Enhancing End-Member Mixing Analysis by Incorporating Concentration-Discharge Analysis: A Case Study in the Silver River Catchment, Great Lakes Basin, Michigan
Abstract
Diagnostic tools of mixing models (DTMM) have been used to determine the conservativity of solutes and the number of end-members in stream water by distinguishing mixing vs chemical reaction through analyzing linear vs non-linear combination of solute concentrations. Concentration-discharge (C-Q) analysis differentiates chemostasis vs chemodynamics through a power-law function. A strong C-Q power-law relationship suggests a conservative mixing with relatively constant chemical concentrations in end-members and sustainable storage to maintain discharge to streamflow. Combining DTMM and C-Q analysis determines not only conservative tracers and the number of end-members but also the hydrologic and hydrochemical characteristics of end-members using streamflow discharge and chemical data in streamflow alone. This new procedure greatly enhances end-member mixing analysis, as demonstrated in the Silver River catchment in the Great Lakes Basin in Michigan, a forested catchment covered by glacial till landforms with underlying Archean and Precambrian bedrocks. Streamflow discharge and chemical data from 2005 to 2008 at eight sub-catchments (ranging in size from 0.5 to 168 km2) were acquired from the US Geological Survey, including major ions, nutrients, and trace metals. The results of DTMM showed that specific conductance (SC), Ca2+, Mg2+, Na+, HCO3-, Si, Al, As, Ba, and U in stream water behaved conservatively and their concentrations resulted from mixing of two end-members in eight catchments. Significant (p < 0.01, n =10) C-Q power-law relationship occurred in all catchments for these conservative solutes above, further suggesting that the concentrations of these solutes in two end-members were relatively constant and their contributions to streamflow were persistent over time. Both DTMM and C-Q analysis indicated that K+, Cl-, SO42-, DON, and Mn were conservative only in some catchments mostly at larger scales but NO3-, P, Cr, Co, Cu, Fe, Pb, Ni, Se, and Zn were strongly impacted by chemical equilibrium in stream water in all catchments. These analyses enable us not only to develop two end-member mixing models with constant but distinct chemical signatures in end-members for all catchments at various scales but also to quantify and understand the fate of nutrients and trace metals in stream water.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H53J1892L
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1832 Groundwater transport;
- HYDROLOGY;
- 1879 Watershed;
- HYDROLOGY