Two soil water-monitoring networks have been established at scales useful for the validation of soil moisture products derived from passive microwave retrievals of brightness temperature. The monitoring networks located in Saskatchewan and Ontario Canada have been in continuous operation since July 2007.  We have used the monitoring network data for several analysis including the spatial scaling of soil water, the validation of soil moisture retrieval algorithms from active and passive remote sensing products and for the development and validation data assimilation systems. In June 2010, the Canadian Experiment for Soil Moisture 2010 (CanEx-10) was carried out over the Saskatchewan network. This experiment combined the collection of data from the field (soil water and vegetation), aircraft (active and passive microwave sensors), and satellites (optical, active and passive microwave sensors) and provided a unique opportunity to evaluate the functioning of regional scale soil moisture networks.  In this presentation we will address network accuracy, representativeness and scaling with implications for the validation of soil moisture retrieval algorithms from passive microwave sensors and evaluation of soil water data assimilation systems.