The ground-water component of stream discharge may be determined from the chemical characteristics of the stream water. A chemical mass-balance is used to relate total, direct, and ground-water runoff. To solve the mass-balance equation, it is necessary to estimate the chemical composition of the ground-water and direct-runoff components. The solute concentration of ground water is determined from total runoff during baseflow; the chemical characteristics of direct-runoff are estimated from samples of total runoff collected from selected locations in a basin during peak discharge periods. In three small watersheds in Nova Scotia ground-water runoff constituted from 32 to 42% of peak discharge for the period of analysis.