The earth is God's farm and the means by which He feeds the world. That is the thanksgiving perspective of this psalm. All life on earth is fed by the world that God maintains. And that is a common grace that should lead us into worship. If the rivers ceased to flow or if the grain would no longer flourish, we would die.
Of course we scientifically-minded late moderns are more impressed with meteorologists and climate science. They tell us how weather works and what to expect. But they cannot change the weather or bring relief. They cannot stop a storm nor can they end a drought. We are as dependent upon God's control of the cycles of this earth as the ancients were!
In tune with the natural order of the seasons, David praised God for the abundant blessings He brought with the rivers and the rain. And that simple reliance was a daily faith that kept worship centered upon God. By God's hand we are fed. It is good to live with that realization in thankfulness.