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Hydrological flow paths controlling stream chemistry in Japanese forested watersheds
Author(s) -
Ohrui Kiyokazu,
Mitchell Myron J.
Publication year - 1999
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/(sici)1099-1085(19990430)13:6<877::aid-hyp762>3.0.co;2-e
Subject(s) - baseflow , watershed , hydrology (agriculture) , precipitation , bedrock , groundwater , streams , water chemistry , environmental science , soil water , streamflow , environmental chemistry , geology , chemistry , soil science , drainage basin , geomorphology , machine learning , meteorology , computer science , geography , computer network , physics , cartography , geotechnical engineering
Water sources and flow paths contributing to stream chemistry were evaluated in four Japanese forested watersheds with steep topography (slopes ≥30°). Stream chemistry during periods without rainfall and during events with less than 100 mm of precipitation was similar to seepage water chemistry, but markedly different from that of soil water which had higher concentrations of NO − 3 and Ca 2+ and lower concentrations of Na + and HCO − 3 . Also, stream Cl − concentrations in a Cl − ‐treated watershed did not increase either during events with less than 100 mm of total rainfall or at baseflow conditions, even three years after the Cl − treatment. These results suggest that groundwater within bedrock fissures of Paleozoic strata had a long residence time and was a major contributor to steam water under baseflow conditions and even during small precipitation events (≤100 mm). In contrast, for large precipitation events (≥100 mm), stream chemistry became more similar to soil water chemistry, especially within the steepest watershed. Also, for large precipitation events, stream Cl − concentrations in the Cl − ‐treated watershed increased markedly. These results suggest that soil water was a major contributor to stream waters only during these large events. Copyright © 1999 John Wiley & Sons, Ltd.