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In Morocco, although it is often classified as a country with a semi-arid climate, floods are very frequent. Like other basins in the kingdom, the Sebou basin with a total area of 40 000 km² has experienced more catastrophic flooding in the past and these floods have caused enormous economic and even human losses. The objective of this study is to apply different methods to calculate a Curve Number values to estimate the potential runoff for this basin. The techniques used are boils down to the different steps. Firstly, the approach was to extract automatically the sub-basins and drainage network, using Geographical Information Systems (GIS) and Digital Elevation Model (DEM) to determine all the physical characteristics of the basin. Then, preparing the land use map using remote sensing and the soil map for determining hydrologic soil Group. Thirdly, the combination of elaborated data for development of a map of Curve Number (CN) and finally, the interpolation of precipitation data recorded at rainfall stations at 30 minutes time steps to the Hydrologic Modeling System (HEC-HMS) model. The results obtained in the above steps are used for the purpose to get a spatial hydrological model and subsequently its calibration. [ABSTRACT FROM AUTHOR]

Highlights • There is no well-established method to quantify the linkages between physical processes of soil erosion provided by ecosystems and consequent economic implications. • This article proposed an analytical framework and indicators for physical measurements and economic valuation of erosion control services provided by forested ecosystems. • Methods and indicators are divided according to three beneficiary groups: (1) private benefits to farmers, (2) benefits to businesses, and (3) societal benefits. Abstract The physical process of soil erosion leads to a range of impacts – both onsite and offsite – such as land degradation, nutrient depletion and sedimentation, which in turn affect different economic sectors that are reliant on productive capacity of land and aquatic resources. This erosion process is highly moderated by undisturbed natural ecosystems through physical and geochemical means. However, methods to quantify these linkages are scarce. The purpose of this article is to demonstrate an analytical framework for physical measurements and economic valuation of erosion control services provided by forested ecosystems. The article is divided into two parts: the first part deals with physical measurements of onsite and offsite erosion control services, and in the second part various economic valuation methods for different beneficiary groups are discussed. Ecosystem services are divided according to three beneficiary groups: (1) private benefits to farmers, (2) benefits to businesses, and (3) societal benefits. The article concludes with implications, challenges and future directions. [ABSTRACT FROM AUTHOR]

This paper presents the development of runoff hydrographs for selected rivers in the Ogun-Osun river catchment, south west, Nigeria using Snyder and Soil Conservation Service (SCS) methods of synthetic unit hydrograph to determine the ordinates. The Soil Conservation Service (SCS) curve Number method was used to estimate the excess rainfall from storm of different return periods. The peak runoff hydrographs were determined by convoluting the unit hydrographs ordinates with the excess rainfall and the value of peak flows obtained by both Snyder and SCS methods observed to vary from one river watershed to the other. The peak runoff hydrograph flows obtained based on the unit hydrograph ordinate determined with Snyder method for 20-yr, 50- yr, 100-yr, 200-yr and 500-yr, return period varied from 112.63 m3/s and 13364.30 m3/s, while those based on the SCS method varied from 304.43 m3/s and 6466.84 m3/s for the eight watersheds. However, the percentage difference shows that for values of peak flows obtained with Snyder and SCS methods varies from 13.14% to 63.30%. However, SCS method is recommended to estimate the ordinate required for the development of peak runoff hydrograph in the river watersheds because it utilized additional morphometric parameters such as watershed slope and the curve number (CN) which is a function of the properties of the soil and vegetation cover of the watershed. [ABSTRACT FROM AUTHOR]

When discharge measurements are not available, design of water structures relies on using frequency analysis of rainfall data and applying a rainfall–runoff model to estimate a hydrograph. The Soil Conservation Service (SCS) method estimates the design hydrograph first through a rainfall–runoff transformation and next by propagating runoff to the basin outlet via the SCS unit hydrograph (UH) method. The method uses two parameters, the Curve Number (CN) and the time of concentration (Tc). However, in data-scarce areas, the calibration of CN andTcfrom nearby gauged watersheds is limited and subject to high uncertainties. Therefore, the inherent uncertainty/variability of the SCS parameters may have considerable ramifications on the safety of design. In this research, a reliability approach is used to evaluate the impact of incorporating the uncertainty of CN andTcin flood design. The sensitivity of the probabilistic outcome against the uncertainty of input parameters is calculated using the First Order Reliability Method (FORM). The results of FORM are compared with the conventional SCS results, taking solely the uncertainty of the rainfall event. The relative importance of the uncertainty of the SCS parameters is also estimated. It is found that the conventional approach, used by many practitioners, might grossly underestimate the risk of failure of water structures, due to neglecting the probabilistic nature of the SCS parameters and especially the Curve Number. The most predominant factors against which the SCS-CN method is highly uncertain are when the average rainfall value is low (less than 20 mm) or its coefficient of variation is not significant (less than 0.5), i.e. when the resulting rainfall at the design return period is low. A case study is presented for Egypt using rainfall data and CN values driven from satellite information, to determine the regions of acceptance of the SCS-CN method.EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR A. Efstratiadis [ABSTRACT FROM AUTHOR]

This research has been carried out for investigation and comparison of the accuracy and reliability of different methods of unit hydrograph estimation, including geomorphologic (GIUH) and geomorphoclimatic (GCIUH) methods as well as methods by Nash (Nash-IUH), Rosso (Rosso-IUH) and the Soil Conservation Service (SCS); the methods simulated the rainfall-runoff process over the Manshad River basin located in central Iran. The first six equivalent rainfall-runoff events were selected, and a hydrograph of outlet runoff was calculated for each event. Compared were peak time, peak discharge, base time, W and W parameters (hydrograph widths at 50% and 75% of peak discharge) and the volume of outlet runoff simulated by the models; then determined was the model that most efficiently estimated the hydrograph of outlet flow. The comparison of calculated and observed hydrographs showed that the Nash model was more efficient in estimating peak discharge, peak time, outlet runoff volume and the shape of direct surface runoff (DSRO) hydrographs, though it could not precisely simulate base time and W and W parameters. The other methods were more accurate in simulating outlet runoff volume of the hydrographs. The Rosso-IUH and SCS models could estimate the base time parameter better than the others. GIUH performance was comparable to the Nash method and was relatively suitable. In spite of these results, the GIUH, GCIUH, Rosso-IUH and SCS models had weak performance for estimating other characteristics of outlet DSRO hydrographs. [ABSTRACT FROM AUTHOR]

The accurate simulation or prediction of storm runoff is one of the most important bases of water resource management and environmental quality assessment of water and soil. The soil conservation service-curve number (SCS-CN) method cannot effectively determine the effect of antecedent precipitation storage and depletion on runoff, which limits the accuracy of the method's runoff prediction. Thus, potential initial abstraction and decay constant were developed in this study to improve the SCS-CN method. Potential initial abstraction determined the maximum rainfall storage before runoff and the threshold of daily effective rainfall, and the decay constant was used to describe the dynamic depletion of antecedent daily effective rainfall induced by evapotranspiration and seepage. The improved SCS-CN method was evaluated withthe runoff data observed in four cropping systems and three drainage areas, and it proved that the improved SCS-CN method predicted runoff more accurately than the original SCS-CN method. The inproved SCS-CN method increased both NSE and R values by more than 20 % for the four cropping systems, and increased R values by 11.9, 13.9 and 9.6 % for the plot, field, and catchment, respectively, compared with the original SCS-CN method. The decay constant did not vary with cropping systems and drainage areas. [ABSTRACT FROM AUTHOR]

Wildfires can alter the hydrological processes in watersheds resulting in increases in peak discharge - one of the most important hydrological variables used in water resources applications. It follows that standard methods used for assessing the rainfall runoff should be modified in order to model the potential changes in watershed response under post-fire conditions. However, no reliable methodology for quantitatively assessing the effects of wildfires on hydrological parameters (such as curve numbers or runoff coefficients) has been identified to date. The approaches currently used are usually site-specific, mainly based on personal experience or very simple empirical strategies, and therefore affected by a degree of uncertainty. This paper addresses the estimation of the Soil Conservation Service Curve Number (SCS-CN or CN) in the district of San Giuliano, L'Aquila (central Italy), a small urban basin recently affected by a wildfire leading to a significant reduction in forest cover. The effects of the fire on runoff were modeled by adjusting CNs according to existing approaches from the literature in order to perform a sensitivity analysis for post-fire conditions; this allowed to examine the effects of the variability in model input parameters (estimates of post-fire CNs) upon expected peak discharges related to different return period storms. The fire effect ratio, which can be seen as a global parameter for describing alterations in the watershed response due to fire, is calculated by dividing post-fire peak discharge by pre-fire peak discharge. For the present case study, this ratio ranged between 1.1 and 2.3, indicating the urgent need for quantitative research on the effects of wildfires on the hydrological variables affecting runoff calculations. [ABSTRACT FROM AUTHOR]

Estimates of design floods are required for the design of hydraulic structures and to quantify the risk of failure of the structures. Many international studies have shown that design floods estimated using a regionalised method result in more reliable estimates of design floods than values computed from a single site or from other methods. A number of regional flood frequency analysis (RFFA) methods have been developed, which cover all or parts of South Africa. These include methods developed by Van Bladeren (1993), Mkhandi et al. (2000), Görgens (2007) and Haile (2011). The performance of these methods has been assessed at selected flow-gauging sites in the province of KwaZulu-Natal (KZN), South Africa. It is recommended that the limitations of available flow records to estimate extreme flow events need to be urgently addressed. From the results for KZN the JPV method, with a regionalised GEV distribution with the veld zone regionalisation, generally gave the best performance when compared to design floods estimated from the annual maximum series extracted from the observed data. It is recommended that the performance of the various RFFA methods needs to be assessed at a national scale and that a more detailed regionalisation be used in the development of an updated RFFA method for South Africa. [ABSTRACT FROM AUTHOR]

The article presents information on the SoilTrEC project, a global initiative on Critical Zone (CZ) research and integration for the preservation of soil ecosystems. Topics include the efforts of the European Union Thematic Strategy for Soil Protection to mitigate soil degradation; the European Commission-funded research project on Soil Transformations in European Catchments (SoilTrEC); soil conservation services; and integrated modeling of soil processes.

Soil and water conservation measures can impact hydrological cycle, but quantitative analysis of this impact is still difficult in a watershed scale. To assess the effect quantitatively, a three-dimensional finite-difference groundwater flow model (MODFLOW) with a surface runoff model–the Soil Conservation Service (SCS) were calibrated and applied based on the artificial rainfall experiments. Then, three soil and water conservation scenarios were simulated on the sand-box model to assess the effect of bare slope changing to grass land and straw mulching on water volume, hydraulic head, runoff process of groundwater and surface water. Under the 120 mm rainfall, 60 mm/h rainfall intensity, 5 m2 area, 3° slope conditions, the comparative results indicated that the trend was decrease in surface runoff and increase in subsurface runoff coincided with the land-use converted from bare slope to grass land and straw mulching. The simulated mean surface runoff modulus was 3.64×10−2 m3/m2/h in the bare slope scenario, while the observed values were 1.54×10−2 m3/m2/h and 0.12×10−2 m3/m2/h in the lawn and straw mulching scenarios respectively. Compared to the bare slope, the benefits of surface water reduction were 57.8% and 92.4% correspondingly. At the end of simulation period (T = 396 min), the simulated mean groundwater runoff modulus was 2.82×10−2 m3/m2/h in the bare slope scenario, while the observed volumes were 3.46×10−2 m3/m2/h and 4.91×10−2 m3/m2/h in the lawn and straw mulching scenarios respectively. So the benefits of groundwater increase were 22.7% and 60.4% correspondingly. It was concluded that the soil and water conservation played an important role in weakening the surface runoff and strengthening the underground runoff. Meanwhile the quantitative analysis using a modeling approach could provide a thought for the study in a watershed scale to help decision-makers manage water resources. [ABSTRACT FROM AUTHOR]

The SCS-CN method is one of the most popular methods for computing runoff from small watersheds (agricultural, forest, rural, and urban) for individual rainfall events. This study revisits the method using the entropy theory, which provides insights into the structure of the method and permits derivation of the probability distributions of the variables (CN = curve number, S = maximum soil moisture retention, P = precipitation, J = cumulative infiltration, Ia = initial abstraction, and Q = surface runoff) inherent in the method if they are assumed random. If the variables are continuous, then the derivation of the distributions is based on the maximization of the Shannon entropy, subject to given constraints, and the derived distributions are non-parametric. If the variables are discrete, then the derivation is based on the maximization of cross entropy, subject to fractile constraints, wherein prior probability distributions are derived by Shannon entropy maximizing. The derived distributions are tested using field data. It is found that the SCS-CN method requires no information for the probability distribution of runoff associated with it, other than obeying the total probability law. Employing four statistical measures, including Akaike information criterion (AIC), Bayesian information criterion (BIC), bias (BIAS), and root mean square error (RMSE), to determine the goodness-of-fit of probability distributions to 100-CN, Q, P, S, Q/(P-Ia), and J/S, it is found that the gamma distribution, on the whole, is the preferred distribution. [ABSTRACT FROM AUTHOR]

Summary: A hybrid model based on Artificial Neural Networks (ANNs) and Soil Conservation Service (SCS) Curve Number (CN) was developed to predict the effect of changes in land use/cover (LULC) on daily streamflows. The developed model makes use of LULC, hydrologic soil groups and climatic factors, such as temperature and precipitation, in order to replicate the hydrologic response of a watershed. The model incorporates data from neighboring watersheds for training purposes. Therefore, it can be used to predict daily streamflows in ungauged watersheds as well. The developed ANN model was trained, validated, and tested using streamflow data from 10 small watersheds in western Georgia, USA. One urban and one forested watershed were selected for both validation and testing purposes, while 4 forested, 1 urban, and 1 pastoral watershed were used for training the model. The model was able to predict daily streamflow in test watersheds with good accuracy. A scenario analysis was also performed to explore the potential responses to LULC changes in the two test watersheds. Ten LULC scenarios were developed by changing the LULC percentages in the forested and urban test watersheds. The developed ANN model predicted increases in average flow and flashiness for the urban and pasture dominant scenarios. For the forest dominated scenarios, the model predicted more stable hydrology (less flashy) with lower average flows. [Copyright &y& Elsevier]

In northern Morocco are located most of the dams and reservoirs of the country, while this region is affected by severe rainfall events causing floods. To improve the management of the water regulation structures, there is a need to develop rainfall--runoff models to both maximize the storage capacity and reduce the risks caused by floods. In this study, a model is developed to reproduce the flood events for a 655 km² catchment located upstream of the 6th largest dam in Morocco. Constrained by data availability, a standard event-based model combining a SCS-CN (Soil Conservation Service Curve Number) loss model and a Clark unit hydrograph was developed for hourly discharge simulation using 16 flood events that occurred between 1984 and 2008. The model was found satisfactory to reproduce the runoff and the temporal evolution of floods, even with limited rainfall data. Several antecedent wetness conditions estimators for the catchment were compared with the initial condition of the model. Theses estimators include an antecedent discharge index, an antecedent precipitation index and a continuous daily soil moisture accounting model (SMA), based on precipitation and evapotranspiration. The SMA model performed the best to estimate the initial conditions of the event-based hydrological model (R² = 0.9). Its daily output has been compared with ASCAT and AMSR-E remote sensing data products, which were both able to reproduce with accuracy the daily simulated soil moisture dynamics at the catchment scale. This same approach could be implemented in other catchments of this region for operational purposes. The results of this study suggest that remote sensing data are potentially useful to estimate the soil moisture conditions in the case of ungauged catchments in Northern Africa. [ABSTRACT FROM AUTHOR]

This study aims to simulate runoff depth using the Soil Conservation Service-curve number (SCS-CN) method with remote sensing and geographic information system (GIS) techniques. In this study, the SCS-CN technique adapted for Indian conditions has been used for the generation of CNs for an ungauged watershed. The USDA SCS-CN method is used for estimating the runoff depth in the Manimuktha subwatershed. Monthly and annual runoff values have been obtained from the daily runoff values of the watershed. A base map, soil map, and land use map of the study area have been prepared using remote sensing data and Survey of India (SOI) toposheets. The vector layers have been generated in GIS software. The SCS model is then applied to estimate the daily runoff from the watershed and validated, comparing it with the observed runoff of a few selected events of the monsoon periods of 1980-2009. The statistical analysis indicates that the SCS-CN method can be applied to predict runoff depths of an ungauged watershed. The present study reveals that the remote sensing and GIS-based SCS-CN model can be used effectively to estimate the runoff from the ungauged Indian watersheds of similar geohydrological characteristics. [ABSTRACT FROM AUTHOR]

The Natural Resources Conservation Service (NRCS) [previously Soil Conservation Service (SCS)] developed the SCS runoff curve-number (CN) method for estimating direct runoff from storm rainfall. The NRCS uses the CN method for designing structures and for evaluating their effectiveness. Structural design is usually based on a single event of a certain probability of occurrence. During the years when many floodwater-retarding watershed projects were planned and constructed (1950-1980), the CN equation was used in a continuous mode to evaluate the projects. To operate CN in a continuous mode, runoff was estimated from a daily rainfall record of approximately 30 years. For each day of recorded rainfall, the five-day antecedent rainfall was used to assign a (dry condition), (average condition), or (wet condition), and runoff was estimated with the appropriate CN. With the development of continuous hydrologic simulation models, CN was related directly to soil water content or estimated using rainfall and potential evapotranspiration (PET) to drive an index. Several methods were attempted and used with different degrees of success over a period of many years. The purpose of this study is to describe the evolution of the continuous CN method and its recent developments. Test results on the basis of the direct-link soil-moisture approach and the revised soil-moisture index method are presented for demonstration purposes. The results indicate that the revised soil-moisture index method is robust and produces realistic runoff estimates over a wide range of soil properties. [ABSTRACT FROM AUTHOR]

Use of the Soil Conservation Service curve number (SCS-CN) approach is very popular among hydrologists. Despite this, its applications in water quality modeling have been very limited. For the first time, the present work explores the potential of the SCS-CN approach in water quality modeling of the river bank filtration process using a theoretical framework. The approach relates the curve number (CN) with the filtration/kinetic coefficient and the input applied to the system. The approach is tested for its effectiveness using the field data collected at the river bank filtration site at Haridwar, India. The CN is found to be dependent on travel time between source water and the abstraction well in addition to the influent concentration. For very low or very high values of influent concentration, the curve number exhibits an asymptotic variation approaching 100 and 0, respectively. Using the data on source water quality and the travel time, it is possible to compute the curve number and, subsequently, the filtrate quality at an abstraction well. [ABSTRACT FROM AUTHOR]

The Soil Conservation Service (SCS) method is widely used to estimate runoff from small- to medium-sized watersheds. The most critical assumption of the SCS method is that the ratio of actual retention to potential retention is the same as the ratio of actual runoff to potential runoff; however, this assumption has not been empirically validated. The paper develops a framework to test this proportionality assumption that underpins the SCS method. Using data on rainfall intensity and storm runoff from 210 site events from Australia and Southeast Asian countries, this paper shows that a strong relationship exists between maximum retention on the basis of the SCS equation and the product of effective storm duration and spatially averaged maximum infiltration rate, and empirical support exists for the proportionality assumption for runoff estimation. Relating the maximum retention to the effective storm duration and maximum infiltration rate provides additional avenues for prediction of storm runoff amount and peak runoff rate, which are the key design parameters for storm water control and management. [ABSTRACT FROM AUTHOR]

The proper assessment of design hydrographs and their main properties (peak, volume and duration) in small and ungauged basins is a key point of many hydrological applications. In general, two types of methods can be used to evaluate the design hydrograph: one approach is based on the statistics of storm events, while the other relies on continuously simulating rainfall-runoff time series. In the first class of methods, the design hydrograph is obtained by applying a rainfall-runoff model to a design hyetograph that synthesises the storm event. In the second approach, the design hydrograph is quantified by analysing long synthetic runoff time series that are obtained by transforming synthetic rainfall sequences through a rainfall-runoff model. These simulation-based procedures overcome some of the unrealistic hypotheses which characterize the event-based approaches. In this paper, a simulation experiment is carried out to examine the differences between the two types of methods in terms of the design hydrograph's peak, volume and duration. The results conclude that the continuous simulation methods are preferable because the event-based approaches tend to underestimate the hydrograph's volume and duration. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The 1936 Omnibus Flood Control Act assigned upstream and downstream missions to the Soil Conservation Service and Army Corps of Engineers. Flood control is a flagrant violation of fundamental physics. In addition, the missions of both agencies fly in the face of the natural role of floods in the aquatic environment. The result is as damaging to human development as the development is to the environment. Human inroads on riverine environments are ramified in economic, policy, and political strategies now and in the future. This paper focuses on the social science issues within an environmental science framework. It discusses economic, historical, political, and sustainability issues. The evidence for what is wrong with the seventy-five year old program from environmental and social science viewpoints is overwhelming. A proposed alternative approach would enable and celebrate natural floods, would manage their hydrological values and not attempt to control them. [ABSTRACT FROM AUTHOR]

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Application of Soil Conservation Service's (SCS) dimensionless unit hydrograph method for ungauged basins in Indiana yields very high peak flows and short time to peaks for the northern region, thus producing unrealistic flow estimates for design purposes. It is hypothesized that the overestimation of peak flows in northern region using SCS method is due to the flat terrain and high surface storage caused by the Wiconsinan glaciations. To incorporate the slope and storage characteristics, the application of Clark synthetic unit hydrograph (SUH), which incorporates time of concentration (tc) and a storage parameter (R) to produce runoff hydrograph, is explored for Indiana. A statistical analysis of 29 geomorphic attributes and past storm hydrographs for thirty watersheds in Indiana show that watersheds in north, central and southern regions are statistically different in terms of slope and storage characteristics. A statistical comparison of Clark parameters (R and tc) estimated for past storm events also support the effect of storage (higher R) in the north, and slope (higher tc) in the south. Linear and nonlinear regression models of R and tc against all geomorphic attributes for all watersheds yielded storage and slope attributes as significant independent variables, thus providing a way to incorporate slope and storage into hydrograph predictions for ungauged watersheds through Clark SUH. Additionally, regional regression of R and tc with geomorphic attributes produced equations that included attributes related to storage and slope for north, and attributes related to land use, slope and stream network for central and southern regions. Validation of regression equations using new storm events for seven watersheds show that the performance of Clark SUH is the best for northern region followed by central and southern regions. The peak estimated by Clark SUH is more than 60% lower compared to SCS method for northern watersheds, but comparable to observed peak. Overall, the use of R and tc estimated through regression for Clark SUH yield better results compared to SCS method for the entire state including central and southern regions, thus providing more confidence in hydrograph prediction for ungauged basins in Indiana. [ABSTRACT FROM AUTHOR]

The Soil Conservation Service Curve Number (SCS-CN) method is widely used for predicting direct runoff volume for a given rainfall event. The applicability of the SCS-CN method and the direct runoff generation mechanism were thoroughly analysed in a Mediterranean experimental watershed in Greece. The region is characterized by a Mediterranean semi-arid climate. A detailed land cover and soil survey using remote sensing and GIS techniques, showed that the watershed is dominated by coarse soils with high hydraulic conductivities, whereas a smaller part is covered with medium textured soils and impervious surfaces. The analysis indicated that the SCS-CN method fails to predict runoff for the storm events studied, and that there is a strong correlation between the CN values obtained from measured runoff and the rainfall depth. The hypothesis that this correlation could be attributed to the existence of an impermeable part in a very permeable watershed was examined in depth, by developing a numerical simulation water flow model for predicting surface runoff generated from each of the three soil types of the watershed. Numerical runs were performed using the HYDRUS-1D code. The results support the validity of this hypothesis for most of the events examined where the linear runoff formula provides better results than the SCS-CN method. The runoff coefficient of this formula can be taken equal to the percentage of the impervious area. However, the linear formula should be applied with caution in case of extreme events with very high rainfall intensities. In this case, the medium textured soils may significantly contribute to the total runoff and the linear formula may significantly underestimate the runoff produced. [ABSTRACT FROM AUTHOR]

The article features the works and leadership of Hugh Hammond Bennett, former director of the Soil Erosion Service (SES) or Soil Conservation Service (SCS), as the "father of soil conservation" in the U.S. His career started after he earned a Bachelor of Science degree majoring chemistry and geology from the University of North Carolina in June 1903 and joined the Bureau of Soils within the Department of Agriculture (USDA). The 1905 survey of Louisa County, Virginia became a stepping stone for Bennett's career where he investigated declining crop yields. He increasing wrote about soil erosion for various journals and was known as expert on soil erosion.

The Soil Conservation Service curve number (SCS CN) model has been used in the GIS environment to compute run-off at spatio-temporal scales using remote sensing-derived rainfall for 2004 and climatic normal (1951-80) rainfall data. The SCS CN model takes into account land use/land cover, antecedent soil moisture condition and hydrological soil groups. Temporal 10-day composite Normalized Difference Vegetation Index images of SPOT-VGT sensor, and daily remote sensing-derived rainfall data at 10 km resolution from the NOAA Climate Prediction Centre have been used to generate the land cover and antecedent moisture condition (degree of saturation) respectively. Hydrological soil groups were prepared using the soil texture and their infiltration and drainage characteristics. Run-off coefficient maps were generated using the CN-based rainfall excess run-off. Wetland rice-growing areas of West Bengal, India were used to calculate threshold run-off coefficient (0.2) to identify run-off potential areas for major river basins of India during the monsoon season (June to September). There was a large difference in the spatial pattern of run-off estimated for the year 2004 compared to using normal climatic rainfall data. Area estimates for run-off potential were also found to vary significantly for the climatic normal and in-season (2004) data. The spatial variability showed high run-off potential in the western India river basins like Mahi, Luni, rivers of Saurashtra and Sabarmati in 2004. Run-off potential areas over India have been found to increase abruptly from June (158,700 km²) to July (712,300 km²), and decrease from August (633,400 km²) to September (142,000 km²) during 2004. [ABSTRACT FROM AUTHOR]

This paper recognises the need for a revision of watershed development policy in India in relation to the planning of development interventions involving agricultural intensification and rainwater harvesting and the need for new approaches to assist the planning process. Building on, and using as an example, the results of biophysical and societal impact studies carried out on two watershed development projects in Karnataka three new management/dissemination tools, are suggested. These are (1) the web-based geographical information systems exploratory, climate land assessment and impact management tool dissemination tool for disseminating to policymakers and non-specialist stakeholders the downstream impacts of watershed interventions, (2) the ‘quadrant’ approach for ensuring that sustainability criteria are met and (3) Bayesian networks to investigate the biophysical and societal impacts of interventions. [ABSTRACT FROM AUTHOR]

Many of the hydrologic methods that are used in engineering practice today resulted from the Spring Flood of 1936, which blanketed the Northeastern portion of the United States. Because of the flood damage that was caused by this rainfall-snowmelt event, many federal agencies including the U.S. Army Corp of Engineers and the Soil Conservation Service (SCS) implemented the hydrologic theories that were available in the literature at this time and developed hydrologic procedures for design flow estimation. Sherman had recently published his unit hydrograph theory in 1932, and later in 1938 Snyder, who had been charged by the Water Resource Council to develop a synthetic unit hydrograph, published his famous paper. The SCS unit hydrograph theory was developed by Victor Mockus in the late 1950s. Most if not all of the theories at that time reported the rainfall-runoff process for floods as a surface phenomenon, and as such those theories all required some type of a timing parameter to estimate watershed response time. This article documents the development of the SCS lag equation. [ABSTRACT FROM AUTHOR]

The article presents a study which discussed modifications to Soil Conservation Service-curve number (SCS-CN) method for long-term hydrologic simulation. The antecedent moisture condition (AMC) and the antecedent moisture amount (AMA) models were applied to estimate annual runoff volumes from daily rainfall depth for large basins in India. The predictive capabilities of selected calibrated procedures in determining average conditions for annual series of rainfall and runoff were analyzed.

The article presents author's insights on making speechwriting in federal governments. The author says that he is a staff in the Soil Conservation Service and is assigned to make a speech writing thus, he take extensive notes during the discussion in specific matter and he organize those notes into an outline of speech. He tells that his next step is to write the first draft of the speech in response to the particular occasion and into the personality of the person who will make the speech.

A hydrological model was integrated with a computational fluid dynamics (CFD) model to determine bacteria levels distributed throughout the Inverness stormwater pond in Calgary, Alberta. The Soil Conservation Service (SCS) curve number model was used as the basis of the hydrological model to generate flow rates from the watershed draining into the pond. These flow rates were then used as input for the CFD model simulations that solved the Reynolds-Averaged Navier-Stokes (RANS) equations with k-ɛ turbulence model. E. coli, the most commonly used fecal indicator bacteria for water quality research, was represented in the model by passive scalars with different decay rates for free bacteria and attached bacteria. Results show good agreement with measured data in each stage of the simulations. The middle of the west wing of the pond was found to be the best spot for extracting water for reuse because it had the lowest level of bacteria both during and after storm events. In addition, only one of the four sediment forebays was found efficient in trapping bacteria. [ABSTRACT FROM AUTHOR]

An introduction to the journal, which focuses on soil conservation service curve number (SCS-CN) methodology and its applications, is presented.