1. One of the obvious reasons why God dried up the Jordan River was to facilitate the conquest of the land of Canaan for His people.
At this time of year the snows of Mount Hermon were melting, the Jordan river would overflow its banks, and become as wide as one mile in places. It was about a mile wide opposite Jericho. At this time of year the inhabitants of Canaan had reason to feel very secure: no invading force would be able to cross the Jordan and attack them. The current of the Jordan was swift; enough rafts could not be made to ferry enough fighting men across so that a siege might be laid to any of the Canaanite cities.
However, God causes the waters of the Jordan river to stand up in heaps and the river bed to dry up. The children of Israel may now march forward and possess the land of Canaan – a way of advance had been opened up for them.
2. A new generation has now succeeded the old: they too needed to witness the power of God in the physical universe.
This demonstration of God’s power would give them assurance as they went into the land of Canaan and were confronted with odds which, from a purely military perspective, would be impossible.
The generation of the Israelites which came out of Egypt had witnessed the mighty power of God over the natural creation in the drying up of the Red Sea (Exodus 14:15-31).
Accordingly, through the miracle of dying up the Jordan (Joshua 3), God reveals His power to the new generation in a similar way that He did to the previous generation of Israelites.
Just the same, just the same, God is just the same today!
Many explanations have been tendered over the years as to how the Jordan river dried up. Most prominent among these explanations is the ‘Landslide Theory.’ The thought is that a landslide took place upstream and Joshua simply took advantage of the landslide to cross over. However, Joshua 3:13 is prophetic.“And it shall come to pass, as soon as the soles of the feet of the priests that bear the ark of the LORD, the Lord of all the earth, shall rest in the waters of Jordan, that the waters of Jordan shall be cut off from the waters that come down from above; and they shall stand upon an heap.” Joshua could not possibly know that a landslide was going to take place.
The Israelites had all of their religious items with them. The tabernacle, representing the capital of God, is there; the ark and all the sacred vessels were there. Joshua 3:15 makes a very definite comment when it says that: “And as they that bare the ark were come unto Jordan, and the feet of the priests that bare the ark were dipped in the brim of the water, (for Jordan overfloweth all his banks all the time of harvest.)” Joshua 3:17 informs us that the priests carried the ark into the Jordan river - then the river dried up and the people crossed over on dry land.
3. Joshua’s position as leader was confirmed in the drying up of the Jordan. Joshua had predicted this event (Joshua 3:13) and it happened. In this way Joshua’s position was validated.
4. The drying up of the Jordan river issued in the psychological devastation of the Canaanites.
To see Israel crossing over a dried up river shattered the security of the Canaanites. If, according to Rahab, the hearts of the people of Canaan had melted when they heard about the miracle at the Red Sea (Joshua 2:10&11), their hearts must have melted again when they saw the Jordan river dry up. Joshua 5:1 confirms that this was the case.