Fig. 5. The Potomac River at Point of Rocks (see Fig. 1) has a long hydrological record with which to characterize low river flow conditions. (A) Statistical analysis of the 30-day low-flow time series shows extreme low flow conditions occur in 13% of the 112 years of records, requiring water release from upstream reservoirs. (B) Peak system water demand occurs during these low flow periods, which means that continued population growth in the lower portion of the basin will require increasingly more manipulation of flows in the upper portion of the basin. BLD = billion liters/day.