Fill in the correct preposition, then choose any three items and make sentences

1) to depend … smth.; 2) to vary in size … smth. … smth.; 3) to be known … smth.; 4) to be filled … smth.; 5) to be called … smth.; 6) … contrast.

21. Fill in the correct words from the list below.

a) artesian d) recharge g) importance

b) a flowing well e) low h) cost

c) pressure f) have i) compared

Sometimes an aquifer is confined by strata of 1)______ permeability. Such an aquifer is called the 2)______ aquifer. They are analogous to pipelines. The static pressure at a point within the aquifer is equivalent to the elevation of the water table in the3)______ area. If the 4)______ is sufficient to raise water above the ground, the well is called 5)______. Artesian aquifers usually 6)______ relatively small recharge areas as 7)______ with other aquifers and yield less water. The econo­mic 8)______ of artesian aquifers lies in the fact that they transmit water substantial distances and deliver it above the level of the aquifer, thus minimizing pumping 9)______.