Answer:
Explanation:
the ratio of 1.8 millimeters / 1 year has to be equivalent with
the ratio of ? millimeters / 2.2 years
? = 1.8*2.2/1 = 3.96
the total variation in water level is 3.96 millimeters per 2.2 years
to check calculate the average annual trend
(1.8 + 3.96 ) millimeters / ( 1+ 2.2) years = 5.76 / 3.2 = 1.8 millimeters annually