Visualizing a polyline with decreasing width towards one end (QGIS)

Question

I am acquiring data related to the hydrography of a territory. I would like to use a symbology that allows me to have a line whose thickness decreases as it reaches its end (like the example in the image).

I could divide each line into many segments and give each one its own thickness, but I'm looking for a much faster and more effective method. The geometry generator could probably be a solution .

Currently, I have vectorized each waterway with a single line.

Answer 1

Try geometry generator:

 tapered_buffer( $geometry, 10, 50)