Make a copy of this layer and blur the copy out, making use of the next selection: Filter - Blur - Smart Blur.



Change the layer's type on Darken this time and merge down the layers (ctrl+e).



Insert on a new layer a picture having portrayed on it a water reservoir:



Choose all the options shown here (Free Transform, Layer Mask and Gradient Tool) and place the layer above the picture to have the impression that the rain is falling out of the reservoir:



Apply to this layer the command Image - Adjustments - Gradient Map to select the same colors we have on the next picture: