Multiscale TROPical CatchmentS (M-TROPICS)

Experimental Tropical Watersheds

M-TROPICS Critical Zone Observatories

The CZO Multiscale TROPIcal CatchmentS (M-TROPICS) consists in the merging of two previously-existing CZOs: BVET (India and Cameroon) and MSEC (Laos, Vietnam, Thailand). The CZO M-TROPICS is included in OZCAR, the French contribution to the international CZO initiative.

The CZO M-TROPICS provides the international scientific community with unique decennial time series of climatic, hydrological and geochemical variables in tropical environments.

More specifically, the CZO M-TROPICS aims at (1) determining the fluxes of water, of inorganic and organic matter present in solution (major anions and cations, carbon) and in suspension (particulate organic carbon); (2) proposing budgets of chemical weathering and physical erosion; and (3) evaluating the impact of global change (land-use, climate) upon the above parameters.

Its strengths are (1) multiscale approaches, both in space (from micro-plot to catchment and larger river basins) and in time (from hourly to multi-decennial time-series); and (2) multidisciplinary approach, currently involving hydrology, biogeochemistry, soil science, agronomy, remote sensing, ecology, experimentation and modelling.

Rationale:

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 availability of life sustaining resources. This concept allows bringing together scientific disciplines in the aim to tackle crucial environmental issues regarding how the various components of the CZ interact with global change, including land use and climatic changes? More specifically, what are the impacts of the conversion of annual to perennial crops upon biodiversity, soils, hydrological, sedimentary and biogeochemical fluxes within the catchments, and with which off-site effects? What are the consequences of climate variability and climate change upon these CZ components and these fluxes?

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 simultaneously time series of climate, hydrology and 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 modeling and for proposing predictive scenarios.

Among the Critical Zone Observatories (CZOs) that have been implemented by the Earth Science community in the past 25 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.

Articles

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 […]

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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 […]

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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 […]

Articles

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

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Understory limits surface runoff and soil loss in teak tree plantations of northern Lao PDR

Many mountainous regions of the humid tropics experience serious soil erosion following rapid changes in land use. In northern Lao PDR, the replacement of traditional crops by tree plantations, such as teak trees, has led to a dramatic increase in floods and soil loss and to the degradation of basic soil ecosystem services. In this […]

Articles

Surface and sub-surface flow estimation at high temporal resolution using deep neural networks

Recent intensification in climate change have resulted in the rise of hydrological extreme events. Hydrological processes modelling at high temporal resolution is required to better understand flow patterns at catchment scale. A physically-based model called Hydrological Simulated Program-FORTRAN and two deep learning-based models were implemented to model surface runoff and sub-surface flow in the tropical […]

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