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[Display omitted] • LVB experienced extensive conversion of forest and grass to agricultural land. • SWAT model presents good applicability in seasonal runoff modeling in LVB. • annual runoff generally increased with seasonal differences due to LULC changes. • hydrological drought aggravated over central western and eastern LVB with increased frequency and lengthened duration. Understanding the hydrological impacts of land use and land cover (LULC) changes is significant for sustainable water resources management and planning. The Lake Victoria basin (LVB) has experienced extensive forest and grass degradation and agricultural land expansion under rapid socio-economic development and population growth in recent decades. However, the hydrological impacts of LULC changes for the whole LVB is still poorly documented. This study first investigated the LULC changing effects of LVB, focusing on its impacts on the annual and seasonal runoff and the hydrological drought based on a distributed hydrological modeling of the Soil and Water Assessment Tool (SWAT). SWAT model showed comparatively good applicability in seasonal runoff simulation of LVB, with the percent bias (PBIAS) kept within ± 20 % and the coefficient of determination (R2) over 0.6 at ten hydrological stations available over the calibration and validation phases. Generally, the annual runoff obtained a monthly increase of 1.5 mm under collective LULC changes. Moreover, the LULC effects presented considerable seasonal dependence. A largest runoff increase of approximately 4 mm was detected in short rainy season attributed to the combined surface runoff and groundwater increase. Insignificant runoff increase was observed in long rainy and dry seasons under the complementary effects of surface runoff increase and groundwater decrease. Additionally, the hydrological drought was generally aggravated with increased drought frequency and lengthened duration, particularly for the central western and eastern regions with massive conversion of forest to agricultural land. The findings provide importance implication for rational water resources management and drought disaster response for the LVB. [ABSTRACT FROM AUTHOR]

• The climatological spatial scales (CSS s) of meteorological droughts are investigated. • The CSS s of multi-timescale droughts in China are determined and attributed. • The CSS s generally show a significant decrease with increasing timescale. • The five climate anomalies have significant impacts on the multi-scale CSS s. • The climate anomalies and the CSS s show complex spatiotemporal interaction effects. This study investigates the climatological spatial scales (CSS s) of meteorological droughts in China and the linkages to climate variability. The Global Precipitation Climatology Centre monthly gridded precipitation with a spatial resolution of 25 km × 25 km for 1961–2010 is used. The standardized precipitation index at different timescales (1-, 3-, 6-, 9-, 12-, 24-, 36-, and 48-month) is applied to characterize meteorological droughts. The CSS s of meteorological droughts are calculated using a method considering spatial correlation and anisotropy. The relationships between the CSS s and main monsoons and climate teleconnections in five selected regions are quantified using dynamic spatial panel models. The five regions are South China (SC), the Yangtze River Valley (YRV), North China (NC), Northeast China (NE), and the Tibetan Plateau (TIB). The following results are obtained: (1) The CSS s of multi-timescale meteorological droughts in China are determined. The means of the CSS s at various timescales in China are 68.9, 73.8, 71.8, 69.7, 68.8, 65.9, 62.9, and 60.8 × 104 km2, respectively. The CSS s in eastern China generally show a significant decrease with increasing timescale. (2) Significant quantification relationships (R2 greater than 0.85) suggest that there is not a simple linear relationship between climate anomalies and the CSS s, but rather a complex spatiotemporal interaction including exogenous and endogenous interaction effects. The CSS s not only strongly depend on their neighbors on the same timescale but also significantly depend on the CSS s of neighbors on adjacent timescales. Three monsoon indices (Indian monsoon, East Asian monsoon, and western North Pacific monsoon) have significant impacts on the multi-timescale CSS variations in the five regions, especially for NE, YRV, SC, and TIB, while the El Niño–Southern Oscillation and Pacific Decadal Oscillation affect mainly SC and YRV. These findings could broaden our understanding of the spatiotemporal relationships of droughts and be useful for drought risk management. [ABSTRACT FROM AUTHOR]

• A method to measure the spatial extent of drought at any location was proposed. • The parameters of the method were reasonably specified using sensitivity tests. • The method was tested over a humid region located in southern China. • The difference in spatial lengths of 8 directions showed the anisotropy of drought. • The spatial extents of multi-scale droughts decreased as the time scales increased. The spatial characteristics of droughts are important for understanding drought development and water resource allocation. Most previous studies mainly focus on the spatial display of drought characteristics and the identification of drought spatial extents. Little attention is given to measuring the spatial extent of drought at any location. To this end, a new framework was proposed for measuring the spatial areal extent of drought based on spatial autocorrelation and anisotropy principle. The Global Precipitation Climatology Centre monthly gridded precipitation data with a spatial resolution of 25 km × 25 km were used. The standardized precipitation index on a three-month scale (SPI-3) was applied to characterize meteorological droughts. The base period of 1961–2010 (50 years) was selected for calculating climatology lengths (Cls)/spatial extents (SPEs) of meteorological droughts over the Poyang Lake basin. The parameters of the proposed method, including the drought threshold (SPI ≤ −1), the number of search directions (8), search radius (500 km), distance step (25 km), bandwidth (56.95 km), and angle tolerance (22.5°), were examined using sensitivity tests. The results showed that notable differences in Cls of 8 search directions confirmed the spatial anisotropy of droughts. The statistics of SPEs of the SPI-3 series over the basin were reported. SPEs were mainly between 50 and 100 × 104 km2. The distinctive spatial pattern of the SPEs was revealed and characterized by a high-value belt from the northeast and southwest and two low-value areas. The SPI on other time scales (SPI-1/SPI-6/SPI-12) revealed similar characteristics as SPI-3. Moreover, SPEs are potentially associated with time scales, revealing a decreasing change (or increasing spatial fragmentation) as time scales increased. The proposed method based on anisotropy is reasonable and useful for mining the spatial characteristics of droughts and can be applied in other fields. [ABSTRACT FROM AUTHOR]