Natural Flow Reconstruction Using Kalman Filter and Water Balance–Based Methods II: Case Studies, Results, and Discussion

During the prereservoir years, when limited data (neighboring basin flow and simulated flow) are available for ungauged basins, simple methods are relevant to reconstruct natural flow (NF). On the other hand, for the postreservoir years, when hydrometric data (water level in the reservoir, turbine flow, and discharged flow) are available for ungauged basins, the classic water balance equation (WBE) method is usually employed to determine NF. However, applying classic methods still produce noisy and unreliable flow data series. In an attempt to produce more reliable NF data, new methods are proposed and described in Part 1 of this paper: the state fusion Kalman filter method (prereservoir construction period) and the deterministic WBE method and the stochastic WBE method (postreservoir construction period). This paper that is presented as Part 2 deals with the execution of these new methods for three subbasins of different sizes in Quebec, Canada. Obtained results are then compared against those produced by the use of the current methods of NF reconstruction: area ratio method, maintenance of variance (Move) type III method, and multivariable regression method (prereservoir construction period), and the classic WBE model (postreservoir construction period). This comparative analysis shows the capability of proposed methods for improving the constructed data series with improved results that do not contain any negative flow. They are less noisy, perfectly matched with regional flows, and are reliable enough for frequency analyses. Because these NF values include evaporation, infiltration, and other losing terms of a closed hydraulic system, with more studies needed in order to define the contribution of each of them.