Hydrologic and carbon services in the Western Ghats

A rain gauge installed in the Aghanashini basin, 2012

The full title of the project is "Hydrologic and Carbon Services in the Western Ghats: Response of Forests and Agro-ecosystems to Extreme Rainfall Events".

Background to the project

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

This is an inter-disciplinary project with four 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.

The UK contribution (University of Dundee and Lancaster University) will focus on Objective 1 with our Indian partners taking the lead on the other objectives.

The NERC team will work with the MoES Indian partners in developing close working links with the Indian Meteorological Department and other Government agencies as part of the identification and analyses of atmospheric and satellite information linked with different rain – producing systems across scales. Data will also be compiled from the existing (but sparse) network of rain gauges and river flow from State and water resource agencies. In addition, new data will be generated by the establishment of a dense rain gauge network in four (4) research basins (~100km2) (sampling both the SW and NE monsoon) as part of the analysis of the temporal and spatial characteristics of rainfall for specific events across scales. These basins will also be instrumented with a nested network of runoff gauging stations.

Location of study basins and schematic nested hierarchical design

Deliverables

Deliverables include:

  • Classification of storms based on the coupling with atmospheric processes -synoptic meteorology (the dynamics of rainfall generating mechanisms) (e.g., Lyons and Bonell, 199, 1994; Yarnall et al, 2001; Wang and Chen, 2008)
  • Enhanced understanding of the spatial-temporal variability of rainfields, i.e., the Houze model, (convective, stratiform, intensity, total) by event linked with ERE (Houze, 1989, Romatschke and Houze, 2011)
  • A contribution towards the development of a rain intensity map for Western Ghats
  • A contribution towards the lack of global availability of in situ precipitation measurements over complex mountainous terrain linked with the need for more calibration of satellite precipitation estimates (Ward et al, 2011)
  • Rainfall, and rain-runoff modelling - Lancaster modelling component will quantify the characteristics of the extreme rainfall properties for raingauge data from the Western Ghats and their evolution over time as applied elsewhere in the humid tropics (Chappell et al, 2009). The relationship of these characteristics to those of the rainfall-runoff behaviour during large rain events within basins of contrasting land-cover will then be quantified using Lancaster’s own CAPTAIN toolbox for time-series analysis (Taylor et al., 2007; Chappell et al, 2006)

Key project members

UK partners

Principal Investigator: Michael Bonell, University of Dundee

Co-Investigators:

Nick Chappell, Lancaster Environment Centre, Lancaster University

Wlodek (Włodzimierz) Tych, Lancaster Environment Centre, Lancaster University

India partners funded by the Govt. of India, Ministry of Education and Science (MoES)

Principal Investigator: Jagdish Krishnaswamy, The Ashoka Trust for Research in Ecology and the Environment (ATREE)

Co-Investigators:

Shrinivas Badiger, (ATREE)

Mahesh Sankaran, National Centre for Biological Sciences (NCBS)

R.S.Bhalla, Foundation for Ecological Research, Advocacy and Learning (FERAL)

Project members at the inaugural Steering meeting

Selected references

Blöschl, G., Ardoin-Bardin, S., Bonell, M., Dorninger, M., Goodrich, D., Gutknecht, D., Matamoros, D., Merz, B., Shand, P., Szolgay, J. 2007. At what scales do climate variability and land cover change impact on flooding and low flows? Hydrol Process 21:1241–1247

Chappell, N.A., Tych, W., Chotai, A., Bidin, K. Sinun, W., Thang H.C. 2006. BARUMODEL: Combined Data Based Mechanistic models of runoff response in a managed rainforest catchment. Forest Ecology and Management 224: 58-80.

Chappell, N.A., Discenza, A.R., Tych, W., Whittaker, J., Bidin, K. 2009. Simulating hourly rainfall occurrence within an equatorial rainforest, Borneo Island. Hydrological Sciences Journal 54(3), 571-581.

Houze, R. A. 1989. Observed structure of mesoscale covective systems and implications for large-scale heating. Q. J. R. Met. Soc. 115: 425–461.

Lyons, W. F. and Bonell, M. 1992. Daily, meso-scale rainfall in the tropical wet/dry climate of the Townsville area, North-East Queensland during the 1988–1989 wet season: synoptic-scale airflow considerations. Int. J. Climatol. 12: 655–684.

Lyons, W. F. and Bonell, M. 1994. Regionalization of daily mesoscale rainfall in the tropical wet/dry climate of the Townsville area of North-East Queensland during the 1988–1989 wet season. Int. J. Climatol. 14: 135– 163.

Romatschke, U., Houze, R.A. 2011. Characteristics of Precipitating Convective Systems in the South Asian Monsoon. J.Hydrometeorology 12: 3-26.

Taylor, C.J., Pedregal, D.J., Young, P.C., Tych, W. 2007. Environmental time series analysis and forecasting with the CAPTAIN toolbox. Environ. Model. Software 22: 797–814.

van Dijk, A.I.J.M., van Noordwijk, M., Calder, I.R., Bruijnzeel, L.A., Schellekens. J., Chappell, N.A. 2009. Forest– flood relation still tenuous – comment on ‘Global evidence that deforestation amplifies flood risk and severity in the developing world’ by C. J. A. Bradshaw, N. S. Sodi, K. S.-H. Peh and B. W. Brook. Glob. Chang Biol 15:110–115. doi:10.1111/j.1365-2486.2008.01708.x

Yarnal, B., Comrie, A.C., Frakes, B., Brown, D.P. 2001. Review: Developments and prospects in synoptic climatology. International Journal of Climatology 21: 1923–1950. DOI: 10.1002/joc.675.

Wang, S-Y., Chen, T-C 2008. Measuring East Asian Summer Monsoon Rainfall Contributions by Different Weather Systems over Taiwan. Journal of Applied Meteorology and Climatology 47: 2068-2080. DOI: 10.1175/2007JAMC1821

Ward, E., Buytaert, W., Peaver, L. Wheater, H. 2011. Evaluation of precipitation products over complex mountainous terrain: A water resources perspective. Advances in Water Resources 34: 1222-1231.

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