We present a new instrument for measuring surface runoff rates ranging from very low (~0.05L min-1) to high (300L min-1, with much higher rates possible depending on the device configuration). The device is economical, simple, rugged, accurate and requires little maintenance (the system is self-emptying and contains no moving parts). We have successfully used this instrument in long-term monitoring studies and expect that it will appeal to other scientists studying runoff processes.