Thermal characteristics of running waters
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This chapter reviews available data on thermal conditions prevailing in lotic ecosystems of the Southern Hemisphere. The primary factors (hydrology, climate, insolation) that interact to determine the thermal régime are examined in the context of southern waters. Maximum temperatures are plotted against annual ranges for equatorial (0–10° latitude), tropical (10–231/2° latitude), and temperate sites. In regions with seasonal climates, running waters exhibit diel and annual thermal periodicity patterns, the phasing of which varies between and within lotic systems. The universality of Illies' river zonation system is analyzed in the context of thermal conditions in Southern Hemisphere running waters.
From the relatively limited data base, it appears that Southern Hemisphere running waters exhibit some distinctive features when viewedin toto, compared with Europe and North America where thermal characteristics of lotic habitats have been reasonably well documented. Such differences relate to the generally warm and dry conditions, and to the highly variable and unpredictable climatic régimes characterizing large areas of the Southern Hemisphere. It is concluded that differences in thermal conditions of running waters between hemispheres are a matter of degree rather than of kind, and partly reflect a small woodland stream bias inherent in Northern Hemisphere stream ecology.
Keywordslimnology Africa Australia New Zealand river zonation running waters South America stream ecology thermal régimes
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