We use the visualization package XmdvTool to enhance the evaluation of the spatio-temporal patterns of the dam-induced hydrologic alternation dominated the middle and upper reaches of East River, south China during non-flood seasons (1952-2002). Results indicate that:1) Along the East River, dams had greatly altered the natural flow regime, range condition and the spatial variability;2) The 6 most remarkable indicators of hydrologic alternation induced by dam-construction were the rise rate, 3-day maximum, Low pulse duration, January and July of the East River during 1952-2002;3) The spatio-temporal hydrologic alternations were different among 3 stations. Under the influences of 2 large multi-purpose dams, the rank of the overall degree of hydrologic change were Lingxia, Heyuan and Longchuan station along the middle and upper reaches of East River. Visualization techniques for the high-dimensional hydrological datasets, together with RVA approach, might be useful to detect the spatio-temporal hydrologic changes. The unique way of integrating spatial, temporal and multi-element hydrological components provided visually-enhanced insights that were not possible with traditional analysis tools for water resources management.