A low‐flow equation is derived from Darcy's law and a mass balance equation for base flow from a hillside by assuming that groundwater recharge is constant over short time periods. This low‐flow equation reduces to many of the existing mechanistic low‐flow equations, but in its general form looks like a linear regression model and captures spatial variability in base flow among hillsides in a basin. As a result, it unifies the mechanics and statistics of low flows in river networks. This equation is tested against low‐flow data from the Flint River basin in Georgia and the Gasconade River basin in Missouri, both of which are approximately 7000 km2 in size.