Ecohydrology of the Venezuelan páramo: water balance of a high Andean watershed

ABSTRACT Background: The páramo provides key ecosystem services, including regulation and provision of water. To understand the underlying functions, an ecosystem approach is necessary. Aims: We quantified the combined effect of vegetation and soils (integrated topographic and vegetation units – TVU) on the hydrological balance of a Venezuelan páramo micro-watershed and analyse its hydrological response to intra- and interannual rainfall variability. Methods: Data (2008–2016) from meteorological stations of TVUs and of a streamflow station was used to calculate watershed level hydrologic balances. We quantified the impact of the TVUs outputs by calculating evapotranspiration under non-standard conditions (ETc adj). Result: Evapotranspiration of wetlands and tarns was high, exceeding annual precipitation. Shrubland had low evapotranspiration. Recharge of páramo reservoirs (soils, wetlands, tarns) occurred when monthly rainfall exceeded 90 mm. In dry years there were lower water yields with less effective hydrological regulation. In average years the differences between input and output in watershed balances were very small. Conclusions: The high and constant evapotranspiration of the wetlands and tarns (due to permanent water availability) suggests they could maintain streamflow during dry periods. Their high evapotranspiration rates are compensated by low rates in shrublands units, reducing the mean total evapotranspiration of the watershed. The watershed balances suggest a limited regulatory capacity in these relatively dry páramos with no volcanic soils.