Springs and streams are the principle water resources in Himalaya catering to 90 % of the hill population. These water resources are governed by complex interactions between climate, topography, hydrogeology and vegetation. The relative control of each factor on the springs and streams varies with scale, space and time. Furthermore, the predicted increase in temperature and precipitation in Sikkim with climate change is likely to disrupt these interactions. However, few studies have empirically investigated the interactions between vegetation, climate and water resources at fine scale in Himalaya. This study aims to fill the knowledge gap by characterizing the ecohydrology of Sikkim Himalaya in the context of climate variability and climate change.

We focus on three key aspects of Himalayan ecohydrology: plant-water relations, the relative controls of hydrogeology, climate and vegetation on spring and stream hydrology, and understanding the impact of climate variability and change on these water resources. We used sapflow probes to empirically estimate stand transpiration from a representative temperate broad-leaved forest and explore its bio-climatic drivers at diurnal and seasonal scales. We instrumented springs of representation hydrogeological typologies, and streams covering gradients of elevation, catchment size and vegetation type to understand the drivers of principle ecohydrological processes at catchment scales. We validated remotely-sensed and gauge-interpolated gridded precipitation products (GPPs) against ground precipitation to explore spatial and temporal patterns in precipitation across Sikkim.