Contribution à l'amélioration des méthodes de suivi des débits des rivières en temps réel et différé

Abstract

Water resources management requires knowledge of current and future discharge of rivers for environmental impact studies, public safety aspects related to flooding, operation of hydraulic structures and hydropower. The traditional approach to measuring streamflow in rivers is to conduct a series of reliable measurements allowing to simultaneously establishing the stage-discharge rating curves. This approach based on a rudimentary instrumentation seems robust, economical and providing satisfactory results. However, in practice the assumption of bijection between the stage and discharge, which is the basic foundation of this approach, is compromised in some flow conditions. This is during flood event where the temporal acceleration significantly modifies the relationship between the stage and discharge by the hysteresis. The rating curve can also be considerably modified by the backwash effect, the presence of ice cover or the morphology of the river changes, for example erosion, vegetation or sedimentation. The hydro acoustic is another relatively recent discharge measurement approach in rivers. This approach is used to measure the speed of flow and the water level, using Doppler to calculate the discharge. The Doppler measured discharge can be done from the surface of water in a short period while the machine is attached to a boat, or continuously when installed at the bottom of river, or on its banks. This makes it possible to obtain reliable continuous measured discharges in all flow conditions. Thus, new measured discharges are not necessary when the river morphology changes. However, the costs of acquisition and operation of this technology are much higher than those associated the use with a rating curve. Moreover, the measurements provided by the Doppler have many noises and contain many outliers. The Doppler is also vulnerable to weather like lightning and becomes inoperative when buried by sediment. Also, it is common to find measurements series truncated during outage. The main objective of this research is to develop an improved approach to estimate river discharges by combining the advantages of the above two approaches mentioned. To achieve this objective involves three steps including specific objectives which are linked and follow a sequence. The first specific objective is the subject of Article 1. This paper deals with the opportunity to exploit long series of measurements provided by the Doppler to calibrate a rating curve representative of a wide range of discharges. Thus, it was necessary to develop filtering techniques that we have applied to the series of measurements provided by the Doppler. The proposed methodology was applied to the river Bostonnais in the province of Quebec in Canada. The application of filtering techniques and validation of the time series measurements obtained by the Doppler has significantly improved the performance of the traditional rating curve. The second specific objective is the subject of Article 2. This paper highlights the analysis of rating curves for monitoring discharge of rivers covered by ice. This approach aims to optimize the traditional rating curve by showing that it is possible to improve the results obtained by traditional rating curve using the validated continuous measurements of Doppler in the presence and absence of ice. The methodology for achieving this objective is to analyze first the impact of the ice cover on water levels and discharge. Then we proposed a concept based on double rating curve to represent the stage-discharge relationship during low water in the presence and absence of ice. The recommended methodology has been successfully applied to the river Bostonnais of Quebec. The results obtained from this dual rating curve previously calibrated using validated measurements by the Doppler show a significant improvement compared to a single rating curve. The third specific objective is the subject of Article 3. This paper highlights the estimation and the real-time validation of the measured discharges of rivers by Doppler. The proposed methodology is based on two tools: the first is based on the model of the rating curve that is used to express the relationship between the water stage and the discharge in a gauging section. The Kalman filter is used as second tool to identify, in real time, the parameters of a dynamic rating curve model based on differences between predicted and measured values. The methodology was successfully tested on the river Bostonnais in Quebec (Canada). The estimation gaps of discharges using the dynamic rating curve are significantly lower than gaps obtained using the traditional static rating curve. The Doppler has the advantage of providing accurately, a large amount of flow measurements covering the range of expected values of the discharges and the stages necessary to calibrate a rating curve. However, this rating curve is more advantageous economically and operationally, to provide less disturbed measurements and in greater quantities. We can therefore conclude that there is a synergy between the two complementary approaches for estimating discharges.

Date	29 Feb 2016
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Saad Bennis (Supervisor)