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Köppen Scheme of Classification Modified by Trewartha (1961)
A. Tropical forest climates; all months above 18°C.
C. Humid sub-tropical.
a. Warmest month above 22°C.
b. Warmest month below 22°C.
c. Less than 4 months above 10°C.
d. Less than 4 months below 10°C.
f. Constantly moist, rainfall every month of year.
s. Dry season in summer.
w. Dry season in winter.
m. Monsoonal rain, short dry season, yearly rainfall sufficient to support tropical rain forest.
Symbols and abbreviations
E0 evaporation from an open water
surface calculated by Penman's equation.
I interception loss
IITA International Institute of Tropical Agriculture
K coefficient of soil permeability
MAB Man and the Biosphere
WMO World Meterological Organization
Bahadur, P., S. Chadra, and D. K. Gupta. 1980. "Hydrological studies on experimental basins in the Himalayan region." In Proceedings of Symposium on the Influence of Man on the Hydrological Regime with Special Reference to Representative and Experimental Basins, Helsinki, IAHS Publ. No. 130, pp. 163-170.
Bailly, C., G. Benoit de Coignac, C. Malves, J. M. Ningre, and J. M. Sarrailh. 1974. Etude de l'influence du couvert naturel de ses modification a Madagascar. Cah. Sc. Publ. Cent. Tech. Trop., Oct. (No. 4), 14 pp.
Benham, A. D. 1974. Determination of the monthly, seasonal, annual, or long-term average yield of a stream. U.N. Water Resources Series No. 34, pp. 56-62.
Bernhard-Reversat, E, C. Jattel, and G. Lemec. 1972. "Quelques aspects de la periodicité écologique et de l'activité végétale saisonnière en fores ombrophile sempervirente de Côte d'lvoire." In F. B. Golley and P. M. Golley, eds., Tropical ecology with emphasis on organic production, pp. 214-234. University of Georgia, Athens, Gal, USA.
Bethlahmy, D. 1963. "Rapid calibration of watersheds for hydrologic studies." IASH Bull., 8 (3): 3842.
Blackie, I. R. 1972. "Hydrological effects of a change in land use from rain forest to tea plantation in Kenya." In Proceedings of Symposium on the Results of Research on Representative and Experimental Basins, Wellington, NZ, IAHS Publ. No. 97, pp. 312-329.
Bonell, M., D. A. Gilmour, and D. S. Cassells. 1983. "Runoff generation in tropical rainforests of north-east Queensland, Australia, and the implications for land use management." In R. Keller, ea., Proceedings of Symposium on the Hydrology of Humid Tropical Regions, Hamburg, IAHS Publ. No. 140, pp. 287-297.
Bordas, M. P., and G. E. Canali. 1980. "The influence of and use and topography on the hydrological and sedimentological behaviour of basins in the basaltic region of South Brazil." In Proceedings of Symposium on the Influence of Man on the Hydrological Regime with Special Reference to Representative and Experimental Basins, Helsinki, IAHS Publ. No. 130, pp. 55-60.
Bosch, J. M. 1979. "Treatment effects on annual and dry period streamflow at Cathedral Peak." S. Africa For. J., 108: 29-38.
———. 1982. "Streamflow response to catchment management in South Africa." In Proceedings of Symposium on Hydrological Research Basins and Their Use in Waler Resources Planning, Sonderh, Landeshydrologie, Bern, pp. 279-289.
Bosch, J. M., and J. D. Hewlett. 1982. "A review of catchment experiments to determine the effect of vegetation changes on water yield and evapotranspiration." J. Hydrol., 55: 3-23.
Bruijnzeel, L. A. 1983. "Evaluation of runoff sources in a forested basin in a wet monsoon environment: A combined hydrological and hydrochemical approach." In R. Keller, ea., Proceedings of Symposium on the Hydrology of Humid Tropical Regions, Hamburg, IAHS Publ. No. 140, pp. 165-174.
Brunig, E. I. 1977. "The tropical rain forest: A wasted asset or an essential biospheric resource?" Ambio, 6 (4): 187-191.
Cailleux, A. 1959. Etudes sur l'érosion et la sedimentation en Guyane. Mem. Serv. Carte Geol. Fr., pp. 49-73.
Colman, E. A. 1953. Vegetation and watershed management. The Ronald Press Co., New York.
Dabin, B. 1957. "Note sur le fonctionnement des parcelles expérimentales de l'érosion a la station d'Apiopodioume (Côte d'lvoire)." Dakar, Décret Permanent Bureau Sols AOF. Mimeographed. 16 pp.
Dickenson, R. E. 1980. "Effects of tropical deforestation on climate." In Blowing in the wind: Deforestation and long range implications, pp. 411 -441. Studies in Third World Societies, no. 14, College of William and Mary, Dept. of Anthrop., Williamsburg, Va., USA.
Edwards, K. A., and J. R. Blackie. 1981. "Results of the East African catchment experiments 195874." In Tropical agricultural hydrology pp. 163-188. See Lal and Russell 1981.
Gilmour, D. A., D. S. Cassells, and M. Bonell. 1982. "Hydrological research in the tropical rainforests of north Queensland: Some implications for land use management." In Proceedings of the First National Symposium on Forest Hydrology, Melbourne, 11-13 May, pp. 145-151.
Golding, D. C. 1980. "Calibration methods for detecting changes in streamflow quantity and regime." In Proceedings of Symposium on the Influence of Man on the Hydrological Regime with Special Reference to Representative and Experimental Basins, Helsinki, IAHS Publ. No. 130, pp. 3-7.
Gupta, R. L. 1980. "Consequences of deforestation and over-grazing on the hydrological regime of some experimental basins in India." In Proceedings of Symposium on the influence of Man on the Hydrological Regime with Special Reference to Representalive and Experimenta/ Basins, Helsinki, IAHS Publ. No. 130, pp. 81-87.
Henderson-Sellers, A. 1981. "Climate sensitivity variations in vegetated land surface albe dos." In Proceedings of the Sixth Annual Climate Diagnostics Workshop, Columbia University, New York, pp. 135-144.
Hibbert, A. R. 1967. "Forest treatment effects on water yield." In Intl. Symp. on Forest Hydrol., pp. 527-543. See Sopper and Lull 1967. d'Hoore, J. D. 1961. "Influence de la mise en culture sur l'evolution des sols den la fores dense de basse et moyenne altitude." In Proceedings of Symposium on Humid Tropical Zone, Abidjan, 1959, pp. 49-58. Unesco.
Hopkins, B. 1960. "Rainfall interception by a tropical forest in Uganda." East African Agr. and Forest J., 25: 225-228.
Asia, Y. J., and C. C. Kohl 1983. "Water yield resulting from clear cutting a small hardwood basin in Central Taiwan." In R. Keller, ea., Proceedings of Symposium on the Hydrology of Humid Tropical Regions, Hamburg, IAHS Publ. No. 140, pp. 215-220.
Jackson, I. J. 1971. "Problem of throughfall and interception assessment under tropical forest." J. Hydrol., 12: 234-254.
Kartawinata, K., S. Adisoemarto, S. Riswan, and A. P. Vayda. 1981. "The impact of man on a tropical forest in Indonesia." Ambio, 2: 115.
Kirby, M. J., and R. J. Chorley. 1967. "Throughflow, overland flow and erosion." IASH Bull., 12: 521.
Klinge, H., K. Furch, U. Irmler, and W. S. Junk. 1981. "Fundamental ecological parameters in Amazonia in relation to the potential development of the region." In Tropical agricultural hydrology, pp. 19-36. See Lal and Russell 1981.
Kovner, J. L., and T. C. Evans. 1954. A method for determining the minimum duration of watershed experiments. Trans. Amer. Geophys. Un., 35: 608-612.
Lal, R. 1983. "Soil erosion in the humid tropics with particular reference to agricultural land development and soil management." In R. Keller, ea., Proceedings of Symposium on the Hydrology of Humid Tropical Regions, Hamburg, IAHS Publ. No. 140, pp. 221-240.
Lal, R., and E. W. Russell, eds. 1981. Tropical agricultural hydrology. John Wiley and Sons, Chichester, UK.
Lawson, T. L., R. Lal, and K. Oduro-Afiriyie. 1981. "Rainfall distribution and microclimate changes over a cleared watershed." In Tropical agricultural hydrology, pp. 141-152. See Lal and Russell 1981.
Lettau, H., K. Lettau, and L. C. B. Molion. 1979. "Amazonia's hydrologic cycle and the role of atmospheric recycling in assessing deforestation effects." Monthly Weather Review, 107 (3): 227238.
Lockwood, J. G. 1976. The physical geography of the tropics An introduction. Oxford University Press, London.
Lomee, O. 1961. "Effete de caractères du sol localisation la vegetation en zones équatoriale humide." In Proceedings of Symposium on Humid Tropical Zone, Abidjan, 1959, pp. 25-39. Unesco.
Marques. J., J. M. Santos, N. A. Vilanova, and E. Salati. 1977. "Precipitable water and water vapour flux between Belem and Manaus." Acta Amazônica, 7 (3): 355-362.
Mathur, H. N., R. Babu, P. Joshik, and R. Singh. 1976. "Effect of clearfelling and reforestation on runoff and peak rates in small watersheds." The Indian Forester, 102: 219-226.
Mistry, P. C., and B. N. Chatterji. 1965. "Infiltration capacities and soils in Ranchi." J. Soil and Wat Cons. India., 13: 43-47.
Molchanov, A. A. 1%3. The hydrological role of forests Israel Programme for Scientific Translations, Jerusalem.
Molion, L. C. B. 1975. "A climatonomic study of the energy and moisture fluxes of the Amazonas
Basin with considerations of deforestation effects." Ph.D. dies., University of Wisconsin, Madison. Report no. INPE 923 TFT/035, 1976, Instituto de Pesquisas Espaciais, S. J. dos Campos, S. P., Brazil.
Myers, N. 1981. "The hamburger connection: How Central America's forests become North America's hamburgers." Ambio, 10 (1): 3-8.
Nänni, U. W. 1970. "Trees, water and perspective." S. Africa For. J., 75: 9-17.
Newell, R. C. 1971. "The Amazon forest and atmospheric general circulation." In W. H. Matheus, W. Kellog, and G. D. Robinson, eds., Man's impact on the climate. MIT Press, Cambridge, Mass., USA.
Pereira, H. C. 1962. "Hydrological effects of changes in land use in some African catchment areas." East African Agr. and Forest. J. 27 (Special issue), 131 pp.
———. 1973. Land use and waler resources. Cambridge University Press, Cambridge, UK. Pereira, H. C., M. Dagg, and P. H. Hosegood. 1961. "An intensive method of catchment basin study." In Inter-African Conference on Hydrology CCAT/CSA Publ. No. 66, pp. 325337.
Potter, G. L., H. W. Ellsaesser, M. C. MacCracken, and F. M. Luther. 1975. "Possible impact of tropical deforestation." Nature, 258: 697-698.
Raghunath, B., D. C. Das, and P. K. Thomas. 1970. "Some results of investigations on hydrology of the sub-watersheds in the Nilgiris (India)." In Proceedings of Symposium on the Results of Research on Representative and Experimental Basins, Wellington, NZ., IAHS Publ. No. 96, pp. 416-440.
Reinhart, K. G. 1967. "Watershed calibration methods." In Intl. Symp. on Forest Hydrol. See Sopper and Lull 1967.
Richards, P. W. 1964. The tropical rainforest: An ecological study. Cambridge University Press, Cambridge, UK.
Roche, M. A. 1981. "Watershed investigations for development of forest resources of the Amazon region in French Guiana." In Tropical agricultural hydrology pp. 75-82. See Lal and Russell 1981.
Rodier, J. 1959. Some data on stream flow in equatorial forests. Association Internationale d'Hydrologie Scientifique, Gentbrugge, no. 48, pp. 155-163.
Rougerie, G. 1960. La façonnement actuel des modèles en Côte d'Ivoire forestière. Mem. Institut Franèais d'Afrique Noire, no. 58, 542 pp.
Salati, E., O. A. Dall'olio, E. Matsui, and J. R. Gat. 1979. "Recycling of water in the Amazon basin: An isotopic study." Waler Res. Res., 15 (5): 1250-1258.
Salati, E., and E. Matsui. 1981. "Isotopic hydrology in the Brazilian Amazon Basin." Inter-American Symposium on Isotope Hydrology Bogota, Colombia, August 1980, Instituto de Asuntos Nucleares, Bogota, pp. 111-120.
Sharp, A. L., A. E. Gibbs, W. J. Owen, and B. Harris. 1960. "Application of the multiple regression approach in evaluating parameters affecting water yield of river basins." J. Geophys. Res., 65: 1273-1286.
Singh, T. 1974. A simplified procedure for detecting changes of specified magnitude on paired plots and watersheds. Fisheries and Environment Canada Forest Service. North Forestry Research Centre Info. Report NOR-X-198.
Sopper, W. E., and H. W. Lull, eds. 1967. International symposium on forest hydrology Pergamon Press, Oxford.
Swanson, R. H., and G. R. Hillman. 1977. Predicted increased wafer yield after clear-culling verified in west-central Alberta. Fisheries and Environment Canada Forest Service. North Forestry Research Centre Info. Report NOR-X-198.
Tejwani, K. G., S. K. Gupta, and H. N. Mathur. 1975. Soil and water conservation research 1959-1971, New Delhi 1-318: ICAR.
Tricart, J.  1973. The landforms of the humid tropics, forests, and savannas. St. Martin's Press, New York.
Tsukamoto, Y. 1975. "Effect of forest litter on runoff cycle in a small experimental watershed." In Proceedings of Symposium on the Hydrological Characteristics of River Basins, Tokyo, IAHS Publ. No. 117, pp. 487495.
Van Lill, W. S., E J. Kruger, and D. B. Van Wyk. 1980. "The effect of afforestation with Eucalyptus grandis Hill ex Maiden and Pinus patula Schlect. et Cham. on streamflow from experimental catchments at Mokobulaan, Transvaal." J. Hydrol., 48: 107-118.
Van Wyk, D. B. 1977. "Die invloed van bebossing met Pinus radiata op die totale jaarlikse aftvoer van die Jonkershoek storme." M.Sc. thesis, University of Stellerbosch, RSA, 206 pp.
Ward, R. C. 1971. Small watershed experiments. Occasional Papers in Geography No. 18, University of Hull, UK.
Wicht, C. L. 1961. "Comments on the design of catchment-management experiments." Paper prepared for the Inter-African Conference on Hydrology, Nairobi, CCTA Publication 66, 15pp.
———. 1967. "The validity of conclusions from South African multiple watershed experiments. In Intl. Forest Hydrol. See Sopper and Lull 1967.
Wilm, H. G. 1949. "How long should experimental watersheds be calibrated?" Trans. Amer. Geophys. Un., 30: 272-278.
WMO. 1983. "Operational hydrology in the humid tropical regions." In R. Keller, ea., Proceedings of Symposium on the Hydrology of Humid Tropical Regions, Hamburg, IAHS Publ. No. 140.
Zadroga, F. 1981. "The hydrological importance of a montane forest area of Costa Rica." In Tropical agricultural hydrology, pp. 59-73. See Lal and Russell 1981.
Assessments of the rate and degree of global and regional deforestation are generally accepted uncritically; any deforestation tends to be equated with absolute forest destruction. Regrowth may be so rapid, however, especially in the tropics, that at any time the area cleared due to forest exploitation may be hydrologically and climatologically insignificant. On the other hand, we must identify the vegetation types and the methods and objectives of forest clearance that preclude regrowth or, at any rate, delay it for a significant period. Forests that owe their existence to the microclimate they produce (such as cloud forests) or to the soils that in turn need their protection are examples of forests that are unlikely to regenerate in the short term after clearance, so that for many practical purposes it becomes irreversible. Where forest clearance is followed by periodic fires, often associated with grazing, a grass fire climax vegetation frequently replaces the forest. Thus the term deforestation should be carefully defined. Different interpretations of the term forest clearance wil apply depending on whether it relates to such diverse interests as forest resources surveys, the conservation of wildlife, soil conservation, landscape aesthetics, or surface parametrization for general circula tion models. Consequently, though very dissimilar, primary forest, secondary forest, plantation crops, and even orchards may be identical from the point of view of some hydrological or climatological studies.
For the purpose of relating vegetation change to regional climate, ecological classes and measurements of a vegetative cover related to its microclimatology, site hydrology, and plant-water relations are extremely useful Ecological methods and descriptions are too frequently considered to be ends in themselves rather than being possible tools to relate to ecosystem processes. Descriptions of vegetation incorporating canopy aerodynamic resistance and the water use strategy of the constituent plants (possibly based on rooting system and stomata! behaviour in relation to water stress) would be valuable, as would descriptions of the carbon reserves of different vegetation covers. While more detailed classification of vegetation types below formations and the life forms and plant architectures of different ecosystems undoubtedly distinguish vegetations with different hydrological and climatological properties, too little attention has been given to them. It is to be hoped that projects such as MAB and the Brazilian RADAM might be reinterpreted along these lines.
One ecological measurement that has been correlated with site hydrology is biomass (more specifically, that above ground). Thus the dry weight of above ground, living plant material may be related, for instance, with transpiration (although the major proportion of forest biomass will commonly be in the stems). However, biomass is a very heterogeneous quantity and is qualitatively different even between temperate and tropical forests. For instance, epiphytes such as the Bromeliads of tropical forests contribute little to the biomass, yet their water trapping adaptations are probably of considerable hydrological significance (incidentally this would be appreciated by most ecological classifications of vegetation types). Similarly biomass measurements fail to give recognition to the deciduous and evergreen components of the vegetation. The leaf area index (LAI) is suggested as a better ecological parameter of vegetation than biomass for correlating with such processes as transpiration, interception, and micrometeorological parameters such as rs and ra.
As yet too little attention has been paid to the infiltration of precipitation into the soil. Often earth surface models simply assume that no water drains from the site until the soil is wetter than field capacity. Thus the available soil water and, in turn, evaporation tend to be overestimated and runoff underestimated. The considerable effort by agronomists to measure infiltration and model it have been neglected by hydrologists relating earth surface and atmospheric processes. We feel that a study of the process in forest soils should reveal the cause of some of the anomalies in reports of water yields. It would also be helpful if data on hydrological processes were reported as absolute values rather than, or as well as, relative values. For instance, interception simply reported as a percentage of gross precipitation has little meaning unless one knows the local conditions. Similarly collation of data from different regions is helped if the measurements are independent of other variables.
It should be emphasized that a change in land use imposes a variety of effects on the site hydrology, some tending to increase and others tending to decrease the water yield. Forests behave like any other land use in this respect. Thus the prediction of the effects of tropical deforestation or afforestation is a complicated task. Successful prediction depends on detailed studies being carried out on every process contributing to the water balance of tropical catchments. Meanwhile the available information indicates that there is no evidence as yet for catastrophic climatic effects on a global or local scale resulting from afforestation. The local hydrological effect of tropical forest clearance, however, will usually be an increase in water yield that will relate to the proportion of the area that has not been covered by a perennial (tree) cover by regeneration or planting. That having been said, such clearance must take into account the effects on surface runoff, soil erosion, and flooding, which can frequently be more serious than a minor climatic change.
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