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Spatial Convergence in Major Dissolved Ion Concentrations and Implications of Headwater Mining for Downstream Water Quality
Author(s) -
Johnson Brent,
Smith Elizabeth,
Ackerman Jerry W.,
Dye Susan,
Polinsky Robyn,
Somerville Eric,
Decker Chris,
Little Derek,
Pond Gregory J.,
D'Amico Ellen
Publication year - 2019
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 - 10.1111/1752-1688.12725
Subject(s) - hydrology (agriculture) , watershed , environmental science , streams , water quality , downstream (manufacturing) , surface water , dilution , upstream and downstream (dna) , aquatic ecosystem , ecology , environmental chemistry , upstream (networking) , chemistry , geology , environmental engineering , computer network , operations management , physics , computer science , economics , biology , thermodynamics , geotechnical engineering , machine learning
Spatial patterns in major dissolved solute concentrations were examined to better understand impact of surface coal mining in headwaters on downstream water chemistry. Sixty sites were sampled seasonally from 2012 to 2014 in an eastern Kentucky watershed. Watershed areas (WA) ranged from 1.6 to 400.5 km 2 and were mostly forested (58%–95%), but some drained as much as 31% surface mining. Measures of total dissolved solutes and most component ions were positively correlated with mining. Analytes showed strong convergent spatial patterns with high variability in headwaters (<15 km 2 WA) that stabilized downstream (WA > 75 km 2 ), indicating hydrologic mixing primarily controls downstream values. Mean headwater solute concentrations were a good predictor of downstream values, with % differences ranging from 0.55% (Na + ) to 28.78% (Mg 2+ ). In a mined scenario where all headwaters had impacts, downstream solute concentrations roughly doubled. Alternatively, if mining impacts to headwaters were minimized, downstream solute concentrations better approximated the 300 μS/cm conductivity criterion deemed protective of aquatic life. Temporal variability also had convergent spatial patterns and mined streams were less variable due to unnaturally stable hydrology. The highly conserved nature of dissolved solutes from mining activities and lack of viable treatment options suggest forested, unmined watersheds would provide dilution that would be protective of downstream aquatic life.