CWC Western Ghats

Hydrologic and Carbon Services in the Western Ghats: Response of Forests and Agro-ecosystems to Extreme Rainfall Events

Although the impact of deforestation on enhancing flood risk is well known (van Dijk et al., 2009), the effects of forest degradation and reforestation on floods and the hydrological cycles in the humid tropics are less well established, especially under scenarios of climate change. Certain combinations of land-cover, soil types and agro-ecosystems in the Western Ghats are already vulnerable to increased surface flows under current rainfall regimes, but the responses of these and other land-cover and soil types to future changes in rainfall regimes is less well understood.

There is presently only a sparse raingauge network over the higher topography of the Western Ghats and a lack of detailed understanding of spatial–temporal variability in rainfall intensities (at fine temporal resolutions) by event linked with atmospheric dynamics of rain-producing systems. Until now studies on floods emanating from Extreme Rainfall Events (ERE) in the Western Ghats have relied on daily or coarser time resolution rainfall data. At present, there is considerable uncertainty in linking finer resolutions of rain intensities to daily totals and the spatial and temporal dimensions of ERE in regions such as the Western Ghats. Moreover, the coupling of synoptic meteorology–rainfall characteristics with storm runoff generation (i.e., hillslope hydrology) in this work will address a global weakness in the humid tropics. Another over-arching issue while studying ERE is that of scales at which the impacts of land cover change (LCC) are overridden by the characteristics of rain–producing systems in terms being the primary source of flood runoff. Blöschl et al. (2007) proposed the concept of a variable “threshold scale”. The latter separates the two dominant controls (LCC and rain-producing systems) across different ecosystems (the spatial dimension) and within an ecosystem (the temporal dimension) depending on antecedent hydrological conditions. However such a concept remains to be proven and is the focus of this study in the context of inter-relating the impacts of ERE with the suite of complex land covers in the Western Ghats.

Objectives:

1/To couple the synoptic and mesoscale meteorology with the spatial and temporal dimensions of Extreme Rainfall Events (ERE) in the Western Ghats (Karnataka and Kerala States) and in turn, the hydrologic responses linked with the spatial patterns of land-cover and land-use

2/ To determine the hydrologic and carbon dynamics consequences of existing land-cover and land-use including large scale forestation in the Western Ghats and adjacent Deccan plateau

3/ To assess the hydrologic and carbon vulnerability of ecosystems, natural, semi-natural and agro-ecosystems, to ERE at various spatial scales

4/ To prioritise sites in the Western Ghats and adjacent Deccan plateau for restoration under the Green India Mission (India is one of the global leaders in forestation of degraded land) and contribute towards water resources management and climate change mitigation policy