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Catchment baseflow is jointly controlled by climate and landscape properties. Previous studies have recognized that spatial variability of mean annual baseflow coefficient (BFC = Qb/P, 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, Ep) and catchment retention capability (ratio of catchment storage capacity to P, i.e., Sp/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. Key Points: An analytical curve was established to depict the spatial variability of mean annual baseflow based on the Budyko "limit" frameworkThe curve directly relates aridity index and storage capacity (Sp) to estimate baseflow and shows dominant control of Sp in humid catchmentsThe developed curve performed well with observed data from 950 catchments located in the Australia, CONUS and UK [ABSTRACT FROM AUTHOR]

Understanding the propagation of prolonged meteorological drought helps solve the problem of intensified water scarcity around the world. Most of the existing literature studied the propagation of drought from one type to another (e.g., from meteorological to hydrological drought) with statistical approaches; there remains difficulty in revealing the causality between meteorological drought and potential changes in the catchment water storage capacity (CWSC). This study aims to identify the response of the CWSC to the meteorological drought by examining the changes of hydrological-model parameters after drought events. Firstly, the temporal variation of a model parameter that denotes that the CWSC is estimated to reflect the potential changes in the real CWSC. Next, the change points of the CWSC parameter were determined based on the Bayesian change point analysis. Finally, the possible association and linkage between the shift in the CWSC and the time lag of the catchment (i.e., time lag between the onset of the drought and the change point) with multiple catchment properties and climate characteristics were identified. A total of 83 catchments from southeastern Australia were selected as the study areas. Results indicated that (1) significant shifts in the CWSC can be observed in 62.7 % of the catchments, which can be divided into two subgroups with the opposite response, i.e., 48.2 % of catchments had lower runoff generation rates, while 14.5 % of catchments had higher runoff generation rate; (2) the increase in the CWSC during a chronic drought can be observed in smaller catchments with lower elevation, slope and forest coverage of evergreen broadleaf forest, while the decrease in the CWSC can be observed in larger catchments with higher elevation and larger coverage of evergreen broadleaf forest; (3) catchments with a lower proportion of evergreen broadleaf forest usually have a longer time lag and are more resilient. This study improves our understanding of possible changes in the CWSC induced by a prolonged meteorological drought, which will help improve our ability to simulate the hydrological system under climate change. [ABSTRACT FROM AUTHOR]

• The first study to characterize the multidimensional behaviors of unregulated floods. • A strong geographic cohesion identified in the multidimensional behaviors of floods. • The geographic cohesion partly explained by the relations between floods and ENSO. • The decreases in floods in southern Australia projected to continue in warmer future. Changes in peak magnitude, volume, frequency and duration of floods obtained from a peak-over-threshold sampling in 780 unregulated catchments show significant differences between northern and southern Australia over 1975–2012. Increases of the flood properties are mainly located in northern Australia, while decreases are mostly in southern Australia. These changes could be dominated by inter-annual and/or decadal variability of floods. The multidimensional behaviors of flood change across Australia can be described by three distinct groups (i.e. no changes, increases and decreases in all flood properties), showing strong geographic cohesion. The geographical consistency between the changing patterns of flood properties and spatial patterns of vapor transport anomalies during the El Niño-Southern Oscillation (ENSO) positive phase could partly explain the geographic cohesion of flood changes. In a warmer future, the observed decreases in floods in southern Australia are projected to continue with high model agreement, while only magnitude and volume of floods in northern Australia are projected to increase but with high uncertainties. The diametric changes in flood magnitude between northern and southern Australia are projected to be more evident in extreme (i.e. 50-year) floods than small (i.e. 5- and 20-year) floods. [ABSTRACT FROM AUTHOR]