How vegetation, soils, and precipitation control passive and dynamic storage change in high–elevation tropical catchments?

Abstract

Understanding how tropical montane catchments store and release water is crucial for water resource management at surrounding elevations and downstream populations. Nevertheless, although research in montane tropical ecosystems has focused on streamflow generation, a lack of knowledge regarding catchments’ water storage remains. Consequently, this study focuses on the investigation of catchment storage and the factors controlling its spatial variability in seven páramo catchments (0.20–7.53 km2) located in south Ecuador. We used a hydrometeorological, water stable isotopic, and soils’ hydrophysical properties dataset collected during Nov 2011–October 2014 to estimate catchments’ passive (PasS) and dynamic (DynS) storages. We also investigated relations between these storages and landscape and hydrometric variables using linear regression analysis. The catchments’ PasS and DynS were 313–617 mm and 29–35 mm, respectively. Catchments’ PasS increased as their areal proportion of wetlands (Histosol soils) increased, and their DynS increased as the intensity of precipitation increased. Results also showed that PasS estimations using different methodologies were in agreement. Altogether, results evidence: 1) that only 6–10% of the catchments’ mixing storage (DynS/PasS) is hydrologically active in their water balance, 2) the importance of wetlands for the provisioning of the catchments’ PasS, and 3) the influence of the constant input of low intensity precipitation to sustain the wetlands recharge, and thus, the year–round water supply of páramo catchments. Findings that are crucial towards improvement of soil, vegetation, and water resources management in the páramo and other environments where the presence of peaty–like soils dominates.