Showing papers in "Journal of Hydrologic Engineering in 2009"
TL;DR: The impervious cover model (ICM) has attracted considerable attention in recent years, with nearly 250 research studies testing its basic hypothesis that the behavior of urban stream indicators can be predicted on the basis of the percent impervious covers in their contributing subwatershed.
Abstract: The impervious cover model (ICM) has attracted considerable attention in recent years, with nearly 250 research studies testing its basic hypothesis that the behavior of urban stream indicators can be predicted on the basis of the percent impervious cover in their contributing subwatershed. The writers conducted a meta-analysis of 65 new research studies that bear on the ICM to determine the degree to which they met the assumptions of the ICM and supported or did not support its primary predictions. Results show that the majority of research published since 2003 has confirmed or reinforced the basic premise of the ICM, but has also revealed important caveats and limitations to its application. A reformulated conceptual impervious cover model is presented in this paper that is strengthened to reflect the most recent science and simplify it for watershed managers and policy makers. A future challenge is to test the hypothesis that widespread application of multiple management practices at the catchment level can improve the urban stream degradation gradient that has been repeatedly observed by researchers across the country.
313 citations
TL;DR: In this article, the authors investigated hydrologic performance at six bioretention cells in Maryland College Park CP, a 181 m 2 cell, 50-80 cm media depth, monitored for 22 events, and Silver Spring SS, a 102 m 2 cells, 90 cm media layer depth monitored for 60 events.
Abstract: As an increasingly adopted storm water best management practice to remedy hydrologic impairment from urban impervious- ness, bioretention facilities need rigorous field performance research and monitoring to confirm performance and improve design and maintenance recommendations. This study investigated hydrologic performance at six bioretention cells in Maryland College Park CP, a 181 m 2 cell, 50-80 cm media depth, monitored for 22 events, and Silver Spring SS, a 102 m 2 cell, 90 cm media depth, monitored for 60 events and North Carolina Greensboro G1 and G2, each approximately 317 m 2 , 120 cm media depth, both monitored for 46 events, and Louisburg L1=surface area of 162 m 2 , L2=surface area of 99 m 2 ; each had 50-60 cm fill depths, monitored for 31 and 33 events, respectively over 10-15 month periods. Outflow from each cell was recorded and inflow was either recorded or calculated from rainfall data. In Louisburg, L2 was lined with an impermeable membrane to eliminate exfiltration while L1 was unlined to allow both exfiltration and evapotranspiration. Results indicate that bioretention facilities can achieve substantial hydrologic benefits through delaying and reducing peak flows and decreasing runoff volume. A large cell media volume: drainage area ratio, and adjustments to the drainage configuration appear to improve the performance. Media layer depth may be the primary design parameter controlling hydrologic performance. Performance diminishes as rainfall depths increase and rainfall durations become longer. Annual water budget analysis suggests that approximately 20-50% of runoff entering the bioretention cells was lost to exfiltration and evapotranspiration.
266 citations
TL;DR: In this article, the authors studied the temporal trend of ETo along with its regionwise spatial variation, 32 years (1971-2002) monthly meteorological data were collected for 133 selected stations evenly distributed over different agro-ecological regions (AERs) of India.
Abstract: Evapotranspiration (ET) is likely to be greatly affected by global warming because of the dependence of ET on surface temperature. The increasing atmospheric concentration of carbon dioxide (C O2 ) and other greenhouse gases is expected to increase precipitation and evaporation proportionally. However, a few studies have shown a decreasing trend for evaporation over the last 50 years globally. In India, earlier works showed that there was a significant increasing temporal trend in surface temperature and a decreasing trend in grass reference ET (ETo). To study the temporal trend of ETo along with its regionwise spatial variation, 32 years (1971–2002) monthly meteorological data were collected for 133 selected stations evenly distributed over different agro-ecological regions (AERs) of India. ETo was estimated by the globally accepted Food and Agriculture Organization (FAO) Penman Monteith (PM) method (FAO-56 PM). These ETo values were then analyzed by a nonparametric Mann–Kendall (MK) test (with modified ...
208 citations
TL;DR: Flood forecasting at Jamtara gauging site of the Ajay River Basin in Jharkhand, India is carried out using an artificial neural network (ANN), an adaptive neuro-fuzzy interference system (ANFIS) model, and an adaptive Neuro-GA integrated system (ANGis) model.
Abstract: Flood forecasting at Jamtara gauging site of the Ajay River Basin in Jharkhand, India is carried out using an artificial neural network (ANN) model, an adaptive neuro-fuzzy interference system (ANFIS) model, and an adaptive neuro-GA integrated system (ANGIS) model. Relative performances of these models are also compared. Initially the ANN model is developed and is then integrated with fuzzy logic to develop an ANFIS model. Further, the ANN weights are optimized by genetic algorithm (GA) to develop an ANGIS model. For development of these models, 20 rainfall–runoff events are selected, of which 15 are used for model training and five are used for validation. Various performance measures are used to evaluate and compare the performances of different models. For the same input data set ANGIS model predicts flood events with maximum accuracy. ANFIS and ANN model perform similarly in some cases, but ANFIS model predicts better than the ANN model in most of the cases.
173 citations
TL;DR: In this paper, the authors proposed the application of a conjunction model (neurowavelet) for forecasting daily intermittent streamflow, which is improved by combining two methods, discrete wavelet transform and artificial neural networks (ANN), for 1 day ahead streamflow forecasting and results are compared with those of the single ANN model.
Abstract: Intermittent streamflow estimates are important for water quality management, planning water supplies, hydropower, and irrigation systems This paper proposes the application of a conjunction model (neurowavelet) for forecasting daily intermittent streamflow The neurowavelet conjunction model is improved by combining two methods, discrete wavelet transform and artificial neural networks (ANN), for 1 day ahead streamflow forecasting and results are compared with those of the single ANN model Intermittent streamflow data from two stations in the Thrace Region, the European part of Turkey, in the northwest part of the country are used in the study The comparison results revealed that the suggested model could significantly increase the forecast accuracy of single ANN in forecasting daily intermittent streamflows The neurowavelet conjunction model reduced the prediction root mean square errors and mean absolute errors with respect to the single ANN model by 74–65% and 43–12%, and increased the determinati
161 citations
TL;DR: In this paper, a set of different methodologies are developed for multiple objective management of coastal aquifers using a numerical simulation model, meta-model, and the multiple objective optimization algorithm NSGA-II.
Abstract: A set of different methodologies are developed for multiple objective management of coastal aquifers. The coastal aquifer management models are developed using a numerical simulation model, meta-model, and the multiple objective optimization algorithm NSGA-II. The NSGA-II algorithm is also modified to accommodate initial solution generation using the Latin hypercube sampling for uniform sampling in bound space. These initial solutions are useful to improve the efficiency of the optimization algorithm. One important issue in developing management models for coastal aquifers incorporating the density dependent flow and transport processes is the computational feasibility. A few variations of the management model are also evaluated to test the potential for improving the computational efficiency. The variations in the formulation of management models include: direct linking of numerical simulation model, introducing meta-models [in this study artificial neural network (ANN)] in place of original numerical si...
143 citations
TL;DR: In this paper, the authors investigated the relationship between the observed degree of saturation, θe, and the potential maximum retention parameter, S, of the soil conservation service-curve number (SCS-CN) method for abstraction using 15 rainfall-runoff events (ten for calibration and five for verification) that occurred in the period 2002-2005.
Abstract: Estimation of antecedent wetness conditions is one of the most important aspects of storm rainfall-runoff modeling. This study investigated the use of observations of near-surface soil moisture carried out in a small experimental plot to estimate wetness conditions of five nested catchments, from 13 to 137 km2 in area, in Central Italy, including the plot itself. In particular, the relationship between the observed degree of saturation, θe , and the potential maximum retention parameter, S , of the soil conservation service-curve number (SCS-CN) method for abstraction was investigated using 15 rainfall-runoff events (ten for calibration and five for verification) that occurred in the period 2002–2005. Two antecedent precipitation indices (API) and one base flow index (BFI) were also considered for the estimation of wetness conditions. When interpreting S as the mean soil water deficit of the catchment, an inverse linear relationship with θe was found with the coefficient of determination decreasing with c...
136 citations
TL;DR: In this paper, gene expression programming (GEP) is used as an alternative approach to modeling stage-discharge relationship, and the results obtained are compared to more conventional methods, such as stage rating curve and multiple linear regression techniques.
Abstract: This study presents gene-expression programming (GEP), which is an extension to genetic programming, as an alternative approach to modeling stage–discharge relationship. The results obtained are compared to more conventional methods, stage rating curve and multiple linear regression techniques. Statistical measures such as average, standard deviation, minimum and maximum values, as well as criteria such as mean square error and determination coefficient, the coefficient of efficiency, and the adjusted coefficient of efficiency are used to measure the performance of the models developed by employing GEP. Also, the explicit formulations of the developed GEP models are presented. Statistics and scatter plots indicate that the proposed equations produce quite satisfactory results and perform superior to conventional models.
130 citations
TL;DR: A trend analysis of annual flood peaks on 12 small urbanizing watersheds in northeastern Illinois indicated that annual peaks and thus frequency and impact of flooding increased over the past several decades as mentioned in this paper.
Abstract: Trend analysis of annual flood peaks on 12 small urbanizing watersheds in northeastern Illinois indicated that annual peaks, and thus frequency and impact of flooding, increased over the past several decades. An increase in flood peaks could be attributed to intensive urbanization and increasing incidences of heavy rainfall. Average urbanization of the 12 watersheds increased significantly from 10.6% in 1954 to 61.8% in 1996. In addition, numerous studies have reported increasing frequency and intensity of heavy rainfall in the region. This outcome is consistent with lower design rainfall estimates produced by older studies, such as U.S. Weather Bureau Technical Paper No. 40 (TP-40), compared to more recent sources, such as National Oceanic and Atmospheric Administration Atlas-14. This study used a design storm approach and the Hydrologic Engineering Center for Hydrologic Modeling System (HEC-HMS) model to calculate design flood peaks. Hydrologic model parameters were calibrated using hourly rainfall-runo...
115 citations
TL;DR: Simulation results indicate that the proposed scheme can improve the accuracy of the Muskingum model for flood routing and reduce the likelihood of finding a local optimum of the parameter values.
Abstract: The Muskingum model is the most widely used method for flood routing in hydrologic engineering. However, the application of the model still suffers from a lack of an efficient method for parameter estimation. Particle swarm optimization (PSO) is applied to the parameter estimation for the nonlinear Muskingum model. PSO does not need any initial guess of each parameter and thus avoids the subjective estimation usually found in traditional estimation methods and reduces the likelihood of finding a local optimum of the parameter values. Simulation results indicate that the proposed scheme can improve the accuracy of the Muskingum model for flood routing. A case study is presented to demonstrate that the proposed scheme is an alternative way to estimate the parameters of the Muskingum model.
112 citations
TL;DR: In this paper, the authors present a review of the literature to synthesize the development-related variables of hydrologic impairment, placing them in a context that is useful in growth management and development mitigation.
Abstract: Urban impacts to water quality and quantity have been a major focus of resource and ecosystem protection efforts since the early 1960s, focusing in the last decade on the impact of impervious thresholds. These are now commonly used as benchmarks of water quality planning and protection in local, watershed, and regional planning efforts. However, the relationship between urbanization and hydrologic impacts is much more complex than this cause-and-effect model would indicate, containing some weaknesses for effective growth management planning. This paper reviews the current literature to synthesize the development-related variables of hydrologic impairment, placing them in a context that is useful in growth management and development mitigation. Through this critical review of the literature, the paper focuses on an outstanding question in land planning: which best management practices, individually or in concert, are the most effective in dealing with the water quality impacts of urban growth and development? Research indicates two largely overlooked areas of potential improvement in water protection efforts: the location of impervious surfaces in the watershed, and the maintenance of adequate areas of forest stands and native vegetation.
TL;DR: In this paper, an artificial neural network (ANN) model is applied to estimate evaporation in a hot and dry region (BWh climate by the Koppen classification).
Abstract: Evaporation plays a key role in water resources management in arid and semiarid climatic regions. This is the first time that an artificial neural network (ANN) model is applied to estimate evaporation in a hot and dry region (BWh climate by the Koppen classification). It has been found that ANN works very well at the study site and, further, an integrated ANN and autoregressive with exogeneous inputs can have an improved performance over the traditional ANN. Both models significantly outperformed the two empirical methods. It has been demonstrated that the important weather factors to be included in the model inputs are wind speed, saturation vapor pressure deficit, and relative humidity. This result is different from all those reported in the literature and is interestingly linked with a 1936 study by Anderson, who emphasized the importance of saturation vapor pressure deficit. As evaporation is a nonlinear dynamic process, the selection of suitable input weather variables has been a complicated and tim...
TL;DR: In this article, a two-step process is proposed to estimate the fraction of an urban watershed covered by a hydraulically effective impervious area, where the first step applies maximum likelihood classification of fine-scale multispectral satellite imagery to derive urban land cover.
Abstract: This paper presents a two-step process to estimate the fraction of an urban watershed covered by a hydraulically effective impervious area. The first step applies maximum likelihood classification of fine-scale multispectral satellite imagery to derive urban land cover. The second step uses an automated macro in a geographic information system to trace the water flow path from pixels classified as impervious and subclassify them as noneffective or effective. The two steps were verified independently, with verification of the second step using idealized data. The two-step process was then tested with a small watershed study of model calibration and rooftop connectivity impact on runoff. At the watershed scale the land cover classification differences were approximately 6%, while at the pixel scale matches of 50, 60, and 83% were achieved for the rooftop, asphalt/concrete, and vegetation land covers, respectively. The effective impervious area was estimated to comprise 16% of the watershed surface, which wa...
TL;DR: In this paper, the standardized precipitation index, water surface supply index, and Palmer drought severity index have been combined to develop an integrated index, called the hybrid drought index (HDI), using associated damage of drought events.
Abstract: Drought is a natural phenomenon that occurs in many places on the planet and may cause considerable damage. Selection of an integrated index for quantifying drought severity is a challenge for decision makers in developing water resources and operation management policies. In this study, the standardized precipitation index, water surface supply index, and Palmer drought severity index have been combined to develop an integrated index, called the hybrid drought index (HDI), using associated damage of drought events. Application of the HDI in drought severity prediction has been examined using two different types of artificial neural networks, namely, a probabilistic neural network and a multilayer perceptron network. These models have been selected due to their special characteristics that are suitable for prediction schemes. The proposed algorithm for developing HDI and drought prediction has been applied to the “Gavkhooni/Zayandeh-rud” basin in the central part of Iran. The results show the merits of ea...
TL;DR: In this article, the authors proposed new objectives for storm-water management, where the ecological objective is to protect stream ecosystems, because the direct connection between impervious surfaces and streams is a severe stressor to stream ecosystems.
Abstract: A major impact on stream ecosystems in urban catchments is the increased frequency of runoff of poor quality storm water. This problem has not been commonly addressed in storm-water management, which usually focuses on pollutant load reduction or abatement of peak flows, or in some cases on minimization of impervious area. If stream ecosystems are to be restored or protected, a greater focus is required on the minimization of hydraulic connection between impervious surfaces and streams for small, frequent rain events. We propose new objectives for storm-water management. We suggest a primary objective of zero directly connected imperviousness for catchments where the ecological objective is to protect stream ecosystems, because the direct connection between impervious surfaces and streams is a severe stressor to stream ecosystems. We then propose an index to quantify the degree of connection of impervious surfaces, scaled to runoff frequency (retention capacity, RC), which can be used as a design objectiv...
TL;DR: In this article, the relationship between flood conditions and the spatial distribution of the urban development has been poorly studied, often because of limitations in streamflow data availability or the common use of lumped watershed models in urban hydrologic modeling.
Abstract: Urban development within a watershed can take on a wide and diverse range of spatial patterns. The terms “sprawl” and “clustered” development, for example, are frequent in the literature, spanning the spectrum of possible spatial patterns of urban development. The relationship between flood conditions and the spatial distribution of the urban development has been poorly studied, often because of limitations in streamflow data availability or the common use of lumped watershed models in urban hydrologic modeling. We study this relationship with an optimization-based approach that accounts directly for the spatial distribution of imperviousness to investigate how the urban spatial pattern will affect flood peaks and how it can be used to reduce or minimize undesirable impacts to water resources. We employ several water resources-based objective functions to perform optimizations that result in distinct spatial patterns of urbanization showing characteristics of both sprawl and clustered development, dependi...
TL;DR: In this paper, the authors examined the effects of aggregation on predictions of water quantity and quality (for a representative contaminant, total suspended solids) for detention, infiltration, and bioretention devices.
Abstract: Spatially distributed on-site devices such as detention tanks and bioretention are becoming more common as a means of controlling urban storm-water quantity and quality. One approach to modeling the cumulative catchment-scale effects of such devices is to resolve the catchment down to the scale of a land parcel or finer, and then to model each device separately. This involves computational and input data demands that may be impracticable, especially in planning or preliminary design stages of storm-water system design. To reduce these demands, the spatial resolution can be coarsened by aggregating land parcels and devices, but this may compromise model accuracy. The focus of this study was examination of the effects of aggregation on predictions of water quantity and quality (for a representative contaminant, total suspended solids) for detention, infiltration, and bioretention devices. A detailed model for urban storm water improvement conceptualization simulation was set up for a 0.83 km2 catchment wit...
TL;DR: In this article, the authors investigated the potential bias in watershed runoff timing using both measured rainfall and computer simulation data from 27 watersheds and found that the difference in timing between the centers of mass of rainfall excess and direct runoff was the least uncertain timing parameter.
Abstract: Because of differences in roughness, flow depth, and slope, the timing of runoff from most parts of a watershed differs from that along the principal flow path, which is generally used to compute times of concentration. Thus, times of concentration computed from principal flow path information do not accurately reflect the timing of runoff from most parts of a watershed. Specifically, travel times based on the principal flow path will be shorter than times based on the entire watershed, which could result in inaccurate computed peak discharge rates. This potential bias in watershed runoff timing was investigated using both measured rainfall—runoff data from 27 watersheds and computer simulation. Multiple definitions of the time of concentration were compared, with the expected uncertainty in the alternative definitions evaluated. The difference in timing between the centers of mass of rainfall excess and direct runoff was found to be the least uncertain timing parameter while the traditional definition of...
TL;DR: In this article, the authors used regression tree methods to relate estimates of current housing density to the 2001 National Land Cover Database (NLCD) percent urban imperviousness, and they estimated that impervious surface from United States census housing density data sets for the conterminous United States to examine the distribution and extent of impaired watersheds.
Abstract: In this paper, we estimated impervious surface from United States census housing density data sets for the conterminous United States to examine the distribution and extent of impaired watersheds, and to estimate the risk to watersheds from development in the near future. We used regression tree methods to relate estimates of current housing density to the 2001 National Land Cover Database (NLCD) percent urban imperviousness. As of 2000, we estimate 83,749 km2 of impervious surface (IS) cover across the United States (about 9.6% lower than the NLCD). We estimate that IS cover will expand to 114,070 km2 by 2030. About 7% of eight-digit Hydrologic Unit Code (HUC) watersheds (3.6% of the conterminous United States) were stressed or degraded ( >5% IS) in 2000, and we estimated that this will increase to nearly double to 8.5% of watersheds by 2030 (6.3% of area). We explored the subtle differences of fine-grain pattern for different urban land use types by comparing our national estimates of IS to those develo...
TL;DR: In this paper, a multicharacteristic synthesis index (MSI) method is developed to describe flood hydrographs in an integrated way by considering the multiple characteristics synthetically, such as flood peak, 1-day maximum flood volume, 3-day max flood volume and 7-day min flood volume.
Abstract: Flood events consist of flood peaks and flood volumes for various durations that are mutually correlated and need to be described by multiple variables. Conventional flood frequency analysis methods are generally based on the univariate distributions of either flood peaks or flood volumes, and hence only provide a limited assessment of flood events. In this paper, a multicharacteristic synthesis index (MSI) method is developed to describe flood hydrographs in an integrated way by considering the multiple characteristics synthetically, such as flood peak, 1-day maximum flood volume, 3-day maximum flood volume, 7-day maximum flood volume, etc. Annual maximum flood hydrograph series are sampled and then are transformed into corresponding MSI series by the MSI method. The quantile of the MSI series corresponding to a specified design return period is estimated by conventional flood frequency analysis method. A procedure for derivation of design flood hydrograph based on the MSI quantile is proposed. An applic...
TL;DR: In this paper, three boundary conditions (rainfall infiltration, seepage faces, and evapotranspiration fluxes) are implemented using the generic boundary condition and internal sink routines provided in COMSOL multiphysics.
Abstract: Modeling of hydrologic processes using multiphysics modeling packages shows significant promise in a number of applications. However, these packages have not yet developed a complete set of implementations for boundary conditions important in hydrologic modeling. Three such boundary conditions—rainfall infiltration, seepage faces, and evapotranspiration fluxes—are implemented using the generic boundary condition and internal sink routines provided in one multiphysics package, COMSOL multiphysics. Comparison with results from previous simulations using dedicated hydrologic models demonstrates that with care and creativity these boundary conditions can be implemented accurately and efficiently. Boundary condition implementation should not limit the applicability of multiphysics models to a broad set of problems of interest to the hydrologic community.
TL;DR: In this paper, the velocity isoline method is used by the longitudinal velocity streamline considering its great impact on flow structure and the discharge ratio also influences the separation zone from bed bottom to s...
Abstract: Confluence zones in rivers are common occurrences in natural rivers, and their flow structures have a great impact on sediment transport and pollutant dispersion in confluence regions. Previous studies mainly focused on two-dimensional properties of the separation zone, and the studies of the variation of the separation zone from the water surface to the bottom are limited. Based on the confluence experiments carried out in a junction flume, the detailed characteristics of the separation zone were analyzed by using the commonly used streamline and the velocity isoline first proposed in this study, respectively. The velocity isoline method is conducted by the longitudinal velocity streamline considering its great impact on flow structure. Based on the analysis of the selected data from experiments, the geometry and the tendency of the separation zone present different forms with variations of distance to the flume bottom. Further, the discharge ratio also influences the separation zone from bed bottom to s...
TL;DR: In this article, a hydrological analysis of rainwater harvesting facilities was conducted using a model based on the IHACRES model, where the rainfall, rainfall loss, inflow to the storage tank, tank storage volume, overflow from the tank, and rainwater consumption data were simulated.
Abstract: In this study, a hydrological analysis of rainwater harvesting facilities was conducted using a model based on the IHACRES model. Using this model, the rainfall, rainfall loss, inflow to the storage tank, tank storage volume, overflow from the tank, and rainwater consumption data were simulated to evaluate the hydrological characteristics of the rainwater harvesting facilities. This study evaluated three rainwater harvesting facilities in Korea. The results of the study are summarized as follows. (1) The proposed model was found to well simulate the rainfall-runoff processes of rainwater harvesting facilities. (2) As the target amount of rainwater consumption increases, the amount of rainwater consumption also increases, but the number of days with available rainwater decreases. Especially in Korea, the difference in rainwater use when applying different target amounts of rainwater consumption is larger during the rainy compared to the dry season. (3) The effect of increasing the tank capacity was found t...
TL;DR: In this article, the authors characterize asphalt parking lot runoff quality and determine factors influencing nutrient concentrations and loads using automated flow meters and rain gauges, and show that nitrogen species' concentrations were slightly lower than those from highway runoff found in the literature.
Abstract: The objectives of this study were to characterize asphalt parking lot runoff quality and determine factors influencing nutrient concentrations and loads. Event mean concentrations (EMCs) and loads were measured from eight asphalt parking lots in North Carolina using automated flow meters and rain gauges. The number of water quality samples collected varied from 11 to 26 per site. EMCs and loads were statistically analyzed for six nutrient forms: total nitrogen, total Kjeldahl nitrogen, ammonia-nitrogen, nitrate-nitrogen, total phosphorus, and ortho-phosphate. The mean EMCs (in mg/L) were 1.57, 1.19, 0.32, 0.36, 0.19 and 0.07, respectively. Nitrogen species’ concentrations were slightly lower than those from highway runoff found in the literature; whereas, phosphorus EMCs were similar to those in highway runoff. Current load prediction models, generally based on highway or roadway nutrient concentrations, are therefore expected to over-estimate nitrogen loads from asphalt parking lots. Spring and summer pr...
TL;DR: In this article, a numerical model is developed for simulating soil moisture flow in layered soil profile with plant growth using a dynamic root compensation mechanism (RCM) to compute water uptake by plants in a moisture scarce environment.
Abstract: A numerical model is developed in this study for simulating soil moisture flow in layered soil profile with plant growth. A dynamic root compensation mechanism (RCM) is used for a nonuniform root distribution pattern to compute water uptake by plants in a moisture scarce environment. The governing soil moisture flow equation integrated with the roots water uptake function is solved numerically by the implicit finite difference method coupled with the Picard iteration technique. The model is first tested for a barren layered soil profile using numerical simulation data available in the literature. A nonlinear function for water uptake by roots is then incorporated in the flow equation and the rate of water removal is simulated with and without considering the RCM for a characteristic example under optimal and water scare conditions. The model is finally applied to a rain-fed wheat (Triticum aestivum) field using a dynamic root growth model. The simulation considering the RCM shows better agreement with the...
TL;DR: A distributed rainfall runoff model, Grid-Xinanjiang model based on the topographical information of each grid cell extracted from the digital elevation model (DEM), was developed to simulate the hydrologic processes within watersheds as mentioned in this paper.
Abstract: A distributed rainfall-runoff model, Grid-Xinanjiang model based on the topographical information of each grid cell extracted from the digital elevation model (DEM), was developed to simulate the hydrologic processes within watersheds. The water exchange among grids within the watershed and the runoff routing along the river drainage networks are taken into consideration in the model. The Grid-Xinanjiang model was applied to the two watersheds in China for flood simulations. The performance of the developed model was compared with that of the original Xinanjiang model. Initial tests show that the Grid-Xinanjiang model can perform well as the original model in terms of estimates of streamflow and of the model efficiency coefficient. All of the qualified ratios relative to peak flow, runoff, and peak time for the two models applied to the Misai watershed and the Xixian watershed are more than 88%. The Grid-Xinanjiang model outperformed the original model in predicting flood runoff and outlet hydrographs, es...
TL;DR: In this paper, the authors derived the optimal weights which provide minimum MSE quantile estimators, which were then used to improve the accuracy of quantile estimates. But, they did not consider the effect of the regional skew.
Abstract: The accuracy of flood quantile estimates is constrained by the data available at a site. To improve the accuracy of quantile estimators, Bulletin 17B recommends combining the station skew with a regional skew using the inverse of their mean square errors (MSEs) as weights. While these weights can yield the minimum MSE skewness estimator, they do not provide the minimum MSE quantile estimators except when the true at-site skew is zero. In this paper, optimal weights which provide minimum MSE quantile estimators are derived. A Monte Carlo experiment illustrates the value of different weighting schemes and the value of using an informative regional skew. For reasonable values of the regional skew, the MSE of quantile estimators is reduced when the sample skew is combined with an informative regional skew. Modest improvements in the MSE of quantile estimates are obtained using optimal quantile weights rather than the MSE-skew weights. When the regional skew is actually very informative, there is a large loss ...
TL;DR: In this paper, an ANN model was used to estimate the volume of sediment retained in a reservoir, which was found to have better accuracy and less effort as compared to conventional regression analysis.
Abstract: Conventional methods and models available for estimation of reservoir sedimentation process differ greatly in terms of complexity, inputs, and other requirements. An artificial neural network (ANN) model was used to estimate the volume of sediment retained in a reservoir. Annual rainfall, annual inflow, and capacity of the reservoir were chosen as inputs. Thirty Two years of data pertaining to Gobindsagar Reservoir on the Satluj River in India, were used in this study (23 years for training and 9 years for testing). The pattern of the sediment volume retained in this reservoir was well captured by the Multi-Layer Perceptron (3–5-1) ANN model using the back propagation algorithm. Based on several performance indices, it was found that the ANN model estimated the volume of sediment retained in the reservoir with better accuracy and less effort as compared to conventional regression analysis.
TL;DR: In this paper, the authors investigated the spatial variation in runoff coefficients and documents the dependence of the rational C on recurrence interval, indicating that the method is acceptable for use on much larger basins than is typically assumed.
Abstract: The rational method for determining peak flood discharges has been used for the design of hydraulic structures for decades. Despite the popularity of the method, little attention has been paid to improving guidance for selection of the runoff coefficient. This study determined rational runoff coefficients (the rational C ) for 72 gauged rural watersheds in Kansas ranging in size from 0.45 to 76.6 km2 using a frequency-based approach. The median rational C values for Kansas ranged from 0.17 for the 2-year recurrence interval in western Kansas up to 0.97 for the 100-year recurrence interval in eastern Kansas. This paper investigates the spatial variation in runoff coefficients and documents the dependence of the rational C on recurrence interval. The rational C values determined in this study do not exhibit dependence on drainage area, indicating that the method is acceptable for use on much larger basins than is typically assumed.
TL;DR: In this article, a generalized artificial neural network (GANN) based reference crop evapotranspiration models were developed using the data from four California Irrigation Management Information System (CIMIS) stations, namely, Davis, Castroville, Mulberry, and West Side Field Station.
Abstract: The present study was carried out to develop generalized artificial neural network (GANN) based reference crop evapotranspiration models corresponding to FAO-56 PM, FAO-24 Radiation, Turc, and FAO-24 Blaney–Criddle methods. The generalized ANN models were developed using the data from four California Irrigation Management Information System (CIMIS) stations, namely, Davis, Castroville, Mulberry, and West Side Field Station. The average weighted standard error of estimate (WSEE) for the developed models, namely, GANN (4-5-1), GANN (3-4-1), GANN (5-6-1), and GANN (6-7-1) corresponding to the FAO-24 Blaney–Criddle, FAO-24 Radiation, Turc, and FAO-56PM was 0.72, 0.85, 0.63, and 0.48 mm day−1 , respectively. The developed ANN models were applied at 2 CIMIS stations namely, Lodhi and Fresno, without any local training. The average WSEE for models GANN (4-5-1), GANN (3-4-1), GANN (5-6-1), and GANN (6-7-1) was 0.68, 0.71, 0.65, and 0.46 mm day−1 , respectively In addition, the GANN (4-5-1) model corresponding to ...