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Open AccessArticle

Multiple Time-Scale Monitoring to Address Dynamic Seasonality and Storm Pulses of Stream Water Quality in Mountainous Watersheds

1
Department of Forest Environment Protection, College of Forest & Environmental Sciences, Kangwon National University, Chuncheon 200-701, Korea
2
Department of Forest Resources, College of Forest & Environmental Sciences, Kangwon National University, Chuncheon 200-701, Korea
3
Department of Hydrology, University of Bayreuth, Bayreuth D-95440, Germany
4
Department of Environmental Science & Engineering, Ewha Womans University, Seoul 120-750, Korea
*
Author to whom correspondence should be addressed.
Academic Editor: Young-Seuk Park
Water 2015, 7(11), 6117-6138; https://doi.org/10.3390/w7116117
Received: 23 September 2015 / Revised: 23 October 2015 / Accepted: 27 October 2015 / Published: 4 November 2015
Rainfall variability and extreme events can amplify the seasonality and storm pulses of stream water chemistry in mountainous watersheds under monsoon climates. To establish a monitoring program optimized for identifying potential risks to stream water quality arising from rainfall variability and extremes, we examined water chemistry data collected on different timescales. At a small forested watershed, bi-weekly sampling lasted over two years, in comparison to three other biweekly sampling sites. In addition, high-frequency continuous measurements of pH, electrical conductivity, and turbidity were conducted in tandem with automatic water sampling at 2 h intervals during eight rainfall events. Biweekly monitoring showed that during the summer monsoon period, electrical conductivity (EC), dissolved oxygen (DO), and dissolved ion concentrations generally decreased, but total suspended solids (TSS) slightly increased. A noticeable variation from the usual seasonal pattern was that DO levels substantially decreased during an extended drought. Bi-hourly storm event samplings exhibited large changes in the concentrations of TSS and particulate and dissolved organic carbon (POC; DOC) during intense rainfall events. However, extreme fluctuations in sediment export during discharge peaks could be detected only by turbidity measurements at 5 min intervals. Concomitant measurements during rainfall events established empirical relationships between turbidity and TSS or POC. These results suggest that routine monitoring based on weekly to monthly sampling is valid only in addressing general seasonal patterns or long-lasting phenomena such as drought effects. We propose an “adaptive” monitoring scheme that combines routine monitoring for general seasonal patterns and high-frequency instrumental measurements of water quality components exhibiting rapid responses pulsing during intense rainfall events. View Full-Text
Keywords: dissolved organic carbon; headwater streams; monsoon rainfall; mountainous watersheds; particulate organic carbon; stream water quality; suspended sediment; turbidity dissolved organic carbon; headwater streams; monsoon rainfall; mountainous watersheds; particulate organic carbon; stream water quality; suspended sediment; turbidity
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Lee, H.-J.; Chun, K.-W.; Shope, C.L.; Park, J.-H. Multiple Time-Scale Monitoring to Address Dynamic Seasonality and Storm Pulses of Stream Water Quality in Mountainous Watersheds. Water 2015, 7, 6117-6138.

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