scholarly journals Following the Curve?

2021 ◽  
Author(s):  
Mike Kirkby ◽  
Artemi Cerda
Keyword(s):  
Field Measurements ◽  
Curve Number ◽  
Storm Runoff ◽  
Algebraic Expression ◽  
Runoff Generation ◽  
Experimental Station ◽  
Total Runoff ◽  
Storm Flow ◽  
And Storage ◽  
Runoff Events

Output from a runoff generation models is compared here with information from field measurements, making use of 11 years data from rainfall and runoff events at the Sierra de Enguera Soil Erosion Experimental Station in Eastern Spain.. The model presented simulates overland storm flow on a sloping rough and unvegetated surface, representing an area of 320x320 m. Green-Ampt infiltration constants are randomly assigned to each cell in a 128x128 grid, and rectangular storms applied at a range of total amounts and intensities to simulate runoff at each transect across the area. A simple algebraic expression is developed to estimate total runoff and storage in terms of storm size and duration, and plot length, with parameters that reflect infiltration behaviour, and this expression is compared with the SCS curve number approach. Output of these simulations is compared with measured storm runoff data on bare runoff plots at the Sierra de Enguera experimental Station in SE Spain and gives further support to the proposed expression for storm runoff.

scholarly journals Investigation of the direct runoff generation mechanism for the analysis of the SCS-CN method applicability to a partial area experimental watershed

2009 ◽  
Vol 13 (5) ◽  
pp. 605-615 ◽  
Author(s):  
K. X. Soulis ◽  
J. D. Valiantzas ◽  
N. Dercas ◽  
P. A. Londra
Keyword(s):  
Curve Number ◽  
Soil Survey ◽  
Generation Mechanism ◽  
Storm Events ◽  
Runoff Generation ◽  
Direct Runoff ◽  
Total Runoff ◽  
Impervious Area ◽  
Linear Formula ◽  
Scs Cn

Abstract. 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.

scholarly journals Analysis of the runoff generation mechanism for the investigation of the SCS-CN method applicability to a partial area experimental watershed

2009 ◽  
Vol 6 (1) ◽  
pp. 373-400 ◽  
Author(s):  
K. X. Soulis ◽  
J. D. Valiantzas ◽  
N. Dercas ◽  
P. A. Londra
Keyword(s):  
Curve Number ◽  
Soil Survey ◽  
Generation Mechanism ◽  
Storm Events ◽  
Runoff Generation ◽  
Total Runoff ◽  
Impervious Area ◽  
Linear Formula ◽  
Service Curve ◽  
Scs Cn

Abstract. 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 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.

scholarly journals Initial abstraction ratio and Curve Number estimation using rainfall and runoff data from a tropical watershed

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
Luiz Claudio Galvão do Valle Junior ◽  
Dulce Buchala Bicca Rodrigues ◽  
Paulo Tarso Sanches de Oliveira
Keyword(s):  
Conversion Factor ◽  
Poor Performance ◽  
Curve Number ◽  
Storm Events ◽  
Rainfall Runoff ◽  
Initial Abstraction ◽  
Rainfall Depth ◽  
Standard Value ◽  
Tropical Watershed ◽  
Runoff Events

ABSTRACT The Curve Number (CN) method is extensively used for predict surface runoff from storm events. However, remain some uncertainties in the method, such as in the use of an initial abstraction (λ) standard value of 0.2 and on the choice of the most suitable CN values. Here, we compute λ and CN values using rainfall and runoff data to a rural basin located in Midwestern Brazil. We used 30 observed rainfall-runoff events with rainfall depth greater than 25 mm to derive associated CN values using five statistical methods. We noted λ values ranging from 0.005 to 0.455, with a median of 0.045, suggesting the use of λ = 0.05 instead of 0.2. We found a S0.2 to S0.05 conversion factor of 2.865. We also found negative values of Nash-Sutcliffe Efficiency (to the estimated and observed runoff). Therefore, our findings indicated that the CN method was not suitable to estimate runoff in the studied basin. This poor performance suggests that the runoff mechanisms in the studied area are dominated by subsurface stormflow.

scholarly journals Bower ratio-energy balance associated errors in vineyards under dripping irrigation

2007 ◽  
Vol 22 (2) ◽  
pp. 233-240 ◽  
Author(s):  
José Monteiro Soares ◽  
Pedro Vieira De Azevedo ◽  
Bernado Barbosa Da Silva
Keyword(s):  
Energy Balance ◽  
Soil Surface ◽  
Field Measurements ◽  
Bowen Ratio ◽  
Global Solar Radiation ◽  
Soil Heat Flux ◽  
Vitis Vinifera L ◽  
Data Logger ◽  
And Storage ◽  
Ratio Energy

This study was conducted at the Bebedouro Experimental Station in Petrolina-PE, Brazil, to evaluate the errors associated to the application of the Bowen ratio-energy balance in a 3-years old vineyard (Vitis vinifera, L), grown in a trellis system, irrigated by dripping. The field measurements were taken during fruiting cycle (July to November, 2001), which was divided into eigth phenological stages. A micrometeorological tower was mounted in a grape-plants row in which sensors of net radiation, global solar radiation and wind speed were installed at about 1.0 m above the canopy. Also in the tower, two psicometers were installed at two levels (0.5 and 1.8 m) above the vineyard canopy. Two soil heat flux plates were buried at 0.02 m beneath the soil surface. All these sensors were connected to a Data logger 21 X of Campbell Scientific Inc., programmed for collecting data once every 5 seconds and storage averages for every 15 minutes. A comparative analysis were made among four Bowen ratio accepting/rejecting rules, according to the methodology proposed by Spano et al. (2000): betar1 - values of beta calculated by Bowen (1926) equation; betar2 - values of beta as proposed by Verma et al. (1978) equation; betar3 - exclusion of the beta values obtained as recommended by Unland et al. (1996) and betar4 - exclusion of the beta values calculated as proposed by Bowen (1926), out of the interval (-0.7 < beta < 0.7). Constacted that the Unland et al. (1996) and Soares (2003) accepting/rejection rules were better than that of Verma et al. (1978) for attenuating the advective effects on the calculations of the Bowen ratio. The comparison of betar1 with betar2 rules showed that the statistical errors reaching maximum values of 0.015. When comparing betar1 with betar3 e betar4, the beta errors reaching maximum values of 5.80 and 3.15, respectively.

scholarly journals Modelling Effects of Rainfall Patterns on Runoff Generation and Soil Erosion Processes on Slopes

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2221
Author(s):  
Qihua Ran ◽  
Feng Wang ◽  
Jihui Gao
Keyword(s):  
Soil Erosion ◽  
Rainfall Intensity ◽  
Temporal Patterns ◽  
Runoff Generation ◽  
Slope Length ◽  
Erosion Processes ◽  
Total Runoff ◽  
Wide Range ◽  
Critical Slope ◽  
Rainfall Patterns

Rainfall patterns and landform characteristics are controlling factors in runoff and soil erosion processes. At a hillslope scale, there is still a lack of understanding of how rainfall temporal patterns affect these processes, especially on slopes with a wide range of gradients and length scales. Using a physically-based distributed hydrological model (InHM), these processes under different rainfall temporal patterns were simulated to illustrate this issue. Five rainfall patterns (constant, increasing, decreasing, rising-falling and falling-rising) were applied to slopes, whose gradients range from 5° to 40° and projective slope lengths range from 25 m to 200 m. The rising-falling rainfall generally had the largest total runoff and soil erosion amount; while the constant rainfall had the lowest ones when the projective slope length was less than 100 m. The critical slope of total runoff was 15°, which was independent of rainfall pattern and slope length. However, the critical slope of soil erosion amount decreased from 35° to 25° with increasing projective slope length. The increasing rainfall had the highest peak discharge and erosion rate just at the end of the peak rainfall intensity. The peak value discharges and erosion rates of decreasing and rising-falling rainfalls were several minutes later than the peak rainfall intensity.

Effects of Geological Structures on Rainfall-Runoff Processes in Headwater Catchments in a Sedimentary Rock Mountain

2021 ◽  
Author(s):  
Jun Inaoka ◽  
Ken'ichirou Kosugi ◽  
Naoya Masaoka ◽  
Tetsushi Itokazu ◽  
Kimihito Nakamura
Keyword(s):  
Sedimentary Rock ◽  
Flow Direction ◽  
Storm Runoff ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Geological Structures ◽  
Headwater Catchments ◽  
Average Flow ◽  
Bedding Planes ◽  
Hydraulic Anisotropy

&lt;p&gt;To clarify rainfall-runoff responses in mountainous areas is essential for disaster prediction as well as water resource management. Runoff is considered to be affected by many factors including evapotranspiration, rainfall, topography, geology, vegetation, and land use. Among them, topography is said to be the most affectable factor. However, previous studies focused on geologies revealed that though catchments in crystalline mountains have less differences among runoffs, catchments in sedimentary rock mountains show great variation in their runoffs. To explain this difference, the geological structures were expected to be the key of runoffs in sedimentary rock mountains. In other words, particularly in headwater catchments located in sedimentary rock mountains, dips and strikes may significantly affect rainwater discharge. Moreover, the groundwater system can significantly be affected by the hydraulic anisotropy originated from geological stratigraphy. Additionally, in sedimentary rock mountains, previous studies suggested convergence of groundwater flows in the direction of strikes, but the effects of dips and strikes on rainfall-runoff responses were not investigated. Furthermore, none of these previous studies focused on the effects of geological structures on storm runoff responses. Therefore, based on the simultaneous observation of twelve catchments that lie radially from a single, isolated mountain peak, this study aims to clarify the effects of dips and strikes, which characterize sedimentary rock mountains, on water discharge.&lt;/p&gt;&lt;p&gt;The results obtained were as follows: (1) Even though the topographic wetness index (TWI) distributions of the twelve catchments were similar, there were significant differences in their runoff characteristics; (2) Catchments with average flow direction oriented toward the strike direction (strike-oriented catchments) are characterized by large baseflows; (3) Catchments with average flow direction oriented toward the opposite dip direction (opposite dip-oriented catchments) are steep, and this results in quick storm runoff generation; (4) Catchments with average flow direction oriented toward the dip direction (dip-oriented catchments) are gentle, and this results in delayed storm runoff generation. It was supposed that in strike-oriented catchments, large quantities of groundwater flowing along the bedding planes owing to hydraulic anisotropy, exfiltrate and sustain the large amount of the observed baseflow, i.e., in strike-oriented catchments, runoff is directly controlled by geological structures. On the other hand, in opposite dip-oriented and dip-oriented catchments, runoff is indirectly controlled by geological structures, i.e., geological structures affect slope gradients, which result in differences in storm runoff generation. Thus, this study clearly explains that geological structures significantly affect rainfall-runoff responses in headwater catchments located in sedimentary rock mountains.&lt;/p&gt;

Surface soil water dynamics in pastures in northern New South Wales. 2. Surface runoff

2004 ◽  
Vol 44 (3) ◽  
pp. 283 ◽  
Author(s):  
S. R. Murphy ◽  
G. M. Lodge ◽  
S. Harden
Keyword(s):  
Soil Water ◽  
Surface Runoff ◽  
New South ◽  
Ground Cover ◽  
Simulation Modelling ◽  
Runoff Generation ◽  
Grazed Pastures ◽  
South Wales ◽  
Runoff Events

Surface runoff can represent a significant part of the hydrological balance of grazed pastures on the north-west slopes of New South Wales, and is influenced by a range of rainfall characteristic, soil property, and pasture conditions. Runoff plots were established on grazed pastures at 3 sites as part of the Sustainable Grazing Systems National Experiment (SGS NE). Pastures were either native (redgrass, wallaby grass and wire grass) or sown species (phalaris, subterranean clover and lucerne) and a range of grazing management treatments were imposed to manipulate pasture herbage mass, litter mass and ground cover. Rainfall and runoff events were recorded using automatic data loggers between January 1998 and September 2001. Stored soil water in the surface layer (0–22.5 cm) was monitored continuously using electrical resistance sensors and automatic loggers. Pasture herbage mass, litter mass and ground cover were estimated regularly to provide information useful in interpreting runoff generation processes.Total runoff ranged from 6.6 mm at Manilla (0.3% of rainfall) to 185 mm at Nundle (5.7% of rainfall) for different grazing treatments, with the largest runoff event being recorded at Nundle (46.7 mm). Combined site linear regression analyses showed that soil depth, rainfall depth and rainfall duration explained up to 30.3% of the variation in runoff depth. For individual sites, these same variables were also important, accounting for 13.3–33.6% of the variation in runoff depth. Continuous monitoring of stored soil water in relation to these runoff events indicated that the majority of these events were generated by saturation excess, with major events in winter contributing substantially to regional flooding. Long-term simulation modelling (1957–2001) using the SGS Pasture Model indicated that most runoff events were generated in summer, which concurred with the number of flood events recorded at Gunnedah, NSW, downstream of the SGS sites. However, floods also occurred frequently in winter, but the simulations generated few runoff events at that time of the year. These results have important implications for sustainability of grazed pastures and long-term simulation modelling of the hydrological balance of such systems, since runoff generation processes are likely to vary both spatially and temporally for different rainfall events.

scholarly journals Improved SMA-based SCS-CN method incorporating storm duration for runoff prediction on the Loess Plateau, China

2020 ◽  
Vol 51 (3) ◽  
pp. 443-455
Author(s):  
Wenhai Shi ◽  
Ni Wang
Keyword(s):  
Loess Plateau ◽  
Curve Number ◽  
The Loess Plateau ◽  
Moisture Condition ◽  
Soil Moisture Accounting ◽  
Antecedent Moisture ◽  
Storm Duration ◽  
Service Curve ◽  
Scs Cn ◽  
Runoff Events

Abstract In the Soil Conservation Service Curve Number (SCS-CN) method for estimating runoff, three antecedent moisture condition (AMC) levels produce a discrete relation between the curve number (CN) and soil water content, which results in corresponding sudden jumps in estimated runoff. An improved soil moisture accounting (SMA)-based SCS-CN method that incorporates a continuous function for the AMC was developed to obviate sudden jumps in estimated runoff. However, this method ignores the effect of storm duration on surface runoff, yet this is an important component of rainfall-runoff processes. In this study, the SMA-based method for runoff estimation was modified by incorporating storm duration and a revised SMA procedure. Then, the performance of the proposed method was compared to both the original SCS-CN and SMA-based methods by applying them in three experimental watersheds located on the Loess Plateau, China. The results indicate that the SCS-CN method underestimates large runoff events and overestimates small runoff events, yielding an efficiency of 0.626 in calibration and 0.051 in validation; the SMA-based method has improved runoff estimation in both calibration (efficiency = 0.702) and validation (efficiency = 0.481). However, the proposed method performed significantly better than both, yielding model efficiencies of 0.810 and 0.779 in calibration and validation, respectively.

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