The volume flow rate (Q) of an incompressible fluid in steady flow remains constant From equation of continuity,   $av=$ constant 

$\therefore Q=a\times v=$constant or, $a\propto \frac{1}{v}$

Where  $a=$ area of cross-section and  $v=$ velocity 

$\Rightarrow$If $v$ decreases $a$ increases and vice – versa

When stream of water moves up, its speed $\left(v\right)$  decreases and therefore $\text{'}a\text{'}$ increases i.e. the water spreads out as a fountain. When stream of water from hose pipe moves down, its speed increases and therefore area of cross-section decreases.