Groundwater gradient is calculated by the equation:
i=dh/dl
Where:
i= groundwater gradient
d= the change in, or Delta
h= groundwater head
l= length of casing in the well
Using this you would...
change in elevation: Distance So if the highest is 300m and the lowest is 100m then the change will be 200m. Pretend the distance between the two places is 1km but you have to make the units the same...
A gradient is another way of describing rate of change. In this case it's temperature per unit distance. A very simplified estimate of the geothermal gradient of the earth could therefore be made...