A thermal management system has a high temperature heat transfer circuit and a low temperature heat transfer circuit for modulating the temperature of heat-generating components having different operating temperatures. The heat transfer circuits are in flow communication and are interdependent so that a single circulating pump can be used to pump a liquid heat transfer medium through both circuits. One of the heat transfer circuits comprises a continuous loop and the other heat transfer circuit comprises an open loop having a first end and a second end at which it is in flow communication with the first heat transfer circuit. Each heat transfer circuit is provided with a heat exchanger to modulate temperature of the heat transfer medium.