Source Water Apportionment of a River Network: Comparing Field Isotopes to Hydrodynamically Modeled Tracers

Abstract

Tributary source water provenance is a primary control on water quality and ecological characteristics in branching tidal river systems. Source water provenance can be estimated both from field observations of chemical characteristics of water and from numerical modeling approaches. This paper highlights the strengths and shortcomings of two methods. One method uses stable isotope compositions of oxygen and hydrogen from water in field-collected samples to build a mixing model. The second method uses a calibrated hydrodynamic model with numerical tracers released from upstream reaches to estimate source-water fraction throughout the model domain. Both methods were applied to our study area in the eastern Sacramento-San Joaquin Delta, a freshwater tidal system which is dominated by fluvial processes during the flood season. In this paper, we show that both methods produce similar source water fraction values, implying the usefulness of both despite their shortcomings, and fortifying the use of hydrodynamic tracers to model transport in a natural system.

Advancing diet reconstruction in fish eye lenses

“…δ¹⁵N is used to quantify trophic position in a food web because there is 3-4‰ enrichment with each consumer (Fry 2006). Therefore, salmon feeding on freshwater aquatic insects have different δ¹⁵N than salmon in hatcheries that feed higher trophically on marine sources of protein in their feed (Hurd et al 2008) advancing the use of eye-lens isotopes in fish ecology (Eckard et al 2007;Barnett-Johnson et al 2008;Johnson et al 2012;Downing et al 2016;Tomkovic et al 2020).…”

“…Within freshwater and estuarine systems, habitats such as tidal wetlands and fluvial floodplains that have large pools of organic matter and long water residence times have exceptionally low δ 34 S values (Limburg et al, 2015; Schlesinger & Bernhardt, 2013). Isotopic gradients in δ 13 C, δ 15 N, δ 18 O, δ 34 S and 87 Sr/ 86 Sr are well characterized across the landscape of habitats used by juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California's Central Valley (USA) making it a model system for advancing the use of eye‐lens isotopes in fish ecology (Barnett‐Johnson et al., 2008; Downing et al., 2016; Eckard et al., 2007; Johnson et al., 2012; Tomkovic et al., 2020).…”

Tracers and Timescales: Tools for Distilling and Simplifying Complex Fluid Mechanical Problems

“…Regardless of how such tracers are introduced into the aquatic environment, these authors demonstrate the valuable role that dissolved radionuclides can play as oceanographic tools. Bailly du Bois et al [1] present an extensive, updated dataset of in situ radionuclide (e.g., 3 H, 137 Cs, 134 Cs, 125 Sb) measurements collected between 1982 and 2016 aboard 80 oceanographic campaigns across the English Channel, Bay of Biscay, Celtic Sea, Irish Sea, and the North Sea. With a focus on the measured tracers behaving most conservatively in seawater ( 3 H and 125 Sb), the authors describe useful applications of radiotracer data for illuminating physical transport processes and pathways and for validating hydrodynamic models.…”

“…The intersection of tracer measurements and modeling is explored by Tomkovic et al [3], who employ both approaches while pursuing a deeper understanding of source water provenance in a branching tidal river system. Their field-based approach focuses on the utilization of stable isotope compositions of oxygen and hydrogen in water samples to build a mixing model.…”

“…The capacity to model whole or multiple connected aquatic systems in multiple dimensions at a spatial resolution of tens to hundreds of meters and timesteps of seconds to minutes, helping us understand how riverine, oceanic, and atmospheric drivers influence constituent transport or habitat connectivity (e.g., [1][2][3]);…”