Whoever chose Psalm 114 for the Lectionary for Easter must have been serious about it. It is the one and only psalm set for both Easter Sunday and Easter vigil services in all three years of the cycle.
Why? This poem is all about the Exodus, the release from slavery in Egypt, and the transit to a new life across the Red Sea and Jordan River. In the Hebrew tradition this is the escape to freedom that is celebrated during Passover (פֶּסַח Pesach in Hebrew, hence Paschal as an adjective or attributive qualifier), also observed this week 8 to 16 April.
So the Lectionary just follows Jewish practice. Psalms 113 to 119 are called the Hallel Psalms, used as prayers before and after the Passover meal. Isaac Everett speculates in The Emergent Psalter that there is a good chance that Jesus sang this psalm at the Last Supper.
The song anticipates freedom in any age, escape from bondage or oppression into a better land, one flowing with milk and honey. So Easter Sunday with its message of hope is an appropriate moment for this song, as are many other situations of relief and thanksgiving for escapes from burdens of whatever hue to freedom and new beginnings.

This song pictures creation celebrating as freedom from bondage brings water into the desert, “turns the rock into a pool of water and flint into a spring”.(8) Descriptions of natural forces, soaring mountains, powerful rushing waters and raw energy remind the reader of occasions watching the unstoppable rush of melting snow or seasonal downpours coursing wildly down from the hills. Close up you can feel the weight of that fast flow on its determined journey to the sea.
For further commentary and a review of some of the music, see the page on Psalm 114.
At South Woden we hear, and join at home, Freedom is coming.