Like so many common verbs, the meaning of "know" in the Bible is varied and dependent on context. And in some cases -- when it is connected to ideas or objects -- its spiritual meaning and natural meaning are essentially the same. When the Bible talks about people knowing each other and especially when it talks about the Lord knowing people, the meaning has more to do with the states of love within people than it does with any factual knowledge. This makes sense if you think about it. When we really "know" somebody, what we mean is that we know what kind of person they are, what their motivations are, what they love, what they hate, what makes them tick. Those things are far more important than knowing their parents' names, where they were born or what year they graduated from school. Most often then, especially applied to people, "knowing" has to do with the perceptions we have about other people's loves and the conjunction that can exist between those with similar loves, not just a collection of facts.

409. And it fell on a third of the rivers and on the springs of water. This symbolically means that consequently all the Word's truths had been completely falsified.

Rivers symbolize truths in abundance, because waters symbolize truths (no. 50); and springs of water or fountains symbolize the Word (no. 384). The meaning is that the Word's truths had been completely falsified, because in the next verse we are told that a third of the waters became wormwood, and wormwood symbolizes hellish falsity (no. 410).

[2] That rivers symbolize truths in abundance can be seen from the following passages:

...I am doing a new thing... ...I will give waters in the wilderness and rivers in the desert, to give drink to My people, My chosen. (Isaiah 43:19-20)

...I will pour water on him who is thirsty, and rivers on the dry ground; I will pour My Spirit on your offspring, and My blessing on your descendants. (Isaiah 44:3)

Then... the tongue of the dumb shall sing; for waters shall burst forth in the wilderness, and rivers in the desert plain. (Isaiah 35:6)

I will open rivers in the heights, and put fountains in the midst of the valleys; I will make the wilderness a pool of water, and the dry land springs of water. (Isaiah 41:18)

(Jehovah) has founded (the world) upon the seas, ...established it upon the rivers. (Psalms 24:2)

I will set His hand over the sea, and His right hand on the rivers. (Psalms 89:25)

Was Jehovah angry with the rivers? Was Your anger against the rivers? Was Your wrath against the sea, that You rode on Your horses...? (Habakkuk 3:8)

There is a river whose streams shall make glad the city of God... (Psalms 46:4)

He showed me a pure river of water of life..., proceeding from the throne of God and of the Lamb. (Revelation 22:1)

He split the rocks in the wilderness, and made the great abysses drink... ...He struck the rock..., and rivers flowed out... (Psalms 78:15-16, 20, cf. 105:41)

The waters will fail in the sea, and the river will be... dried up. (Isaiah 19:5-7; cf. 42:15; 50:2, Nahum 1:4, Psalms 107:33, Job 14:11)

(Jesus said, "If anyone comes to Me,) as the Scripture has said, out of his belly will flow rivers of living water." (John 7:37-38)

And so, too, elsewhere, such as Isaiah 33:21, Jeremiah 17:7-8, Deuteronomy 8:7.

[3] In an opposite sense, however, rivers symbolize falsities in abundance, as can be seen from the following:

(It) will send ambassadors by sea... to a nation... downtrodden, whose land the rivers have despoiled. (Isaiah 18:2)

If not for Jehovah on our side..., ...the waters would have overwhelmed us, (and) the river would have gone over our soul. (Psalms 124:2, 4-5)

When you pass through the waters, I will be with you; and through the rivers, they shall not overwhelm you. (Isaiah 43:2)

The cords of death surrounded me, and the rivers of Belial terrified me. (Psalms 18:5)

(The dragon) spewed water out of its mouth like a river after the woman, that it might cause her to be swallowed up by the stream. (Revelation 12:15)

...behold, Jehovah will cause to rise over them the waters of the river, strong and many..., and it will... overflow and pass through, and reach up to the neck. (Isaiah 8:7-8)

...the floods came, and... rushed upon that house; and (yet) it did not fall, for it was founded on the rock. (Matthew 7:25; cf. 7:27, Luke 6:48-49)

Rivers here, too, stand for falsities in abundance, because the rock symbolizes the Lord in relation to Divine truth.

Rivers also symbolize temptations or trials, because temptations or trials are inundations of falsities.