-resistant Escherichia coli (E. coli NAR) through two soils of sandy loam and clay loam was investigated. Saturated and unsaturated flow conditions were applied at two temperatures of 5 and 20ºC. Leaching was done using large repaired soil columns which had been subjected to physical weathering. A 20-cm diameter disk infiltrometer was set up to establish the steady-state flow conditions. Effluent was sampled at three depths of 15, 30 and 45 cm of soil columns. Saturated flow condition, temperature of 20 ºC and clay loam soil resulted in increasing the bacteria concentration in the leachate. Filtration coefficient and relative adsorption indices in sandy loam soil (average flow conditions, temperature and depth) were greater than those of clay loam soil with the respective values of 33% and 23%. These results may be related to the instability of soil structure and abundance of micropores in the sandy loam columns. In other words, the bacteria were physically blocked and entrapped in the fine pores of sandy loam soil. Effluent bacteria concentration decreased by depth of soil column, indicating the effect of soil on bacterial filtration as a natural filter. Leaching with cold water led to decrement of flow rate and consequently increment of bacterial filtration in the two soils of clay loam and sandy loam (average flow conditions, temperature and depth) with the respective values of 100% and 68%.

Electrical conductivity and acidity of soil are the most important chemical factors of soil for agriculture. The nature of soil is in such a way that its change has a continuous form. The method that can take into account this continuity will be able to show a better picture of change in soil characteristics. Objectives of this research are to investigate the relations between measured electrical conductivity and soil acidity of Qom plain, and clustering, compare the clustering methods, determine the optimum numbers of cluster, and to zone the clusters in the study area. Accordingly, two fuzzy clustering methods FCM and GK, were used for data mining and clustering of 465 measured data. For estimating the appropriateness and comparison of two methods, some criteria including Partition Coefficient, Classification Entropy, Partition Index, Separation Index and Xie and Beni's Index were used. Data mining results showed that the optimum number of clusters for FCM and GK method was 15 and 17, respectively. After investigating the results of clustering and based on the criteria of appropriateness, it was indicated that GK was the best clustering method. According to this method, 295 data from 465 measured samples had more than 40 percent of membership function. So, 9 clusters from 17 clusters had more than 20 members. Then salinity-alkalinity zoning based on GK method to show the clusters distribution better in the study area was prepared. This prepared fuzzy map explained that most of Northwest and west belonged to cluster 1 and eastern parts of study area include belonged to cluster 17. Based on this, salinity-alkalinity and the ensuing soil degradation in east of study area is more likely than the west of it.

In order to evaluate the effects of nitrogen fertilizer levels on grain yield and nitrogen use efficiency in corn cultivars, a split plot experiment based on randomized complete block design with three replications was conducted at the Research Farm of Islamic Azad University of Ardabil during 2006-2007 cropping seasons. Factors consisted of nitrogen fertilizer at four levels (0, 80, 160 and 240 kg/ha) and corn cultivars at three levels (SC-310, SC-404 and DC-370). The results showed that grain yield was significantly affected by nitrogen levels, corn cultivar and nitrogen level × corn cultivars. The highest grain yield was related to application of 240 kg/ha nitrogen with SC-404 cultivar. Nitrogen levels of 160 and 240 kg/ha had similar yields, but more yield than 80 kg/ha. With increasing of nitrogen levels, plant height, the number of grains per ear rows significantly increased. Comparisons of means showed that increasing the application of nitrogen fertilizer decreased nitrogen use efficiency. Nitrogen use efficiency decreased from 17.13 kg/kg with application of 80 kg/ha nitrogen fertilizer to 12.4 kg/kg in application of 240 kg/ha nitrogen fertilizer. Nitrogen use efficiency was affected by corn cultivar. Nitrogen use efficiency in SC-404 was higher than SC-301. In conclusion, in order to increase grain yield and nitrogen use efficiency, SC-404 hybrid should be applied with 160 kg N/ha in climatic conditions of Ardabil Plain.

Baseflow separation has long been an important topic in hydrology and has a crucial role in water resources management in arid and semi-arid regions like Iran. In this paper, a comparison among commonly used automated techniques for hydrograph separation including theoretical method of local minimum and digital filter of one parameter with different filtering parameters of 0.9 to 0.975 and two parameter methods was done to estimate baseflow using baseflow index. For this purpose, daily flow data in some stream gauging stations in west Azarbaijan province were used. For comparison, in addition to baseflow index the graphical method based on the observed daily flow data and correlation coefficient among them was utilized. The main aim of this research is distinguishing the most suitable method in hydrograph separation and estimating the baseflow. Results showed that in different methods baseflow largely contributes to streamflow and also has high fluctuations. However, the results of the digital filter with two parameters appear to be hydrologically more plausible than those of the other methods, but the results of digital filter with proper parameter - in this region one parameter method with filter of 0.925- has proper estimation accuracy. Also, the baseflow index based on method of two parameter digital filtering varies from 0.54 to 0.78 in this study area.

In this research, 5 percent of normal Precipitation Index (PNPI), Deciles of Precipitation(DPI),Rainfall Anomaly Index (RAI), Bahlme & Mooley Drought Index (BMDI) and standardized Precipitation Index (SPI) were used in order to investigate drought in Yazd synoptic station and 31 non synoptic stations all around this province. For this purpose, the present statistical errors were reconstructed via correlation between the stations, after raining data collection from the considered stations. Then, calculation of PNPI, DPI, RAI, BMDI and SPI indexes were calculated on monthly and annual scales. Situation of drought was determined based on the obtained values from calculation of each index according to tables related to the considered indexes in different classes of drought during the statistical period. Then indexes were compared to each other, considering drought given situation for each station. The difference and similarity of each index with other 4 indexes were calculated and investigated. Also after determination of drought situation in each station, given percentage of drought different situations via each Index was determined on annual scales, in 33 study stations. After passing the above mentioned stages, it was found that there was the highest percentage value of similarity between the two indexes RAI & DPI, as both indexes indicated similar situation of hard drought in the stations. These two indexes are considered most efficient to investigate aerology drought. But considering that static indexes are faced with problem on monthly scales and in stations located in drought regions, it is recommended to use SPI & BMDI dynamic indexes whose similarity percentages are acceptable.

Land cover maps derived from satellite images play a key role in regional and national land cover assessments. In order to compare maximum likelihood and minimum distance to mean classifiers, LISS-III images from IRS-P6 satellite were acquired in August 2008 from the western part of Isfahan. First, the LISS-III image was georeferenced. The Root Mean Square error of less than one pixel was the result of registration. After creating false color composite and calculating transformed divergence index, the images were classified using maximum likelihood and minimum distance to mean classifiers into six categories including river, bare land, agricultural land, urban area, highway and rocky outcrops. The results of classification showed that the dominant land cover type is urban area, occupying about 6821.1 ha representing 38.86% of total area. The accuracy of maximum likelihood and minimum distance to mean classifiers was obtained using error matrix and Kappa analysis. According to the results, the maximum likelihood algorithm had an overall accuracy of 94.93% and the minimum distance to mean method was 85.25% accurate. The results illustrate that the maximum likelihood method is superior to minimum distance to mean classifier.