In large scale I think the data assimilation based on GLDAS is one of the best sources for runoff and other hydrological features. in the following link you can find more about GLDAS :
Moreover, you can use eartH2Observe in order to access several large scale and regional scale models that simulate runoff and other hydrological terms. I think it is more complete and comperhnsive than GLDAS. Try it..