When I look up any definition in the dictionary I have never found the word I was trying to understand as part as the definition as is the case with the wdfw's definition of the mouth.

I have read the definition forwards and backwards and have come the the conclusion it can be interpreted many different ways and is confusing at best.

The way I understand the definition, I take it as drawing a line at the high tide mark. After all, rivers are not saltwater.

How do you all interpret the definition?

Good post. This has me puzzled also.

Good question...and I'll add, what about river confluences? Most don't have tidewater issues to deal with (although the Pilchuck is one exception), but I'm assuming that the line is dependant on where the water level is and is not simply a static line drawn on a map.

The mouth of a river or stream is a nebulous concept that is not all that closely defined. I typically take it where the shoreline of the lake, sea, river or other waterbody intersects the river or stream.

Usually extending out into the waterbody is the delta of the river, and it may influence the shoreline.

In fishing, I consider I am fishing the mouth if I am fishing near the mouth of the river, maybe up stream a bit, or on the delta, or maybe off the delta a bit.

And most tidewater rivers fill with saltwater at high tide. The Green does to Tukwila on big tides, the Stilly gets saltwater up it well past Marine View Drive.

Well, if you want to talk about the mouth of a river or creek in terms of one that flows into saltwater, boy I have got a curveball to throw your way!

When the tide comes in the river gets "backed up" right? Nope! Since freshwater is denser than saltwater the river flows under the saltwater. What you get is essentially a separation of the two bodies of water as a result of salinity differences. So the river is not really "backed up" it just isn't visible since the saltwater is on top of it. This oceanographical event is referred to as the saltwedge.

Imagine you were looking at the river from the side, the tidewater section of river could be best represented by a simple diagram in the form of a rectangle. The river flows to toward the left side of the rectangle while the saltwater flows toward the right side. Based on the previously given info from the saltwedge explanation, we can draw a diagonal line from the lower left corner to the upper right corner to indicate the halocline(salinity boundary for water) and pycnocline(density boundary water). What you now see is two triangles within a rectangle, the triangle on top would represent the saltwater and the one on the bottom would represent the freshwater.

Now that you people know what a saltwedge is like, we can proceed to define the river mouth. We know the river flows into the ocean when not influenced by an incoming tide. When viewed from above, you would see the river form a fan-shaped delta under the saltwater where it flows into the ocean. Despite the fact that we are some distance out in the ocean, the seafloor is influenced by the river as evidenced by the delta. You would determine where the river "ends" by lowering a probe to the bottom from a floating device and measuring the salinity. You would keep moving offshore until your meter reading stops changing. This number is your normal ocean salinity. At this point there is no longer a freshwater influence.

Based on the above statements, I conclude that river mouth is determined to be the point at which salinity change ceases and an equilbrium is reached. Basically despite no longer being bounded by land on two sides, the river continues when it enters the ocean and the mouth is where it stops.

By the way, this is just my opinion and it will likely never be accepted by the WDFW for regulation purposes.

Good reply Rockhopper, except you got it backwards. Freshwater is lighter than saltwater and floats on top.

I guess with that definition you can say that there are rivers in the ocean. I.E the freshwater that flows from the polar ice cap around the world.

Heres the definition.

Unless otherwise defined. The mouth of a stream river or slough is a line projected between the outermost uplands at the mouth.
Outermost uplands are those lands not covered at ordinary high water.

OOPS!
Thanks for the clarification sea claire!
Looks like I really did throw a curveball there. :p