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Principal components of thermal regimes in mountain river networks

Posted date: December 07, 2018
Publication Year: 
2018
Publication Series: 
Scientific Journal (JRNL)
Source: Hydrology and Earth Systems Sciences. 22: 6225-6240.

Abstract

Description of thermal regimes in flowing waters is key to understanding physical processes, enhancing predictive abilities, and improving bioassessments. Spatially and temporally sparse data sets, especially in logistically challenging mountain environments, have limited studies on thermal regimes, but inexpensive sensors coupled with crowd-sourced data collection efforts provide efficient means of developing large data sets for robust analyses. Here, thermal regimes are assessed using annual monitoring records compiled from several natural resource agencies in the northwestern United States that spanned a 5-year period (2011-2015) at 226 sites across several contiguous montane river networks. Regimes were summarized with 28 metrics and principal component analysis (PCA) was used to determine those metrics which best explained thermal variation on a reduced set of orthogonal axes. Four principal components (PC) accounted for 93.4% of the variation in the temperature metrics, with the first PC (49% of variance) associated with metrics that represented magnitude and variability and the second PC (29% of variance) associated with metrics representing the length and intensity of the winter season. Another variant of PCA, T-mode analysis, was applied to daily temperature values and revealed two distinct phases of spatial variability - a homogeneous phase during winter when daily temperatures at all sites were

Citation

Isaak, Daniel J.; Luce, Charles H.; Chandler, Gwynne L.; Horan, Dona L.; Wollrab, Sherry P. 2018. Principal components of thermal regimes in mountain river networks. Hydrology and Earth Systems Sciences. 22: 6225-6240.