Testing and application of a two-dimensional hydrothermal model for a water supply reservoir: implications of sedimentation

Abstract

Validation of a two-dimensional hydrothermal stratification model for 14 years for Schoharie Reservoir, N.Y., an impoundment that experiences substantial drawdown, is documented. The model is demonstrated to perform well in simulating the various features of the reservoir's thermal stratification regime in each of the years, including the timing and duration of stratification, the dimensions and temperature of the layers, and the periods of internal wave oscillations in stratified layers. The average root mean square error for temperature predictions for the 14 years is 1.30 • C. The validated model is applied in a probabilistic manner to investigate the impacts of sedimentation on the temperature of the withdrawn water (T w ) that enters a stream with a salmonid fishery, and features of the stratification regime. The predicted effects of sedimentation include a shift toward higher T w values, a shortening of the duration of stratification, and decrease in the depth of the epilimnion in fall. The effects on T w are exacerbated for the reservoir because of localized sedimentation adjoining the intake that increasingly limits access to cooler layers.Résumé : Cet article documente la validation d'un modèle de stratification hydrothermique bidimensionnel sur 14 années au réservoir Schoharie, NY, une retenue qui connaît des rabattements substantiels. Il est démontré que le modèle travaille bien lors de simulations des diverses caractéristiques du régime de stratification thermique du réservoir pour chacune des années, incluant le moment et la durée de la stratification, les dimensions et la température des couches ainsi que les périodes d'oscillations des vagues internes dans les couches stratifiées. L'erreur quadratique moyenne pour les prévisions de température pour les 14 années est de 1,30 • C. Le modèle validé est appliqué de manière probabiliste afin d'étudier les impacts de la sédimentation sur la température de l'eau soutirée (T w ), qui entre dans un ruisseau comportant une pêcherie de salmonidés; le modèle étudie aussi les caractéristiques du régime de stratification. Les effets prévus de la sédimentation comprennent un déplacement vers des valeurs T w plus élevées, un raccourcissement de la durée de stratification et une diminution de la profondeur de l'épilimnion à l'automne. Les effets sur les valeurs T w sont exacerbés pour le réservoir en raison d'une sédimentation localisée près de la prise d'eau en réservoir, ce qui limite de plus en plus l'accès aux couches plus froides.

Probabilistic model for temperature and turbidity in a reservoir withdrawal

“…Monitoring of the withdrawal shows that these goals have been exceeded irregularly in recent years. These occurrences follow runoff events in the case of T n,w (Gelda and Effler 2007b), while T w > 21.1 °C has been observed in late summer of certain years of extensive drawdown of Schoharie Reservoir (Gelda and Effler 2007a). The disparate runoff conditions that drive these two features of water quality confound a priori identification of a single set of critical forcing conditions.…”

“…The computer code adopted for the transport/hydrothermal submodel (Gelda and Effler 2007a) for the reservoir was that embedded in CE-QUAL-W2 (W2/T, Version 3.1). This is a dynamic, laterally averaged, two-dimensional (vertical and longitudinal) model (Cole and Wells 2002).…”

“…The features of lake and reservoir thermal stratification regimes, including vertical dimensions of layers, temperatures of layers, duration of stratification, and therefore temperature(s) of outflows, are subject to substantial variations associated with natural variations in meteorological drivers (Effler et al 1986, Owens andEffler 1989). Variations in operations can also influence the thermal stratification regime and outflow temperatures of reservoirs , Hanna et al 1999, Martin and McCutcheon 1999, Gelda and Effler 2007a. High turbidity levels occur irregularly in many reservoirs in response to external particulate loads received during runoff events (Kirk 1985, Effler et al 2002.…”

Eco-hydraulic Modelling of Eutrophication for Reservoir Management

“…Previous verification studies using LARM (Laterally Averaged Reservoir Model), GLVHT (Generalized Longitudinal-Vertical Hydrodynamics and Transport Model), and CE-QUAL-W2 that was developed by expanding LARM have been presented by Gordon (1980Gordon ( , 1981Gordon ( and 1983; Edinger et al (1983); Kim et al (1983);and Martin (1988). The successfiil testing of a two-dimensional hydrothermal and hydrodynamic model for a reservoir is documented by Gelda and Effler (2007). Mass-balance based eutrophication simulation models are commonly used tools for predicting the ecological response of a surface water body to potential changes in anthropogenic nutrient loading (Arega and Lee, 2000) under existing conditions and for various levels of nutrient load reduction.…”

Particle Swarm Optimization for Automatic Calibration of Large Scale Water Quality Model (CE-QUAL-W2): Application to Karkheh Reservoir, Iran

“…Based on traditional techniques, calibration parameters of complex water quality models has been identified through a trial-and-error calibration procedure, which is often subjective, inefficient, and time consuming process. In most previous studies on calibration of CE-QUAL-W2, the goodnessof-fit of the calibrated model is generally based on a visual judgment by comparing the simulated and the field data (Baker and Dycus 2004;Nielsen 2005;Sullivan and Round 2005;Kuo et al 2006;Chung and Oh 2006;Gelda and Effler 2007;Diogo et al 2008;Liu et al 2008;Afshar and Saadatpour 2009;Etemad-Shahidi et al 2009). …”