جستجوی مقالات مرتبط با کلیدواژه « surface runoff » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

LAndscape ProcesS modeling atmUlti dimensions and scaleS (LAPSUS) model is one of the models that can calculate the multiple flow direction routing. In this model, according to the topography of the watershed, a constant value between 1 and 10 is defined as the convergence factor for the entire studied watershed. The value of this factor is considered constant through calibration or the values considered in previous studies. In this research, to solve the problem of constant convergence factor value, the flow distribution function was defined for this model. This study was conducted in five sub-catchments in the Kakhk experimental watershed located in the northeast of Iran in Gonabad county. In this research, the flow distribution function was defined instead of the convergence factor for the LAPSUS model. In this function, the slope parameter is used to model the effect of topographic characteristics on the flow distribution. In this way, the flow trending part in the LAPSUS model was developed by changing its programmed code in the C++ environment for the flow distribution function. Based on the calibration results, the best value of the convergence factor can be between 1 and 10. After applying the flow distribution function to the model, the value of the flow distribution function was calculated to be 6.3 for sub-catchment 4 and between 5.7 and 6.5 for other sub-catchments. The results of validation of the model outputs showed that the value of the coefficient of determination is 0.99 for runoff volume and 0.92 for erosion and sediment. Also, the amount of normalized RMSE was 3.5% for runoff and 5.5% for erosion and sediment. Based on the results, the flow distribution function can define the value of the convergence factor based on the topographic slope for the LAPSUS model. The value of the convergence factor can be defined for the model by entering the average slope of the watershed. Therefore, one of the main issues in the multiple flow direction routing was solved.

Water stresses are one of the most important issues that the world is facing today. Following the increase in population, climate, and land use change, Iran is also facing serious challenges in achieving sustainable water management on basin scale. In recent decades, climate and land use changes at the level of watersheds have had adverse effects on socio-environmental and economic issues. The case considered in this study is the Tajan watershed, located in Mazandaran province, northern Iran. This watershed is crucial in terms of ecosystem services (runoff generation, sediment delivery) for the residents living in the area and the Caspian Sea, which consists of the terminal part of the watershed. Temporal analysis of trends in hydro-climatic data is important to increasing our knowledge about the variations of such variables over time.

Tajan watershed with an area of 3,970 square kilometers is located in the northern part of Iran, which discharges the generated runoff into the Caspian Sea. Contrary to other watersheds, the amount of rainfall decreases with increasing altitude (i.e., the gradient of precipitation is negative with the change in altitude). An analysis of the temporal trend of the precipitation and discharge was conducted using the long-term monthly data (50 years from 1971 to 2021) collected in four rain gauges and two hydrometric stations. The rescaled adjusted partial sums (RAPS) index, non-parametric Mann-Kendall test, and Sen’s slope method were adopted to reveal the changes in precipitation and discharge data. Moreover, the state of land use changes in 37 years (1984-2021) were extracted using the Maximum Likelihood Classification method on the satellite images.

The results of this study showed that the trend of discharge does not match the rainfall, because during the 30 years of 1969-1999, the rainfall data of the studied stations had a decreasing trend with an average slope of -0.463 mm/year, while the discharge in watershed outlet indicates an increasing trend with an average slope of +1.02 cubic meters per second per year. On the other hand, during the period between 1999-2021, despite the positive trend of precipitation data with an average slope of +0.343 mm per year, the discharge shows a decreasing trend with an average slope of -2.249 cubic meters per second per year. By examining the state of land use changes in 1984 and 2021, the results indicate a decrease of 16 and 11 percent of areas for pasture and forestlands and an increase of 110 and 670 percent of irrigated lands and urban areas. The findings of this research showed that the trend of temporal changes in the discharge of sub-basins does not follow the rainfall, and the main factor in reducing the runoff generated in the Tajan watershed is the land use changes over the studied catchment.

The following conclusion could be drawn upon an evaluation of the temporal changes in rainfall and runoff data in the Tajan watershed: 1) the change of land use in the study area from forest to agricultural and urban areas caused an increase in the volume of runoff generated in the watershed. 2) The construction of the Shahid Rajaei reservoir dam in the study area has caused a change in the discharge trend of the mainstream. This affects the region's ecosystem as well as the morphology of the river channel that passes through the city of Sari. 3) The hydrological response of the studied watershed is not only influenced by climatic factors, the human activities (e.g., land use change and damming) has significant contribution. The authors suggest future researchers conduct more extensive research on the effect of dams on the hydromorphological characteristics of the downstream river.

The SCS-curve number is one of the common methods to estimate drirect runoff in the watershed scale. There is often an uncertainty in predicting runoff in many areas due to to the model’s assumption on the initial abstraction ratio (l= 0.20). This study was conducted to evaluate the accuracy of SCS-CN method in estimating runoff in some semi-arid subbasins of the Aras river consits of the Livar, Kalaleh and Shekaralichay in northwest of Iran. Runoff values were obtained from hydrometery stations for a 30-year period from 1987-2017) and compared with the estimated values which were determined using the maximum retention capacity (S). Based on the results, mean annual runoff in the Livar, Kalaleh and Shekaralichay subbasins is is 6.4, 1.45 and 9.5 mm, respectively. The model accuracy of the Livar, Kalaleh and Shekaralichay was -0.44, -0.25 and -0.27 percent, respectively. It showed over-estimations for small runoff values and down-estimation for large values. The model was calibrated usingthe revision of the initial abstraction ratio value (l= 0.08) and the model accuracy improved to 95, 96 and 93 percent, respectively. As a conclution, the calibration of l is essential to acuurate prediction of runoff in the the Aras river and similar basins.

Today population growth, inaccurate management practices and land degradation processes have caused many watersheds to be severely degraded, leading to increased runoff and sediment. In this study, the aim of the study was to investigate the effect of land use change on surface water fluctuations in the Doiraj watershed. Landsat satellite imagery was used for three periods of 1995, 2006, and 2015, it was found that the major changes occurred with decreasing forest and rangelang  levels and increasing land barren. For modeling rainfall-runoff, a SWAT computer model was used. Then, using the SWAT_CUP model, The performance of the model was evaluated using statistics, NS, R2, P_FACTOR and R_FACTOR. After calibration and validation, the values of these coefficients were 0.58, 0.60, 0.81, 0.87 for the calibration period and 0.56, 0.57, 0.81 and 89 for the validation period of the model, respectively was obtained. Annual runoff estimation indicated that changes in forest, pasture and wasteland land use from 1995 to 2015 increased the outflow runoff the basin from 3.91 to 5.85 m3 / s.

In the present research, the climate change effect on variation of surface runoff of Zarrinehrud located in the Miandoab plain was investigated. In this direction, the scenarios including A1B, A2 and B1 via LARS-WG downscaling model and with applying the HadCM3 general circulation model and artificial neural network model in two different periods (2046-2065, 2080 -2099) were studied. For this purpose, the best combination of input parameters of the MLP artificial neural network model was selected to estimate the runoff among various meteorological parameters with time delay of zero and one day and runoff parameter with one-day delay. Then, the meteorological data predicted by the LARS-WG in the future were used as inputs for the selected neural network model and consequently the runoff was predicted. The comparison of results between observed and simulated data by LARS-WG model using different statistical and error measurement indices indicates that there is no significant difference between simulated and observed values. Performance analysis of the artificial neural network model indicates that the mentioned model has good and suitable accuracy to simulate the runoff variations in the studied area. The results showed that the average annual runoff in the period of 2046-2065 will increase about 4.62 CMS than base period and it will decrease about 14.7 CMS during the period 2080-2099 compared to the base period.

Water balance and flow analysis within a basin is particularly important in terms of water development and utilization programs. Therefore, the purpose of this study is to evaluate and predict the outflow rate of Baghan watershed in Bushehr province. The data required for the implementation of the rainfall and discharge models were used to obtain the precipitation data of the Baghan Meteorological Station and the discharge of Baghan Hydrometric Station from 1981 to 2010. The Salas model is derived from a number of simple sub models that characterize different flow processes in the basin such as surface runoff, infiltration, evapotranspiration, deep infiltration and base flow. Error squares were used to calibrate the function model. The results of this study showed that the highest amount of rainfall in the basin was evacuated from the basin by evapotranspiration. The results showed Relative root mean square error before and after optimization of the coefficients of the four-variable Salas model decreased from 2.18% to 1.5% and the mean absolute error from 10.13 to 0.73. and mean error of the Salas four-variable model showed that in the years when the discharge value is almost average, the simulation value is very close to the observed value, and when the discharge value is much higher than the normal years, the simulation value is the less than its observed value.

Rangelands provide a diverse array of vital services that pertain to human life. But market failure to consider the value of these ecosystem services has disturbed provision of many ecosystem services. In this study the economic value of water conservation functions by Arnaveh basin located in northwestern Iran was estimated. Rainfall-runoff simulation was carried out by using Curve Number (CN) method. Also by means of Replacement Cost method the value of the hydrological services were quantified. The role of vegetation cover in water conservation was estimated by comparing the surface runoff under current condition and uncovered soil conditions. Moreover the role of rangelands on water retention and surface runoff reduction by devising three more hypothetical scenarios and then the effects of land use changes associated with these scenarios on rainfall-runoff rate of the region were compared. Results showed that the role of rangelands vegetation cover in water conservation and surface runoff reduction was 7.19×106 m3, with the economic value of 123×109 IRR. Also, the results of a comparing between 3 hypothetical scenarios and current conditions showed that, under the case of scenario one which assumes that the entire of rangelands area is becoming to rain-fed farming, total outflow would be in the maximum amount and the most negative effects will accrue. Also the scenarios of improvement of vegetation cover to 25-50 percent has the most positive effects (1.95×106 m3 yr-1 decrease) on water retention. The results of this study could help decision-makers in selecting appropriate and economically feasible development strategies.

In this research, LAPSUS model is introduced as a suitable model to surface runoff rutting by Multiple Flow Direction (MFD) algorithms. Flow distribution algorithms grouped into two main types including Single Flow Direction (SFD) and MFD algorithms. LAPSUS model is a landscape evolution and a multi-module dynamic landscape evolution model. Studied processes included overland erosion, land sliding, tillage erosion and tectonics. Input data in LAPSUS model was DEM, rainfall, runoff coefficient and convergence factor. This model has written in C++. This model has been used for runoff rutting in Kakhk watershed of Gonabad, Iran, for the first time. For this purpose, surface runoff resulted from 34 rainfall events was simulated for multiple flow direction analysis between 2008 and 2018. Results showed that LAPSUS model can simulate total volumes of events with a high accuracy by MFD with the amount of nRMSE of 3.9 percent.

Correct and consistent uses of natural resources preserve this valuable wealth. Using optimization knowledge can assist us to achieve this object. Thus, this study aims to compare linear programming as a classical method of optimization with genetic evolutionary algorithm for land use optimization of the Bayg watershed. Results showed that linear programming reduced dry farming acreage and increased the acreage of irrigated agriculture. After minimization, surface runoff and sediment yield declined by 1.16, 12.91 percent, respectively. Genetic algorithm led to an increase in rangeland, irrigated agriculture and horticulture acreages, while almond orchard and dry farming acreages were reduced. Furthermore, surface runoff and sediment yield declined by 13.95 and 31.99 percent, respectively. Linear programming acted stronger in satisfying the constraints, as compared with genetic algorithm. The constraint “total acreage” was satisfied by linear programming, while genetic algorithm could not meet this constraint. Sensitivity analysis of linear programming showed that the most critical factor in minimizing runoff and sediment yield function was the coefficient of dry farming with a reduced cost of 67.52. Results also established that the constraints “total acreage and minimum acreage of rangeland” with the shadow prices of 397.40 and 233.28, respectively had the highest negative impact on the optimal solution. Meanwhile, the constraints “maximum acreages of irrigated horticulture and almonds garden” with the shadow prices of -134.97 and -118.44, respectively had the highest positive impact on the optimal solution. As a general conclusion it can be stated that in land use optimization problems with a large number of constraints, genetic algorithm show poorer performance in satisfying constraints, as compared with linear programming.

Flooding due to the failure of drainage systems is a serious problem for many urban watershed of Iran. This paper shows how flooding in urban drainage systems can be simulated by one- dimensional hydrodynamic modeling incorporating the interaction between (I) the buried pipe systems (II) the streets with open channel flow. The values of the NS, RMSE, and %BIAS statistics were also calculated to assess the validity of the model structure. The NS results for calibration and validation of the case study demonstrate that the calibrated model simulated acceptably the shape of the actual hydrograph. The lower RMSE values also support the accuracy of the calibrated model in simulating the shape of the hydrograph. The absolute value of %BIAS is never more than 20%, which demonstrates that the calibrated model simulated acceptably the total flow volume. The results of this study emphasize the use of one-dimensional hydrodynamic model to Simulation of flooding in urban drainage systems.

Gully erosion has an important role in Fars province due to sediment production and enormous damages to land, roads and infrastructures. In this research, 15 gullies were selected to measure their morphometric characteristics. The length, depth, top and bottom width and volume of gully erosion were then measured. Influential factors on the sediment production and gully development were analyzed and determined by using stepwise method in SPSS software. The results indicate that sediment production due to gully development is related to three variables including drainage area, silt and the sand percent of the watershed above the gully heads. These results imply that surface runoff is acting as dominant hydrologic process on gully development. Investigation on the topographic threshold reveals that drainage area exponent (b) is negative and these results are in the same line with the results of some recent relevant studies. The results also indicate the watershed characteristics and geological formation impact on the gully sediment production. Gully development could be reduced by decreasing the area of bare land as the main source of surface runoff by vegetation planting and terracing. Constructing of small earth dams at the end of gullies collect surface runoff and provides better situations for vegetation establishment around gullies.

The existence of vegetation cover in a region can reduce the velocity of surface run-offand prevent soil erosion. This can substantially control the occurrence of destructivefloods in the region. One reliable method used in protecting flood-forming catchmentsis the biological method. Also, one factor that represents the hydraulic resistance inplants is roughness coefficient. Measuring the coefficient and its impact on the flowvelocity and shear stress reduction in the plants is of outmost importance. One of theknown species used extensively in soil stabilization and protection is Tamarix sricta.This species resists against various climates and is easy to be planted. With its needleleaves and rough external organs, Tamarix sricta reduces the flow velocity and preventsfurther soil erosion. In this research roughness coefficient of the Tamarix sricta wasinvestigated. The plant studied in non-submerged and sub critical condition flow using aflume with the length of 12.6 m, width of 0.5 m and height of 0.6 m in differentvelocity, discharge and depths. The height of plants in this is 35 cm with a naturalarrangement in trays of 2.8 m in length laid over the bed of the flume. The total numberof the experiments is 22.The results of this study show that roughness coefficient ofplants is function of velocity, depth, hydraulic radius and plant types. Because of itshigh roughness, this species is an appropriate alternative to be used in reducing the flowvelocity and protecting the soil from any erosion possibility.

Many different runoff prediction methods are being used among which SCS model hasbeen applied throughout the globe. It is therefore very important to evaluate thecircumstances and input specifications under which such models could be applied. Thepresent study was conducted to investigate the role of rainfall main characteristics onaccuracy of SCS model in runoff prediction for Kasilian and Darjazin watersheds. Forthis purpose, the simultaneous rainfall-runoff data were selected and the storm runoffwas estimated using determining rainfall characteristic, providing Curve Number mapand calibrating the model. In order to determine the effects of rainfall characteristics onmodel output, the standardized values of regression coefficient (β) of the best fittedmultiple regression, developed between rainfall circumstances and maximum storageindex coefficient, were determined. The results of the study showed the depth,maximum rainfall in concentration time, maximum 30 minutes intensity, 2nd quartileand 1st quartile have the highest rate of effectiveness on model output respectively.