مقدار ضریب ذخیره آبخوانهای آزاد و تحت فشار

Specific Yield (%)

Material

Maximum

Minimum

Average

coarse gravel

26

12

22

medium gravel

26

13

23

fine gravel

35

21

25

gravelly sand

35

20

25

coarse sand

35

20

27

medium sand

32

15

26

fine sand

28

10

21

silt

19

3

sandy clay

12

3

7

clay

5

0

2

(Johnson (1967) as quoted by C.W. Fetter)