Understanding spatial drought characteristics is vital for planning adaptation and mitigation measures in river catchments. In many parts of the world, spatial drought information is not available due to lack of adequate evenly distributed data for spatial drought analyses. This study elucidates a spatial drought analysis in a data-scarce tropical catchment using remote sensing actual evapotranspiration (ET) and potential evapotranspiration (PET) data. Firstly, the time series of 690 images of remotely sensed ET and PET between the years 2000 and 2014 were spatially analyzed using the evapotranspiration deficit index (ETDI) approach to obtain ETDIs in the Kilombero River catchment (Tanzania). Then, spatio-temporal patterns of ETDIs were used to characterize drought frequency, total drought durations, total drought severity, and drought intensity. The frequency, durations, severity, and intensity of drought increased from the year 2000 towards 2014, causing substantial drought changes in the catchment. However, drought intensity revealed that those changes were mainly from no drought and mild drought to moderate drought. Between the years 2000 and 2014, no-drought areas and mild drought areas declined from 10% to 0% and from 42% to 19%, respectively, whereas moderate drought areas increased from 47% to 81% of the catchment size. Those changes of drought conditions were partly attributed to anthropogenic land cover change, especially in the southwest grasslands, and were partly attributed to meteorological factors in other parts of the catchment. This information is crucial for further land cover change and climate change investigations, as well as planning water and land resources in the Kilombero River catchment. Moreover, the study also demonstrates the potential of using publicly available remote sensing ET products and the ETDI approach for spatially characterizing drought in ungauged regions.

中文翻译：

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在数据稀缺的流域中使用遥感蒸发蒸腾分析农业干旱

了解空间干旱特征对于规划河流集水区的适应和缓解措施至关重要。在世界许多地方，由于缺乏用于空间干旱分析的足够均匀分布的数据，因此无法获得空间干旱信息。本研究利用遥感实际蒸散量 (ET) 和潜在蒸散量 (PET) 数据阐明了数据稀缺的热带集水区的空间干旱分析。首先，使用蒸散亏缺指数（ETDI）方法对 2000 年至 2014 年间 690 幅遥感 ET 和 PET 图像的时间序列进行空间分析，以获得基隆贝罗河集水区（坦桑尼亚）的 ETDI。然后，使用 ETDI 的时空模式来表征干旱频率、总干旱持续时间、总干旱严重程度和干旱强度。从 2000 年到 2014 年，干旱的频率、持续时间、严重程度和强度都有所增加，导致流域干旱发生显着变化。然而，干旱强度显示，这些变化主要是从无干旱和轻度干旱到中度干旱。2000 年至 2014 年间，无干旱区和轻度干旱区分别从 10% 下降到 0% 和从 42% 下降到 19%，而中度干旱区从流域面积的 47% 增加到 81%。这些干旱条件的变化部分归因于人为土地覆盖变化，特别是在西南草原，部分归因于流域其他地区的气象因素。这些信息对于进一步的土地覆盖变化和气候变化调查至关重要，以及规划基隆贝罗河集水区的水土资源。此外，该研究还证明了使用公开可用的遥感 ET 产品和 ETDI 方法对未测量区域的干旱进行空间表征的潜力。