Premium
TRENDS IN PRECIPITATION AND STREAM CHEMISTRY IN A PRISTINE OLD‐GROWTH FOREST WATERSHED, OLYMPIC NATIONAL PARK, WASHINGTON 1
Author(s) -
Edmonds Robert L.,
Blew Roger D.
Publication year - 1997
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.1997.tb04105.x
Subject(s) - precipitation , watershed , acid rain , weathering , bedrock , hydrology (agriculture) , streams , environmental science , water chemistry , national park , physical geography , chemistry , environmental chemistry , geology , geography , archaeology , geochemistry , meteorology , geomorphology , computer network , geotechnical engineering , organic chemistry , machine learning , computer science
Human induced long‐term changes in precipitation and stream chemistry have been observed in eastern North America and Europe, but few long‐term studies have been conducted in coastal western North America. The objectives of this research were to determine: (1) time trends in precipitation and stream chemistry in a pristine old‐growth forest watershed, and (2) seasonal patterns in precipitation and stream chemistry. It was conducted in 58 ha West Twin Creek Watershed, Hoh River Valley, Olympic National Park, Washington from 1984 to 1993. Vegetation consists of old‐growth forest, with western hemlock, Douglas‐fir, western redcedar, Pacific silver fir, and Sitka spruce being the dominant tree species. Annual precipitation varied from 2336 to 4518 mm during the study period with the majority of the rain falling between October and May. Chemistry of precipitation was strongly dominated by oceanic influences with Na and Cl being the dominant ions. The chemistry of the stream was influenced by bedrock weathering and was dominated by Ca, HCO 3 , and SO 4 and was not strongly related to precipitation chemistry. The pH of precipitation averaged 5.3 over time and ranged from 4.3 to 7.1, while the stream pH averaged 7.5 and ranged from 5.5 to 9.0. There were few long‐term trends in the chemical constituents of bulk precipitation or stream water with the exception of a slight decrease in NO 3 in precipitation and an increase of SO 4 in stream water. A trend of decreasing concentrations of Ca, Mg and Na in precipitation also occurred. There were no significant seasonal patterns in precipitation although the highest SO 4 concentrations usually occurred in late spring and summer perhaps due marine algal activity. Strong seasonal trends occurred in concentrations of HCO 3 , SO 4 , Ca, Mg, and Na in stream water resulting from weathering and stream flow patterns, with highest ion concentrations occurring just before the onset of the rainy season. Pulses of NO 3 in the stream were observed during fall and early winter resulting from the release of NO 3 which had accumulated in soils or sediments.