Establishing streamflow drought characteristics in an inter-Andean Mountain catchment

Drought is the most damaging natural phenomena for large areas and populations. Places such as the Andean tropics have not been exempt from the presence of these events. Among these, hydrological droughts play a critical role because streamflow is closely related to the development of the population living in mountains. The study of these droughts has been neglected because, most of the time water availability has exceeded the water demand. However, this has caused a high vulnerability in the region due to the lack of knowledge and preparation for these events. In addition, the intensification of the water cycle due to climate change aggravates the situation. In this context, the objective of this study was to characterize streamflow droughts in an inter-Andean catchment. The study was performed in four near-natural headwater catchments distributed in a nested approach. Catchments are located in the southern Ecuadorian Andes, between 4550 and 2500 m a.s.l. where groundwater contribution is significantly reduced. Between 25 and 44 years of daily streamflow data was used. To identify streamflow droughts, the threshold method was used on a fixed and daily basis. In addition, different threshold levels obtained from the 70th, 80th, 90th, 95th and 98th percentiles of the duration curve were used. From the events identified, the characteristics of duration, magnitude and intensity were calculated. The five percentiles identified a minimum and maximum number of 40 and 670 events, respectively. On the other hand, the fixed threshold detected on average 27% more events compared to the daily threshold. The average duration, magnitude and intensity varied between: 3.2 and 12.85 days; 0.12 and 5.31 mm; and 0.02 and 0.24 mm day^-1, respectively. Despite the existence of events with more extreme characteristics, on average, the presence of events of short duration and magnitude prevail. These results are very different compared to those produced in lowlands, where the contribution of groundwater is important. Additionally, the lag between a meteorological and hydrological drought is very small, and therefore other ways to identify droughts should be studied. Results provide insight into the identification and characteristics of streamflow droughts in a poorly studied region such as the Andes. These can help to improve water resource management rules and evaluate water stress scenarios.