A new probability density function for spatial distribution of soil water storage capacity leads to the SCS curve number method
A new probability density function for spatial distribution of soil water storage capacity leads to the SCS curve number method
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DOI：
10.5194/hess-22-6567-2018
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发表时间：
2018-12
影响因子：
6.3
通讯作者：
Dingbao Wang
中科院分区：
文献类型：
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作者：
Dingbao Wang
抽象的。在Budyko框架下，利用土壤保持服务曲线数（SCS-CN）方法和变入渗能力（维克）模型，推导出土壤湿润比（土壤湿润量与降水量之比）与土壤蓄水指数（土壤湿润量与降水量之比）的函数关系。对于SCS-CN方法，当土壤储水指数接近∞时，土壤湿润比接近1，这是由于SCS-CN方法的局限性，其中初始土壤水分条件没有明确表示。然而，对于维克型模型，土壤湿润比等于土壤蓄水指数时，土壤蓄水指数小于一定值，由于广义Pareto分布函数的上界有限的存储容量。本文提出了一个新的分布函数，它支持在半无限区间x∈[0，∞）上，用于描述存储容量的空间分布。从这个新的分布函数，土壤湿润比和存储指数之间的关系方程推导。在导出的方程中，当蓄水指数接近0时，土壤湿润比接近0;当蓄水指数趋于无穷大时，土壤湿润比接近某一值（≤1），这取决于初始蓄水量。当初始蓄水量为0时，推导出的方程可用于精确的SCS-CN方法。因此，新的土壤蓄水量分布函数解释了SCS-CN方法作为饱和过量径流模型，并统一了SCS-CN方法和维克型模型的地表径流模拟。
Abstract. Following the Budyko framework, the soil wetting ratio (the ratio between soil wetting and precipitation) as a function of the soil storage index (the ratio between soil wetting capacity and precipitation) is derived from the Soil Conservation Service Curve Number (SCS-CN) method and the variable infiltration capacity (VIC) type of model. For the SCS-CN method, the soil wetting ratio approaches 1 when the soil storage index approaches ∞, due to the limitation of the SCS-CN method in which the initial soil moisture condition is not explicitly represented. However, for the VIC type of model, the soil wetting ratio equals the soil storage index when the soil storage index is lower than a certain value, due to the finite upper bound of the generalized Pareto distribution function of storage capacity. In this paper, a new distribution function, supported on a semi-infinite interval x∈[0,∞), is proposed for describing the spatial distribution of storage capacity. From this new distribution function, an equation is derived for the relationship between the soil wetting ratio and the storage index. In the derived equation, the soil wetting ratio approaches 0 as the storage index approaches 0; when the storage index tends to infinity, the soil wetting ratio approaches a certain value (≤1) depending on the initial storage. Moreover, the derived equation leads to the exact SCS-CN method when initial water storage is 0. Therefore, the new distribution function for soil water storage capacity explains the SCS-CN method as a saturation excess runoff model and unifies the surface runoff modeling of the SCS-CN method and the VIC type of model.