نشریه پژوهش های حفاظت آب و خاک
سال بیستم شماره 1 (فروردین و اردیبهشت 1392)

One of the best indicators of the geological and environmental events in the Quaternary is the alternation of loess-paleosol. In this study, for paleoenvironmental identification of buried paleosols in loess sequences, 14 sections located between 36˚ 49′ 6˝ to 36˚ 49′ 20˝ northern latitude and 54˚ 26′ 45˝ to 54˚ 26′ 52˝ eastern longitude in the southern part of Gorgan (Kharazmi town) were studied. The disturbed soil samples for physico-chemical analysis and clay mineralogy and undisturbed samples for prepration of thin sections were collected. The physico-chemical results (calcium carbonate content, particle size distribution, cationexchangable capacity and Feo/Fed) indicated that the soils had experienced several pedogenic periods. The result of mineralogy showed that a high amount of smectite, vermiculite and mixed layer mica-smectite in paleosols compared to loess deposits probably indicates moister regims through interglacial compared to glacial periods. The micromorphological observations revealed many evidences on the occurance of pedogenic processes. One of the most important index of pedogenesis, clay coating and hypocoating around void are presented only in buried paleosols, which is the evidence for moist climate conditions, enough for leaching and translocation of clay. Formation of the studied loess and paleosols, probably took place in glacial and interglacial cycles with different climate condition, respectively.

The results of various studies state that a large part of water waste is in the route of water transmission to the fields. Thus, it is essential to optimize the consumption of water by using modern irrigation channels. The purpose of this study is to evaluate predictive models of farmers’ adoption of modern irrigation channels. Therefore diffusion, economic constraints and multidimensional models were examined. The research method was correlative- descriptive and data analysed using discriminant analysis. The study was conducted in Siakh Darenjan region in Fars province. Stratified random sampling was used to collect data from 207 farmers consists of 156 adopters and 51 non-adopters of modern irrigation channel. Data for the study were acquired by the use of questionnaire. A panel of experts confirmed the “Face Validity” of the questionnaire items. A draft questionnaire was pilot-tested using a sample of 28 farmers in a village outside the study area and cronbach’s alpha coefficient for variables was calculated that confirmed the reliability of variables. The results revealed that perceived behavioral control variable in multidimensional and economic constraints models and attitude toward water organization activities in multidimensional and diffusion models are the most important distinctive variables between adopters and non-adopters groups. Also the finding indicated that multidimensional model has a higher ability in classification of adopters and non-adopters of modern irrigation channel. The survey provides multidimensional model for prediction adoption of water irrigation channel. The function obtained from this model, calculates the possibility of adoption of modern channel among farmers. Finally based on the results some practical recommendations have been provided.

Wind erosion is one of the main factors damaging the soils and natural resources, agricultural soils degradation, air pollution, particles transport, damaging equipments, machines and practical operations etc. Although application of polymeric materials for improvement of structural stability, increasing aggregate stability and soil stabilization increased in recent years, but a number of key parameters should be considered to select a suitable polymer as a soil stabilizer for wind erosion control. In this research, performance of Polyvinyl Acetate polymer in three different soil textures was experimentally investigated against wind together with sand particles. So, after design and fabrication of experimental wind tunnel, the erosion of polymer treated samples, was studied under maximum wind velocity of 26 m/s (at 15 cm height) together with sand particles and compared with water treated soil samples. The studied treatments were polymeric emulsion (25 g/lit) and water as stabilizer and three different soils (sand, silt loam and silty clay) in three replications. The results showed that there was significant difference between the erosion of polymer treated and water treated samples. The results also showed that, application of 25 gr/m2 Polyvinyl Acetate in the experimental conditions, reduced the soil erosion against the wind together with sand particles, due to development of interconnecting ties between the particles and covering of the soil particles surface with a thin polymer film. Adding this polymer reduced the erosion of Aeolian sands to zero and the soil erosion reduction in silty loamy and silty clayey soil samples, was 76% in comparison with water treated samples.

One of the most important factors in sustainable development of watersheds is suitable water resources availability in terms of quantity and quality. Along with industrial development, population increase and lack of proper environment control, contamination risk threats the water resources. Water quality properties are the very important component of water resources management and a watershed health assessment. In the case study undertaken, based on data available in the Zarringol station located on the Gorgan river of Golestan province in 1998 to 2007 water quality analysis with drawing Piper, Schoeller, Wilcox, Durov, Gips and Stiff, diagrams was performed. For comparing of treatments ANOVA, to test the statistical difference between the years, the LSD, and to determine trends in the test data Kendall test were used. Results showed that the Zarringol water was the saline water type and is approaching to chloride type. Calcium and magnesium ions have an important role in determining the type of river water quality. This river was assessed as moderate to low that had been placed in C3S1 class in Schoeller diagram and suitable for irrigation in lands with good drainage and coarse soil texture. Chemical quality of Zarringol River has been affected by evapotranspiration reactions. The magnesium risk increased and the risk of salinity in the river is too high. Generally it can be said that because of severe manipulation of the natural environment including roads building and mining in the Zarringol river, water quality declined. It can be recommended that water quality monitoring in head waters of Zarringol River will be done in order to show the effects of each branches in water quality at Zarringol River.

Gamma test is an appropriate tool for determining the optimum input combination and suitable number of data to achieve minimum mean square error in any continuous nonlinear modeling approaches. In this study, at first Gamma test technique was used to determine the optimum input variables from measured input parameters (including soil properties, topographic and vegetation attributes) affecting soil shear strength (SSS) prediction. Two different artificial neural network (ANN) models were then constructed using different input data (Models 1 and 2) to predict SSS. In Model 1, all of the measured parameters (12 parameters) were used as input variables of the model and Model 2 was constructed using only the optimum 5 parameters resulted from the Gamma test trails. According to the Gamma test trail results, fine sand and mean weight diameter (MWD) parameters had the lowest and highest Gamma and v-ratio values among the other parameters, respectively. Furthermore, the vegetation index (NDVI), sand, very fine sand, and aspect parameters had a Gamma values of 0.2177, 0.2280, 0.2313, and 0.2318 in comparison with the other investigated parameters, respectively. Therefore, sand, fine sand, very fine sand, NDVI, and aspect parameters were selected as the optimum 5 input variables for modeling of SSS using ANNs. The proposed ANN model using the optimum 5 input variables, selected from the Gamma test trails (Model 2), had a similar accuracy with the proposed ANN model using all of the 12 input variables (Model 1). The correlation coefficient (r) and root mean square error (RMSE) values for Model 2 were 0.885 and 0.045, respectively, while these indices for Model 1 were 0.891 and 0.058, respectively. Therefore, it appears that the Gamma test technique can be used for choosing optimum input variables affecting SSS prediction to reduce experimental expenses and to save a great amount of time and effort in modeling approaches.

Potassium (K) as a macroelement is frequently made available by weathering of aluminosilicates such as K-feldspar and micaceous minerals in the soils. The objectives of this study were to determine the effect of mineral grain size and type of extractant on the different forms of K of micaceous and K-feldspar minerals and to find out a relationship between aqua-regia extractable K and type of K-bearing minerals. Water soluble, exchangeable, non-exchangeable and aqua-regia exteractable K of 50-100 and <50 μm sizes of biotite, phlogopite, muscovite, zanjan and yazd K-feldspars were investigated. The amount of released K was measured by flame photometer. The results indicated that the amounts of soluble and exchangeable K of trioctahedral micas (biotite and phlogopite) and feldspars are not greatly different, but in this regards, diotahedral muscovite is less important even than feldspars. Soil reservoir of non-exchangeable potassium is significantly higher in trioctahedral micas (up to 17 g kg-1) than muscovite and feldspars (up to 3 g kg-1). The small particles (<50 μm) had a significant effect on the different forms of K in all minerals. The amount of aqua-regia extractable K from trioctahedral micas exceed to 81 g kg-1. This value was 4 g kg-1 for other minerals. The mineral size had no effect on the aqua-regia extractable K in trioctahedral micas while in muscovite and feldspars this form of K increase up to 3.5 times with particle size reduction. More investigations are necessary to propose aqua-regia extractable K as an indicator for assessing type and amount of K-bearing minerals and soil potassium supplying power.

Side weir is one of the most common structures for flow control and diversion in hydraulic laboratories, irrigation and drainage networks and water and waste water channels. Side weirs are generally sharp crested and have limitations in measuring discharge, hence in this study, the compound sharp crested side weirs have been suggested, for the first time. Accurate flow measurement in wide range of discharges in comparison with simple side weirs, is one of the main characteristics of these weirs. Some experiments have been carried out in a rectangular-rectangular compound side weir with variable heights and widths. Dimensional analysis of effective parameters on flow discharge of a compound weir illustrates that its discharge coefficient is a function of upstream Froude number, ratio of weighted height of weir crest to upstream water depth and ratio of channel width to upstream water depth. Based on the experimental data and optimization technique, a dimensionless equation has been developed for calculation of the discharge coefficient. Then, a new equation has been proposed for prediction of flow discharge in compound rectangular-rectangular sharp crested side weirs. Through comparison of results of this new equation and experimental data, the determination coefficients of training and testing data were calculated as 0.96 and 0.98, respectively. Also, mean average relative error was 6.4%.

Water resources scarcity and increasing demand have led to unbalanced supply-demand in the watersheds and water systems. Therefore, planning for efficient allocation has been a matter of importance. To resolve water allocation problems, various models and tools have been developed. Selection of these models is also another issue that needs to be done by an holistic approach. WEAP and MIKE BASIN are two of the well known models in this regard and comparison of their abilities construct objective of the present paper. To do this, capabilities and features of the two models were firstly outlined. Then in two assumptive examples, models were compared based on priority-base allocation and reservoir operation. Furthermore, models ran for a part of Talvar River as one of the main tributaries of the Ghezelozan River. This system consists of ten water demand nodes (domestic and agriculture) and three reservoirs. The results showed that in the priority-base allocation the performances were different, but they were identical in the operation rules and reservoir simulation. The results of reliability index showed that MIKE BASIN simulation matched better with reality due to their ability to extract more water. While, WEAP showed better results for optimization and even distribution of deficits among nodes.

The particle size distribution (PSD) of suspended sediment has fundamental importance in understanding its role in a variety of environmental processes, modeling the transport of sediment and sediment-associated contaminants including heavy metals, nutrients, radionuclide and synthetic organic compounds in river systems. This paper aimed to assess spatial variation of relationship between transport of heavy metals (iron, chromium, nickel and zinc) and PSD of suspended sediment. The study was conducted in Educational and Research Watershed of Tarbiat Modares University comprises some 50000 ha. Towards this attempt, twenty two sediment samples were collected from beginning and end of a study reach (700 m) during May 2007 to June 2008. The samples were then prepared through direct digestion and finally analyzed by atomic absorption spectrophotometer (AAS). The sediment samples were also analyzed for PSD determination based on Stokes’ law with the help of modified pipette method after sample preparation. The relationship between PSD and heavy metals contents were thus evaluated applying bivariate regression models. Proposed models were then selected based on statistical criteria. The results showed a quite high correlation between iron, nickel, chromium and zinc content in suspended sediment and fine PSD (silt and clay) at confidence level of beyond 95% and with correlation coefficient greater than 0.71%. However, the variability of type and quality of relationships at two study points were also well proved.

Combined structure of weir and gate is utilized extensively in hydraulic engineering because of advantages than using each separately, such as passing the floated (ice, wood etc) and settlement of materials together at the same time. Cylindrical weir-gate is one of these structures that has features such as being economical, simple design, ease of construction and high discharge coefficient. Effects of hydraulics and geometric parameters of cylindrical and semi cylindrical (two conditions: curvature in upstream side and curvature in downstream side) weir-gate on discharge coefficient are investigated in this article. The tests were done in a laboratory 6 meters length and 75 mm wide flume and used cylindrical and semi cylindrical pipes with 40, 50, 60, 70 and 85 mm diameters. The results show increase in ratio of upstream depth to gate opening (H/a) and to pipe diameter (H/D) cause growing discharge coefficient. Also with a constant H/D, the flow coefficient for cylindrical weir-gate is close to its value for semi cylindrical weir-gate with curvature in upstream side and is about 12 percent more than semi cylindrical with curvature in downstream side. For each three modes in the range of experiments the discharge coefficient varies between 38-96 percent.

Since trickle irrigation system efficiency depends on the physical and hydraulic characteristics of the drippers and specially water application uniformity, therefore evaluation of drippers as the most important section of a trickle irrigation system will be very important to have an efficient irrigation system. The objective of present study was to measure discharge rates of three different kinds of emitters (including Siplast, Inline168 and Katif8) at four different pressure levels of 50, 100, 150 and 200 kPa to assess the hydraulic performances, calculating the coefficient of manufacturing variation, water distribution uniformity of emitters and emitter discharge exponent, in order to establish the emitter´s flow rate sensitivity to pressure and comparing the results to the manufactures´ specifications. Based on results, Katif8 was classified as pressure compensating and inline168 and Siplast were classified as non-compensating pressure as expected. All three emitters distributed water uniformly at all operating pressures. Results indicated that designing trickle irrigation specially relationship between discharge and pressure should be based on reliable test data, not on manufacturer´s supplied data.

To determine the critical level of zinc in soil and evaluation of the zinc nutritional status in peach orchards, composite soil samples (depths of 0-30 and 30-60 cm) were collected from 39 peach orchards of Golestan province. Soil samples of 24 gardens were selected for the following experiments on the basis of basic experiments results and extracted soil zinc contents. The extractants applied in the study were DTPA and SB-DTPA. An experiment was carried out as a split plot in randomized complete block design including two factors, with four replications. The main plots included 24 orchard soils and sub plots contained three levels of zinc treatments from zinc sulphate (34% Zn) source in 0, 10 and 20 kg/ha rates utilized in banded application on the shade area of tree. Leaf samples were randomly collected from all treatments in mid-season growth and their zinc contents were analyzed. Visual zinc deficiency symptoms were recorded in the orchards at the time of leaf sampling. Critical levels of soil zinc for DTPA and SB-DTPA were estimated by visual inspection method 0.90 and 1.00 mg/kg, respectively and by Cate-Nelson graphical method 0.70 and 0.85 mg/kg, respectively.

Landslides are one of the destructive erosion events in slopes that cause financial losses on the roads. Nowadays landslides are more influenced by human activities than natural aspect. But one of the important human activities in landslide event is road construction in most of Watersheds. In this research the effect of the road in landslide event in part of the Ilam dams, in southeast Ilam with 18360 hectare was evaluated by slope stability model (FLAC SLOP). After selecting the slopes, requirement parameters by soil sampling were done in each slope. To determine the factor of safety (FS), these parameters were considered as the input in the model and FS values were calculated. In the next step effect of road on selected slopes was applied in the model. The results indicated that the road building in slopes with more than 15 percent steepness decreased the stability of slopes. Also using this model could help recognize unstable slopes and could characterize conservation operations to increase slop stability. Based on results operations like nailing and terraces increase slope stability up to 20 percent.

Carbon sequestration in soil through rangeland reclamation and planting new species, in view point of economics, is one of the practical ways to reduce CO2 concentration in the atmosphere. Study about carbon sequestration cost and identification of low-cost species is necessary to recommendation of low-cost suitable species for reclamation of rangeland. Economic aspects of soil carbon sequestration were evaluated in two sites of Chapar Ghoymeh region planted by Agropyon elomgatum and Atriplex lentiformis. Therefore soil annual sequestrated carbon amount per hectare was determined after laboratory analyzing of random soil samples of two species planted sites and comparing with soil carbon of control site. Thus final annual cost of carbon sequestration per hectare was assessed using of cost and income data of sites driven of handbook of rangeland reclamation plans and interview with experts. Overall results of this study showed that reclamation of rangeland by Atriplex lentiformis and Agropyron elongatum have sequestrated 21.974 and 12.872 ton carbon per hectare in soil respectively. The cost of sequestrating carbon in soil of Atriplex lentiformis and Agropyron elongatum sites were 17,056,172 and 20,115,109 Rials respectively. Therefore Atriplex lentiformis is more suitable and low-cost species in reclamation of rangeland in view point of soil carbon sequestration and continuing reclamation of this region by planting Atriplex lentiformis would contain low cost for sequestration carbon in soil.

Soil test is necessary to identify optimal concentrations of phosphorus required for plant growth. A greenhouse experiment was conducted using 30 soils with widely different properties to compare Soltanpour method with conventional method of Olsen. Phosphorus extracted from soil by this method, has a high correlation with P extracted by Olsen extractor (r=0.97**) and also with various plant factors such as plant dry matter yield, the amount of phosphorus in the tissue and phosphorous uptake. The critical levels in studied soils for Olsen and Soltanpour methods were 15 and 6.5 mg/kg in soil, respectively.