Changes in water age during dry-down of a non-perennial stream

Swenson, Logan; Zipper, Samuel C.; Peterson, Delaney; Jones, C. Nathan; Burgin, Amy J.; Seybold, E. C.; Kirk, M.; Hatley, Camden

doi:10.31223/x55s99

Cited by 2 publications

(2 citation statements)

References 51 publications

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“…The data and scripts associated with this study are available in the Zenodo repository at: https://doi.org/10.5281/zenodo.10364905; Swenson et al. (2023).…”

Section: Data Availability Statementmentioning

confidence: 99%

Changes in Water Age During Dry‐Down of a Non‐Perennial Stream

Swenson,

Zipper,

Peterson

et al. 2024

Water Resources Research

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Non‐perennial streams, which lack year‐round flow, are widespread globally. Identifying the sources of water that sustain flow in non‐perennial streams is necessary to understand their potential impacts on downstream water resources, and guide water policy and management. Here, we used water isotopes (δ18O and δ2H) and two different modeling approaches to investigate the spatiotemporal dynamics of young water fractions (Fyw) in a non‐perennial stream network at Konza Prairie (KS, USA) during the 2021 summer dry‐down season, as well as over several years with varying hydrometeorological conditions. Using a Bayesian model, we found a substantial amount of young water (Fyw: 39.1–62.6%) sustained flows in the headwaters and at the catchment outlet during the 2021 water year, while 2015–2022 young water contributions estimated using sinusoidal models indicated smaller Fyw amounts (15.3% ± 5.7). Both modeling approaches indicate young water releases are highly sensitive to hydrological conditions, with stream water shifting to older sources as the network dries. The shift in water age suggests a shift away from rapid fracture flow toward slower matrix flow that creates a sustained but localized surface water presence during late summer and is reflected in the annual dynamics of water age at the catchment outlet. The substantial proportion of young water highlights the vulnerability of non‐perennial streams to short‐term hydroclimatic change, while the late summer shift to older water reveals a sensitivity to longer‐term changes in groundwater dynamics. Combined, this suggests that local changes may propagate through non‐perennial stream networks to influence downstream water availability and quality.

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“…The data and scripts associated with this study are available in the Zenodo repository at: https://doi.org/10.5281/zenodo.10364905; Swenson et al. (2023).…”

Section: Data Availability Statementmentioning

confidence: 99%

Changes in Water Age During Dry‐Down of a Non‐Perennial Stream

Swenson,

Zipper,

Peterson

et al. 2024

Water Resources Research

Self Cite

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“…Late season stream flow is predominantly older Mor water (Hatley et al 2023;Swenson et al 2023). Macpherson (1996).…”

Section: Chapter 2 -Study Areamentioning

confidence: 99%

Impacts of Woody Encroachment on the Fate of Soil Co2 in Grassland Watersheds

Anhold,

Hatley,

Alcantar-Velasquez

et al. 2023

Geological Society of America Abstracts With Programs

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Woody vegetation is encroaching into grasslands worldwide. Previous research has shown that woody encroachment impacts stream flow, nutrient concentrations, and suspended solid loads. However, little is known about deeper subsurface impacts, including impacts to groundwater residence time and composition. We examined these impacts at Konza Prairie Biological Station, a native tallgrass prairie in the Flint Hills of Kansas, USA. Previous research in the study area has found that groundwater CO2 levels are rising, and we hypothesize that woody encroachment may be a driver. To help test this hypothesis, we compared groundwater chemistry and residence time between two watersheds, which differ in levels of woody encroachment (20% and 40%) as a result of differences in watershed burn frequency (1 yr vs 4 yr, respectively). Every three to four weeks during the 2022 water year, we collected groundwater and stream samples from each watershed and analyzed them for major ion chemistry. Geochemical modeling calculations indicate that an average of 4.4 mmol of CO2 is added per liter of recharge in the more encroached watershed whereas 4.9 mmol of CO2 is added per liter of recharge in the less encroached watershed. Groundwater residence time tracers, SF6 and CFCs, collected at four times during the study period do not reveal clear differences between the watersheds. Groundwater residence time varied mostly as a function of the source of groundwater and the time of sample collection and thus do not appear to explain differences in CO2 inputs between watersheds. Instead, we interpret that differences in CO2 inputs reflect differences in the residence time of recharge water in the overlying soils. Woody encroachment alters soil root distributions, which in turn can increase soil hydraulic conductivity. If water passes through soils more quickly during recharge, kinetic reaction path modeling indicates that greater weathering occurs deeper in the subsurface rather than in the soil, which decreases the

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Changes in water age during dry-down of a non-perennial stream

Cited by 2 publications

References 51 publications

Changes in Water Age During Dry‐Down of a Non‐Perennial Stream

Changes in Water Age During Dry‐Down of a Non‐Perennial Stream

Impacts of Woody Encroachment on the Fate of Soil Co2 in Grassland Watersheds

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