Reservoir outlets must provide their outlet geometry and elevation place to support the implementation of a WQ rule in HEC-ResSim. The user may optionally define a WQ control device, which may be assigned to a single outlet or outlet group. WQ Operation rule can be operated as a release from a dam or outlet group. If it needs to be operated as a release from any other outlet, a water quality control device needs to be defined for that outlet. A WQ control device is designed to let the operator withdraw different amounts of water from different levels in the pool. User has to define the shape of the outlet and the withdrawal range from the outlet.