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Thursday, May 29, 2008 - 2:45 PM
561
How much water does a stream need? A study of environmental flows in Hong Kong streams
Qian Niu and David Dudgeon. Division of Ecology & Biodiversity, School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, China
Environmental flows can be defined as the amount of water required to maintain ecosystem structure and function in regulated streams. The objectives of this investigation were to model the effects of flow reduction on streams in monsoonal Hong Kong, and determine a qualitative threshold of environmental flow requirements. Ten unpolluted hill streams with water extraction ranging from 0% to >90% were studied to establish a relationship between ecological response variables and percentage flow reduction during the wet (2007) and dry (2008) seasons. Periphyton composition, benthic macroinvertebrate diversity, and breakdown rate of Liquidambar formosana (Hamamelidaceae) leaf litter were compared in each season in reaches upstream (control) and downstream (impacted) of water extraction points. Macroinvertebrate species richness was reduced by 4-34% due to water extraction in the wet season, while litter breakdown rate declined by 4-58%. Regression models indicated that the extent of flow regulation among streams explained almost half (42% and 48% respectively) of the variation in species richness and litter breakdown rates. The influence of flow reduction on periphyton health (indicated by chlorophyll a : pheophytin a) was generally negative but weak. Studies of the consequences of reduced flows during the dry season are ongoing.
Web Page: environmental flows, ecological function, macroinvetebrate diversity
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See more of The Nabs 56th Annual Meeting (25-28 May, 2008)