Evaluation of Canadian National Hydrometric Network density based on WMO 2008 standards

Since its establishment in the 1890s, the Canadian National Hydrometric Network (CNHN) has become the main source of water information for various users across the country. The CNHN provides the essential information and data on the status of one of the most precious natural resources of Canada: its surface water resources. However, the CNHN has never been evaluated based on international standards such as the World Meteorological Organization (WMO) guidelines for hydrometric network density. This preliminary analysis aims to fill that gap and provide background information on CNHN density. In this study, the CNHN is evaluated using WMO (2008) guidelines as a benchmark. Spatial analysis techniques are applied to determine the areas that meet the WMO (2008) minimum network density standards and those that do not meet the minimum standards. It was found that only about 12% of the Canadian terrestrial area is covered by hydrometric networks that meet the WMO (2008) minimum standards, while 49% of the terrestrial area is poorly gauged and about 39% is ungauged. The poorly gauged and ungauged areas are largely located in the mountainous and northern regions. Only a few spots in the southern parts of the country have a streamflow network density that meets the WMO (2008) minimum recommendation. An estimated total of about 5041 new stations are needed to bring the CNHN up to WMO (2008) minimum standard level. The study results clearly confirm the necessity to continue operating all existing streamflow stations and the need to add new streamflow stations. However, further analysis is required to optimize the CNHN at the regional scale by accounting for other factors such as population density, specific needs and economic constraints.