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HUMID TROPICS - Homage à
Bultot
The hydrology and water management of the humid tropical regions has been and is one of the priorities of IHP.
The origins of the Humid Tropics Hydrology Programme date back to 1987, coinciding with an IHP Working Group meeting held at the University of Hawaii's Water Resources Center. In recognition of the escalating socio-economic problems of the humid tropics and the urgency of the need to address associated water management issues, it was proposed that a more comprehensive programme needed to be developed under the auspices of IHP. An international meeting was suggested to formulate the directions of this programme. Subsequently, this was held at the James Cook University in Townsville, Australia in 1989, entitled `International Colloquium on the Development of Hydrologic and Water Management Strategies in the Humid Tropics'. A series of recommendations on follow-up actions emanated from that Colloquium which are currently being implemented in Member States and form the backbone of UNESCO's Humid Tropics Hydrology Programme.
During the Fourth Phase of IHP which ended last December, the Humid Tropics Hydrology Programme grew and expanded into various regional activities while supporting the development of improved methodologies to model the land phase of the hydrological cycle that represents a major feed-back in the climate system. Still, if someone looks at how this land phase is generally handled in global scale models the picture is rather disturbing. Areas of continental size are often represented by simple elementary reservoirs. Therefore, the hydrological uncertainties and risks associated with different climate change scenarios are still too great - H.R.H. Prince Laurent of Belgium also pointed this out in his address - not only due to our limited understanding but also due to the very limited data available. Again, there are continents where there are less hydrological data than in a medium-sized industrialized country. Thus, it is an extremely important mission to build up and maintain endogenous, hydrological science capacities in the developing world. This is not only a moral obligation but also a rational must. Take, for example, Africa, where the hydrological capacity is less than it was fifteen years ago. There are more data on the hydrology of Africa outside the continent than inside. So, how can we talk of understanding and modelling global processes if the sample data sets refer almost exclusively to the developed world? Any conclusion drawn from such data is necessarily biased and subject to huge uncertainties. We need to focus all our efforts on changing this bad situation. Of course, it is primarily not the global modelling that necessitates smoothly running operational data collection services, but rather the dire needs of the countries concerned. This is one of the points Franz Bultot never stopped emphasizing.
A host of IHP activities have recently taken place concerning humid tropics hydrology in Latin America and the Caribbean. With the launching of the UNESCO-sponsored Regional Center for Humid Tropics Hydrology in Panama City, with the strong support of the Panamanian and US Governments, activities took a new momentum. In the meantime the hydrology component of a large-scale, multidisciplinary field experiment in the Amazon basin, known as LBA which stands for: Large-Scale Biosphere-Atmosphere Experiment in the Amazon Basin, is being planned in conjunction with the biohydrological core project of the International Geosphere/Biosphere Programme of ICSU. The establishment of a Regional Humid Tropics Hydrology Center for South-East Asia and the Pacific is currently being negotiated.
All these IHP Centers will ultimately be devoted to assisting sustainable development as it is absolutely clear that the growing population in the humid tropics obviously requires that future actions be carried out in terms of sustainable development. Several reasons have encouraged some clearly unsustainable development policies and practices concerning water management in developing nations of the humid tropics. Environmentally unsound development of the water and related sources has been further aggravated by the rapid economic, social and political changes resulting from the rapidly growing tropical urban populations. This complex social structure, combined with a lack of knowledge of hydro-ecological relationships of the natural systems clearly shows that the humid tropics is an extremely vulnerable environment that, acting as a boiler for the climate system, is also of great importance from a global change perspective.
It has been estimated that by the year 2000 the countries within the humid tropics and the other warm humid regions will represent almost one-third of the total world population. This proportion will continue to rise in the twenty-first century. The humid tropics regions are quite clearly the zones which are potentially facing the most serious social and economic problems.
For example, it is common knowledge that small tropical islands are particularly subject to an ever-increasing risk concerning their water management.
The pertinent question to ask is: what is special about tropical islands in terms of their hydrology and water management? The `low' or `atoll' islands present a distinctive physical basis for the occurrence of ground water, the so-called `freshwater lenses'. In fact the term `freshwater lens' is a misnomer because there is no distinct fresh water body floating on sea water. In reality there is a gradual transition from the freshest water at the water table to sea water at depth. Comprehensive knowledge of the physical basis of such water bodies, application of the most appropriate groundwater models, and in turn, their management to avoid their temporary or even irreversible destruction by sea-water intrusion poses major problems. Otherwise there is `nothing special' about tropical islands - the problems highlighted apply to other coastal areas as well, e.g. water quality/pollution issues of both surface and subsurface water bodies, hydrological impacts from the conversion of forests (on high islands), coastal saline intrusion of groundwater aquifers connected with high islands and last but not least the possible impact of sea level rise. What enhances the environmental focus of attention on islands in general is their sheer limited size which make their natural resources extremely vulnerable to environmental mismanagement in response to socio-economic pressures for development. Their limited areas and the conflicting as well as competing demands on natural resources, such as a limited water supply, is further aggravated by the escalation in population densities in many islands.
Paradoxically, at a time when potable water demands are increasing in response to population and tourism pressures, the limited freshwater resource is the ultimate recipient of all the pollution resulting from various socio-economic activities associated with urbanization, agriculture, conversion of native vegetation.
It is urgent to question whether the fields of hydrology and water resources management have the appropriate methods in place to meet the rising demands that will be made on the water resources of the humid tropics and other warm humid regions. The analysis of humid tropical hydrological phenomena at different scales is of utmost importance and a matter of urgency, particularly in light of the critical role the humid tropics play in the global atmospheric and hydrological processes. As I mentioned already, with the present level of data availability in the humid tropics there is no hope of reducing uncertainties in any global consideration.
Some of the most urgent hydrological and water resource management problems that need to be addressed from an integrated environmental and socio-cultural perspective include the issues of:
The General Conference of UNESCO, held last October, approved the continuation of the International Hydrological Programme into its Fifth Phase which will be devoted to `Hydrology and water resources development in a vulnerable environment' and will lead us into the next century. Out of the eight themes of IHP-V one theme is dealing with humid tropics problems with the basic aims of: .
First, assessing the vulnerability of the humid tropical environment with
respect to different water and land use techniques to assure sustainable
development at short-term and long-term scales;
Second, developing networks of water and water-related experts and research
organizations involved in warm humid regions hydrology and water management
studies.
Third, evaluating, understanding and defining the spatial and temporal
variability of key hydrological variables along with the modelling of
hydrologic processes in the tropics at different scales;
Fourth, evaluating the impact of human activities on the hydrological cycle of
the tropical forests to better understand the global climate system.
To reach these goals interdisciplinary co-operation is required between tropical hydrologists, climatologists and meteorologists. We are very grateful to the organizers, the Belgian authorities and the various sponsoring agencies for making this event, which is an extremely important contribution to IHP, possible. Special thanks also go to Professor Gaston Demarée for the enormous amount of work he put into this venture.
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