Abstract
In some hydrological systems, mitigation strategies are applied based on short-range water temperature forecasts to reduce stress caused to aquatic organisms. While various uncertainty sources are known to affect thermal modeling, their impact on water temperature forecasts remain poorly understood. The objective of this paper is to characterize uncertainty induced to water temperature forecasts by meteorological inputs in two hydrological contexts. Daily ensemble water temperature forecasts were produced using the CEQUEAU model for the Nechako (regulated) and Southwest Miramichi (natural) Rivers for 1–5-day horizons. The results demonstrate that a larger uncertainty is propagated to the thermal forecast in the unregulated river (0.92–3.14 °C) than on the regulated river (0.73–2.29 °C). Better performances were observed on the Nechako with a mean continuous ranked probability score (MCRPS) <0.85 °C for all horizons compared to the Southwest Miramichi (MCRPS ≈ 1 °C). While informing the end-user on future thermal conditions, the ensemble forecasts provide an assessment of the associated uncertainty and offer an additional tool to river managers for decision-making.
Highlights
The inherent links between fish biological processes and water temperature have been well documented over the last fifty years [1,2,3]
In this paper: (1) we present a modeling framework used to produce ensemble water temperature forecasts in two different hydrological contexts ((a) a strongly regulated system; and (b) a natural system); (2) we quantify the uncertainty associated with forecasts of eight input variables from an atmospheric model that propagates to water temperature forecasts; and (3) we compare the propagation of the uncertainty in the regulated and the natural systems mentioned above
One of the main objectives of this work is to assess and represent the uncertainty that is propagated to a water temperature forecast by the meteorological inputs
Summary
The inherent links between fish biological processes and water temperature have been well documented over the last fifty years [1,2,3]. The impoundment of a watercourse can alter this thermal regime in different ways depending on the type of dam, the timing and magnitude of the water releases, reservoir stratification [9,10,11] and the depth in the upstream reservoir from which water is released [12,13]. Research on water temperature has provided the water management community with a plethora of modeling tools (see Benyahya et al [14] for a partial review). Many of these models are key elements for dam operators because they help to meet environmental flow requirements and water quality criteria, while at the same time assisting in the optimization of operations [13,15]
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