Hydrological partitioning in contrasting tropical montane forests types in Eastern Himalaya
Abstract
Studies describing runoff processes from different forest types are rare in tropical montane forests (TMFs) with steep slopes and complex geomorphology, such as the Himalaya. The study compares the hydrological functioning of three streams in Eastern Himalaya using a physically-based, data-driven mechanistic baseflow-separation filter developed by Furey and Gupta (2001). The filter uses the conservation of mass approach to empirically derive coefficients of quick/overland flow (c1), evapotranspiration (c2), and groundwater recharge (c3). The three instrumented catchments ranged from first (0.2 km2) to third (13.4 km2) orders, dominated by temperate broad-leaved (henceforth temperate) and sub-alpine conifer-mixed (henceforth alpine) forests, and cover wide elevation (1800-4050 masl) and precipitation (3750-4900 mm) gradients.
Overall, the filter performed better in temperate streams than in the alpine stream. The overland and rapid sub-surface flow characteristics varied considerably with time, antecedent moisture conditions, catchment, and vegetation. The quick/overland flow coefficients were significantly higher in temperate streams than in alpine stream. Conversely, the groundwater recharge coefficient (c3) was lower in the alpine stream, influenced by transient storage in the moraine-based flat valley, than in the steeply-sloped temperate streams. Groundwater storage and recession patterns were dominated by hydrogeological and catchment characteristics than vegetation. Instead, vegetation and climate were primary factors governing evapotranspiration and overland flow characteristics across the streams, where catchment properties like area and stream slope were critical secondary factors. Seasonally, the low flows were primarily governed by local hydrogeology, catchment size, and snowmelt, whereas vegetation characteristics modulated high flows. The study provides a mechanistic understanding of vegetation-streamflow interactions in wet high elevation TMFs in Eastern Himalaya, one of the 30 global biodiversity hotspots and global 200 ecoregions of importance, where changes in vegetation cover and rainfall patterns with a changing climate may significantly impact the vegetation-streamflow linkages and thereby regional water security.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H43D..06K