Catchment baseflow is jointly controlled by climate and landscape properties. Previous studies have recognized that spatial variability of mean annual baseflow coefficient (BFC = , ratio of baseflow to precipitation) is primarily controlled by aridity index and storage capacity. However, an analytical solution of BFC in terms of the dominant controlling factors has not yet been established. The objective of this study was to develop an analytical BFC curve to depict spatial variability of BFC based on the “limit” concept of the Budyko framework. The BFC curve relates the baseflow coefficient to aridity index and storage capacity without resolving complex interactions between evapotranspiration and baseflow generation. The proposed BFC curve showed that, in the arid catchments, baseflow coefficient was primarily limited by available water (precipitation, P) and, in the humid catchments, was jointly controlled by both the available energy (potential evapotranspiration, E_p) and catchment retention capability (ratio of catchment storage capacity to P, i.e., S_p/P). Observed hydrological data from 950 catchments in Australia, the conterminous United States and the United Kingdom with diverse hydro-climatic conditions (BFC = 0.001–0.650) were collected to demonstrate the capability of the developed curve. Results showed that the BFC curve captured the spatial variability of observed BFC in the 950 study catchments (R² = 0.75, RMSE = 0.058). Mean annual baseflow estimated by the BFC curve agreed well with observed baseflow (R² = 0.86, RMSE = 0.19 mm). The developed analytical curve provides an analytical solution for understanding how aridity index and storage capacity control mean annual catchment baseflow, and will improve predictability of baseflow at ungauged basins.

中文翻译：

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用于描述年平均集水区基流空间变异性的分析基流系数曲线

集水区基流受气候和景观特性共同控制。以前的研究已经认识到平均年基流系数（BFC = ，基流与降水的比率）主要受干旱指数和蓄水能力控制。然而，BFC 在主导控制因素方面的解析解尚未建立。本研究的目的是基于 Budyko 框架的“极限”概念开发一条分析 BFC 曲线来描述 BFC 的空间变异性。BFC 曲线将基流系数与干旱指数和存储容量联系起来，而没有解决蒸散和基流生成之间复杂的相互作用。所提出的BFC曲线表明，在干旱流域，基流系数主要由可用的水（沉淀，限制P），并在潮湿的集水区，通过两者的可用能量是共同控制（潜在蒸散，È_p ) 和流域保持能力（流域蓄水能力与P 的比率，即S _p / P）。收集了来自澳大利亚、美国本土和英国具有不同水文气候条件 (BFC = 0.001–0.650) 的 950 个流域的观测水文数据，以证明开发曲线的能力。结果表明，BFC 曲线捕获了 950 个研究流域中观察到的 BFC 的空间变异性（ R ²  = 0.75，RMSE = 0.058）。BFC 曲线估计的平均年度基流与观察到的基流（ R ² = 0.86，RMSE = 0.19 毫米）。开发的分析曲线为理解干旱指数和存储容量控制如何平均集水区基流提供了分析解决方案，并将提高未测量流域基流的可预测性。