To what extent does hydrological connectivity control dynamics of faecal indicator organisms in streams? Initial hypothesis testing using a tracer-aided model

Neill, Aaron; Tetzlaff, Doerthe; Strachan, Norval James Colin; Soulsby, Chris

doi:10.1016/j.jhydrol.2018.12.066

Cited by 16 publications

(13 citation statements)

References 94 publications

(111 reference statements)

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“…Alternatively, models can be calibrated via Monte Carlo approaches, allowing multiple criteria to be applied to parameter selection, including both flow and isotope error (e.g., Dehaspe et al, 2018; Delavau et al, 2017; Neill et al, 2019; Piovano et al, 2019; Smith et al, 2016). Recent studies have used the multiobjective (MO) calibration algorithm NGSAII by Deb et al (2002) to calibrate both flow and isotopes simultaneously, with some success (e.g., Birkel & Soulsby, 2015; He et al, 2019; Tunaley et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Regional Calibration With Isotope Tracers Using a Spatially Distributed Model: A Comparison of Methods

Holmes

Stadnyk

Kim

et al. 2020

Water Resources Research

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Accurate representation of flow sources in process-based hydrologic models remains challenging for remote, data-scarce regions. This study applies stable isotope tracers (18 O and 2 H) in water as auxiliary data for the calibration of the isoWATFLOOD ™ model. The most efficient method of those evaluated for introducing isotope data into model calibration was the PA-DDS multiobjective search algorithm. The compromise solutions incorporating isotope data performed slightly inferior in terms of streamflow simulation compared to the calibrated solution using streamflow data only. However, the former solution outperformed the latter one in terms of isotope simulation. Approximation of the model parameter uncertainty into internal flow path partitioning was explored. Inclusion of isotope error facilitated a broader examination of the total parameter space, resulting in significant differences in internal storage and flow paths, most significantly for soil storage and evapotranspiration loss. Isotope-optimized calibration reduced evaporation rates and increased soil moisture content within the model, impacting soil water velocity but not streamflow celerity. Flow-only calibration resulted in artificially narrow model prediction bounds, significantly underestimating the propagation of parameter uncertainty, while isotope-informed calibrations yielded more reliable and robust bound on model predictions. Our findings demonstrate that the accuracy of a complex, spatially distributed, and process-based model cannot be judged from one summative flow-based model performance evaluation metric alone. Plain Language Summary To predict how water moves through watersheds and adequately anticipate hydrologic response to a changing climate, we depend on numerical models to estimate transport and storage of water on and below Earth's surface. These models are only as good as the observation data we have to test them against, which can be insufficient for many remote parts of the world. Our study introduces a new source of data (i.e., isotope tracers, a fingerprint of water's origin) into a model to improve parameter estimation and overall reliability. The largest benefit of adding these data is that it nudges the model into a more realistic distribution of water storage and flow paths to the rivers, particularly soil storage and evaporation loss. This is important for improving the reliability of model projections under changing climates and to better understand how the distribution of water on Earth is changing.

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Section: Introductionmentioning

confidence: 99%

Regional Calibration With Isotope Tracers Using a Spatially Distributed Model: A Comparison of Methods

Holmes

Stadnyk

Kim

et al. 2020

Water Resources Research

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“…Of these two FIOs, E. coli was more susceptible to die-off when exposed to the F–T cycle with the lower temperature, consistent with enterococci being recognised as a more robust indicator when exposed to freezing stress [ 23 ]. Across all treatments, there was very little FIO growth, with temperatures <4 °C known to retard metabolic processes in E. coli [ 19 ].…”

Section: Discussionmentioning

confidence: 94%

“…The findings from this series of experiments therefore contribute to an improved understanding of how catchment FIO burden can vary over time, which is fundamentally important for accurate assessment of the risk of microbial contamination of watercourses at the catchment scale [ 22 ]. In particular, these data help constrain the parameterisation of die-off coefficients used in the modelling of fate and transfer of FIOs in landscapes where F–T cycling is common (e.g., [ 23 ]). The inclusion of laboratory-derived process representation into catchment-scale models needs careful assessment but, given that temperature is such a well-recognised driver of FIO survival, any additional understanding regarding more nuanced temperature-driven FIO responses in both agricultural and wildlife sources is likely to be important for advancing both our predictive capability and appreciation of uncertainty in catchment-scale modelling [ 7 ].…”

Section: Discussionmentioning

confidence: 99%

“…Cooling rates would therefore have been similar in both treatments, potentially explaining the lack of difference in λ associated with the models of FIO die-off. However, further research on how the magnitude of the F–T fluctuation impacts on FIO persistence in faeces in relation to differential cooling rates is warranted, and sample size in terms of faecal load or water volume is likely to play a role in the rate of cooling and hence population die-off characteristics (e.g., [ 23 ]).…”

Section: Discussionmentioning

confidence: 99%

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Impact of Freeze–Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses

Afolabi¹,

Oliver²

2020

IJERPH

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Characterising faecal indicator organism (FIO) survival in the environment is important for informing land management and minimising public health risk to downstream water users. However, key gaps in knowledge include understanding how wildlife contribute to catchment-wide FIO sources and how FIO survival is affected by low environmental temperatures. The aim of this study was to quantify E. coli and intestinal enterococci die-off in dairy cow versus red deer faecal sources exposed to repeated freeze–thaw cycles under controlled laboratory conditions. Survival of FIOs in water exposed to freeze–thaw was also investigated to help interpret survival responses. Both E. coli and intestinal enterococci were capable of surviving sub-freezing conditions with the faeces from both animals able to sustain relatively high FIO concentrations, as indicated by modelling, and observations revealing persistence in excess of 11 days and in some cases confirmed beyond 22 days. Die-off responses of deer-derived FIOs in both faeces and water exposed to low temperatures provide much needed information to enable better accounting of the varied catchment sources of faecal pollution and results from this study help constrain the parameterisation of die-off coefficients to better inform more integrated modelling and decision-making for microbial water quality management.

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“…This may also limit the effectiveness of forest regeneration in regulating certain water quality parameters by reducing redistribution of contaminants from the hillslope to the riparian zone (e.g. faecal indicator organisms - Neill et al, 2019).…”

Section: Implications Of Regeneration For Hydrological Source Areas Amentioning

confidence: 99%

Structural changes to forests during regeneration affect water flux partitioning, water ages and hydrological connectivity: Insights from tracer-aided ecohydrological modelling

Neill¹,

Birkel²,

Maneta³

et al. 2021

Preprint

Self Cite

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Abstract. Increasing rates of biodiversity loss are adding momentum to efforts seeking to restore or rewild degraded landscapes. Here, we investigated the effects of natural forest regeneration on water flux partitioning, water ages and hydrological connectivity, using the tracer-aided ecohydrological model EcH2O-iso. The model was calibrated using ~3.5 years of diverse ecohydrological and isotope datasets available for a catchment in the Scottish Highlands, an area where the impetus for regeneration of native pinewoods is growing. We then simulated two land cover change scenarios that incorporated forests at early (thicket) and late (old-open forest) stages of regeneration, respectively, and compared these to a present-day baseline simulation. Changes to forest structure (proportional vegetation cover, vegetation heights and leaf area index of pine trees) were modelled for each stage. Establishment of thicket forest had the greatest effect on water partitioning/ages and connectivity, with increased losses to interception evaporation driving reductions in below-canopy fluxes (soil evaporation, groundwater recharge and streamflow) and generally slower rates of water turnover. Effects on streamflow were most evident for low and moderate summer flows rather than winter high flows. Whilst full forest regeneration was limited to hillslopes, resultant changes to the spatial dynamics of flux partitioning could also cause drying out of the valley bottom. The more open nature of the older forest generally resulted in water fluxes, ages and connectivity characteristics returning towards baseline conditions. Our work implies that the ecohydrological consequences of natural forest regeneration on degraded land depend on the structural characteristics of the forest at different stages of development. Consequently, future land cover change investigations need to move beyond consideration of simple forest vs. non-forest scenarios to inform management that effectively balances landscape restoration with demand for ecosystem services. Tracer-aided ecohydrological models were also shown to be useful tools for land cover change simulations and further potential of such models was highlighted.

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To what extent does hydrological connectivity control dynamics of faecal indicator organisms in streams? Initial hypothesis testing using a tracer-aided model

Abstract: To what extent does hydrological connectivity control dynamics of faecal indicator organisms in streams? Initial hypothesis testing using a traceraided model,

Cited by 16 publications

References 94 publications

Regional Calibration With Isotope Tracers Using a Spatially Distributed Model: A Comparison of Methods

Regional Calibration With Isotope Tracers Using a Spatially Distributed Model: A Comparison of Methods

Impact of Freeze–Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses

Structural changes to forests during regeneration affect water flux partitioning, water ages and hydrological connectivity: Insights from tracer-aided ecohydrological modelling

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