Curve Number Hydrology in Water Quality Modeling: Uses, Abuses, and Future Directions

Garen, David C.; Moore, Daniel

doi:10.1111/j.1752-1688.2005.tb03742.x

Cited by 220 publications

(149 citation statements)

References 38 publications

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“…Simonit and Perrings (1) applied the empirical CN model in a humid tropical forest, where it is known not to work, at an inappropriate spatial scale (pixels), and used an invalid monthly time step requiring use of an invalid value of the parameter λ. Hydrological modeling of land-use change effects requires a model that is capable of predicting the effects of those changes on flow path and groundwater dynamics, which the CN methodology cannot (4). The cumulative effects of these hydrological modeling errors render the land-use change-related hydrological conclusions in Simonit and Perrings (1) invalid.…”

mentioning

confidence: 99%

Land use effects on ecosystem service provisioning in tropical watersheds, still an important unsolved problem

Ogden

Stallard

2013

Proc. Natl. Acad. Sci. U.S.A.

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Simonit and Perrings (1) endeavor to assess effects of land use decisions on hydrological behavior of the Panama Canal watershed. Although this is a worthy study topic, the authors used the US Department of Agriculture-Natural Resources Conservation Service Curve Number (CN) model to predict hydrologic response. Modeling of land-management effects on tropical hydrological behavior requires a model that can describe detailed spatial variability in watershed characteristics, properly simulate the effects of tropical land use on rainfall partitioning, and groundwater dynamics. The CN model does none of these (2).The empirical CN method was developed to predict direct (nongroundwater) runoff from single storms, although some models use daily intervals, assuming that typical storms last about 1 d (2). The performance of the CN method is documented as being poor (2) in humid forest settings with deep soils, such as the Canal watershed. The authors erroneously cite , to justify the selection of a CN parameter of 75. The primary conclusion of CalvoGobbeti et al. was that the CN method is not applicable in the Canal headwaters because the CN parameter is nonstationary, varying between 64 and 98 as a result of seasonality and unknown factors. Moreover, Simonit and Perrings (1) applied the CN methodology on a pixel-by-pixel basis to simulate heterogeneous response. The CN methodology was developed to predict the response of watersheds, not pixels. Use of the CN method on individual pixels is meaningless (2, 4).Simonit and Perrings (1) used a monthly time step, which is unsupported by hydrologic research and violates the single-event assumption of the CN method (2). The monthly time step required use of an invalid value of 0.7 for the initial-abstraction ratio, λ. In applying the time step this way, Simonit and Perrings treat λ as a parameter that can assume any value. This is not correct, and use of λ = 0.7 causes their model to disregard periods where total rainfall is less than 70% of the maximum storage capacity of the watershed. Hawkins et al. (2) concluded that λ is more appropriately nearer to 0.0 and definitely less than 0.2. Finally, the monthly time step and large value of λ render Simonit and Perrings' model incapable of predicting landuse effects on droughts or peak flows. In fact, Ferguson (5), used by the authors to justify a monthly time step, specifically states that "average monthly analysis does not, by its nature, produce the same information that daily can, such as magnitudes of individual short-term high or low flows."Simonit and Perrings (1) applied the empirical CN model in a humid tropical forest, where it is known not to work, at an inappropriate spatial scale (pixels), and used an invalid monthly time step requiring use of an invalid value of the parameter λ. Hydrological modeling of land-use change effects requires a model that is capable of predicting the effects of those changes on flow path and groundwater dynamics, which the CN methodology cannot (4). The cumulative effects of these hydrologic...

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mentioning

confidence: 99%

Land use effects on ecosystem service provisioning in tropical watersheds, still an important unsolved problem

Ogden

Stallard

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Another example is the use of runoff curve number to simulate the surface runoff behavior. This approach does not account for saturation excess runoff or contributions from variable source areas (Garen and Moore, 2005;Easton et al, 2008). Although the simulation results in our research met the calibration criteria, the model performance can be improved if precipitation data from additional gages become available in the basin.…”

Section: Discussionmentioning

confidence: 97%

Spatiotemporal response of the water cycle to land use conversions in a typical hilly–gully basin on the Loess Plateau, China

Qiu

Wang

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. The hydrological effects of the "Grain for Green" project (GFGP) on the Loess Plateau have been extensively debated due to the complexity of the water system and its multiple driving factors. The aim of this study was to investigate the response of the hydrological cycle to the GFGP measures based in a case study of the Yanhe Basin, a typical hilly-gully area on the Loess Plateau of China. First, we analyzed the land use and land cover (LULC) changes from 1990 to 2010. Then, we evaluated the effects of LULC changes and sloping land conversion on the main hydrological components in the basin using the Soil and Water Assessment Tool (SWAT). The results indicated that cropland exhibited a decreasing trend, declining from 40.2 % of the basin area in 1990 to 17.6 % in 2010, and that the woodland and grassland areas correspondingly increased. With the land use changes from 1990 to 2010, the water yield showed a decreasing trend which was mainly due to decrease in surface runoff. In contrast, evapotranspiration (ET) showed an increasing trend over the same period, resulting in a persistent decrease in soil water. The conversion of sloping cropland to grassland or woodland exerted negative effects on water yield and soil water. Compared with the land use condition in 2010, the negative effects were most evident where cropland with a slope ≥ 15 • was converted to woodland, with decreases in surface runoff and soil water of 17.1 and 6.4 %, respectively. These results suggest that the expansive reforestation on sloping land in the loess hilly-gully region decreased water yield and increased ET, resulting in reduced soil water. The results of this study can be used to support sustainable land use planning and water resource management on the Loess Plateau in China.

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“…[12] The spatial scale of conservation planning depends upon numerous factors, including management objectives, available data resolution, dominant ecological processes, and potential sociopolitical constraints [Garen and Moore, 2005;Walter et al, 2007]. To achieve the specific goals of water quality control, conservation practices targeting should be performed within a smaller geographic unit, which ultimately allows us to better evaluate targeted management plan.…”

Section: Methodsmentioning

confidence: 99%

A mixed discrete-continuous variable multiobjective genetic algorithm for targeted implementation of nonpoint source pollution control practices

et al. 2013

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[1] Implementation of nonpoint source (NPS) pollution control strategies at the watershed scale hinges on abating pollutant movement from the landscape to water bodies at minimum cost. This paper presents an integrated simulation-optimization approach for targeted implementation of agricultural conservation practices at the watershed scale. A multiobjective genetic algorithm (NSGA-II) with mixed discrete-continuous decision variables was coupled with a distributed watershed model, Soil and Water Assessment Tool (SWAT), to identify optimal types and locations of conservation practices for nutrient and pesticide control at the watershed scale. Previous optimization studies have used binary representation of nonpoint source pollution controls, even though many could be better characterized as continuous variables. In this study, a novel discrete-continuous decision variable, also known as mixed-variable, representation was used to enhance the versatility of the approach by evaluating more options during the search process. Application of the proposed framework in the Eagle Creek Watershed, Indiana, indicated that the optimal suite of conservation practices from the mixed-variable NSGA-II was more effective in meeting water quality targets at lower costs than the solution from binary-variable optimization. However, the mixed-variable approach was considerably more computationally demanding for assessing tradeoffs between environmental and economic factors. A method for hybridization of binary and mixed-variable NSGA-II methods in the context of nonpoint source pollution control practices was developed to enhance the computational efficiency of the optimization procedure. As a result, the number of model simulations required for convergence to the Pareto-optimal solutions was reduced by 96%. The conceptual complexity and computational requirements of optimization-based approaches are impediments to their wider application for targeted implementation of NPS pollution control strategies. The methods and finding of this study address these issues and could result in a more effective implementation of management strategies at the watershed scale. Hoag, and B. A. Engel (2013), A mixed discrete-continuous variable multiobjective genetic algorithm for targeted implementation of nonpoint source pollution control practices, Water Resour. Res., 49,[8344][8345][8346][8347][8348][8349][8350][8351][8352][8353][8354][8355][8356]

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Curve Number Hydrology in Water Quality Modeling: Uses, Abuses, and Future Directions

Cited by 220 publications

References 38 publications

Land use effects on ecosystem service provisioning in tropical watersheds, still an important unsolved problem

Land use effects on ecosystem service provisioning in tropical watersheds, still an important unsolved problem

Spatiotemporal response of the water cycle to land use conversions in a typical hilly–gully basin on the Loess Plateau, China

A mixed discrete-continuous variable multiobjective genetic algorithm for targeted implementation of nonpoint source pollution control practices

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