Showing 1096 results for Ro
H. Rezaei-Sadr, A. M. Akhoond-Ali, F. Radmanesh, G. A. Parham,
Volume 17, Issue 66 (2-2014)
Abstract
In this study, the influence of spatial heterogeneity of rainfall on flood hydrograph prediction in three mountainous catchments in south west of Iran was studied. Two interpolation techniques including Thiessen polygons method and Inverse Distance Weighting method were applied to compare the rainfall patterns of surrounding rain-gages in hydrograph simulation with rainfall patterns of nearest rain-gage from the catchment outlet. It was found that the best simulated hydrograph is obtained from rainfall pattern of the nearest rain gage. Moreover, the results did not show any relationship between spatial variation of rainfall and outlet hydrograph. Formation of different local rainfall patterns due to non-stationary rainfall field provoked by irregular topography and their effect on interpolation procedure caused important biases in interpolated rainfall hyetographs obtained by Thiessen and IDW methods. It seems that the observed biases in the response of the catchments are the result of inaccurate representation of spatially averaged rainfall rather than its spatial variability. Hence, in mountainous catchments with irregular topography, the lack of sufficient records caused by poor rain gage arrangement can be highlighted as the dominant source of uncertainty in modeling the spatial variations of rainfall.
A. Morshedi, M. Naderi, S. H. Tabatabaei, J. Mohammadi,
Volume 17, Issue 66 (2-2014)
Abstract
It is necessary that ETr (Alfalfa-reference evapotranspiration) values be converted to ETo (Grass-reference evapotranspiration) or vice versa. The main objective of this study was to develop ETr to ETo ratios (Kr values) for a growing season in Shahrekord plain, Shahrekord, Iran. Mean monthly and total (growing season) values of Kr were calculated based on 185 daily ET data set in Chaharthakhteh Agricultural Resaerch Station of Shahrekord. The ETr and ETo values were calculated using six models for developing Kr values. The models included the Standardized American Society of civil Engineers Penman-Monteith (ASCE-stPM), American Society of Civil Engineers Penman-Monteith (ASCE-PM), 1982 Kimberly-Penman (KP), and modified Jensen-Haise (JH). Kr values as a function of some of the climatic variables in FAO56 Irrigation and Drainage Paper were compared with lysimeter ETr values. For the growing season, Kr values based on lysimeter study was 1.12, which was comparable to 1.12, and 1.16 for ASCE-PM, and JH, respectively, but was far from 1.27 for 1982 KP models. ETr values in each method compared to ASCE-stPM-ETo were not comparable to 1.40 derived from Kr value based on FAO56 method.
M. Nouri, M. Homaee, M. Bybordi,
Volume 17, Issue 66 (2-2014)
Abstract
In order to assess hydraulics of LNAPLs in soil, the soil retention curves of petroleum and water were both determined through hanging column method. And, the hydraulic conductivity of petroleum and water were determined by steady head method. The water and petroleum hydraulic conductivities were 7.27 and 57.84 cm.day-1, respectively. The soil retention parameters were obtained based on van Genuchten, Brooks-Corey and Campbell models. In addition, the soil hydraulic conductivity for both fluids was predicted based on Mualem- Brooks-Corey, Burdine- Brooks-Corey, Mualem-van Genuchten and Campbell models. The accuracy assessment of models was performed by ME, RMSE, CD, EF and CRM. The results indicated that the magnitudes of the pore-size distribution parameters and the bubbling pressure parameters were reduced in NAPL-air system compared to water-air system. Due to unusual hydraulic behavior of petroleum and soil-petroleum interactions leading to remaining substantial petroleum content in porous media, more matric potential is needed to drain out petroleum from soils compared to water. Thus, soil provides more retention for petroleum at a given quantity of fluid. Owing to high amount of petroleum kinematic viscosity, the saturated soil hydraulic conductivity of petroleum was lower than that of water. However, soil hydraulic conductivity for petroleum was larger than water at more than 100 cm matric head.
S. A. A. Hashemi,
Volume 17, Issue 66 (2-2014)
Abstract
Check dams are considered as main measures for flood and sediment control in watersheds, and their uses have been rapidly increased from 1990 onward in Iran. This research is done in Darjazin watershed in north of semnan city. The check dams have been constructed from 15 years ago in two sub basins of the watershed for flood control in Mahdishar. More than 650 check dams were evaluated for effects on flood. The collected data in the field was fed to ArcGIS software. The effects of these structures on flood reduction were evaluated by HEC-GeoHMS extension and HEC-HMS model. Because of homogeneity of watershed management projects in the basin due to building more check-dams in different watercourses, any flood discharge is related to check dams. Evaluating the effects of check dams on flood by t-test showed significant differences between flood discharge before and after construction of check dams at 5 percent level. So, check dams have been able to reduce flood discharge by 16.7 percent on average.
N. Besharat, A. Tajabadi Pour, V. Mozafari,
Volume 18, Issue 67 (6-2014)
Abstract
To study the effects of soil phosphorus (P) application on growth and water relations and nutrient concentration of pistachio seedlings (Badami-e-Zarand) under water stress, a greenhouse experiment was conducted. Treatments were arranged in a factorial manner as a completely randomized design with three replications. Treatments consisted of six P levels (0, 30, 60, 90, 120 and 150 mg P Kg-1 soil as H3PO4) and three irrigation intervals (2, 4 and 8 days). Results showed that as water stress increased, growth parameters significantly decreased. As irrigation interval was increased to 8 days, shoot and root dry weights, shoot/root ratio, leaf area and leaf number and stem height decreased. Photosynthesis parameters were significantly decreased by increasing water stress. Also, P and Zn concentrations decreased as irrigation interval increased. Analysis of variance indicated that P application had no significant effect on growth parameters, transpiration rate and photosynthesis. It seems that Olsen extractable P (5.35 mg kg-1 soil) was sufficient for optimum growth of pistachio seedlings and thus, no growth responses were observed from P application in this experiment. Application of phosphorus significantly increased P and decreased Zn concentrations.
M. B. Heyderianpour , A. M. Sameni, J. Sheikhi, N. Karimian, M. Zarei,
Volume 18, Issue 67 (6-2014)
Abstract
A study was conducted to evaluate the effect of vermicompost and nitrogen (N) on growth, nutrient concentration and uptake of N, phosphorus (P), potassium (K), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) in sunflower shoots as a factorial experiment arranged in completely randomized design (CRD) with three replications under greenhouse conditions. Treatments included three levels of vermicompost (0, 2.5, and 5 % by w/w) and three N levels (0, 90, and 180 mg kg-1) as urea. Application of 2.5% vermicompost significantly increased the average fresh and dry weights, and uptake of K, Fe, Zn, Mn, and Cu of shoots as compared when no vermicompost was applied, but decreased Zn and Cu concentrations. Application of 90 mg N, increased fresh and dry weights, and concentration of N, Zn, and Mn, total uptake of N, P, K, Fe, Zn, Mn, and Cu in sunflower shoots, but decreased P concentration. Application of 180 mg N increased total N uptake than that of 90 mg N kg-1 treatment. Combination of 2.5% vermicompost with 90 mg N, significantly (p<0.05) increased dry matter yield of sunflower as compared to 2.5% vermicompost without N treatment
A. Masjedi, A. Taeedi,
Volume 18, Issue 67 (6-2014)
Abstract
Floor intake is one of the best options for diverting mountain rivers' flow. Determination of discharge diverted in different conditions of flow in main channel is one of the main objectives for intake under rack floor condition. Gradient and shape of grid rod floor can affect the discharge deviated. In this experiment, placement and gradient of grid rods and also their effects on the discharge coefficient and hydraulic parameters were investigated. For this purpose, a physical model made of glass with variable gradient was used for the main channel. To conduct and measure the discharge diverted, a sub-channel 8 meters away from the entrance of main channel was installed below the main channel. Length and width of intake entrance were 10 and 50 cm, respectively. At the entrance of intake a longitudinal grid with four different rod diameters, constant-space passing, and four different gradients were used. Meanwhile, for the investigation of flow rate four discharges were used. The results showed that intake discharge coefficient was increased with an increase in diameter of grid rod floor, reduction in floor gradient, and increasing of depth in the upstream network. In all cases, increasing the Froude number resulted in an increase in the intake discharge coefficient in the upstream network
A. Heidari, A. Hemmat, S.m Rezvani,
Volume 18, Issue 67 (6-2014)
Abstract
efficiency was investigated during a 2-year period (2009-2010) in a silty clay loam soil in Tajarak Research Station
(Kaboudarahang Township), Hamedan. The experimental design was a strip-plot within a randomized complete blocks
design. The horizontal band, the irrigation water rate after flowering, included full and deficit irrigation (100% and 75%
potato water requirement) and the vertical band, kind of inter-planting row tillage including 1- subsoiling to 30-35 cm
soil depth, 2- chiseling to 20-25 cm soil depth, 3- sweeping to 5 cm soil depth and 4- no-till. During the growing
season, soil mechanical resistance (cone index) in two stages and water infiltration into the soil were measured. At the
end of the growth season (harvesting time), potato yield quantity and quality were measured. Result showed that the
effect of inter-row tillage on soil mechanical resistance was significant. Subsoiling and chiseling had lower soil
mechanical resistance and higher water permeability between treatments, respectively. The effect of inter-row tillage on
potato yield was significant so subsoiling and chiseling had a higher potato yield between treatments, respectively. The
effect of irrigation water rate on potato yield was not significant. The effect of inter-row tillage on water use efficiency
wasn’t significant.
J. Abedi Koupai, J. Khajeali, R. Soleimani, R. Mollaei,
Volume 18, Issue 67 (6-2014)
Abstract
As increasing of disaster such as drought and pest invasion in recent decades, it is essential to find out practical
approaches in optimizing water use and water management for reduce the adverse effects of this disaster in agriculture.
In order to study the effects of water stress and pest stress on corn yield, an experiment was conducted in the research
farm of Isfahan University of Technology. In sprayed and non sprayed of the field, a factorial design, based on the
completely randomized block, was carried out with three treatments of irrigation regimes including intensive stress
(50% water requirement), moderate stress (75% water requirement) and no water stress in four stages of corn growth
from seed germination until tasseling, from tasseling until milky, from milky until harvest and the whole period of corn
growth, in four replications for one year (2005). The results showed that applying water stress on corn reduced seed
yield between 6-62% and also decreased other agronomic characters except protein percentage. Water stress in non
sprayed condition, reduced significantly more physiological characteristics of corn compared to the sprayed condition.
Intensive water stress and pests stresses increasd 3 and 13% of percentage protein, respectively. In sprayed condition
applying moderate stress in first stages of corn until the first of third stage is suggested in drought condition.
A. Khanamani, E. Dodangeh, F. Soleymani , H. Karimzadeh, S. Soltani,
Volume 18, Issue 67 (6-2014)
Abstract
Underground water resources considered as a major source of fresh water. Increasing need to water in Iran, causing to
immensely utilization and ground water balance disorder, so that state of ground water in many of area is negative.The
purpose of this study is to investigate the trend of changes in some of the characteristics of groundwater during the
period 1374 to 1387 is Segzi plain. For this purpose, data gathered from the Organization of regional water and
homogenous test with Tom test (Run-test) at 95% confidence level was performed on the data. The independence of
data evaluated by time series auto correlated functions (ACF), to do this, the amount of auto correlated data computed
in different time delays and finally Mann- Kendall test used to evaluate the trend of time series properties in
groundwater. The results of Run-Test showed that all of used series in this study were homogenous (P value< 0.05).
The result of trend analysis test for region’s wells showed a significant increase in chlorine in underground water
resources (P value< 0.05). Calcium has an increasing Trend too about 3 units. Results also showed that all used series in
this study are random and Mann- Kendall trend analysis test can be an appropriate for trend evaluating in data series. As
regard to irregular utilization of underground water resources by increasing depth of water level, amount of different
salts such as chlorine and sodium increased, that causing to surface source degradation like soil and plant cover in
agricultural area.
M. Zare, M. Soufi, M. Nejabat, L. Jokar,
Volume 18, Issue 67 (6-2014)
Abstract
Gully erosion and sedimentation have high priority in Fars Province due to the losses from destruction of lands, roads and civil structures. In the present study, in order to evaluate the threshold for the development and initiation of gully topography in Fars province, two regions were selected including Allamarvdasht, Lamerd and Fedagh, Larestan. 30 gullies were selected in each mentioned area. Morphometric parameters were measured and topography threshold was drawn. To evaluate the effect of measured parameters on topography threshold, each gully was clustered based on parameters and cluster analysis. To determine the effect of dominant hydrologycal processes on gully initiation and development, the multivariate analysis was employed using SPSS (version 14) software. Using the power relationship between watershed area and slope of each gully, the dominant hydrological processes in gully initiation and development were determined by means of Excel software and were compared with coefficients of foreign regional studies. The results showed that in the two studied regions, the most effective hydrologycal process was surface runoff. Results also demonstrated that in these regions changing the shape of upstream basin topography to circle and their expansion have increased the threshold of watershed topography of gully erosion. Increasing the sodium absorbtion ratio and removing the ground cover reduce the threshold of gully erosion topography. Increasing the depth of gullies and soil organic matters resulted in greater relative threshold of topography.
H. Modabberi, M. Mirlatifi, M. A. Gholami,
Volume 18, Issue 67 (6-2014)
Abstract
Since more than 75% of the rice fields in Iran are located in the Northern provinces i.e. Mazandaran, Guilan, and
Golestan identifying the crop water requirement of rice fields is essential for water resources planning in the Northern
provinces. The objective of this research was to ascertain the crop water requirement of two rice cultivars namely
Hashemi and Khazar in Guilan province during 1389 growing season. Four iron barrels with diameter of 56 cm were
used as lysimeters to grow the cultivars mentioned. According to a simple volume balance approach the crop water use
of the four lysimeters were determined during the growing season. The elements of volume balance approach such as
the depths of drainage, precipitation, and irrigation were recorded daily and the average of 5-day and 10-day periods
were reported. The daily rice crop water use during the growing season was found to range from 2.4 to 6.3 mm/day with
a seasonal crop water use ranging from 430 to 470 mm for Hashemi and Khazar cultivars, respectively. Daily reference
evapotranspiration was computed by the FAO-Penman-Montith equation and accordingly rice crop coefficients were
computed. The crop coefficient of Hashemi variety was found to be 1.1, 1.3, and 1.1 during the initial, mid, and end
growth stages, respectively. In addition, the aforementioned parameters for Khazar variety were 1.2, 1.3, and 1.1.
E. Habibi, M. A. Asoodar, B. Khalil Mogaddam,
Volume 18, Issue 67 (6-2014)
Abstract
Extensive tillage leads to the degradation of soil structure and aggregate stability. The effects of three different tillage implements including (combination tillage, chisel packer and disk), three levels of soil water content including (0.5, 0.7 and 0.9 plastic limit), three working speeds including (6, 8 and 10 km/hr) and two soil textures including (loam and silty clay loam soils) were studied. The study was carried out in Khuzestan Ramin Agriculture and Natural Resources University, in 2011. Soil aggregate mean weight diameter (MWD), geometric mean diameter (GMD) as determined by wet sieving method and soil surface roughness (SSR) were measured. Results showed that chisel packer with 0.744 mm MWD produced largest soil aggregates in both soils because of using narrow blade and shanks and small rake angles compared to other tillage treatments. Soil aggregate size was shown larger than other tillage treatments where chisel packer was employed but it was not suitable because of deep furrow shapes. Combination tillage was able to make a better soil condition to be used for seeding where the experiment was conducted.
N. Pourabdollah, T. Honar, R. Fatahi,
Volume 18, Issue 67 (6-2014)
Abstract
Most of researches related to hydraulic jump have been done on horizontal and rough beds, and little attempt has been made on rough beds with adverse slopes. The aim of this study was to investigate the influence of rough beds with adverse slope on hydraulic jump characteristics. The variations of energy loss in stilling basins with three adverse slopes and three different roughnesses were studied. Results showed that increase of roughness caused that relative depth of jump in stilling basins with rough bed and adverse slope decreased as compared to horizontal smooth beds. The experiments were performed on rough beds in different conditions where Froude number ranging between 4.9 and 7.8. Result showed that reduction of relative depth was about 31.15%. Results also showed that in such cases the relative energy losses are more than that for classic conditions.
M. Khodagholi, R. Saboohi, Z. Eskandari,
Volume 18, Issue 67 (6-2014)
Abstract
The geographical location of Isfahan province has led the province to be at risk of drought. One of the ways to mitigate drought is evaluation and monitoring of drought based on indices that can determine its intensity and permanence in each region. In this research, for drought and trend analysis standard precipitation index and Mann-Kendall test were used, respectively. Also, monthly precipitation time series of Isfahan province was applied to forecast drought from 1970 to 2009. For this purpose, Box and Jenkins modeling approach (1976) was used which has three main steps, namely model identification, parameter estimation, goodness of fit test or time independency and normal test of residual. The results showed that most of the stations in Isfahan province were faced with severe drought in the year 2000 and this situation was repeated one more time in 2008. Also, the results brought forth multiplicative models in all the stations. ARIMA (1,0,0) (0,1,1) showed the highest correlations between control and forecast data in Isfahan, Meime and Ardestan stations, and the model ARIMA (0,0,1) (0,1,1) displayed the highest correlation between control and forecasted data in Naein, Freydoonshahr, Khansar and Natanz. These models were selected as the best models through which the amount of precipitation was predicted till 2015. The trend of forecast data across Isfahan province showed that in most months the trend is not significant.
H. Azimzadeh, F. Fotoohi, M. R. Ekhtesasi,
Volume 18, Issue 68 (9-2014)
Abstract
Soil surface roughness (SSR) is one of the important factors in wind and water erosion studies and control. Several parameters such as surface rock fragments influence SSR. Main objectives of this paper are to study and compare (Allmarass) random roughness (RR) and tortuosity (Tb) indices in coarse, medium and fine grain plains of Yazd-Ardakan and investigate the relationship between indices and desert pavement coverage. Roughness data were obtained by pin roghness-meter and roller chain in the three mentioned plains. RR and Tb were measured in 90cm transect length with systematic sampling pattern after determining the boundary of three kinds of plains. In each plain, 30 transects were randomly sampled and the height of soil surface roughness fractions was recorded. Distance of pins in the applied roughness meter is about 2cm. Therefore, in each 90 cm transect the height of 46 points was measured. Desert pavement coverage was measured in 20×20cm2 plots. The result showed that desert pavement coverage in coarse, medium and fine grain plains were in the range of 55-100, 40-85 and less than 5%, respectively. The relationship between RR and desert pavement was significant. The result of ANOVA (Duncan) showed, RR and Tb were significantly different in coarse, medium and fine grain plains (p-value<0.01). In addition, by increasing desert pavement percentage RR and Tb increased exponentially in base of Neper number. The relation between RR and desert pavement coverage is stronger than Tb and desert pavement coverage. Correlation between the two measured indices was calculated and compared in different plains. The result revealed that about 54, 33 and 14% of the arability in Tb could be explained by RR in coarse and medium grain plains, respectively. The correlations of two indices were significant in coarse and medium plain and insignificant in fine grain plain. The trend of RR and Tb decreased from mountain to plain center. Although RR increased slightly in fine grain plain, the difference was not significant.
N. Nourmahnad, H. Tabatabaei, A. R. Hoshmand, M. R. Nouri Emamzadei, Sh. Ghorbani Dashtaki,
Volume 18, Issue 68 (9-2014)
Abstract
Usually, dry soil readily absorbs water .However, not all soils display such characteristics. Some soils (hydrophobic soils) show resistance to wetting. Because of the importance of this subject and lack of research, we evaluated the effect of heating on water repellency and some of soil physical and chemical characteristics. So soil was combined with compost and heated at deferent temperatures, 100, 200, 300, 400 and 500 °C for 30 minutes in an oven or muffle furnace. The results showed that control treatment and heated soil at 300 °C had WDPT and MED 45 (s), 17% and 80 (s), 23% respectively. So, little water repellency was present prior to heating the soil. When soil was heated up to 300°C, intense water repellency resulted, but it was abruptly eliminated by increasing the heating. The soil texture was changed from loam to sandy loam at high temperatures (400 & 500 °C) and the sand percentage was increased. Organic matter decreased by increasing the temperature. Amount of pH decreased up to 200 °C and then increased at 500°C because of increasing ash in soils. Diminution of mineral and organic matter caused EC to decline in all the heated soils.
M. Sarmast, M. H. Farpoor, M. Sarcheshmehpoor, M. Karimian Eghbal,
Volume 18, Issue 68 (9-2014)
Abstract
Biocalcite infilling and bridging in a sandy soil was studied in the present research. Effects of 2 bacterial species (Sporosarcina pasteurii and Sporosarcina ureae), 3 reactant concentrations (0.5, 1.0, and 1.5 M of urea and CaCl2 mixture), and 6 reaction times (12, 24, 48, 96, 192, and 288 hr) on saturated hydraulic conductivity and mechanical strength of a sandy soil were studied as a factorial experiment. Soil samples were selected from sand dunes of Joopar area, Kerman Province. Bacterial inoculums and reactant solutions were daily added to soil columns. Results of the study showed that S. pasteuriihad had a higher effect on decreasing hydraulic conductivity of the treated samples (11.57 cm/h) compared to the blank (41.61 cm/h) than S. ureae. Increasing reaction times (from 12 to 288 hrs) and reactant concentrations (from 0.5 to 1.5 M) decreased hydraulic conductivity by 49 and 16 %, respectively. S. pasteurii increased strength of treated samples up to 2.6 Mpa pressure compared to S. ureae. Reactant concentrations and reaction times increased soil strength significantly (2.13 and 4.1 Mpa, respectively). Micromorphological observation showed calcite crystals bridging soil particles and filling pore spaces.
S. Razavizadeh, A. Kavian, M. Vafakhah,
Volume 18, Issue 68 (9-2014)
Abstract
Prediction of sediment load transported by rivers is a crucial step in the management of rivers, reservoirs and hydraulic projects. In the present study, in order to predict the suspended sediment of Taleghan river by using artificial neural
network, and recognize the best ANN with the highest accuracy, 500 daily data series of flow discharge on the present day, flow discharge on the past day, flow depth and hydrograph condition (respectively with the average of 13.83 (m
3/s), 15.42 (m
3/s), 89.83 (cm) and -0.036) as input variables, and 500 daily data series of suspended sediment, as the output of the model were used. The data was related to the period of 1984-2005. 80 different neural networks were developed using different combinations of variables and also changing the number of hidden-layer neurons and threshold functions. The accuracy of the models was then compared by R
2 and RMSE. Results showed that the neural network with 3-9-1 structure and input parameters of flow discharge on the present day, flow discharge on the past day and flow depth was superior (R
2= 0.97 and RMSE= 0.068) compared to the other structures. The average of the observed data of sediment and that predicted by the optimal model (related to test step) were 1122.802 and 1184.924 (tons per day), respectively.
M. Hosseini, S. A. Movahedi-Neeni, M. Zeraat Pishe,
Volume 18, Issue 68 (9-2014)
Abstract
Effects of five various tillage systems on soil porosity, volumetric water content, diurnal and nocturnal soil temperatures, plant water uptake and dry matter yield was investigated using a completely randomized design with five treatments and four replications in Gorgan University of Agricultural Sciences and Natural Resources research farm located in Seyed-Miran during 2009-2010 growing season. Tillage systems were: moldboard plough followed by one discing (20-25 cm) rototiller (12-17 cm) double disc (8-10 cm) Chisel plow (25-30 cm) No-tillage. Results show that during all stages of wheat growth, the highest and the lowest soil porosities at 0-8 cm depth were obtained by moldboard plough and No-tillage treatments respectively. For all stages except before tillering and harvest, the highest soil porosity obtained by moldboard treatment at 8-16 cm depth. Increasing tillage intensity increased those porosity that keep water in potentials greater than -5 and those in potentials less than -15 bar. No-tillage and moldboard induced the highest and the lowest soil temperatures respectively before earring stage. Tillage intensification, increased soil porosity and root density. More roots reduced soil water content in response to increased water uptake by wheat, resulting greater dry matter accumulation.
