The gradient of a stream depends on its base level.
Explanation;
Stream gradient is the grade measure by the ratio of drop in elevation of stream per unit horizontal distance.
A stream flows from higher elevations such as mountains to lower elevations such as oceans.
Base level is the limiting level below which a stream cannot erode its channel. in other words base level is where a stream meets a large body of standing water, such as an ocean, lake or even a pond.