Specific yield is a key parameter for estimating water table depth in land surface models, which can strongly modulate the interaction between soil moisture and groundwater and further affect the water budget between the land surface and the atmosphere. The error in water table simulation comes mainly from the uncertainty in determining the specific yield. The determination of specific yield in land surface models is simplified, and a uniform empirical constant value of specific yield is generally used in global simulations, especially for deep aquifers, for its convenience. However, a uniform fixed value is insufficient for worldwide aquifers with diverse environments. Before estimating specific yields for global aquifers in Earth system simulations, a comprehensive understanding of the specific yield and comparison of current determination methods are required. This study provides a comprehensive review of the literature focusing on different concepts of the specific yield, complex variabilities, and various determination methods. Specifically, we detail the distinction and interconversion of different subconcepts that are used to reflect the influence of different factors on the specific yield and are likely to confuse scholars; present the representative comparisons of previous estimated specific yields using different methods, and summarize the applicabilities and limitations of these methods, indicating directions for their future improvement.

中文翻译：

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土地表层和地下水研究的单产综合综述

比产量是估算地表模型中地下水位深度的关键参数，它可以强烈地调节土壤水分与地下水之间的相互作用，并进一步影响地表与大气之间的水平衡。地下水位模拟中的误差主要来自确定比产量的不确定性。简化了陆地表面模型中比产量的确定，并且为方便起见，通常在全局模拟中，尤其是对于深层含水层，使用比产量的统一经验常数值。但是，统一的固定值不足以用于具有不同环境的全球含水层。在估算地球系统模拟中全球含水层的具体产量之前，需要对特定产量有一个全面的了解，并需要对当前测定方法进行比较。这项研究对文献进行了全面的综述，重点关注比产率，复杂变异性和各种测定方法的不同概念。具体来说，我们详细介绍了不同子概念的区别和相互转换，这些子概念用于反映不同因素对单位收益率的影响，并可能使学者们感到困惑。介绍了使用不同方法对先前估计的特定产量进行的代表性比较，并总结了这些方法的适用性和局限性，为它们的未来改进指明了方向。复杂的变异性和各种确定方法。具体来说，我们详细介绍了不同子概念的区别和相互转换，这些子概念用于反映不同因素对单位收益率的影响，并可能使学者们感到困惑。介绍了使用不同方法对先前估计的特定产量进行的代表性比较，并总结了这些方法的适用性和局限性，为它们的未来改进指明了方向。复杂的变异性和各种确定方法。具体来说，我们详细介绍了不同子概念的区别和相互转换，这些子概念用于反映不同因素对单位收益率的影响，并可能使学者们感到困惑。介绍了使用不同方法对先前估计的特定产量进行的代表性比较，并总结了这些方法的适用性和局限性，为它们的未来改进指明了方向。