This study aimed to understand the dynamics of river space use based on mobile spatial statistics data. This study proposed a method to estimate the number of visits to river spaces and to the river waterfront facilities, considering the areal ratio of the river space to the data mesh, visiting time, and visitors living area. The estimated results for the 109 target rivers using the proposed method captured the inter-rivers variability well (R=0.92) but were about 10 times higher than the values obtained from the national field survey of the river space use in average. Our analysis suggested that the population dynamics can be captured with a certain degree of accuracy both on an annual and daily basis. In the estimation of the number of visitors to 240 river waterfront facilities in Japan, multiple regression analysis using the number of visitors as the objective variable was performed. Though our multiple regression analysis did not necessarily result in developing an accurate model, we found that the accessibility to the river water facilities showed statistically significant results, indicating its influence on the number of visitors.