Daily Maximum Water Temperatures Research Articles

Observation and Simulation of Mosquito Breeding Site Water Temperature for Malaria Transmission at Kaita Local Governmet Township of Katsina State, Nigeria

Studies showed that transmission of malaria is influenced by environmental factors such as temperature. This work is aimed at finding the impact of mosquito's breeding site water temperature on mosquito's larva development time. An artificial mosquito's breeding habitat was created. The water temperature of the habitat was measured at an hourly interval, then it is averaged into daily time scale. Weather variables of the experimental site were inpu into the the energy balance model to simulate the breeding habit water temperature. The mosquito's larva development time was then predicted by inputting both the observed water and simulated water temperature into the vector borne disease community model (VECTRI) .The daily maximum, and minimum observed water temperatures were 27.9°C, 32.6°C and 21.7°C, respectively. The daily mean, maximum, and minimum simulated water temperatures were 29.8°C, 35.6°C, and 23.5°C respectively. These temperatures are within the temperature range that supports mosquito’s larva development. Mosquito's larva development was predicted using the VECTRI model. According to this study larva development reached completion in 7.1 days using the observed water temperature, 6.03 days using the simulated water temperature and 8.01days using the observed air temperature. This energy balance model is an improved water temperature scheme over the assumption that air temperature is equal to air temperature. This work shows the importance of water temperature and the value of degree day required for emergence of an adult mosquito in the simulation of aquatic stage development. Both the observed water and simulated water temperatures are higher than the on observed air temperature, thus air temperature cannot be used as the water temperature in the simulation of the mosquito’s larva development time. The finding of the work can be used as source toward mosquito's larval control through water temperature. It is however clear from the finding that could be as result of temperature due to shorter time predicted for mosquito's larval development.

Near‐term forecasts of stream temperature using deep learning and data assimilation in support of management decisions

AbstractDeep learning (DL) models are increasingly used to make accurate hindcasts of management‐relevant variables, but they are less commonly used in forecasting applications. Data assimilation (DA) can be used for forecasts to leverage real‐time observations, where the difference between model predictions and observations today is used to adjust the model to make better predictions tomorrow. In this use case, we developed a process‐guided DL and DA approach to make 7‐day probabilistic forecasts of daily maximum water temperature in the Delaware River Basin in support of water management decisions. Our modeling system produced forecasts of daily maximum water temperature with an average root mean squared error (RMSE) from 1.1 to 1.4°C for 1‐day‐ahead and 1.4 to 1.9°C for 7‐day‐ahead forecasts across all sites. The DA algorithm marginally improved forecast performance when compared with forecasts produced using the process‐guided DL model alone (0%–14% lower RMSE with the DA algorithm). Across all sites and lead times, 65%–82% of observations were within 90% forecast confidence intervals, which allowed managers to anticipate probability of exceedances of ecologically relevant thresholds and aid in decisions about releasing reservoir water downstream. The flexibility of DL models shows promise for forecasting other important environmental variables and aid in decision‐making.

Refining real-time predictions of Vibrio vulnificus concentrations in a tropical urban estuary by incorporating dissolved organic matter dynamics

The south shore of Oʻahu, Hawaiʻi is one of the most visited coastal tourism areas in the United States with some of the highest instances of recreational waterborne disease. A population of the pathogenic bacterium Vibrio vulnificus lives in the estuarine Ala Wai Canal in Honolulu which surrounds the heavily populated tourism center of Waikīkī. We developed a statistical model to predict V. vulnificus dynamics in this system using environmental measurements from moored oceanographic and atmospheric sensors in real time. During a year-long investigation, we analyzed water from 9 sampling events at 3 depths and 8 sites along the canal (n = 213) for 36 biogeochemical variables and V. vulnificus concentration using quantitative polymerase chain reaction (qPCR) of the hemolysin A gene (vvhA). The best multiple linear regression model of V. vulnificus concentration, explaining 80% of variation, included only six predictors: 5-day average rainfall preceding water sampling, daily maximum air temperature, water temperature, nitrate plus nitrite, and two metrics of humic dissolved organic matter (DOM). We show how real-time predictions of V. vulnificus concentration can be made using these models applied to the time series of water quality measurements from the Pacific Islands Ocean Observing System (PacIOOS) as well as the PacIOOS plume model based on the Waikīkī Regional Ocean Modeling System (ROMS) products. These applications highlight the importance of including DOM variables in predictive modeling of V. vulnificus and the influence of rain events in elevating nearshore concentrations of V. vulnificus. Long-term climate model projections of locally downscaled monthly rainfall and air temperature were used to predict an overall increase in V. vulnificus concentration of approximately 2- to 3-fold by 2100. Improving these predictive models of microbial populations is critical for management of waterborne pathogen risk exposure, particularly in the wake of a changing global climate.

Predicting Latent and Sensible Heat Fluxes in Stream Temperature Models: Current Challenges and Potential Solutions

AbstractStream temperature studies typically use either the Penman combination equation (PCE) or empirical wind functions to compute the latent heat flux, which can be an important control on daily maximum water temperature. The sensible heat flux is usually computed from the latent heat flux via the Bowen ratio or a bulk transfer model. Unfortunately, both the PCE and empirical wind functions involve challenges. The PCE is inappropriate for application to subdaily stream evaporation because, as implemented in many stream temperature studies, it does not account for energy associated with warming or cooling of the water column or bed heat fluxes. The PCE thus tends to overestimate evaporation under conditions typical of warm summer days during the diurnal warming phase, which is when evaporation is likely to be an important heat loss mechanism. Empirical wind functions involve substantial uncertainty given the broad range of coefficient values that have been reported in the literature and the lack of above‐stream meteorological data to use in their application. We provide suggestions for improving current practice and also identify research directions to support development of robust approaches to computing the latent and sensible heat fluxes.

Woody buffer effects on water temperature: The role of spatial configuration and daily temperature fluctuations

AbstractWater temperature is a key driver for riverine biota and strongly depends on shading by woody riparian vegetation in summer. While the general effects of shading on daily maximum water temperature Tmax are well understood, knowledge gaps on the role of the spatial configuration still exist. In this study, the effect of riparian buffer length, width, and canopy cover (percentage of buffer area covered by woody vegetation) on Tmax was investigated during summer baseflow using data measured in seven small lowland streams in western Germany (wetted width 0.8–3.7 m). The effect of buffer length on Tmax differed between downstream cooling and heating: Tmax approached cooler equilibrium conditions after a distance of 0.4 km (~45 min travel‐time) downstream of a sharp increase in canopy cover. In contrast, Tmax continued to rise downstream of a sharp decrease in canopy cover along the whole 1.6 km stream length investigated. The effect of woody vegetation on Tmax depended on buffer width, with changes in canopy cover in a 10 m wide buffer being a better predictor for changes in Tmax compared to a 30 m buffer. The effect of woody vegetation on Tmax was linearly related to canopy cover but also depended on daily temperature range Trange, which itself was governed by cloudiness, upstream canopy cover, and season. The derived empirical relationship indicated that Tmax was reduced by −4.6°C and increased by +2.7°C downstream of a change from unshaded to fully shaded conditions and vice versa. This maximum effect was predicted for a 10 m wide buffer at sunny days in early summer, in streams with large diel fluctuations (large Trange). Therefore, even narrow woody riparian buffers may substantially reduce the increase in Tmax due to climate change, especially in small shallow headwater streams with low baseflow discharge and large daily temperature fluctuations.

Seasonal macrophyte growth constrains extent, but improves quality, of cold‐water habitat in a spring‐fed river

AbstractRooted aquatic macrophytes affect abiotic conditions in low‐gradient rivers by altering channel hydraulics, consuming biologically available nutrients, controlling sediment transport and deposition, and shading the water surface. Due to seasonal macrophyte growth and senescence, the magnitude of these effects may vary temporally. Seasonal changes in aquatic macrophyte biomass, channel roughness and flow velocity, were quantified and trends were related to spatiotemporal patterns in water temperature in a low‐gradient, spring‐fed river downstream from high‐volume, constant‐temperature groundwater springs. Between spring and summer, a nearly threefold increase in macrophyte biomass was positively correlated with channel roughness and inversely related to flow velocity. On average, flow velocity declined by 34% during the study period, and channel roughness increased 63% (from 0.064 to 0.104). During the spring and fall period, the location of a minimum water temperature variability “node” migrated upstream more than 4 km, whereas daily maximum water temperature cooled by 2–3°C. Water temperature modelling shows that the longitudinal extent of cold‐water habitat was shortened due to increased channel roughness independent of seasonal surface water diversions. These results suggest that macrophyte growth mediates spatiotemporal patterns of water temperature, constraining available cold‐water habitat while simultaneously improving its quality. Understanding complex spatial and temporal dynamics between macrophyte growth and water temperature is critical to developing regulatory standards reflective of naturally occurring variability and has important implications for the management and conservation of cold‐water biota.

Analysis of air/river maximum daily temperature characteristics using the peaks over threshold approach

AbstractThe understanding of river temperature is very important when assessing fish habitat conditions in terms of fish growth as well as fish distribution within river systems. The quantification of extreme water temperatures is also important, especially when studying the suitability of thermal habitats during high air/water temperature events. The present study deals with the analysis of extreme air and water temperatures using the partial duration series approach, also known as the peak over threshold (POT) approach. The advantage of the POT approach is that extreme air and water temperatures can be described not only in magnitude but also in duration and degree day accumulation for each event. In the present study, 74 years of air temperature data (Miramichi meteorological station) were analysed as well as 21 years of river temperature data from the Little Southwest Miramichi River. For example, results showed that the 0.01 exceedance probability (F(x) = .99) for maximum daily air temperature event was calculated at 38.4°C whereas for the same exceedance probability, the maximum daily water temperature event was slightly lower at 32.7°C. The duration of events varied between 1 and 5 days for air temperature and between 1 and 7 days for water temperature. Maximum daily water temperature exceeding 30°C generally occurred over a period of 3 days or more, and the degree day accumulation was higher than 6°C·day. This study showed that the POT approach was effective in quantifying both air and water temperature extremes within the Miramichi River study area.

Modelling of Maximum Daily Water Temperature for Streams: Optimally Pruned Extreme Learning Machine (OPELM) versus Radial Basis Function Neural Networks (RBFNN)

This study proposed two data-driven models, namely the optimally pruned extreme learning machine (OPELM) and the radial basis functions neural networks (RBFNN) to predict maximum daily water temperature in streams. Air temperature (Ta), flow discharge (Q) and the day of the year (DOY) were used as predictors. Four indicators, including the coefficient of correlation (R), the Willmott index of agreement (d), the root mean squared error (RMSE), and the mean absolute error (MAE) were used in evaluating the performances of different models. The present study was conducted according to four different scenarios. First, the OPELM and RBFNN models were developed and validated for each station separately. For the three other scenarios, the models were developed using data from one station and validated for the two other stations separately. Modelling results showed that in the proposed models Ta and Q may not be sufficiently informative and the addition of DOY significantly contributes to better capturing the seasonal pattern of the maximum daily water temperature in streams. Generally, OPELM models outperformed RBFNN models, and overall, the modelling results indicated that the OPELM models developed in this study can be effectively used for predicting maximum water temperature in streams.

Experimental investigation of shading façade-integrated solar absorber system under hot tropical climate

In this paper, a shading façade-integrated solar absorber system has been assessed outdoors under the hot tropical climate. The system was developed, and its performance was tested for 79 days under a standard system operating condition. The outdoor field test has demonstrated that the system was principally dependent on the available global irradiance, and its performance was impaired by the high occurrence of afternoon rain. On average, the system was capable to achieve a daily efficiency of 50.5%, maximum daily water temperature attained at 48.9 °C, and solar water heating rate of 2.9 °C/h. Findings showed that the system could perform most frequently at a daily efficiency ranging from 45% to 60%, and the maximum daily water temperature attained from 45 °C to 57 °C during the test period. Empirical results indicate that there exist several linear regressions between the variables that show acceptable correlations. An additional experiment was carried out to assess the heat distribution mapping of the experimental model.

Temporal thermal refugia and seasonal variation in upper thermal limits of two species of riverine invertebrates: the amphipod, Paramelita nigroculus, and the mayfly, Lestagella penicillata

Understanding the response of aquatic organisms to elevated water temperatures offers insight into the ecological consequences of climate change on riverine species. Upper thermal limits were determined for two riverine invertebrates, the amphipod Paramelita nigroculus (Paramelitidae) and the mayfly Lestagella penicillata (Teloganodidae), in two rivers in the south-western Cape, South Africa. Limits were estimated using the critical thermal method (reflected as the critical thermal maxima—CTmax) and the incipient lethal temperature method (reflected as the incipient lethal upper limit—ILUT). Thermal signatures of these rivers were characterized using hourly water temperatures. CTmax for seasonally acclimatized and laboratory-acclimated P. nigroculus varied significantly amongst months and acclimation temperature. CTmax for seasonally acclimatized L. penicillata varied significantly amongst months, but not with acclimation temperature. 96-h ILUT values for seasonally acclimatized individuals varied significantly amongst months for both species. CTmax values, 96-h ILUT and Maximum Weekly Allowable Temperature thresholds were lower for P. nigroculus compared to L. penicillata. Seven-day moving averages of daily mean and maximum water temperatures were significantly correlated with upper thermal limits for seasonally acclimatized L. penicillata but not P. nigroculus. The proportion of time within a 24-h period that chronic thermal stress thresholds are not exceeded provides a measure of monthly or seasonal chronic thermal stress, and reflects the quantity of temporal thermal refugia for vulnerable organisms. Further testing of these relationships for other species, rivers and regions is recommended, to evaluate the potential for stream temperature averaging statistics to serve as proxies for biological thresholds.

Effects of shading on stream ecosystem metabolism and water temperature in an agriculturally influenced stream in central Wisconsin, USA

Headwater streams with a forested riparian zone and canopy cover have regulated stream temperatures and stream ecosystem metabolism because of shading. Agricultural practices have dramatically altered riparian corridors with the removal of mature vegetation, which consequently alters natural stream processes. The objective of this study was to investigate the effects of shading on stream temperature and ecosystem metabolism in an agriculturally influenced, low order stream. We examined three stream reaches; two in a recently restored stream (Lost Creek) and one in a nearby-unimpacted reference stream (Little Plover River). The two reaches in Lost Creek included a 100-m artificially-shaded stream reach and a control reach immediately upstream of the shaded reach. The Little Plover River included one reference reach with a fully forested canopy. Both streams are located in agricultural watersheds and based on phosphorus levels would be classified as meso-eutrophic. Each stream reach was assessed during stable flow conditions once each month between June and October of 2016. Rates of gross primary production (GPP), ecosystem respiration (ER), and net ecosystem production (NEP) were determined using the open system, two-station diel dissolved oxygen change method, and reaeration (k) was calculated using the nighttime regression method. Based on stream discharge data, we corrected metabolism values for groundwater when inputs exceeded 7% (Hall and Tank 2005). We also measured water temperature, PAR (photosynthetically active radiation), soluble reactive phosphorus (SRP), periphytic chlorophyll a content, and organic matter content at each site as potential controlling variables. Surprisingly, no significant differences were observed in daily maximum water temperatures among the three sites; however, GPP levels were significantly lower (ANOVA F2,14 = 45.45; p < 0.001) in the artificially shaded reach and the reference site compared to the control indicating that shading reduced GPP. ER was not significantly different among the reaches and remained relatively low, which resulted in the control reach having a highly positive and significantly higher NEP (ANOVA F2,14 = 17.656 p < 0.001) compared to the shaded and reference reaches. Redundancy analysis revealed that GPP and NEP were strongly correlated with PAR. Our findings suggest that shading can improve dissolved oxygen dynamics in an agriculturally-influenced stream by lowering GPP.

Western Pearlshell Mussel Life History in Merrill Creek, Oregon: Reproductive Timing, Growth, and Movement

Abstract Most freshwater mussel species in North America are imperiled. Life history traits of many species have been documented but information regarding western pearlshell mussels (Margaritifera falcata Gould) is scarce. Our goal was to improve understanding of western pearlshell mussel reproduction, growth, and movement. The study area was a 250 m reach in Merrill Creek, Oregon. We examined 1389 mussels for gravidity and examined water samples for glochidia during presumed spawning times over a 4-year period. We tagged 415 mussels for mark-recapture observations for growth and movement. No mussels showed signs of gravidity. However, four mussels near our study transects were observed releasing conglutinates. Glochidia were present from April to mid-June. Glochidia were not detected until maximum daily water temperature had reached 10.0 °C, and were no longer detected once minimum daily water temperature remained above 9.0 °C. There was a negative relation between growth rate and mussel size. Growth rat...

Thermal modelling and experimental validation of a semi-transparent water wall system for Sydney climate

A transient heat balance model (THBM) based on energy conservation is developed for predicting the thermal performance of a semi-transparent water wall system. In order to validate the THBM against field measurements, real climate conditions in Sydney, Australia are adopted and the time variations of both internal and external convective and radiative heat transfer coefficients are calculated using empirical correlations from the literature. An alternative concrete wall model is also developed for further validation of the THBM. Good agreements between the THBM simulation and field data are achieved for both the water wall and concrete wall systems. The validated THBM is then adopted in a sensitivity analysis in order to assess the thermal performance of the semi-transparent water wall system under different configurations. It is found that the daily maximum water and air temperatures decrease significantly with the decrease of the transmissivity of the semi-transparent panels, whereas an increase of the attenuation coefficient of solar radiation in water has an insignificant impact on the water and air temperatures. The present results also indicated that increasing the thickness of the water column can reduce the fluctuations of the water temperature and the diurnal peak air temperature. From the practical application point of view, reducing the transmissivity of the external panel provides the most effective way to mitigate over-heating in the semi-transparent water wall system.

Estimating Hourly Water Temperatures in Rivers Using Modified Sine and Sinusoidal Wave Functions

AbstractAir temperature is often used to estimate stream water temperature by developing regression models. A method using modified sine functions and sinusoidal wave functions (MSSWF) was proposed for estimating hourly water temperatures in rivers. Estimates of daily maximum and minimum water temperatures from sine functions (SFs) were corrected using linear regressions as functions of deviations of estimates of daily maximum and minimum air temperatures from SFs, and then modified sinusoidal wave functions (SWFs) were used to estimate hourly water temperatures. Excellent agreement was found between observed and estimated hourly water temperatures using MSSWF models developed for 13 rivers in Alabama. The average Nash-Sutcliffe efficiency (NSE) for the MSSWF models developed for individual rivers is 0.94. The distance of a river monitoring station from the weather station has very little effect on the performance of individual MSSWF models when the distance is less than approximately 300 km. A lumped MSS...

Early warning system to forecast maximum temperature in drinking water distribution systems

Climate change poses new challenges in preventing the exceedance of the maximum allowed temperature in the drinking water distribution system (DWDS). The objective of this article is to evaluate the feasibility of forecasting the maximum temperature in the DWDS. Two options were analysed: (1) using the records of the last day as forecast for the coming 2 days and (2) using 2-day weather forecast data. The maximum water temperature in the DWDS was modelled for a Dutch city for a warm period during summer 2006. Actual meteorological records and historical weather forecasts were used. Results for the daily maximum temperature for June–July 2006 based on the high resolution limited area model predictions showed a 0.09 °C average mean error and a maximum error of 0.3 °C, while using the last day record as forecasted showed a mean error of 1.09 °C and a maximum error of 2.5 °C. These results indicate that it is possible to predict the daily maximum water temperature in the DWDS using the weather forecast information or using actual records as a short-term prediction. These types of simulations can serve as an ‘early warning system’ to monitor drinking water temperature for taking measurements to avoid exceeding the maximum allowed temperature.

Performance Analysis of Integrated Collector System with Immersed Coil Heat Exchanger

The performance of integrated solar collector / thermal energy storage with immersed heat exchanger was investigated experimentally at the Solar Research Site, University Technology PETRONAS, (4.4224oN, 100.9904oE), Malaysia. The experimental set up consisted of 150 liters storage tank capacity with immersed coil heat exchanger, single glazing 1.5m2 flat plate collector with 15o tilt to the horizontal. The circulation of the working fluid was by forced in closed loop with a mini solar pump. Aluminum cell foam was attached to the absorber as extended surface. The surface of the collector was coated with black ornament to improve its absorption. The system was tested under clear skys, for two cases; with and without water drawn-off for seven days per case studied. The performance evaluation data obtained for case1 at the mean maximum solar intensity was 503.98 W/m2 were: maximum daily water temperature 63°C, average daily water temperature 46°C, collector efficiency 63% and system efficiency 43%. Whilst for case 2, the mean maximum solar intensity was 473.11 W/m2, the maximum daily water temperature 54°C, average daily water temperature 39.36°C, collector efficiency 54% and system efficiency 39%. The system efficiency for case 2 showed that the heat exchanger performed slighlty better and the water drawn-off effect is minimal.

A stakeholder project to model water temperature under future climate scenarios in the Satus and Toppenish watersheds of the Yakima River Basin in Washington, USA

The goal of this study was to support an assessment of the potential effects of climate change on select natural, social, and economic resources in the Yakima River Basin. A workshop with local stakeholders highlighted the usefulness of projecting climate change impacts on anadromous steelhead (Oncorhynchus mykiss), a fish species of importance to local tribes, fisherman, and conservationists. Stream temperature is an important environmental variable for the freshwater stages of steelhead. For this study, we developed water temperature models for the Satus and Toppenish watersheds, two of the key stronghold areas for steelhead in the Yakima River Basin. We constructed the models with the Stream Network Temperature Model (SNTEMP), a mechanistic approach to simulate water temperature in a stream network. The models were calibrated over the April 15, 2008 to September 30, 2008 period and validated over the April 15, 2009 to September 30, 2009 period using historic measurements of stream temperature and discharge provided by the Yakama Nation Fisheries Resource Management Program. Once validated, the models were run to simulate conditions during the spring and summer seasons over a baseline period (1981–2005) and two future climate scenarios with increased air temperature of 1 °C and 2 °C. The models simulated daily mean and maximum water temperatures at sites throughout the two watersheds under the baseline and future climate scenarios.

Development and validation of two fish-based indices of biotic integrity for assessing perennial coolwater streams in Wisconsin, USA

Perennial coolwater streams (maximum daily mean water temperature 20.7–24.6°C; 90th percentile annual exceedence flow≥0.0283m3/s) are common in the Laurentian Great Lakes region of North America, including the state of Wisconsin, but they lack specific and effective bioassessment tools. I used landscape-scale ecological modeling of geographically referenced data on stream location, stream and valley slope, watershed surficial geology, air temperatures, riparian and watershed land cover, watershed road and population densities, and watershed nutrient and wastewater inputs to classify Wisconsin stream sites based on water temperature, flow, and degree of environmental degradation. Fish data from sites classified as perennial coolwater were then analyzed with objective standardized procedures to develop coolwater indices of biotic integrity (IBI). Because of substantial differences in their fish assemblages, separate IBI's were formulated for cool-cold transition (20.7–22.5°C) and cool–warm transition (22.6–24.6°C) streams. The cool–cold transition IBI had five metrics: numbers of darter, madtom, and sculpin species, of coolwater species, and of intolerant species, and the percentages of individuals as tolerant species and as generalist feeders. Scoring criteria differed between northern and southern Wisconsin (boundary at 44.6°N latitude) for the coolwater species metric. The cool–warm transition IBI also had five metrics: numbers of native minnow, of intolerant, and of benthic invertivore species, and percentages of individuals as tolerant species and as omnivores. Scoring criteria differed between small and large streams (boundary at 200km2 watershed area) for the intolerant species, benthic invertivore species, and percentage tolerants metrics. In validation tests, scores for both IBI's were significantly related to independent measures of human disturbance, indicating that the IBI's would be useful tools for assessing the environmental quality of coolwater streams. However, for any given level of human disturbance, scores for both IBI's varied substantially, suggesting that multiple IBI samples from multiple sites would be needed to provide a reliable evaluation of a particular stream segment.

Elevated summer temperatures delay spawning and reduce redd construction for resident brook trout (Salvelinus fontinalis)

AbstractRedd (nest) surveys for resident brook trout (Salvelinus fontinalis) were conducted annually in a mountain lake in northern New York for 11 years with multiple surveys conducted during the spawning season in eight of those years. Repeated surveys throughout the spawning season allowed us to fit an individually based parametric model and estimate the day of year on which spawning was initiated, reached its midpoint, and ended during each year. Spawning phenology was then assessed relative to (1) mean of maximum daily air temperature and (2) mean of maximum daily water temperature at the lake bottom during summer in each year using a linear model. Elevated temperatures in summer were correlated with a delay in spawning and a reduction in the total number of redds constructed. Increasing the summer mean of maximum daily air temperatures by 1 °C delayed spawning by approximately 1 week and decreased the total number of redds constructed by nearly 65. Lake spawning brook trout select redd sites based on the presence of discharging groundwater that is relatively constant in temperature within and across years, leading to relatively consistent egg incubation times. Therefore, delayed spawning is likely to delay fry emergence, which could influence emergence synchrony with prey items. This work highlights non‐lethal and sub‐lethal effects of elevated summer temperatures on native resident salmonids in aquatic environments with limited thermal refugia.

Use of Frequency and Duration Analysis for the Determination of Thermal Habitat Thresholds: Application for the Conservation of Alasmidonta heterodon in the Delaware River

AbstractA novel approach for setting thermal habitat recommendations for an endangered aquatic species will be proposed in this paper. The method, uniform continuous above-threshold (UCAT) analysis, evaluates the duration and frequency of continuous events in which the temperature is higher than a specified value and identifies temperature levels that, because of their rare occurrence in the past, can be considered stressor thresholds. The UCAT analysis was applied to set thermal habitat recommendations for Alasmidonta heterodon, an endangered mussel species in the Upper Delaware River. It was found that a maximum daily water temperature of 26.5°C lasting for more than 7 days is a rare event in the A. heterodon population centers in Upper Delaware River and consequently this condition should be avoided by adjusting already regulated cold-water releases from upstream reservoirs. Knowledge of temperature thresholds and their relationship with persistent low-flow periods provided further decision support for...