Water and Soil Science
Year:2011 | Volume:21 | Issue:2|Papers Count:14

Although there is considerable volume of information regarding the design loads on coastal protective structures (such as groin and breakwater), in literature, however, the main load is taken to be the wave force and there has not been enough concern on lateral force due to earthquake. Since northern and southern coastlines of the country are located in the potentially seismic zones, investigating the behavior of coastal structures against such force is of the great importance. In this paper, the groins constructed in the estuary of Sefidrood River are modeled and analyzed under the earthquake and under wave induced loads. The main objective of this study is to obtain the suitable dimensions for groins to resist the earthquake induced lateral loads. The analyses are performed on a number of the groin’s cross sections using a multi-purpose F.E. package called ABAQUS6.8. The results obtained from the present study indicate that in some cases and at the different locations along the groin, the earthquake forces can be as important as wave forces and it can affect the results of the analyses. The results are plotted and illustrated in such a way that to be used by designers.

Deficit of sediment measuring stations and limited number of years containing historical data, have made it difficult to analyze the river’s sediment load. Hence, using methods such as regional analysis to access suitable models to estimate the sedimentary load seems to be necessary. Regional analysis of sediment consists of two parts, 1) determining homogeneous areas and 2) deriving regional models of sediment suspended load of homogeneous regions that involve local characteristics and regional coefficients for the sub-basins being studied. In order to access such models, this study has been conducted in Aji-Chai River basin with area of some 13853 Km2. In the present study, the mean daily sediment production of the sub-basins and 14 physiographic and hydrologic characteristics related to 10 selected sub-basins with 34 years of statistical period were selected as dependent and independent variables, respectively. After determining homogeneous regions a mathematical model for predicting suspended sediment load at each homogeneous region was proposed based on physiographic and hydrologic parameters together with amount of error of each model.

Streamflow processes are commonly accepted as a nonlinear over space and times. In many researches linear time series models have been used for streamflow processes with assumption of linearity. It is better to test nonlinearity of these series before modeling. However, it is not clear what kind of nonlinearity is acting underlying the streamflow processes and how strong the nonlinearity is for the streamflow processes at different time scales. Streamflow data of Shaharchai River in Urmia on four timescales (i.e. yearly, monthly, 10-days and daily) were investigated with BDS test in order to study the character and type of nonlinearity that are present in streamflow dynamics. First stationarity was tested with ADF and KPSS tests then after pre-whitening series with AR models, BDS test was applied to the residuals. All daily and 10 days and monthly streamflow series appeared to be nonlinear but yearly series were linear. It is found that as the timescale increases from a day to a year, the nonlinearity weakens and there are stronger and more complicated nonlinear mechanisms acting at small timescales than at large ones. Standardization with seasonal variance indicated nonlinearity in series. BDS test is not enough powerful for detecting weak nonlinearity like monthly series in the current study and need further investigations. Thus nonlinear time series modeling should be used for daily, 10 days and monthly series. Linear time series models may be applied for yearly series as utilized in this study.

Water hammer is one of the destructive hydraulic phenomena that occurs in the form of pressure waves in the Pressurized fluid flow systems such as pumping stations, water and oil pipe lines, and hydro-electric installations. Due to importance of water hammer and its destructive effect on pipeline networks, this phenomenon was studied in this investigation by using experimental and numerical models considering two different cases, with and without surge pipe. Data collected for different discharges in arbitrary time intervals were compared with results of CFD numerical model. After determining the optimum network and proper turbulence model the effect of unexpected stopping of water valve on fluid motion and reaction between water and structure was simulated using Fluent software. After testing k-e and RSM turbulence models, the k-e Realizable model found to be the best model. Finally, the results of the numerical model were compared with those of experimental model using the statistical analysis, R2, RMSE and RE. The results showed a good agreement between CFD numerical model and experimental model. So CFD model can be used as a suitable numerical model for computing maximum and minimum pressure.

Homogeneous earth dam is constructed with the optimized use of local materials, to control and store runoffs. One of the most important destructive factors, in this structure, is the seepage through dam body and below its foundation. There are some methods to prevent the internal erosion, among which the horizontal toe drain is the most common alternative. In this research, the effect of applying various thicknesses of horizontal drain in laboratory model and within the proposed range of lengths derived from the analytical relationships was investigated. Results showed that the increase in thickness and length led to significant increase in downstream slope cover while the effect of thickness has not been considered in similar analytical relationships. In addition, the seepage rate would increase dramatically with the increase in drain thickness but the rate of this increase would decline if the thickness exceeded the proposed maximum limit of this research.

Appropriate knowledge about soil properties is essential for sustainable land management. In the present research, soil physical, chemical and mineralogical properties in southern Ahar, the area affected by different landforms, were studied. Six soil profiles on the pediment (high land) and on the floodplain landform (low land) were dug and classified according to the keys of soil taxonomy 2010. Profiles located on the pediment showed higher degree of development based on higher clay content (especially kaolinite) and greater solum depth in comparison with flood plain or low land. Carbonates in the soils of both landforms are predominantly pedogenic, but inherited carbonates were observed more frequently in the pediment soil, which increased with depth. Electrical conductivity decreased downward in soil profiles located on the pediment landform while it increased in floodplain profiles. In spite of pH increase in the soils of both landforms, organic carbon decreased in these soils. Cation exchange capacity and organic carbon content in the soils of floodplain were higher than those on the pediment. Mineralogical analysis using XRD spectrums showed that chlorite, montmorillonite, illite, kaolinite and quartz are dominant clay minerals in the soils of the study area.

The objective of this research was to study simultaneous trends of precipitation and evapotranspiration in the frame of aridity index at southern half of Iran. The time period of this study was from 1961 to 2000. Preliminary results of the synoptic stations time series revealed that the variation of evapotranspiration was less than other two factors (precipitation and evapotranspiration). At the next stage non-parametric Mann-Kendall trend test was conducted for detecting the trends of each factor. Results showed that there was an upward trend for precipitation, however, there was a downward trend for evapotranspiration in almost all stations. Furthermore, trends were statistically significant for about 70% of sites in the cases of precipitation and aridity index and for about 90% of sites in the case of ET0. Trend analysis of aridity index showed that the climate of nearly all sites (about 80%) had tendency to a humid climate to some degree. Mann- Kendall trend diagrams revealed that for all sites the year 1963 was the starting point of trend. Both the maximum and minimum values of significant trends of the three parameters belonged to Esfahan and Ahwaz, with steppe and desert climates.

The current research was conducted, to evaluate groundwater quantity and quality in two aquifers of Saveh and Arak plains, IRAN. Geographic information system software, (version 9.2) was used for studies of spatially and temporally changes in the groundwater level fluctuations and their quality analysis. Results showed that the average drop of groundwater levels during 7 years in 57 wells at Arak plain was 3.38 and in 63 wells at Saveh plain was 10.19 meters. Annual average drop in groundwater level at the same area before construction of Saveh reservoir dam (1987-1994) was 0.98 meters, which increased to 1.47 meters after the reser voir construction (1995-2008). According to Wilcox method, several water qualities were recognized in both regions. In Saveh plain four classes of C4-S2, C4-S1, C3-S1 and C2-S1 made up, respectively, 16, 46, 30 and 16 percent of the ground water in the rogion. The C4-S1, C3-S1 and C2-S1 classes made up, respectively, 42, 56 and 2 percent of the whole ground water in the area. Regarding to the effects of wet and dry seasons, it was found that the water quality during wet seasons specially in deeper wells became better than during dry seasons.

The precision of soil data at any region depends largely on the nature of their variation which often is described by studying of their spatial variability. The location should be considered when analyzing such data because variation of soil properties depends on many process that act in space and time scale, therefore, potentially depends on a scale. This research was carried out to study the effect of scale on estimation precession of organic carbon and bulk density in paddy soils. Three different scales of study were selected at the field of the Rice Research Institute Iran in Rasht. At the first scale, 172 soil samples were taken from the center of 200×50 meter plots. At the second and third scales, 357 and 72 samples were taken from the center of 100×50 and 3×4m plots, respectively. The measured soil properties were organic carbon content and bulk density. All data had non-normal distribution, except bulk density in the third scale. Organic carbon in the second scale and bulk density in the third scale had the maximum and minimum coefficient of variation, respectively. A spherical model was fitted to the varigrams of organic carbon in all scales, which indicated that a single main factor affected organic carbon variations. In the other hand for bulk density, a linear model was fitted to the variograms of first and second scales, a spherical model was fitted to the third scale. Results showed that the first scale with the sampling distance of 200m may be the best scale for studying of organic carbon, and the second scale of 100m distance seems the best for the bulk density.

Limitation of water resources in the country and its great impact on agricultural and natural resources play a crucial role in the efficiency of water use pattern. Using super absorbent polymer may be one of the methods to minimize the stress of weather dryness in the arid and semi-arid regions. The main purpose of this study was to investigate the effects of super absorbent application and increasing irrigation intervals on the growth of almond Amygdalus communis sapling. The experimental design was factorial based on randomized complete block design with two factors, super absorbent at 4 levels (0, 60, 100 and 125 g/100kg soil) and irrigation intervals at 4 levels (7, 12, 18 and 24 day periods), with 3 replication in 2 years. Result of the study provided evidence that the use of super absorbent at the end of first growth season in all irrigation intervals did not produce any significant effect on the growth behavior of almond sapling. However, only in the middle of growth season (July) significant effect was observed in some of growth parameters such as branch height and average canopy cover diameter at 24 days irrigation interval with 60 g. of super absorbent application. For all of growth parameters in the second year, the 7-day irrigation interval showed significant differences with other three intervals. Only the height of main branch at 7-day and 12-day irrigation intervals fell in one group and showed no significant differenc.

Improving soil microbial activity and using synergistic relations including plant growth-promotingrhizobacteria (PGPR) as well as arbuscular mycorrhizal fungi (AMF) are profitable and have economical significance for plant growth in soils with heavy metals contamination. A greenhouse factorial experiment with corn plant was carried out using factorial design with four Zn levels (mg kg-1) Zn0, Zn100, Zn200 and Zn400 and three microbial inoculations including control (C), PGPR inoculation (B), AMF inoculation (F) and PGPR+AMF (BF). PGPRs inoculants were mixtures of fluorescent Pseudomonas spp and the AMF islolate belonged to Glomus versciforme. After 14 weeks plants were harvested and shoots and roots separately were weighed and dried. Growth parameters, Zn concentration and Zn content (accumulation) were determined in different parts of plants. Analysis of variances showed that Zn levels and microbial inoculations significantly affected the measured indices. High Zn levels decreased shoot dry weight (15%) and increased its Zn concentration as well as content compared to the sterile condition 2.6 and 2 folds, respectively. Accumulated Zn in Zn0 treatment (907 mg/pot) was significantly increased in Zn300 treatment (2855 mg/pot). Microbial inoculation of corn has led to an increase in plant biomass compared to sterile plants at contaminated conditions. The highest plant biomass (21.6 g/pot) was achieved in PGPR inoculation which was 2.28 times higher than that of sterile plants (6.6 g/pot). Microbial inoculation particularly with PGPR significantly increased (2.95 fold) Zn uptake in comparison with sterile conditions. It is concluded that inoculation with PGPR decreased Zn concentration in the leaves but drastically raised its accumulation in the whole plant and thus PGPR seems to have the potential that can be used in soil phytoremediation process.

Soil erosion and sediment yield from watersheds restrict sustainable use of land resources. Evaluation of governing process is, therefore, necessary for better understanding of the watershed system leading to appropriate management approaches. On the other hand, different behaviors of soil erosion and sediment yield as well as the necessity of regional studies have been often emphasized. The purpose of this study was to evaluate the applicability of rainfall and runoff variables of 8 storm events occurred during 2008 in prediction of storm-wise sediment yield in Educational and Research Watershed of Tarbiat Modares University (Kojour) with about 500 Km2 in Mazandaran Province. Both bivariate and multivariate regression models were applied with using simple and transformed dependent and independent variables. Results showed that the developed regression models had good capability for estimation of storm-wise sediment yield with coefficient of determination, above 0.76, estimation error below 69% and efficiency coefficient of greater than 0.52. These findings may be convincing for the application of the developed models in this investigation to other ereas similar to the studied area and laeaing to suitable soil and water management.

In this study, raw and treated wastewaters were used for potato cultivation in lysimeters. Five irrigation water treatments were included as: raw wastewater, treated wastewater, fresh water, a combination of 50% raw wastewater and 50% fresh water and a combination of 50% treated wastewater and 50% fresh water. The experiments were run within greenhouse during a period of four months. After construction and preparation of the lysimeters, they were filled with a twolayered soil. The textures of the upper and lower soil layers were sandy loam and sandy clay loam, respectively. In order to create the structure and conditions of the natural soil and develop macropores and preferential pathways, lysimeters were irrigated systematically each week during a period of five months before plantation. A total of eight irrigation programs with an interval of eleven-days were applied during the growth season. Unsaturated water infiltration into the soil was measured using a disk infiltrometer at the beginning and at the end of growth season. In order to evaluate the irrigation effects on soil physical properties, DISC Software (numerical) and Wooding (analytical) methods were employed to analyze the infiltration data. The results of saturated hydraulic conductivity were compared with direct measurements of the constant-head method, in which the numerical method (DISC software) was identified as the best method. The results showed that in all treatments, the saturated hydraulic conductivity and steady-state infiltration rate at matric suctions 5 and 10 cm increased after irrigations when compared with the initial values. Result also indicated that the unsaturated hydraulic conductivity and steady-state infiltration rate increased significantly in the wastewater treatments compared to the fresh water. Also, the maximum values of the steady-state infiltration rate and saturated hydraulic conductivity were observed in the raw wastewater and the combination of treated wastewater and fresh water treatments. The minimum value also belonged to fresh water treatment. Moreover, the highest changes in qs, aVG and nVG were recorded in the combined fresh water-treated wastewater treatment. The lowest variations of these parameters (except qs) were observed in fresh water treatment.

Salinity stress is of great importance due to reducing crop yield in arid and semiarid areas of the world. This research was conducted to evaluate of fluorescent pseudomonads with ACC deaminase activity on growth characteristics of canola (Brassica napus L.) under salinity conditions. The experiment was conducted by factorial experiments on the basis of completly randomized design with four replicationas and under controlled conditions in a green house. The bacterial species included P.p11, P.p.108, P.f.169 and P.f.196 and the control, the salinity levels were 0.335 (control), 5, 10, and 15 dS/m created by diluting a highly natural saline water by various degrees. According to the results inoculation with the selected species was effective on alleviating the unfavorable effects of salinity on canola growth during the vegetative and reproductive growth stages. Increase in salinity reduced plant height, leaf area index, fresh and dry weight, relative water content, leaf water potential, fertile ears, biological and grain yield. It, however, increased stomatal resistance. The mean comparisons indicated that at each level of salinity inoculation with the selected bacteria decreased the negative effects of salinity on the examined parameters.