Multiscale TROPical CatchmentS (M-TROPICS)

Experimental Tropical Watersheds

M-TROPICS Critical Zone Observatories

The CZO Multiscale TROPIcal CatchmentS (M-TROPICS) provides the international scientific community with unique decennial time series of meteorological, hydrological, geochemical, and ecological variables in tropical environments. The CZO M-TROPICS involves academic and governmental partners in tropical countries (Cameroun, India, Lao PDR, and Vietnam) and is included in the Research Infrastructure OZCAR, the French contribution to the international CZO initiative.


  • Long-term monitoring of the variables needed for establishing water, biogeochemical (including particulate matter), and energy budgets: water and inorganic and organic matter in solution (major anions and cations, carbon), in suspension (suspended particulate matter, including organic carbon), and bed particulate matter
  • Impact assessment of global change (land-use, climate) on water fluxes, chemical weathering, and physical erosion
  • Data and information dissemination to the scientific and stakeholder communities
  • Capacity building in the field of catchment hydrology and soil erosion, through on-the-job training, teaching, and student internships, and basic geochemistry through analytical platforms
  • Recommendations on land use policy to the national authorities


  • Multiscale approaches, both in space (from microplot to catchment and larger river basins scales) and time (from sub-hourly to multi-decennial time-series)
  • Multidisciplinary approaches, currently involving hydrology, biogeochemistry, soil science, agronomy, ecology, remote sensing, experimentation, and modelling


Besides data collection and dissemination, the achievements of M-TROPICS on May 2021 are:

  • 235 scientific publications in international journals
  • 32 scientific publications in national journals
  • 1 special issue in the Lao Journal of Agriculture and Forestry (2008): Management of soil erosion and water resources in the uplands of Lao P.D.R., by Ribolzi O. (Ed.), Pierret A. (Ed.), Gebbie L. (Ed.), Sengtaheuanghoung O. (Ed.), and Chanphengxay M. (Pref.)
  • 57 PhDs, 7 post-docs, and 281 MSc, BSc and Agric. Eng. degrees


Hand pump well, Berambadi catchment.

The Earth Critical Zone (CZ) is defined as the thin layer between the top of the canopy and the bottom of groundwater aquifer in which complex interactions involving rock, soil water, air and living organisms regulate the natural habitat and determine the availability of life sustaining resources. This concept brings together scientific disciplines in the aim to tackle crucial environmental issues regarding how the various components of the CZ react to global changes, including land use and climate changes:

  • What are the water, solute, and particulate fluxes exported from tropical catchments?
  • What is the impact of rapid land use changes on hydrology, water quality, soil resources?

The strategies adopted to answer these questions are often integrated approaches on experimental catchments, where hydrological, sedimentary, biogeochemical and ecological studies can be coupled. Acquiring simultaneous time series of meteorological, hydrological, geochemical, and ecological data over decades on river systems (both small experimental watersheds and larger basins) representative of the diversity of ecosystems is pivotal for the understanding of these processes, building integrated modelling and for proposing predictive scenarios.

Houay Pano catchment.

Among the Critical Zone Observatories (CZOs) that have been implemented by the Earth Science community in the past 30 years, very few were set up in the Tropics despite the huge importance of these regions in terms of population density, fast-changing land use, biodiversity hotspots, biomass stock on continents (humid forests), size of river systems. In addition, rainfall in the Tropics is mostly governed by monsoon systems, which are particularly sensitive to climate change.


The M-TROPICS CZO releases long-term meteorological, hydrological, sedimentary geochemical, and land use datasets in Cameroon, Lao PDR, and India

The CZO M-TROPICS (Multiscale TROPIcal CatchmentS) investigates the response of tropical catchments to global change based on long-term collection of meteorological, hydrological, sedimentary, geochemical, and land use data in partnership with academic and governmental institutions in various tropical countries. M-TROPICS includes in particular the experimental watersheds of Nyong in Cameroon (1994-), Houay Pano in Lao […]


Response of tropical experimental catchments to global changes: the M-TROPICS CZO network

Jean Riotte (IRD) presented the key questions and findings from the three experimental catchments Nyong (Cameroon), Mule Hole (India), and Houay Pano (Laos), at the Cyberseminar Series of CUAHSI: “Research and Observatory Catchments: the Legacy and the Future” on March 10. This presentation is related to the submission of three data papers to the eponymous […]


Experimental and modelling evidence of splash effects on manure borne Escherichia coli washoff

In tropical montane South-East Asia, recent changes in land use have induced increased runoff, soil erosion and instream suspended sediment loads. Land use change is also contributing to increased microbial pathogen dissemination and contamination of stream waters. Escherichia coli (E. coli) is frequently used as an indicator of faecal contamination. Field rain simulations were conducted […]


Special Issue “Multiscale Impacts of Anthropogenic and Climate Changes on Tropical and Mediterranean Hydrology”

This Special Issue published in the Water journal and co-authored by Olivier Ribolzi (IRD-GET) shows the great interest of the scientific community in investigating how to characterize the environmental impact of anthropogenic and climatic changes on Tropical and Mediterranean hydrology, and also in determining which is the main source of changes depending on the regional […]


Effects of hydrological regime and land use on in-stream Escherichia coli concentration in the Mekong basin, Lao PDR

In the basin of Mekong, over 70 million people rely on unimproved surface water for their domestic requirements. Surface water is often contaminated with fecal matter and yet little information exists on the underlying mechanisms of fecal contamination in tropical conditions at large watershed scales. The objectives of this paper were to (1) investigate the […]


Quantifying the effect of overland flow on Escherichia coli pulses during floods: use of a tracer-based approach in an erosion-prone tropical catchment