Fig. 9.3 a&b. Positive and negative
temperature gradients:
Fig. 9.3 a illustrates a positive temperature
gradient — ground cooler shaded by trees —
rainwater warmer than the ground surface will
soak in easily, recharging the groundwater. But
where the surface is unprotected (Fig. 9.3 b) it
heats up, does not allow the rainwater to
penetrate (negative temperature gradient), causing
the water table to be forced upwards, with the
dissolved salts, which remain near the surface,
possibly causing problems of salination.
HIDDEN NATURE