Hydrologic and carbon services in the Western Ghats: Response of forests and agro-ecosystems to extreme rainfall events

Hydrologic and carbon services

The Western Ghats mountain range is a global biodiversity hotspot located on the western edge of peninsular India. It is a complex mosaic of natural and degraded forests and agro-ecosystems under intense human use and dependency, and is one of India’s most important regions from the point of ecosystem services, especially hydrology and carbon.

The properties and functions of natural forest ecosystems regulate how rain water is partitioned into surface flow, sub-surface flow, groundwater and evapotranspiration and also the export of sediment in streams. They also determine how and how much carbon is fixed, stored and lost from these ecosystems. We know very little about how hydrologic and carbon functions of ecosystems respond to extreme rain events (lots of rain per hour) and high intensity rain. Extreme rain events are occurring with greater frequency and are likely to increase in the future, with climate change impacting the ghats.One of the gaps in our knowledge is how such extreme rain storms are distributed over space and time, and how this spatial distribution of rain events interacts with different land-use and land-cover in large landscapes to influence hydrology and carbon dynamics. We also do not know how such increased rainfall variability is likely to interact with smaller-scale processes, such as deforestation and degradation, to influence the provisioning of ecosystem services to humans in landscapes such as the Western Ghats.

This project aims to understand the nature of extreme rainfall events and hydrologic and carbon regulatory effects of forest degradation and reforestation. It will enable us to assess the ability of different ecosystems--natural forests, degraded forests, reforested sites and agro-ecosystems- to perform these functions under future conditions of high intensity or extreme rain events. It will also help agricultural planners determine the sustainability of agricultural land-use under conditions of extreme rain. Information such as best possible sites to target for restoration, along with advice on vegetation type, will be useful to projects such as the Green India Mission

This project will try to understand the synergies and trade-offs between, and hydrologic functions related to mitigation of extreme rain events, that is, infiltration, flow pathways, delayed flow, evapotranspiration; and soil carbon storage dynamics of natural and semi-natural ecosystems, which is critical to evaluating the effectiveness of reforestation programmes.

Project objectives are to:

  • Understand the spatial and temporal dimensions of extreme rain events (ERE) in the Western Ghats in relation to spatial patterns of land-cover and land-use.
  • 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.
  • Assess the hydrologic and carbon vulnerability of ecosystems, natural, semi-natural and agro-ecosystems, to extreme rain events at various spatial scales.
  • Prioritize sites in the Western Ghats and adjacent Deccan plateau for restoration under Green India Mission and other watershed management programmes.

There are three components to this project: hydrology, carbon flux measurement and meteorology and spatio-temporal dimensions.


We have installed 26 rain gauges, 8 water level recorders (WLR) for stream monitoring and 2 for groundwater monitoring and 26 temperature-humidity sensors (hygrochrons) in the Aghnashini basin (Uttar Karnataka). Likewise, we have installed 26 rain gauges, 9 water level loggers and
26 hygrochrons in the Nilgiris. Flumes have been installed for getting direct discharge data during low flows, and current meters are being employed for measuring stream velocity. An automatic weather station has been installed in both the sites. The data is downloaded weekly. Water samples are being collected from both the sites using depth integrated and grab sampler. The samples are being analyzed for nitrates, phosphates and sediment loads and forother physico-chemical parameters. The method of salt dilution (slug and constant rate) is being applied for discharge measurements during very low and heavy flows at both the sites.

Carbon fluxes

The team has established an intensive 1 ha forest plots for monitoring carbon dynamics at Sirsi, (Uttar Karnataka) and the establishment of a second plot is in progress. Within the plot, all trees >10cm dbh have been measured, tagged, spatially mapped and fitted with dendrobands to quantify growth and carbon accumulation patterns. Seedlings have been mapped and measured, and are being monitored in smaller subplots. Further, 50 stem respiration collars and 25 soil respiration collars have been set-up in plots to quantify CO2 fluxes from tree stems and soil, respectively. Collars are now being monitored at two- week intervals to determine background CO2 respiration rates.

In the Nilgiris, established respiration collars in grassland, shola, wattle and pine plantations have been set up to investigate links between land-use type, rainfall and soil CO2 efflux patterns in
this ecosystem.

Meteorology and spatio-temporal dimensions

This team deals with the first objective of the project, that is, to understand the spatial and temporal dimensions of extreme rain events in the Western Ghats in relation to spatial patterns of land-cover and land-use. The team has collected baseline meteorological data from the Indian Meteorological Department, which form a basis for the identification of different rainfall-producing systems (using classification procedures) across both the synoptic scale and mesoscale.

Using TRMM 3B42 (Version 7), the diurnal rainfall occurrence at three-hourly intervals (0.25 ̊ x 0.25 ̊) over the Western Ghats for the period 1998-2012 has been analyzed across four meteorological systems to identify likely areas of flood-producing rains and place the experimental basins in the context of such diurnal rain occurrence. This work was supported by the use of 6-hourly surface winds reanalysis data from NCEP and NCAR at a spatial resolution of 2.5 ̊ x 2.5 ̊.


  • Krishnaswamy J., V. Srinivas, R. Balaji, M. Bonell, M. Sankaran, R. S. Bhalla, S. Badiger. 2014. Non-stationary and non-linear influence of ENSO and Indian Ocean Dipole on the variability of Indian monsoon rainfall and extreme rain events. Climate Dynamics (August 23): 1-10. doi:10.1007/s00382-014-2288-0
  • Bhalla, R. S., K. V. Devi Prasad and Neil W. Pelkey. 2013. Impact of India’s watershed development programs on biomass productivity. Water Resources Research 49 (3): 1568–1580. doi:10.1002/wrcr.20133
  • Krishnaswamy. J., M. Bonell, B. Venkatesh, B. K. Purandara, K. N. Rakesh, S. Lele, M. C. Kiran, V. Reddy and S. Badiger. 2013. The groundwater recharge response and hydrologic services of tropical humid forest ecosystems to use and reforestation: support for the "infiltration-evapotranspiration trade-off hypothesis. Journal of Hydrology 498 (August 19): 191-209. doi:10.1016/j.jhydrol.2013.06.034
  • Krishnaswamy, J., M. Bonell, B. Venkatesh, B. K. Purandara, S. Lele, M. C. Kiran, V. Reddy, S. Badiger, and K. N. Rakesh. 2012. The rain–runoff response of tropical humid forest ecosystems to use and reforestation in the Western Ghats of India. Journal of Hydrology 472–473 (November 23): 216–237. doi:10.1016/j.jhydrol.2012.09.016



Jagdish Krishnaswamy, Senior Fellow and Convenor, Suri Sehgal Centre for Biodiversity and Conservation, is one of India’s leading landscape hydrologists, combining expertise on surface hydrology, dynamic models, applied statistics and applications of remote sensing in quantifying and mapping ecosystem services. He has worked on hydrological processes at multiple spatio-temporal scales, from soil plots to catchments across the globe. Jagdish Krishnawamy will contribute to study design, hydrologic modeling, and Bayesian statistical modelling.

Shrinivas Badiger, Fellow, is a hydrologist with expertise in surface and groundwater interactions in agricultural landscapes. His interests are in understanding the agricultural land-use change linkages with hydrologic regimes, more specifically in ways spatial and temporal patterns of irrigation and rainfed systems co-influence the stream flow and groundwater recharge patterns He has extensive experience applying hydrologic modelling within a GIS frame-work as mediated by climate uncertainties. Shrinivas Badiger will contribute to the study design of process dynamics in the agro-ecological system and its linkages to the hydrologic cycle including forest ecosystems.


Mahesh Sankaran (Reader) is a community ecosystem ecologist with extensive experience in tropical ecosystems in India and Africa. His expertise lies biodiversity-ecosystem function relationships, biogeochemical cycling and tropical ecosystem ecology, and is interested in understanding these interactions in relation to climate change. Mahesh Sankaran will contribute to the the quantification of carbon patterns and dynamics and jointly analyzing the trade-offs and synergies between carbon functions and hydrologic functions with Jagdish.


R.S.Bhalla (Sr. Research Fellow). His main area of work is community based natural resources management with focus on watersheds and coastal areas. His PhD analyses the policy framework for India's watershed development programmes (Bhalla, et al., 2010). He has published on the role of natural defences against coastal hazards (Baird, et al., 2010). He makes extensive use of spatially explicit and quantitative tools in his research which has largely been supported by the Dept. of Science and Technology, FAO and UNDP.

Srinivas Vaidyanathan (Sr. Research Fellow) His research interest lies in integrating landscape processes, biodiversity and ecology. His recent publication (Vaidyanthan et al, 2010) with Jagdish Krishnaswamy demonstrates the complex linkage between rainfall trends and human impacts on tropical forests dynamics in India.
Srinivas Vaidyanathan and R.S. Bhalla will contribute to the GIS and remote sensing components including analysis and running models and simulations.


Michael Bonell, a recognized global expert on tropical forest hydrology, established the integration of surface water-groundwater-ecohydrology applications across international hydrology whilst a staff member of UNESCO-Paris (Turner et al. 2006; Smith et al. 2008). Bonell was the first to demonstrate that large storage capacity in deep groundwater is more closely coupled with hillslope hydrology than was previously thought.
Mike Bonell was to contribute to the study of streamflow responses to rainfall and rainfall intensity regimes.

Note: Unfortunately, Prof Bonell demised on july 11 2014.

This three-year project is jointly supported by the Ministry of Earth Sciences, Government of India and the Natural Environmental Research Council of the UK, and includes researchers from the National Centre for Biological Sciences, Bangalore; Foundation for Ecological Research Advocacy and Learning, Pondicherry, University of Dundee and Lancaster University.