In the present study, the multivariate statistical technique cluster analysis (CA) is used to eva... more In the present study, the multivariate statistical technique cluster analysis (CA) is used to evaluate the spatial and temporal variations in the water quality data for the Karun River, which was gathered during 46 years of monitoring (from 1968 to 2014). The data recorded electrical conductivity (EC) in the river at six water monitoring stations along its course. The mean of EC was 972.05 ± 365.466 micromhos per centimeter (mhos/cm) at the most upstream station and showed an increase to 1458.41 ± 675.048 mhos/cm at the most downstream of the stations. By using hierarchical CA, the six sampling stations were grouped into three clusters of similar characteristics, which may be a result of different land uses in proximity to the stations. Furthermore, two-way analysis of variance showed that EC had a significant correlation (p < 0.001) with the season, and the mean of the pollution depended on the level of the cluster and the season (spring, summer, autumn, and winter).
Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Amon... more Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Among various sources of uncertainty, precipitation plays a particular role. Rainfall rates as the main input data of RRS are of the first factors controlling the accuracy. In addition to the depth, spatial and temporal distributions of rainfall impact the flood discharge. Most of the previous studies on RRS uncertainty have ignored rainfall spatial distribution, where in large catchments, it is necessary to be modeled explicitly. Karoon III is one most important basin of the Iran because of the Karoon III dam in the outlet. In the present work, effect of spatial correlation of rainfall on HEC-HMS (SMA) continuous RRS uncertainty is evaluated using 2variate copula (2copula). Monte Carlo simulation (MCS) approach was used to consider the rainfall spatial dependence. To reduce the computational expense, sampling efficiency and convergence for MCS, Latin hypercube sampling (LHS) was used. Copula functions consider wide range of marginal probability distribution functions (PDFs), eliminating limits of regular join PDFs. For this aim, two scenarios were investigated. In the first scenario, sub-basin rainfall was considered independent, and in the second scenario, 2copula was adopted to model spatial correlation of rainfall. Dimensionless rainfall depths were calculated for each sub-basin, and the PDFs were determined. The generated random dimensionless rainfalls were reweighted and multiplied by watershed’s mean rainfall value. Stochastic Climate Library was used to generate continuous daily rainfalls. Sampling from dimensionless rainfalls using LHS algorithm, 100 runs of calibrated model-simulated 100 flows for each day following MCS, and 80 % certainty bound was calculated. Results showed that considering dependence decreased 18 % of the maximum uncertainty bound width, so the methodology could be recommended for decreasing predicted runoff error.
Drought is a natural phenomenon which occurs in different climate regimes. In the present study, ... more Drought is a natural phenomenon which occurs in different climate regimes. In the present study, hydrological drought of the Roud Zard basin has been investigated based on run theory. Daily runoff data of Mashin hydrometery station during 1970 to 2012 was assessed using 70 % of mean daily runoff as threshold level. Results showed that the maximum drought duration of 309 days occurred in 1998 and 1999 and max drought deficit of 117.217 million cubic meters per second in 1983 with 275 days duration. Time series of the annual maxima values of duration and volume deficit showed similar trend of increase and decreasing. Burr statistical distribution, as the most suitable one fitted to the drought duration data, forecasted 339 days duration for drought event with 20 years return period and generalized extreme value forecasted 37.9 million cubic meters of deficit volume for this return period. Severity-durationfrequency (SDF) curves were prepared, classifying drought durations to four intervals and fitting statistical distribution to each. Resulted SDF curves showed that, in each period, increase of duration resulted in increased value of the volume deficit with a non-linear trend, though predicted drought volume with 20 years return period was 2.1 million cubic meters for 1 to 10 days duration, 6.9 for 11 to 30 days, 34.5 for 31 to 120 days, and 79.1 for more than 120 days duration drought event. Drought deficit volume increasing rate was also different in each class of duration interval. Drought SDF curves derived in this study can be used to quantify water deficit for natural stream and reservoir. SDFs could also be extended to allow for drought regional frequency analysis to be used in ungauged sites.
With respect to the effect of precipitation loss on runoff generation, different loss methods of ... more With respect to the effect of precipitation loss on runoff generation, different loss methods of Soil and Conservation Service (SCS), Green and Ampt (G.A.), Initial-Constant (I.C.), Deficit-Constant (D.C.), Constant Fraction (C.F.), exponential (Exp.) and Soil Moisture Accounting (SMA) have been compared by HEC-HMS event based on Rainfall-Runoff modeling in Roud Zard basin. The SMA method with max average Nush-Sutcliffe (N.S.) and min Peak Weighted Root Mean Square Error (PWRMSE) in calibration and verification was the best method in stream flow simulation. The SCS and Exp. methods with similar N.S. and PWRMSE were placed as second suitable methods in sub-daily (2 h) event simulation, and the G.A., C.F. and I.C. methods were the lasts. The comparison between simulated and observed key variables showed that SMA with Mean Absolute Error (MAE) of 0.05 in volume and 3.34 in peak flow simulation was the best in both calibration and verification, and in time to peak, in verification events. In volume simulation I.C. was the second and SCS and G.A. were the worst but in peak flow, SCS was second and others were similar. It could be concluded that SMA as a continuous infiltration method is preferred to the other methods for event based Rainfall-Runoff modeling.
In contrast to event based hydrologic models which reveal how a basin responds to an individual r... more In contrast to event based hydrologic models which reveal how a basin responds to an individual rainfall event, continuous ones synthesize hydrologic processes over a longer time period that includes both dry and wet conditions. With respect to the importance of infiltration method in Rainfall-Runoff (RR) modeling, the objective of this study was to assess HEC-HMS with Soil Moisture Accounting (SMA) infiltration algorithm, considering several components of hydrologic cycle such as canopy interception, surface depression, infiltration into the soil profile storage, percolation to the ground water aquifer and base flow caused by available soil storage vs. maximum saturated capacity of soil layer, to model daily flows of Karoon III basin (Iran). The model showed satisfied performance by accounting initial moisture condition by SMA model with Nash-Sutcliffe (NS) coefficient of 0.76 and 0.64 for calibration and verification. Sensitivity analysis showed that saturated hydraulic conductivity (K), Clark storage coefficient (R) and time of concentration (tc) were the most effective parameters on the simulated Peak Over Thresholds (POT). Results from this study assist in improving model accuracy and ability to predict future conditions based upon basin characteristic change.
The SPI is the most widely used drought index to provide an acceptable estimation of drought char... more The SPI is the most widely used drought index to provide an acceptable estimation of drought characteristics. The objective of this study was to compare different threshold levels effect on derived drought characteristics, assessment of the spatial variation of meteorological drought properties as well as drought frequency, duration, and value in Kohgilooyeh and Boyer Ahmad Province, Iran, using SPI for 1, 3, 6, 12, 24 and 48 months lead-times, and finally SPI forecasting using Artificial Neural Networks (ANNs). For the first threshold level (scenario), drought properties are extracted based on the standard level of zero, and for the second one,-1 is considered. Results showed that the frequency of drought and wet periods decreased from SPI-1 33 to 48 for both scenarios in all stations. Max drought duration of stations had an increasing trend 34 from SPI-1 to 48. The average duration of dry periods changed as a function of the time scales; it 35 increased from SPI-1 to 48. Spatial variation of the drought average duration was considerable for 36 long-term drought. Max SPI value did not follow any spatial variation, as it was constant for all 37 2 lead times in all stations. Average SPI values had a decreasing trend from SPI-1 to 9 but increased from SPI-9 to 48 in all stations. Max average of SPI value observed in short-term drought and min value in medium-term. SPI value general trend was similar in both scenarios, therefore drought threshold level did not affect the results. The third objective was to develop neural network models for drought forecasting. Different architectures are applied to find the best models to forecast SPI over various lead times. The best forecasting results for SPI-3 and 6, obtained from the Quasi-Newton training algorithm, when for SPI-1, 9, 12, 24, and 48, Levenberg-Marquardt was the best. There was an increasing trend in performance measure R2 from SPI-1 to 48 and a decreasing trend in Root Mean Square Error (RMSE). The best input lead-time for SPI-1 to 48 decreased from 11 to 1, the number of hidden layers decreased, but there was no significant trend in hidden neurons. Drought properties could be considered in water resources management to supply water for various demands.
⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle... more ⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle. Uncertainty arises from a variety of sources such as input error, calibration and parameters. Hydrologic modeling researches indicate that parametric uncertainty has been considered as one of the most important source. The objective of this study was to evaluate parameter uncertainty and its propagation in rainfall-runoff modeling. This study tried to model daily flows and calculate uncertainty bounds for Karoon-III basin, Southwest of Iran, using HEC-HMS (SMA). The parameters were represented by probability distribution functions (PDF), and the effect on simulated runoff was investigated using Latin Hypercube Sampling (LHS) on Monte Carlo (MC). Three chosen parameters, based on sensitivity analysis, were saturatedhydraulic-conductivity (Ks), Clark storage coefficient (R) and time of concentration (t c). Uncertainty associated with parameters were accounted for, by representing each with a probability distribution. Uncertainty bounds was calculated, using parameter sets captured from LHS on parameters PDF of sub-basins and propagating to the model. Results showed that maximum reliability (11%) resulted from Ks propagating. For three parameters, underestimation was more than overestimation. Maximum sharpness and standard deviation (STD) was resulted from propagating Ks. Cumulative Distribution Function (CDF) of flow and uncertainty bounds showed that as flow increased, the width of uncertainty bounds increased for all parameters.
Multivariate analysis of flood frequency was used extensively in water resources research. Often ... more Multivariate analysis of flood frequency was used extensively in water resources research. Often the only flood peak or volume is analyzed with statistical distributions, but for a perfect and exact result, the four main characteristics of a flood event, as well as peak, volume, duration, and time-to-peak, are needed. For this reason, multivariate statistical approaches like copula functions developed. This research aims to define and use the bivariate copula (2-copula) probability distribution functions (PDF) for flood characteristics multivariate analysis. When the joint distribution of characteristics such as volume and peak is known, it is possible to define the probability of simultaneous occurrence of design volume and peak flow values.
⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle... more ⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle. Uncertainty arises from a variety of sources such as input error, calibration and parameters. Hydrologic modeling researches indicate that parametric uncertainty has been considered as one of the most important source. The objective of this study was to evaluate parameter uncertainty and its propagation in rainfall-runoff modeling. This study tried to model daily flows and calculate uncertainty bounds for Karoon-III basin, Southwest of Iran, using HEC-HMS (SMA). The parameters were represented by probability distribution functions (PDF), and the effect on simulated runoff was investigated using Latin Hypercube Sampling (LHS) on Monte Carlo (MC). Three chosen parameters, based on sensitivity analysis, were saturatedhydraulic-conductivity (Ks), Clark storage coefficient (R) and time of concentration (t c). Uncertainty associated with parameters were accounted for, by representing each with a probability distribution. Uncertainty bounds was calculated, using parameter sets captured from LHS on parameters PDF of sub-basins and propagating to the model. Results showed that maximum reliability (11%) resulted from Ks propagating. For three parameters, underestimation was more than overestimation. Maximum sharpness and standard deviation (STD) was resulted from propagating Ks. Cumulative Distribution Function (CDF) of flow and uncertainty bounds showed that as flow increased, the width of uncertainty bounds increased for all parameters.
This study compares Severity-Duration-Frequency (SDF) curves (SDFs) of stream flow drought derive... more This study compares Severity-Duration-Frequency (SDF) curves (SDFs) of stream flow drought derived from threshold level methods. For this purpose hydrological drought of Roudzard river basin was investigated, based on run theory. Daily runoff data of Mashin hydrometery station (1970-2012) assessed using 70% (Q 70), 90% (Q 90) of mean daily and 70% of monthly average runoff (monthly) as threshold level methods. Time series of the annual maxima values of duration and volume deficit showed similar trend of increase and decreasing in different thresholds. SDFs were prepared, classifying drought durations to four intervals and fitting statistical distribution to each one. Resulted SDFs showed that, in each period, increasing of duration resulted to increased value of the volume deficit with a nonlinear trend while duration and severities from the threshold levels were different. Drought deficit-volume increasing rate was also different in each class of duration-interval. For the additional analysis, the duration-frequency and deficit-frequency curves were also prepared to quantify the extent of drought duration and deficit more. SDFs developed in this study can be used to quantify water deficit for natural stream and reservoir. They could be an effective tool to identify multivariate hydrological drought using severity, duration and frequency.
Hydrological models are widely used to investigate practical issues of water resources. Parametri... more Hydrological models are widely used to investigate practical issues of water resources. Parametric uncertainty is considered as one of the most important sources of uncertainty in environmental researches. Generally, it is assumed that the parameters are independent mutually, but correlation within the parameter space is an important factor having the potential to cause uncertainty. The objective and innovation of this study was to address the effects of parameters correlation on a continuous hydrological model uncertainty. HEC-HMS with soil moisture accounting (SMA) infiltration method was used to model daily flows and simulate certainty bounds for Karoon III basin, southwest of IRAN, in two scenarios, independent and correlated parameters using 2-copula. The parameters were represented by probability distributions, and the effect on prediction error were evaluated using Latin hypercube sampling (LHS) on Monte Carlo simulation (MCS). Saturated hydraulic conductivity (K), Clark storagecoefficient (R), and time of concentration (tc) were chosen for investigation, based on observed sensitivity analysis of simulated peak over threshold (POT). One hundred runs were randomly generated from 100 parameter sets captured from LHS of parameters distributions in each sub-basin. Using generated parameter sets, 100 continuous hydrographs were simulated and values of certainty bounds calculated. Results showed that when 2-copula correlated R and tc, with 0.656 Kendall's Tau and 0.818 Spearman's Rho coefficients, were propagated, decreasing of outputs' sharpness was more than when considering K and R (K-R), with 0.166 and 0.262; therefore, incorporation of correlations in the MCS is important, especially when the correlation coefficients exceed 0.65. The model was evaluated at the outlet of the basin using daily stream flow data. Model reliability was better for abovenormal flows than normal and below-normal. Reliability increases of simulated flow when considering correlated R-tc was more than K-R because of the correlation values. Incorporation of copula for K-tc not only did not improve the model reliability but also decreased it. Results showed improvement of model reliability, by decreasing predicted error of hydrologic modeling, when dealing with correlated parameters in the system.
In contrast to event based hydrologic models which reveal how a basin responds to an individual r... more In contrast to event based hydrologic models which reveal how a basin responds to an individual rainfall event, continuous ones synthesize hydrologic processes over a longer time period that includes both dry and wet conditions. With respect to the importance of infiltration method in Rainfall-Runoff (RR) modeling, the objective of this study was to assess HEC-HMS with Soil Moisture Accounting (SMA) infiltration algorithm, considering several components of hydrologic cycle such as canopy interception, surface depression, infiltration into the soil profile storage, percolation to the ground water aquifer and base flow caused by available soil storage vs. maximum saturated capacity of soil layer, to model daily flows of Karoon III basin (Iran). The model showed satisfied performance by accounting initial moisture condition by SMA model with Nash-Sutcliffe (NS) coefficient of 0.76 and 0.64 for calibration and verification. Sensitivity analysis showed that saturated hydraulic conductivity (K), Clark storage coefficient (R) and time of concentration (tc) were the most effective parameters on the simulated Peak Over Thresholds (POT). Results from this study assist in improving model accuracy and ability to predict future conditions based upon basin characteristic change.
Drought is a natural phenomenon which occurs in different climate regimes. In the present study, ... more Drought is a natural phenomenon which occurs in different climate regimes. In the present study, hydrological drought of the Roud Zard basin has been investigated based on run theory. Daily runoff data of Mashin hydrometery station during 1970 to 2012 was assessed using 70 % of mean daily runoff as threshold level. Results showed that the maximum drought duration of 309 days occurred in 1998 and 1999 and max drought deficit of 117.217 million cubic meters per second in 1983 with 275 days duration. Time series of the annual maxima values of duration and volume deficit showed similar trend of increase and decreasing. Burr statistical distribution, as the most suitable one fitted to the drought duration data, forecasted 339 days duration for drought event with 20 years return period and generalized extreme value forecasted 37.9 million cubic meters of deficit volume for this return period. Severity-durationfrequency (SDF) curves were prepared, classifying drought durations to four intervals and fitting statistical distribution to each. Resulted SDF curves showed that, in each period, increase of duration resulted in increased value of the volume deficit with a non-linear trend, though predicted drought volume with 20 years return period was 2.1 million cubic meters for 1 to 10 days duration, 6.9 for 11 to 30 days, 34.5 for 31 to 120 days, and 79.1 for more than 120 days duration drought event. Drought deficit volume increasing rate was also different in each class of duration interval. Drought SDF curves derived in this study can be used to quantify water deficit for natural stream and reservoir. SDFs could also be extended to allow for drought regional frequency analysis to be used in ungauged sites.
Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Amon... more Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Among various sources of uncertainty, precipitation plays a particular role. Rainfall rates as the main input data of RRS are of the first factors controlling the accuracy. In addition to the depth, spatial and temporal distributions of rainfall impact the flood discharge. Most of the previous studies on RRS uncertainty have ignored rainfall spatial distribution, where in large catchments, it is necessary to be modeled explicitly. Karoon III is one most important basin of the Iran because of the Karoon III dam in the outlet. In the present work, effect of spatial correlation of rainfall on HEC-HMS (SMA) continuous RRS uncertainty is evaluated using 2variate copula (2copula). Monte Carlo simulation (MCS) approach was used to consider the rainfall spatial dependence. To reduce the computational expense, sampling efficiency and convergence for MCS, Latin hypercube sampling (LHS) was used. Copula functions consider wide range of marginal probability distribution functions (PDFs), eliminating limits of regular join PDFs. For this aim, two scenarios were investigated. In the first scenario, sub-basin rainfall was considered independent, and in the second scenario, 2copula was adopted to model spatial correlation of rainfall. Dimensionless rainfall depths were calculated for each sub-basin, and the PDFs were determined. The generated random dimensionless rainfalls were reweighted and multiplied by watershed’s mean rainfall value. Stochastic Climate Library was used to generate continuous daily rainfalls. Sampling from dimensionless rainfalls using LHS algorithm, 100 runs of calibrated model-simulated 100 flows for each day following MCS, and 80 % certainty bound was calculated. Results showed that considering dependence decreased 18 % of the maximum uncertainty bound width, so the methodology could be recommended for decreasing predicted runoff error.
With respect to the effect of precipitation loss on runoff generation, different loss methods of ... more With respect to the effect of precipitation loss on runoff generation, different loss methods of Soil and Conservation Service (SCS), Green and Ampt (G.A.), Initial-Constant (I.C.), Deficit-Constant (D.C.), Constant Fraction (C.F.), exponential (Exp.) and Soil Moisture Accounting (SMA) have been compared by HEC-HMS event based on Rainfall-Runoff modeling in Roud Zard basin. The SMA method with max average Nush-Sutcliffe (N.S.) and min Peak Weighted Root Mean Square Error (PWRMSE) in calibration and verification was the best method in stream flow simulation. The SCS and Exp. methods with similar N.S. and PWRMSE were placed as second suitable methods in sub-daily (2 h) event simulation, and the G.A., C.F. and I.C. methods were the lasts. The comparison between simulated and observed key variables showed that SMA with Mean Absolute Error (MAE) of 0.05 in volume and 3.34 in peak flow simulation was the best in both calibration and verification, and in time to peak, in verification events. In volume simulation I.C. was the second and SCS and G.A. were the worst but in peak flow, SCS was second and others were similar. It could be concluded that SMA as a continuous infiltration method is preferred to the other methods for event based Rainfall-Runoff modeling.
Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water suppl... more Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water supply, storage, industry and other consumption. Certainly hydrologic study is an important issue for these project programming. Data deficiency in most of watersheds has forced us to use indirect methods such empirical relations for flood runoff prediction. Preventing over and underestimation in predictions, It is necessary to calibrate equations for the slightly watershed. In this research we are going to calibrate some common empirical equations like Horton and Fuller. For this reason regionalization with cluster analysis to determine homogenous regions will be done at first. Statistical probability analysis, another issue to estimate peak flood runoff at different return period, and evaluation of Doroodzan dam effect on the statistical characteristics of river regime, also will be assessed in this research.
Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water suppl... more Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water supply, storage, industry and other consumption. Certainly hydrologic study is an important issue for these project programming. Data deficiency in most watersheds has tend us to use indirect methods such as flood frequency analysis, a technique for peak flood runoff estimation at different return periods. In this research flood runoff will be forecasted by flood frequency analysis after selection of most suitable statistical distribution in each station
In the present study, the multivariate statistical technique cluster analysis (CA) is used to eva... more In the present study, the multivariate statistical technique cluster analysis (CA) is used to evaluate the spatial and temporal variations in the water quality data for the Karun River, which was gathered during 46 years of monitoring (from 1968 to 2014). The data recorded electrical conductivity (EC) in the river at six water monitoring stations along its course. The mean of EC was 972.05 ± 365.466 micromhos per centimeter (mhos/cm) at the most upstream station and showed an increase to 1458.41 ± 675.048 mhos/cm at the most downstream of the stations. By using hierarchical CA, the six sampling stations were grouped into three clusters of similar characteristics, which may be a result of different land uses in proximity to the stations. Furthermore, two-way analysis of variance showed that EC had a significant correlation (p < 0.001) with the season, and the mean of the pollution depended on the level of the cluster and the season (spring, summer, autumn, and winter).
Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Amon... more Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Among various sources of uncertainty, precipitation plays a particular role. Rainfall rates as the main input data of RRS are of the first factors controlling the accuracy. In addition to the depth, spatial and temporal distributions of rainfall impact the flood discharge. Most of the previous studies on RRS uncertainty have ignored rainfall spatial distribution, where in large catchments, it is necessary to be modeled explicitly. Karoon III is one most important basin of the Iran because of the Karoon III dam in the outlet. In the present work, effect of spatial correlation of rainfall on HEC-HMS (SMA) continuous RRS uncertainty is evaluated using 2variate copula (2copula). Monte Carlo simulation (MCS) approach was used to consider the rainfall spatial dependence. To reduce the computational expense, sampling efficiency and convergence for MCS, Latin hypercube sampling (LHS) was used. Copula functions consider wide range of marginal probability distribution functions (PDFs), eliminating limits of regular join PDFs. For this aim, two scenarios were investigated. In the first scenario, sub-basin rainfall was considered independent, and in the second scenario, 2copula was adopted to model spatial correlation of rainfall. Dimensionless rainfall depths were calculated for each sub-basin, and the PDFs were determined. The generated random dimensionless rainfalls were reweighted and multiplied by watershed’s mean rainfall value. Stochastic Climate Library was used to generate continuous daily rainfalls. Sampling from dimensionless rainfalls using LHS algorithm, 100 runs of calibrated model-simulated 100 flows for each day following MCS, and 80 % certainty bound was calculated. Results showed that considering dependence decreased 18 % of the maximum uncertainty bound width, so the methodology could be recommended for decreasing predicted runoff error.
Drought is a natural phenomenon which occurs in different climate regimes. In the present study, ... more Drought is a natural phenomenon which occurs in different climate regimes. In the present study, hydrological drought of the Roud Zard basin has been investigated based on run theory. Daily runoff data of Mashin hydrometery station during 1970 to 2012 was assessed using 70 % of mean daily runoff as threshold level. Results showed that the maximum drought duration of 309 days occurred in 1998 and 1999 and max drought deficit of 117.217 million cubic meters per second in 1983 with 275 days duration. Time series of the annual maxima values of duration and volume deficit showed similar trend of increase and decreasing. Burr statistical distribution, as the most suitable one fitted to the drought duration data, forecasted 339 days duration for drought event with 20 years return period and generalized extreme value forecasted 37.9 million cubic meters of deficit volume for this return period. Severity-durationfrequency (SDF) curves were prepared, classifying drought durations to four intervals and fitting statistical distribution to each. Resulted SDF curves showed that, in each period, increase of duration resulted in increased value of the volume deficit with a non-linear trend, though predicted drought volume with 20 years return period was 2.1 million cubic meters for 1 to 10 days duration, 6.9 for 11 to 30 days, 34.5 for 31 to 120 days, and 79.1 for more than 120 days duration drought event. Drought deficit volume increasing rate was also different in each class of duration interval. Drought SDF curves derived in this study can be used to quantify water deficit for natural stream and reservoir. SDFs could also be extended to allow for drought regional frequency analysis to be used in ungauged sites.
With respect to the effect of precipitation loss on runoff generation, different loss methods of ... more With respect to the effect of precipitation loss on runoff generation, different loss methods of Soil and Conservation Service (SCS), Green and Ampt (G.A.), Initial-Constant (I.C.), Deficit-Constant (D.C.), Constant Fraction (C.F.), exponential (Exp.) and Soil Moisture Accounting (SMA) have been compared by HEC-HMS event based on Rainfall-Runoff modeling in Roud Zard basin. The SMA method with max average Nush-Sutcliffe (N.S.) and min Peak Weighted Root Mean Square Error (PWRMSE) in calibration and verification was the best method in stream flow simulation. The SCS and Exp. methods with similar N.S. and PWRMSE were placed as second suitable methods in sub-daily (2 h) event simulation, and the G.A., C.F. and I.C. methods were the lasts. The comparison between simulated and observed key variables showed that SMA with Mean Absolute Error (MAE) of 0.05 in volume and 3.34 in peak flow simulation was the best in both calibration and verification, and in time to peak, in verification events. In volume simulation I.C. was the second and SCS and G.A. were the worst but in peak flow, SCS was second and others were similar. It could be concluded that SMA as a continuous infiltration method is preferred to the other methods for event based Rainfall-Runoff modeling.
In contrast to event based hydrologic models which reveal how a basin responds to an individual r... more In contrast to event based hydrologic models which reveal how a basin responds to an individual rainfall event, continuous ones synthesize hydrologic processes over a longer time period that includes both dry and wet conditions. With respect to the importance of infiltration method in Rainfall-Runoff (RR) modeling, the objective of this study was to assess HEC-HMS with Soil Moisture Accounting (SMA) infiltration algorithm, considering several components of hydrologic cycle such as canopy interception, surface depression, infiltration into the soil profile storage, percolation to the ground water aquifer and base flow caused by available soil storage vs. maximum saturated capacity of soil layer, to model daily flows of Karoon III basin (Iran). The model showed satisfied performance by accounting initial moisture condition by SMA model with Nash-Sutcliffe (NS) coefficient of 0.76 and 0.64 for calibration and verification. Sensitivity analysis showed that saturated hydraulic conductivity (K), Clark storage coefficient (R) and time of concentration (tc) were the most effective parameters on the simulated Peak Over Thresholds (POT). Results from this study assist in improving model accuracy and ability to predict future conditions based upon basin characteristic change.
The SPI is the most widely used drought index to provide an acceptable estimation of drought char... more The SPI is the most widely used drought index to provide an acceptable estimation of drought characteristics. The objective of this study was to compare different threshold levels effect on derived drought characteristics, assessment of the spatial variation of meteorological drought properties as well as drought frequency, duration, and value in Kohgilooyeh and Boyer Ahmad Province, Iran, using SPI for 1, 3, 6, 12, 24 and 48 months lead-times, and finally SPI forecasting using Artificial Neural Networks (ANNs). For the first threshold level (scenario), drought properties are extracted based on the standard level of zero, and for the second one,-1 is considered. Results showed that the frequency of drought and wet periods decreased from SPI-1 33 to 48 for both scenarios in all stations. Max drought duration of stations had an increasing trend 34 from SPI-1 to 48. The average duration of dry periods changed as a function of the time scales; it 35 increased from SPI-1 to 48. Spatial variation of the drought average duration was considerable for 36 long-term drought. Max SPI value did not follow any spatial variation, as it was constant for all 37 2 lead times in all stations. Average SPI values had a decreasing trend from SPI-1 to 9 but increased from SPI-9 to 48 in all stations. Max average of SPI value observed in short-term drought and min value in medium-term. SPI value general trend was similar in both scenarios, therefore drought threshold level did not affect the results. The third objective was to develop neural network models for drought forecasting. Different architectures are applied to find the best models to forecast SPI over various lead times. The best forecasting results for SPI-3 and 6, obtained from the Quasi-Newton training algorithm, when for SPI-1, 9, 12, 24, and 48, Levenberg-Marquardt was the best. There was an increasing trend in performance measure R2 from SPI-1 to 48 and a decreasing trend in Root Mean Square Error (RMSE). The best input lead-time for SPI-1 to 48 decreased from 11 to 1, the number of hidden layers decreased, but there was no significant trend in hidden neurons. Drought properties could be considered in water resources management to supply water for various demands.
⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle... more ⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle. Uncertainty arises from a variety of sources such as input error, calibration and parameters. Hydrologic modeling researches indicate that parametric uncertainty has been considered as one of the most important source. The objective of this study was to evaluate parameter uncertainty and its propagation in rainfall-runoff modeling. This study tried to model daily flows and calculate uncertainty bounds for Karoon-III basin, Southwest of Iran, using HEC-HMS (SMA). The parameters were represented by probability distribution functions (PDF), and the effect on simulated runoff was investigated using Latin Hypercube Sampling (LHS) on Monte Carlo (MC). Three chosen parameters, based on sensitivity analysis, were saturatedhydraulic-conductivity (Ks), Clark storage coefficient (R) and time of concentration (t c). Uncertainty associated with parameters were accounted for, by representing each with a probability distribution. Uncertainty bounds was calculated, using parameter sets captured from LHS on parameters PDF of sub-basins and propagating to the model. Results showed that maximum reliability (11%) resulted from Ks propagating. For three parameters, underestimation was more than overestimation. Maximum sharpness and standard deviation (STD) was resulted from propagating Ks. Cumulative Distribution Function (CDF) of flow and uncertainty bounds showed that as flow increased, the width of uncertainty bounds increased for all parameters.
Multivariate analysis of flood frequency was used extensively in water resources research. Often ... more Multivariate analysis of flood frequency was used extensively in water resources research. Often the only flood peak or volume is analyzed with statistical distributions, but for a perfect and exact result, the four main characteristics of a flood event, as well as peak, volume, duration, and time-to-peak, are needed. For this reason, multivariate statistical approaches like copula functions developed. This research aims to define and use the bivariate copula (2-copula) probability distribution functions (PDF) for flood characteristics multivariate analysis. When the joint distribution of characteristics such as volume and peak is known, it is possible to define the probability of simultaneous occurrence of design volume and peak flow values.
⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle... more ⎯Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle. Uncertainty arises from a variety of sources such as input error, calibration and parameters. Hydrologic modeling researches indicate that parametric uncertainty has been considered as one of the most important source. The objective of this study was to evaluate parameter uncertainty and its propagation in rainfall-runoff modeling. This study tried to model daily flows and calculate uncertainty bounds for Karoon-III basin, Southwest of Iran, using HEC-HMS (SMA). The parameters were represented by probability distribution functions (PDF), and the effect on simulated runoff was investigated using Latin Hypercube Sampling (LHS) on Monte Carlo (MC). Three chosen parameters, based on sensitivity analysis, were saturatedhydraulic-conductivity (Ks), Clark storage coefficient (R) and time of concentration (t c). Uncertainty associated with parameters were accounted for, by representing each with a probability distribution. Uncertainty bounds was calculated, using parameter sets captured from LHS on parameters PDF of sub-basins and propagating to the model. Results showed that maximum reliability (11%) resulted from Ks propagating. For three parameters, underestimation was more than overestimation. Maximum sharpness and standard deviation (STD) was resulted from propagating Ks. Cumulative Distribution Function (CDF) of flow and uncertainty bounds showed that as flow increased, the width of uncertainty bounds increased for all parameters.
This study compares Severity-Duration-Frequency (SDF) curves (SDFs) of stream flow drought derive... more This study compares Severity-Duration-Frequency (SDF) curves (SDFs) of stream flow drought derived from threshold level methods. For this purpose hydrological drought of Roudzard river basin was investigated, based on run theory. Daily runoff data of Mashin hydrometery station (1970-2012) assessed using 70% (Q 70), 90% (Q 90) of mean daily and 70% of monthly average runoff (monthly) as threshold level methods. Time series of the annual maxima values of duration and volume deficit showed similar trend of increase and decreasing in different thresholds. SDFs were prepared, classifying drought durations to four intervals and fitting statistical distribution to each one. Resulted SDFs showed that, in each period, increasing of duration resulted to increased value of the volume deficit with a nonlinear trend while duration and severities from the threshold levels were different. Drought deficit-volume increasing rate was also different in each class of duration-interval. For the additional analysis, the duration-frequency and deficit-frequency curves were also prepared to quantify the extent of drought duration and deficit more. SDFs developed in this study can be used to quantify water deficit for natural stream and reservoir. They could be an effective tool to identify multivariate hydrological drought using severity, duration and frequency.
Hydrological models are widely used to investigate practical issues of water resources. Parametri... more Hydrological models are widely used to investigate practical issues of water resources. Parametric uncertainty is considered as one of the most important sources of uncertainty in environmental researches. Generally, it is assumed that the parameters are independent mutually, but correlation within the parameter space is an important factor having the potential to cause uncertainty. The objective and innovation of this study was to address the effects of parameters correlation on a continuous hydrological model uncertainty. HEC-HMS with soil moisture accounting (SMA) infiltration method was used to model daily flows and simulate certainty bounds for Karoon III basin, southwest of IRAN, in two scenarios, independent and correlated parameters using 2-copula. The parameters were represented by probability distributions, and the effect on prediction error were evaluated using Latin hypercube sampling (LHS) on Monte Carlo simulation (MCS). Saturated hydraulic conductivity (K), Clark storagecoefficient (R), and time of concentration (tc) were chosen for investigation, based on observed sensitivity analysis of simulated peak over threshold (POT). One hundred runs were randomly generated from 100 parameter sets captured from LHS of parameters distributions in each sub-basin. Using generated parameter sets, 100 continuous hydrographs were simulated and values of certainty bounds calculated. Results showed that when 2-copula correlated R and tc, with 0.656 Kendall's Tau and 0.818 Spearman's Rho coefficients, were propagated, decreasing of outputs' sharpness was more than when considering K and R (K-R), with 0.166 and 0.262; therefore, incorporation of correlations in the MCS is important, especially when the correlation coefficients exceed 0.65. The model was evaluated at the outlet of the basin using daily stream flow data. Model reliability was better for abovenormal flows than normal and below-normal. Reliability increases of simulated flow when considering correlated R-tc was more than K-R because of the correlation values. Incorporation of copula for K-tc not only did not improve the model reliability but also decreased it. Results showed improvement of model reliability, by decreasing predicted error of hydrologic modeling, when dealing with correlated parameters in the system.
In contrast to event based hydrologic models which reveal how a basin responds to an individual r... more In contrast to event based hydrologic models which reveal how a basin responds to an individual rainfall event, continuous ones synthesize hydrologic processes over a longer time period that includes both dry and wet conditions. With respect to the importance of infiltration method in Rainfall-Runoff (RR) modeling, the objective of this study was to assess HEC-HMS with Soil Moisture Accounting (SMA) infiltration algorithm, considering several components of hydrologic cycle such as canopy interception, surface depression, infiltration into the soil profile storage, percolation to the ground water aquifer and base flow caused by available soil storage vs. maximum saturated capacity of soil layer, to model daily flows of Karoon III basin (Iran). The model showed satisfied performance by accounting initial moisture condition by SMA model with Nash-Sutcliffe (NS) coefficient of 0.76 and 0.64 for calibration and verification. Sensitivity analysis showed that saturated hydraulic conductivity (K), Clark storage coefficient (R) and time of concentration (tc) were the most effective parameters on the simulated Peak Over Thresholds (POT). Results from this study assist in improving model accuracy and ability to predict future conditions based upon basin characteristic change.
Drought is a natural phenomenon which occurs in different climate regimes. In the present study, ... more Drought is a natural phenomenon which occurs in different climate regimes. In the present study, hydrological drought of the Roud Zard basin has been investigated based on run theory. Daily runoff data of Mashin hydrometery station during 1970 to 2012 was assessed using 70 % of mean daily runoff as threshold level. Results showed that the maximum drought duration of 309 days occurred in 1998 and 1999 and max drought deficit of 117.217 million cubic meters per second in 1983 with 275 days duration. Time series of the annual maxima values of duration and volume deficit showed similar trend of increase and decreasing. Burr statistical distribution, as the most suitable one fitted to the drought duration data, forecasted 339 days duration for drought event with 20 years return period and generalized extreme value forecasted 37.9 million cubic meters of deficit volume for this return period. Severity-durationfrequency (SDF) curves were prepared, classifying drought durations to four intervals and fitting statistical distribution to each. Resulted SDF curves showed that, in each period, increase of duration resulted in increased value of the volume deficit with a non-linear trend, though predicted drought volume with 20 years return period was 2.1 million cubic meters for 1 to 10 days duration, 6.9 for 11 to 30 days, 34.5 for 31 to 120 days, and 79.1 for more than 120 days duration drought event. Drought deficit volume increasing rate was also different in each class of duration interval. Drought SDF curves derived in this study can be used to quantify water deficit for natural stream and reservoir. SDFs could also be extended to allow for drought regional frequency analysis to be used in ungauged sites.
Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Amon... more Lack of accuracy of rainfall-runoff simulation (RRS) remains critical for some applications. Among various sources of uncertainty, precipitation plays a particular role. Rainfall rates as the main input data of RRS are of the first factors controlling the accuracy. In addition to the depth, spatial and temporal distributions of rainfall impact the flood discharge. Most of the previous studies on RRS uncertainty have ignored rainfall spatial distribution, where in large catchments, it is necessary to be modeled explicitly. Karoon III is one most important basin of the Iran because of the Karoon III dam in the outlet. In the present work, effect of spatial correlation of rainfall on HEC-HMS (SMA) continuous RRS uncertainty is evaluated using 2variate copula (2copula). Monte Carlo simulation (MCS) approach was used to consider the rainfall spatial dependence. To reduce the computational expense, sampling efficiency and convergence for MCS, Latin hypercube sampling (LHS) was used. Copula functions consider wide range of marginal probability distribution functions (PDFs), eliminating limits of regular join PDFs. For this aim, two scenarios were investigated. In the first scenario, sub-basin rainfall was considered independent, and in the second scenario, 2copula was adopted to model spatial correlation of rainfall. Dimensionless rainfall depths were calculated for each sub-basin, and the PDFs were determined. The generated random dimensionless rainfalls were reweighted and multiplied by watershed’s mean rainfall value. Stochastic Climate Library was used to generate continuous daily rainfalls. Sampling from dimensionless rainfalls using LHS algorithm, 100 runs of calibrated model-simulated 100 flows for each day following MCS, and 80 % certainty bound was calculated. Results showed that considering dependence decreased 18 % of the maximum uncertainty bound width, so the methodology could be recommended for decreasing predicted runoff error.
With respect to the effect of precipitation loss on runoff generation, different loss methods of ... more With respect to the effect of precipitation loss on runoff generation, different loss methods of Soil and Conservation Service (SCS), Green and Ampt (G.A.), Initial-Constant (I.C.), Deficit-Constant (D.C.), Constant Fraction (C.F.), exponential (Exp.) and Soil Moisture Accounting (SMA) have been compared by HEC-HMS event based on Rainfall-Runoff modeling in Roud Zard basin. The SMA method with max average Nush-Sutcliffe (N.S.) and min Peak Weighted Root Mean Square Error (PWRMSE) in calibration and verification was the best method in stream flow simulation. The SCS and Exp. methods with similar N.S. and PWRMSE were placed as second suitable methods in sub-daily (2 h) event simulation, and the G.A., C.F. and I.C. methods were the lasts. The comparison between simulated and observed key variables showed that SMA with Mean Absolute Error (MAE) of 0.05 in volume and 3.34 in peak flow simulation was the best in both calibration and verification, and in time to peak, in verification events. In volume simulation I.C. was the second and SCS and G.A. were the worst but in peak flow, SCS was second and others were similar. It could be concluded that SMA as a continuous infiltration method is preferred to the other methods for event based Rainfall-Runoff modeling.
Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water suppl... more Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water supply, storage, industry and other consumption. Certainly hydrologic study is an important issue for these project programming. Data deficiency in most of watersheds has forced us to use indirect methods such empirical relations for flood runoff prediction. Preventing over and underestimation in predictions, It is necessary to calibrate equations for the slightly watershed. In this research we are going to calibrate some common empirical equations like Horton and Fuller. For this reason regionalization with cluster analysis to determine homogenous regions will be done at first. Statistical probability analysis, another issue to estimate peak flood runoff at different return period, and evaluation of Doroodzan dam effect on the statistical characteristics of river regime, also will be assessed in this research.
Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water suppl... more Kor as an important large river in Marvdasht zone, has been utilized for agriculture, water supply, storage, industry and other consumption. Certainly hydrologic study is an important issue for these project programming. Data deficiency in most watersheds has tend us to use indirect methods such as flood frequency analysis, a technique for peak flood runoff estimation at different return periods. In this research flood runoff will be forecasted by flood frequency analysis after selection of most suitable statistical distribution in each station
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