Abstract ID: 3.13121 | Accepted as Talk | Requested as: Talk | TBA | TBA

The headwaters of the Tropical Andes are characterized by year-round precipitation, historically providing a reliable water supply for downstream populations. However, climate projections consistently indicate a reduction in precipitation during the driest months (July–November), highlighting a potential intensification of drought conditions in the future. Additionally, increasing water demand is exacerbating the impact of these events. Unlike many other mountain regions, these headwater basins lack snow, glaciers, or large aquifers that typically buffer drought conditions. As a result, their drought characteristics and processes remain poorly understood, despite their vast extent across the Tropical Andes. Furthermore, the limited monitoring network, uncertainties in global models and satellite products, and the historical lack of preparedness for such events have constrained the study of droughts. In order to improve the understanding of drought processes, we characterized droughts in a headwater basin of the southern Ecuadorian Tropical Andes (above 2550 m a.s.l.) using 42 years of observed daily streamflow and precipitation data. First, drought events in streamflow and precipitation were independently identified using the threshold method. Then, these events were linked based on their temporal occurrence. Finally, event characteristics were classified using k-means clustering. The average duration of streamflow and precipitation droughts was 10 and 15 days, with a maximum duration of 53 and 95 days, respectively. Short-duration events reflect the rapid hydrological response of the region and suggest a small lag between meteorological and streamflow drought. Two distinct drought groups were identified. The first primarily occurred during the rainy season (March–May) and was characterized by short durations. The second group, occurring in the dry months (August, November–February), exhibited longer durations and lower minimum streamflow and precipitation values. Additionally, traditional indicators such as the Consecutive Dry Days (CDD) index, commonly used to assess drought in climate projections, failed to capture the characteristics of the most recent and severe drought in the region (2024). Here, we demonstrate that these basins experience fast droughts and show different patterns across the year. These findings provide new insights into drought dynamics in high-altitude tropical basins, with implications for water resource management and climate ada