The Natural Resources Conservation Service Curve Number (NRCS-CN) is a popular rainfall-runoff modeling method. In this study the performance of the NRCS-CN method in runoff estimation for single storms based on a new initial abstraction ratio ( in the semi-arid climate of Khorasan Razavi, Iran, is presented. The method utilizes public domain Geographic Information Systems (GIS) software for the Geospatial analysis and generating the CN map of the study area. CN values provided in the standard Service Curve Number-tables (CN_0.2) were found to overestimate runoff potential compared to modified tables of CN_0.05. Evaluation of the performance of CN_0.05 for runoff estimation was undertaken using data collected in thirty-five rainfall-runoff events in the Kardeh watershed. A strong correlation (R = 0.97) was found between the observed and estimated direct runoff when CN_0.05 was used for the runoff estimation as well as between the observed and estimated runoff based on Nash-Sutcliffe efficiency (0.88). Overall, runoff predictions were improved with the revised NRCS-CN method in semi-arid climatic settings when is set to 0.05. We provide an easy-to-use relationship between CN_0.2 and CN_0.05 that improves Runoff estimation from NRCS-CN.

中文翻译：

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通过基于栅格的自然资源保护服务曲线数调整改进半干旱气候下新的初始取水率的径流估计

自然资源保护服务曲线数 (NRCS-CN) 是一种流行的降雨径流建模方法。在这项研究中，NRCS-CN 方法在基于新的初始取水率（在伊朗呼罗珊拉扎维的半干旱气候中）的单一风暴径流估计中的性能被提出。该方法利用公共领域地理信息系统（GIS ）软件的地理空间分析和生成所述研究区的CN图。CN值在标准服务曲线数台（CN提供_0.2）被发现相比CN的修改的表高估径流潜在_0.05。评价的性能的CN _0.05径流估计是使用在 Kardeh 流域的 35 次降雨径流事件中收集的数据进行的。 当 CN _0.05用于径流估计时，观测到的和估计的直接径流之间以及基于 Nash-Sutcliffe 效率 (0.88) 的观测和估计的径流之间存在强相关性 ( R = 0.97 )。总体而言，当设置为 0.05时，在半干旱气候环境中使用修订的 NRCS-CN 方法改进了径流预测。我们在 CN _0.2和 CN _0.05之间提供了一个易于使用的关系，它改进了 NRCS-CN 的径流估计。