Soil science
S. Sanjari; M.H. Farpoor; M. Mahmoodabadi; S. Barkhori
Abstract
Introduction: Playa, as an important geomorphic position in arid areas, covers about 1% of the continents and has attracted attention of soil scientists and geomorphologists. Soil genetic processes related to landforms and geomorphic processes are of great importance. Micromorphology is among necessary ...
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Introduction: Playa, as an important geomorphic position in arid areas, covers about 1% of the continents and has attracted attention of soil scientists and geomorphologists. Soil genetic processes related to landforms and geomorphic processes are of great importance. Micromorphology is among necessary techniques in soil studies which has been used by several researchers. Micromorphological features together with other soil characteristics provide invaluable data for reconstructing soil genetic processes. Moreover, classification and identifying characteristics of soils are pre-requisites for the optimum use and management of soil resources. Soil Taxonomy and World Reference Base (WRB) is among the most extensively used classification systems worldwide. Since no data about soils of the Jazmoorian Playa is available, the present research was performed with the following objectives: 1) studying physical, chemical, and micromorphological properties of soils in the Jazmoorian Playa related to different geomorphic surfaces, and 2) classifying soils of the region by Soil Taxonomy (2014) and WRB (2015) systems. Materials and Methods: The Jazmoorian playa is located in Kerman and Sistan Baloochestan provinces. The Jazmoorian Playa is a continental depression of late Pliocene. The playa is about 360 m above sea level with about 65 km length and 45 km width located between 58 ˚ to 60 ˚ longitudes and 27 ˚ to 28 ˚ latitudes. The area extends to the igneous Bazman Mountains to the northeast, the igneous Jebalbarez Mountains (granodiorite, andesite, granite) to the north and northwest, the Beshagard Ophiolite Mountains of Cretaceous and Paleocene to the south, and the colored Mélanges to the Oman Sea. Soil moisture and temperature regimes of the area were aridic (and aquic in limited areas) and hyper thermic, respectively. Wet zone, fan delta, clay flat, puffy ground clay flat, sodic clay flat, and salt crust were among the geomorphic surfaces investigated in the playa. In order to study the maximum soil variations in the area, eight representative pedons were described and sampled. Collected soil samples were air dried, grounded, and passed through a 2 mm sieve, and routine physical and chemical soil properties were then analyzed. Undisturbed soil samples were used for micromorphological observations. The soils were classified according to Soil Taxonomy (33) and WRB (11) systems. Results and Discussion: Results showed that EC contents of the saturated extracts ranged from 0.5 (fan delta) to 222.2 (salt crust) dS/m. The soils of the playa in Kerman Province affected by the Halilrood River had less salinity compared to the soils on playa surfaces in Sistan Baloochestan Province under influence of the Bampoor River. In addition, salt crust was only formed in parts of the playa located in Sistan Baloochestan Province. Clay coating and lenticular gypsum crystals were among the micromorphological features observed in the Jazmoorian Playa’s soils. The clay coating was formed due to high Na content. However, lenticular gypsum was formed due to small volume pore spaces as well as high salinity of the area. High soluble salts (Table 3) caused a salt coating around pore spaces to be formed due to evaporation of saline water table. WRB system could better classify soils into Solonchak and Solonetz RSGs compared to Soil Taxonomy system which classifies all soils as the Salids sub order. Natric Aquisalids, Typic Natrisalids, Natric Haplosalids, and Puffic Haplosalids sub groups and Natrisalids great group are recommended to be added to Soil Taxonomy system for more harmonization between the two classification systems. Furthermore, the definition of salic horizon in WRB system (EC of at least 15 dS/m and the EC multiplied by thickness of at least 450) is recommended to be included in Soil Taxonomy, because of limitations induced by salts and for a better correlation of the two systems. Conclusion: Results of physicochemical properties clearly showed that electrical conductivity of soil saturated extracts was in the range of 0.5 to 222.2 dS/m. The part of the playa located in Sistan Baloochestan Province is more saline than the part in Kerman Province. More salinity of playa in Sistan Baloochestan Province was attributed to the Bampoor River which passes through evaporative formations located in east and southeast of the area. Micromorphological observations showed clay coatings and lenticular gypsum crystals as pedogenic features. The soils of the area were classified as Aridisols and Entisols (according to Soil Taxonomy system) and Solonetz, Solonchaks, Fluvisols, and Regosols Reference Soil Groups based on WRB classification system. Moreover, WRB system was capable of separating saline from saline-sodic soils, however, Soil Taxonomy classifies both soils as Salids suborder. Therefore, WRB system is better suited for classification of the soils of our study area as compared with Soil Taxonomy.
Mohammad Akbar Bahoorzahi; Mohammad Hady Farpoor; Azam Jafari
Abstract
Introduction: The optimum and sustainable use of soil is only possible with correct and complete understanding of its properties. The objectives of the present research were to study 1) genesis and development of soils related to different geomorphic surfaces in Kouh Birk Area (Mehrestan City), 2) Soil ...
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Introduction: The optimum and sustainable use of soil is only possible with correct and complete understanding of its properties. The objectives of the present research were to study 1) genesis and development of soils related to different geomorphic surfaces in Kouh Birk Area (Mehrestan City), 2) Soil classification according to Soil Taxonomy (2014) and WRB (2014) systems, and 3) physicochemical properties, clay mineralogy and micromorphology of soils.
Materials and Methods: Mean annual rainfall and soil temperature in the selected location are 153.46 mm and 19.6 oC, respectively. From geological point of view, the studied area is a part of west and south west zones and Flysch zone of east Iran. Soil temperature and moisture regimes of this part are thermic and aridic, respectively. Eight representative pedons on different surfaces including rock pediment, mantled pediment, Alluvial fan and Upper terraces were selected, sampled, and described. Routine physicochemical analyses, clay mineralogy, and micromorphological observations performed on soil samples. Soil reaction, texture, electrical conductivity, calcium carbonate, and gypsum were identified. Four samples including Bt horizon of pedon 1, Bk1 horizon of pedon 4, By2 horizon of pedon 5 and Bk1 horizon of pedon 7 were selected for clay mineralogy investigations. Four slides including Mg saturated, Mg saturated treated with ethylene glycol, K saturated, and K saturated heated up to 550 oC were analyzed. A Brucker X-Ray diffractometer at 40 kV and 30 mA was used for XRD analyses. Undisturbed soil samples from Bt horizon of pedon 1, Bk2 horizon of pedon 2, Btn horizon of pedon 3, By2 horizon of pedon 5, Bk1 horizon of pedon 7, and By1 horizon of pedon 8 were selected for micromorphological observations. A vestapol resin with stearic acid and cobalt as hardener was used for soil impregnation. Bk-Pol petrographic microscope was used for micromorphology investigations.
Results and Discussion: Due to the presence of argillic and petrocalcic horizons in rock pediment, soils of this surface were more developed compared to other landforms. High amount of CaCO3 (39.5%) was observed in pedon 4 on rock pediment geomorphic surface which is attributed to calcareous parent material. The presence of argillic horizon in this geomorphic position is due to the more available water of the past climate. The maximum salinity was observed in the mantled pediments. Calcic over gypsic horizons formed in pedon 7 on alluvial fan surface due to higher solubility of gypsum than calcium carbonate. Kaolinite, illite, chlorite, and palygorskite clay minerals were found in pedons 1 and 4 on rock pediment. Palygorskite in this position seems to be pedogenic, but kaolinite, illite, and chlorite are inherited from parent material. Mantled pediment and alluvial fan showed smectite, kaolinite, illite, chlorite, and palygorskite clay minerals. Pedogenic smectite in this position is probably formed from weathering of illite and chlorite. On the other hand, palygorskite stability decreased in mantled pediment surface. This is the reason why smectite was the dominant clay mineral in this landform. Clay and calcite coatings were investigated in Bt horizon of pedon 1 (rock pediment). Coatings and infillings of calcite in Bk2 horizon of the same geomorphic position caused a calcic crystallitic b fabric. A diffused clay coating due to the presence of Na in Btn horizon of pedon 3 in rock pediment was observed. Micromorphological observations of By2 horizon in pedon 5 (mantled pediment) showed gypsum interlocked plates and gypsum infillings. Interlocked plates formed due to re-solubility of gypsum crystals. Micro spars and infillings of calcite are among dominant pedofeatures found in Bk1 horizon of pedon 7 (alluvial fan geomorphic surface). A calcic crystallitic b fabric and Primary calcite mineral were also observed in this pedon. Release of Ca from calcareous parent material caused Ca+2 to SO4-2 ratio to be increased which could be a probable source of gypsum formation. Results of the study showed that more and less developed soils formed on rock pediment and upper terrace geomorphic surfaces, respectively. Illuviation of clay, gypsum, and CaCO3 together with formation of cambic, calcic, petrocalcic, gypsic, argillic, and natric horizons were among the dominant pedogenic processes in studied soils. Paleosols containing Bt horizons were only observed on rock pediment geomorphic surface. Kaolinite, illite, chlorite, and palygorskite clay minerals were observed in almost all surfaces. Smectite was not discovered in rock pediment, but was only investigated in mantled pediment and alluvial fan which could be attributed to higher available moisture of formation time in these surfaces. Secondary calcite and gypsum caused stability of pedogenic palygorskite in soils under study. Micromorphological observations proved the presence of clay and calcite coatings, calcite and gypsum infillings, and gypsum interlocked plates. Gypsum pedofeatures were not observed in rock pediment, but clay and calcite pedofeatures were only found. On the other hand, clay and calcite pedofeatures were not observed in upper terraces and gypsum pedofeatures were the only features determinded in this position.
Conclusion Results of the present research showed that difference in soil characteristics is highly affected by geomorphology.
Ahmad Fakheri Fard; Vahid Nourani; Faegheh Niazi
Abstract
Introduction: The influence of urbanization, as one important form of land use, on runoff and floods within watersheds has been a major topic of research during the past few decades. Urbanization affects the hydrology processes of a watershed by replacing the vegetated land cover with impervious surfaces. ...
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Introduction: The influence of urbanization, as one important form of land use, on runoff and floods within watersheds has been a major topic of research during the past few decades. Urbanization affects the hydrology processes of a watershed by replacing the vegetated land cover with impervious surfaces. This can have a substantial effect on the hydrological response of a watershed to rainfall, potentially resulting in faster response, greater magnitude of river flow, higher recurrence of small floods and reduced base-flow, and groundwater recharge. The direct runoff hydrograph generated by rain falling on a watershed reflects the characteristics of both the effective rain hyetograph and the relevant surface features that control the runoff generation and surface-water flow processes.
Materials and Methods: In this study, the effect of land use investigated using GUHCR model and adjusted GUHRLU model is presented. These models and Nash’s conceptual model used to investigate land use impacts for a small, well instrumented watershed consisting of two different land uses sub-watershed in the city of Sierra Vista, Cochise County, Southeastern Arizona. Geomorphological factors for the sub-watersheds extracted by GIS. In this study 13 storm events occurring on both sub-watersheds were selected to examine the proposed model’s performance. Nine events were selected for model calibration. The remaining four events were used to examine the simulated hydrographs for the outlet and the interior natural sub-watershed. The model parameter ( ) was estimated for each event using the moment method and the average of the calibrated values was used for evaluation of the model. The model's performance demonstrated through four popular criteria (i.e. The Nash–Sutcliffe efficiency (NE), the Correlation Coefficient (R), the ratio of the absolute error of peak flow (EP) and the ratio of the absolute error of hydrograph’s volume (Ev)) using available hydro-geomorphological data.
Results and Discussion: The results show that although all studied models forecast the outlet hydrographs with acceptable accuracy, only the presented GUHRLU model shows appropriate results at sub-watershed outlet considering the effect of land use. Clearly, accounting for land use properties in the model formulation leads to improved efficiency at the internal sub-watershed. The Nash model as a lumped model, calculates the hydrography just at the watershed outlet without any information about the hydrological behavior of the interior watershed. Therefore, internal hydrography estimation is impossible via this model. In general, urban runoff tends to have a sharper rising limb and higher peak values while runoffs in natural watersheds have smaller peak values and the rising limb climbs more slowly. The hydrographs show that the overall shapes of the urban sub-watershed hydrographs are similar to each other, while those in the natural sub-watershed tend to be more different, as expected. Simultaneous consideration of geomorphological and land use parameters in the formulation of the proposed model (GUHRLU) provides this capability. As indicated by Ep and Ev, the error of peak flow and the volume of hydrographs show acceptable accuracy. It can be noted that some events show high values of error of peak flows (Ep), however, the model results in small values of Ev that is of great importance in water resource management. Note that, the performance values obtained for the watershed outlet were, for most events, higher than those of the internal sub-watershed outlet in both formulations, which may be due to the use of outlet hydrographs for calculating the model parameter ( )., This might also be due to less uncertainty in urban watersheds where runoff to rainfall ratios is much larger than in the natural sub-watershed. The GUHCR model has slightly better performance at watershed outlet, but it is unable to detect land use variability in its model formulation and so to estimate the internal watershed hydrographs appropriately. Overall, peak discharge and runoff volume for the natural sub-watershed was over-estimated via GUHCR model. The average values for Nash-Sutcliffe criteria at the internal watershed outlet for GUHCR and GUHRLU models are 0.47 and 0.78 respectively. Over 40% improvement is achieved in simulated peak discharge and runoff volume at interior watershed outlet using GUHRLU in compared with GUHCR model.
Conclusion: GUHRLU model considers not only the geomorphologic properties of the watershed, but also the land use variation of the sub-watershed in parameter formulation. This model can also reflect the hydrological conditions of the internal parts of the watershed with divergent land uses. The GUHRLU model is able to improve the efficiency of geomorphological rainfall-runoff simulations at the interior part of the study watershed, located in southeastern Arizona, by taking into account land use. Consideration of land use in the model leads to acceptable results at both watershed and interior sub-watershed outlets, particularly for watersheds like the studied watershed where different land uses sub-watersheds have. The overall efficiency of prediction was slightly poorer for the internal sub-watershed than for the outlet. Application of three models reveals that only the presented GUHRLU model shows appropriate results at sub-watershed outlet in which the land use variation is considered in the model formulation.
Mohammad Ghasemzadeh Ganjehie; Ali reza Karimi; Ali Zeinadini; Reza Khorasani
Abstract
Introduction: Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of playas is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. ...
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Introduction: Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of playas is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. More than 60 playas have been identified in Iran. Considering the fact that playas and surrounding landforms are important archive of landscape evolution and paleoenvironmental variations, it seems that less attention has been paid to them so far. Soils are known as indicators of the landscapes evolution. Previous studies in arid regions of Iran imply different periods of deposition and soil formation in playa and alluvial fans or pediments. Bajestan playa is one of the known playa in northeastern Iran, and the largest clay flat exists in this playa. There is no information on the soils and their evolution in Bajestan playa. The objective of this study were to 1) identify the soils in different landforms along a transect from alluvial fan to clay in Bajestan playa 2) determine the morphological, micromorphological and mineralogical characteristics of these soils 3) determine the periods of soil and landform evolution and 4) comparison of soils evolution of the study area to other arid regions of Iran.
Material and Methods: The study area of approximately 20000 hectares is located in southeastern of KhorasanRazavi province. The climate of the study area is hot and dry with mean annual temperature and rainfall of 17.3 °C and 193 mm, respectively. Soil moisture regime is aridic with subdivisions of weak aridic and soil temperature regime is thermic. Firstly, landforms and geomorphic surfaces of the study area were recognized based on Google Earth images interpretations and field observations. Four main landforms were recognized in the study area. The landforms from north to the south of the study area were alluvial fan, intermediate alluvial fan- clay flat, pediment and clay flat. Considering the diversity of geomorphic units, 11 soil profiles were described and diffrenet soil layers and horizons were sampled. Undisturbed soil samples were taken micromorphological studies. Some horizons were selected for clay mineralogy analysis. The mineralogy of clay fraction was determined using X-ray diffraction method.
Results and discution: All studied soils except the profiles in the pediment were classified in the Aridisols order. There were two geomorphic surfaces in alluvial fans. In the first geomorphic surface a soil with the Bk horizon buried a soil with red Btk horizon. In the second geomorphic surface, it seems that the erosion has been removed the overlying soil. The Bk horizon showed the maximum soil development in the clay flat and intermediate alluvial fan-clay flat landforms. Clay coating on sand in thin section was the evidence of clay illuviation in Btk horizon. Carbonate nodules associated with clay coating are the compound pedofeature in Btk horizon. These evidences reflect polygenetic nature of the soils and different period of climate change and soil formation. Smectite, mica, chlorite and palygorskite are the clay minerals in the studied soils. Similar to soils in arid regions of Iran, palygorskite was found in Bk, Bt and Bz horizons. The existence of Bk horizon in overlying soils, buried Btk horizon, removal of surface horizon in alluvial fan are the evidences of regressive and progressive of pedogenic processes in the study area. Btk horizon represents a warm and wetter and Bk horizon indicates a relatively wetter period in comparison to present time.
Conclusion: Btk was the most developed horizon in the study area that occurred as buried paleosol in alluvial fan. Bk, Bw, By and Bz were the common horizon in other landforms. Clay coating and red color of Btk horizon might seem as indicators of hot and humid conditions in the past, during the argillic horizon formation. Covered carbonate nodules with clay coating can also be mentioned as sign of a hot and wet period which is suitable for clay illuviation and weathering after a period of carbonate accumulation. The buried Btk horizon under alluvial layers in the alluvial fan indicates that after apedogenic period, alluvial processes have been responsible in burying this horizon. Bk horizon in overlying soil of all landforms represents a less intense period of soil formation. The dominant clay minerals in the study area were Illiite, cholorite, kaolinite, and palygorskite. The sequence of Bk and Btk horizons in this research and the occurrence of these soils in central, eastern and northeastern Iran imply the similar pedogenetic conditions in arid regions of Iran.
Ali Golkarian
Abstract
One of the most important objectives in hydrological studies is quantitative rainfall-runoff process estimation at the basin. Several methods and models have been created in order to simulate the Rainfall-Runoff process that each one has its’ own advantages and disadvantages. The aim of this study ...
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One of the most important objectives in hydrological studies is quantitative rainfall-runoff process estimation at the basin. Several methods and models have been created in order to simulate the Rainfall-Runoff process that each one has its’ own advantages and disadvantages. The aim of this study is to investigate the capability of the Geomorphologic Instantaneous Unit Hydrograph model in flood hydrograph development and comparing its’ performance with Snyder, SCS and Triangular models. In order to implement the mentioned methods, Rainfall-runoff data were collected for 14 events and direct hydrograph was obtained. According to the statistical indicators such as RMSE, MRE and Nash-Sutcliff Coefficient, comparison of the observed and estimated hydrographs depicted that the GIUH method was the most efficient in peak discharge estimation, and Triangular, SCS and Snyder models were the next, respectively. Also according to the results, Snyder, GIUH, Triangular and SCS methods have the most efficiency to predict the time to peak, respectively. In addition the results indicate a low estimation for GIUH and SCS methods in peak discharge prediction and over estimation for Snyder and low estimation for GIUH method in time to peak prediction.
