The Rain–Runoff Response of Tropical Humid Forest Ecosystems to Use and Reforestation in the Western Ghats of India

Background

This study expands on a previous study in the Western Ghats of India (Uttar Kannada, Karnataka State), that suggested a greater occurrence of infiltration-excess and potentially higher streamflow in degraded and reforested areas. Analyzing rainfall–streamflow data, the authors attempt to determine the impacts of different land cover types on stream discharge hydrograph components (viz, total flow, quickflow and delayed flow), the dominant stormflow pathways, and the impact of reforestation efforts on these processes.

Research Goals & Methods

Eleven experimental basins ranging from 7 to 23 ha were established in remnant tropical evergreen forest, degraded forest, and Acacia plantations in both coastal and upland locations and rainfall–streamflow observations were collected (daily and at 36 min intervals) between 2003–2005. The authors used a variety of field (rainfall-runoff, permeability) and analytical methods (Double mass curves, HYDSTRA, linear model/ANOVA, and time-series lag analyses).

Conclusions & Takeaways

Degraded forests have enhanced total stream discharge and quickflow both seasonally and by storm event while base flow is reduced. Acacia plantations also have increased overland flow which suggests that they may not be very effective in restoring hydrologic functions in the short-term. However, subsurface water flow still continues in both degraded forest and Acacia plantations partly because their sub-soils are comparatively permeable. Since evapotranspiration is less during the monsoon, differences in streamflow and run-off responses between land-cover is largely attributed to differences in soil infiltration and hydrologic pathways.