The usual, reliable, background level of a river, maintained by seepage from groundwater and by throughflow, which means that the river can maintain the base flow during dry periods. The base flow index is the contribution of base flow to a stream. Total flow to stream systems consists of surface run-off, interflow, and base flow; streamflow partitioning methods are used for finding the relative contributions of each (try Morgan (1972) TIBG 56). With prolonged drought, base flow itself will diminish, the rate of flow falling in a depletion curve (Gebert et al. (2007) J. Am. Water Resources Ass. 43, 1).

Base flow