Jesus is saying He will quench that thirst within you and make you a channel to bring living waters to others. Living waters are flowing waters - life giving.

When you have had dry, barren times in your life spiritually, the living waters are real and powerful. After my Mom's funeral, I just felt so empty and was crying out to the Lord - and opened up His Word to the very next chapter I was reading in Isaiah and came across this promise:

Isaiah 41:17-18 When the poor and needy seek water, and there is none, and their tongue faileth for thirst, I the LORD will hear them, I the God of Israel will not forsake them. I will open rivers in high places, and fountains in the midst of the valleys: I will make the wilderness a pool of water, and the dry land springs of water.

Jesus quenches that thirst within - it is a spiritual promise fulfilled literally.

As far as power goes though, the Holy Spirit is still there to give us all the power we need to serve the Lord and live for Him each day. It is not manifestations and signs and wonders - but power and boldness for witnessing, strength to serve Him, peace of mind as we stay focussed on Him - all that we need every day when we walk closely by His side.