Abstract: Techniques for large-scale Lagrangian monitoring of an aquatic resource are presented. The techniques use a system that includes an autonomous surface vehicle, where the autonomous surface vehicle includes: an electronic controller; a power source coupled to the electronic controller; a plurality of sensors communicatively coupled to the electronic controller, the plurality of sensors including: a water quality sensor and a GPS sensor; and a propulsion system communicatively coupled to the electronic controller, the propulsion system including a thruster and at least one rudder; where the system determines a velocity of water in the aquatic resource based on a plurality of position signals from the GPS sensor.