Steam

The river is from a hot spring 

so we must make it bubble and steam. 

Save the image. 

and use it as the basis for your particle object.

Place Steam bottom centre in the River.

Change the settings of the Steam particles as shown

Angle the particles upwards

Make them mostly transparent.

Change the emission rate

Narrow the angle of the cone

Change the initial properties of the particle as shown.

Change the lifetime properties as shown

Test your game to see the Steam rising from the River