Heed the data gap: Guidelines for using incomplete datasets in annual stream temperature analyses

Johnson, Zachary C.; Johnson, Brittany G.; Briggs, Martin A.; Snyder, Craig D.; Hitt, Nathaniel P.; Devine, Warren D.

doi:10.1016/j.ecolind.2020.107229

Cited by 16 publications

(13 citation statements)

References 45 publications

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“…Data are then reconstructed from the principal components and the initial analysis step repeated but with missing values replaced using estimates from the reconstructed data (Josse and Husson 2016). Similar to what others have shown (Isaak et al 2018;Johnson et al 2021), we found that the quality of imputed data based on temporal covariation from nearby stream sites was good, and all of the correlations between daily observed records and predictions from the imputation were high (r ≥ 0.99). After imputation, all stream site records consisted of 1127 mean daily temperature records across 3 years.…”

Section: Stream Temperature Datasetssupporting

confidence: 83%

An ecothermal paradox: bull trout populations diverge in response to thermal landscapes across a broad latitudinal gradient

et al. 2022

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Maintaining natural thermal regimes in montane stream networks is critical for many species, but as climate warms, thermal regimes will undoubtedly change. Mitigating impacts of changing thermal regimes on freshwater biodiversity requires knowledge of which elements of the thermal regime are limiting factors for aquatic biota. We used full-year stream temperature records sampled across a broad latitudinal gradient to describe the diversity of the thermal landscapes that bull trout (Salvelinus confluentus) occupy and identify potential divergences from thermal regimes where this species has been studied previously. Populations of bull trout occupied stenothermic, cold thermal niches in streams that exhibited low to moderate thermal sensitivity throughout the species’ range. However, winter thermal regimes in the central and northernmost streams were colder and more stable than in the southernmost streams, reflecting differences in sensitivity to air temperature variation and contributions of perennial groundwater to baseflow. In the southernmost streams, bull trout distributions appeared to be regulated by warm summer temperatures, whereas in northern streams, unsuitably cold temperatures may be more limiting. Our results also suggest that local differences in the extent of complete freezing during winter among northern streams may further limit the distributions of suitable habitats. Contrasts in limiting factors at bull trout range extents would suggest differential responses to climate warming wherein northern populations extend their range while southern populations contract, and an overall change in species status that is less dire than previously anticipated.

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Section: Stream Temperature Datasetssupporting

confidence: 83%

An ecothermal paradox: bull trout populations diverge in response to thermal landscapes across a broad latitudinal gradient

et al. 2022

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“…These models can also be used to fill gaps in stream temperature data records needed for other analyses (Glover et al, 2020). Their high accuracy suggests they would compare well with imputation methods used in recent daily year-round stream temperature analyses (Isaak et al, 2020;Z. C. Johnson et al, 2021).…”

Section: Applications and Management Implicationsmentioning

confidence: 99%

Modeling Seasonal Effects of River Flow on Water Temperatures in an Agriculturally Dominated California River

Asarian

Robinson

Genzoli

2023

Water Resources Research

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Low streamflows can increase vulnerability to warming, impacting coldwater fish. Water managers need tools to quantify these impacts and predict future water temperatures. Contrary to most statistical models' assumptions, many seasonally changing factors (e.g., water sources and solar radiation) cause relationships between flow and water temperature to vary throughout the year. Using 21 yr of air temperature and flow data, we modeled daily water temperatures in California's snowmelt‐driven Scott River where agricultural diversions consume most summer surface flows. We used generalized additive models to test time‐varying and nonlinear effects of flow on water temperatures. Models that represented seasonally varying flow effects with intermediate complexity outperformed simpler models assuming constant relationships between water temperature and flow. Cross‐validation error of the selected model was ≤1.2°C. Flow variation had stronger effects on water temperatures in April–July than in other months. We applied the model to predict effects of instream flow scenarios proposed by regulatory agencies. Relative to historic conditions, the higher instream flow scenario would reduce annual maximum temperature from 25.2° to 24.1°C, reduce annual exceedances of 22°C (a cumulative thermal stress metric) from 106 to 51 degree‐days, and delay onset of water temperatures >22°C during some drought years. Testing the same modeling approach at nine additional sites showed similar accuracy and flow effects. These methods can be applied to streams with long‐term flow and water temperature records to fill data gaps, identify periods of flow influence, and predict temperatures under flow management scenarios.

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“…Salmonids and other cold-water species have been documented as far south as Mexico [66], indicating that cool-and cold-water regimes extend further south than shown in this study. Though data gaps were not filled in this analysis, recent interpolation methods show promising utility for stream temperature records [67], which could potentially increase the number of sites included in the analysis and expand the geographic scope. Finally, while USGS and CDEC databases have many long-term temperature datasets, and temperature monitoring tends to focus on short-term summer periods, additional data may be available through other public, crowd-sourced sites as more comprehensive temperature data are collected [68].…”

Section: Plos Onementioning

confidence: 99%

Classifying California’s stream thermal regimes for cold-water conservation

2021

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Stream temperature science and management is rapidly shifting from single-metric driven approaches to multi-metric, thermal regime characterizations of streamscapes. Given considerable investments in recovery of cold-water fisheries (e.g., Pacific salmon and other declining native species), understanding where cold water is likely to persist, and how cold-water thermal regimes vary, is critical for conservation. California’s unique position at the southern end of cold-water ecosystems in the northern hemisphere, variable geography and hydrology, and extensive flow regulation requires a systematic approach to thermal regime classification. We used publicly available, long-term (> 8 years) stream temperature data from 77 sites across California to model their thermal regimes, calculate three temperature metrics, and use the metrics to classify each regime with an agglomerative nesting algorithm. Then, we assessed the variation in each class and considered underlying physical or anthropogenic factors that could explain differences between classes. Finally, we considered how different classes might fit existing criteria for cool- or cold-water thermal regimes, and how those differences complicate efforts to manage stream temperature through regulation. Our results demonstrate that cool- and cold-water thermal regimes vary spatially across California. Several salient findings emerge from this study. Groundwater-dominated streams are a ubiquitous, but as yet, poorly explored class of thermal regimes. Further, flow regulation below dams imposes serial discontinuities, including artificial thermal regimes on downstream ecosystems. Finally, and contrary to what is often assumed, California reservoirs do not contain sufficient cold-water storage to replicate desirable, reach-scale thermal regimes. While barriers to cold-water conservation are considerable and the trajectory of cold-water species towards extinction is dire, protecting reaches that demonstrate resilience to climate warming remains worthwhile.

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Heed the data gap: Guidelines for using incomplete datasets in annual stream temperature analyses

Cited by 16 publications

References 45 publications

An ecothermal paradox: bull trout populations diverge in response to thermal landscapes across a broad latitudinal gradient

An ecothermal paradox: bull trout populations diverge in response to thermal landscapes across a broad latitudinal gradient

Modeling Seasonal Effects of River Flow on Water Temperatures in an Agriculturally Dominated California River

Classifying California’s stream thermal regimes for cold-water conservation

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