Water Quality: Current Trends and Expected Climate Change Impacts

Water quality describes the chemical, physical, and biological characteristics of water. Water quality not only encompasses the myriad of naturally derived chemicals, but also several million human-derived chemicals and incorporates a broadening suite of biological components such as microbes and descriptions of habitats and biotic communities, i.e. plants and animals. The physical characteristics include temperature, dissolved gases, and specific conductance, which is a measure of the electrical transmissivity of water. In the absence of the effects of human activities, water quality is primarily controlled by climate (precipitation and temperature) and geology (lithology, geomorphology, soil). The understanding of basic processes affecting chemical transport and transformation, and related effects on biota continues to improve, but is orders of magnitude more complex than the understanding of the physical characteristics of water. Water quality is a rapidly evolving environmental science discipline, primarily due to the increasing demand on water resources and the intricate linkage between water quality and use, particularly with the highly deleterious impacts of degraded water quality on human and ecosystem health. Water quality, when coupled with water quantity, determines the suitability of that water for a particular use, including natural ecosystems, fisheries, recreation, potable water, agriculture, and industry. The quantity and quality of freshwater reflect the combined effects of many processes operating along hydrological pathways. Primary drivers for the availability of water are landscape changes and patterns, and the processes affecting the timing, magnitude, and intensity of precipitation, including global climate change. Furthermore, temperature, another climate change characteristic, intricately affects chemical reactions and biological behaviours. ... The objective of the 'Water Quality: Current Trends and Expected Climate Change Impacts' symposium was to bring water quality scientists together for a dialogue on the evaluation of climate change impacts on a broad range of water quality issues. The authors of the papers of this symposium were asked to provide input regarding the effects of climate change on the focal issue of their paper. To this end, the 27 papers included herein provide a broad spectrum of water quality issues and have been grouped accordingly.