Rain water saturates the ground at higher levels and travels downhill by force of gravity where it is trapped by the impermeable layer of rock or clay.
(Rain water; saturates; the ground; at higher levels) (Rain water; travels; downhill) (it; is trapped; by the impermeable layer of rock or clay)
Rain water Rain water it
saturates travels is trapped
the ground at higher levels
downhill
by the impermeable layer of rock or clay