## 2 Methodology  
The global workflow of the entire optimization process of a WQMP is illustrated in Figure 1: (1) Identify stakeholder concerns through a participative approach to elicit knowledge needs supported by a public participation geographical information system (PPGIS), (2) identify new monitoring and optimization objectives and validate the attainment of past monitoring objectives, (3) understand the rationale behind the existing WQMP, (4) integrate data from the existing WQMPs into the database connected to the IDSS, (5) interrogate the IDSS on optimization suggestions based on the input from the first three points, (6) propose optimized WQMPs and validate proposals with the decision-makers of the existing WQMPs. Stakeholders, as illustrated in this figure, are defined as citizens and representatives of organized stakeholders (e.g., industry, agriculture, ministries, municipalities, watershed organizations, associations, etc. that were identified through the stakeholder analysis) [16]. 1. In this paper, we present the test of the IDSS and show how it contributes to understanding the initial WQMPs (Method Section 2.1),
2. Supplies decision support in data validation, data quality assessment and storage (Method Section 2.2),
3. Proposes optimization procedures (Method Section 2),
4. Contributes to the application of the optimization procedures (Method Section 2.4),Provides decision support to finalize the optimization procedure (Method Section 2.5),
* Is instrumental in the redesign of the WQMPs (Results and discussion Section 3). The IDSS was tested with two watersheds in the province of Quebec, Canada. The optimization objectives were specific to each watershed. The first to be tested was Lac Saint-Charles, a lake WQMP (size of the watershed: 198 km\({}^{2}\) - hereafter W1). This lake is the main drinking water reservoir of the city of Quebec where an extensive cyanobacteria monitoring program was implemented in 2011 to obtain a spatio-temporal portrait of the cyanobacteria community in the lake [21]. This WQMP is operated by the Association pour la protection de l'environnement du lac Saint-Charles et des Marais du Nord (APEL) and financed by the city of Quebec. Given the cost of the analysis of the cyanobacteria species of nearly 300 samples per year, the main optimization objective here was to evaluate whether a reduction in sampling frequency, sampling points and the number of samples per sampling station for cyanobacteria (up to three at different water depths) would result in a loss of information. The general characteristics of the W1 WQMP are presented in Figure 2.  
Figure 1: Global workflow of the optimization process of WQMPs. The purpose of the participative approach is to assess the attainment of past monitoring objectives and yield new monitoring objectives and optimization objectives. The results will influence the questions that the WQMP manager asks the IDSS to help the WQMP manager redesign the WQMP. The second watershed was the watershed of the river, Riviere du Nord (hereafter W2), north-east of Montreal. In this watershed (size of the watershed: 2222 km\({}^{2}\)), a river monitoring program was implemented in 2009 to assess water quality to protect public health and follow nutrient concentrations and erosion [22]. This WQMP is operated by the watershed organization of the Riviere du Nord river (Abrinord) and financed by several municipalities within the territory. Given the vast territory, financial limitations and new monitoring objectives, the optimization objective was to evaluate whether a reduction in the number of sampling sites would be possible. In addition, the objective was to find out whether sufficient samples had been taken in wet weather conditions and whether the sampling frequency was sufficient to respond to the initial monitoring objectives. The objective of capturing wet weather conditions is to capture water quality impairment due to runoff from non-point pollution sources [23].