The role of vegetation, soils, and precipitation on water storage and hydrological services in Andean Páramo catchments

Abstract

Understanding how tropical montane catchments store and release water, and the resulting water ecosystem services they provide is crucial for improving water resource management. But while research in high–elevation tropical environments has made progress in defining streamflow generation processes, we still lack fundamental knowledge regarding water storage characteristics of catchments. Here we explore catchment storage and the factors controlling its spatial variability in seven Páramo catchments (0.20–7.53 km 2 ) in southern Ecuador. We applied a field-based approach using hydrometeorological, water stable isotopic, and soils hydrophysical data from a 3 year collection period to estimate the passive (PasS) and dynamic (DynS) storage of the catchments. We also investigated relations between these storages and landscape and hydrometric variables using linear regression analysis. PasS estimates from hydrophysical soil properties and soil water mean transit times were consistent with estimates using streamflow mean transit times. Computed catchment PasS and DynS for the seven watersheds were 313–617 mm and 29–35 mm, respectively. PasS increased directly with the areal proportion of Histosol soils and cushion plant vegetation (wetlands). DynS increased linearly with precipitation intensity. Importantly, only 6–10% of the mixing storage of the catchments (DynS/PasS) was hydrologically active in their water balance. Wetlands internal to the catchments were important for PasS, where constant input of low intensity precipitation sustained wetlands recharge, and thus, the water regulation capacity (i.e., year–round water supply) of Páramo catchments. Our findings provide new insights into the factors controlling the water regulation capacity of Páramo catchments and other peaty soils dominated environments.