XXXll. 
Charles Austin Gardner. 
The third climatic region, the vast central area, receives nothing of the 
pluvial wealth of the northern ami southern systems. If, as sometimes hap- 
pens, the southern system sets in over a wide front in conjunction with an 
active low-pressure northern system, then the central area may receive heavy 
and useful precipitations, and in such years the Wiluna district may receive 
more annual rainfall than many coastal stations. On the other hand, the ac- 
tive hurricanes of the months of February and March may bring widespread 
rains to the north-west and extend far inland, bringing disastrous floods. 
There are thus two months in the year which receive more rainfall than any 
others- — March and June, the foriner being summer rain, the latter winter 
rain. Having no rainfall system peculiar to itself, this central region relies 
entirely upon extensions of the northern and southern systems, experiencing 
sometimes a comparatively rich rainfall in March, or in June, with lighter 
precipitations at other times, w'hile on the other hand, one or both of these 
may fail, and a prolonged period of drought ensues, sometimes extending 
over two or more years. On the other hand, it may experience two heavy 
rainfall systems within the one year, as was the case at Wiluna in 1900 and 
1942. It is this climatic instability that determines the character of the vege- 
tation of the middle zone. The following table illustrates the annual rainfall 
for two selected stations : Wiluna being typical for the middle of the dry 
area, and Katanning in the South-West being typical of the winter rainfall area. 
These tables are interesting in that they indicate the high fluctuations 
in the annual rainfall for Wiluna when compared with the relatively reliable 
rainfall of Katamiing. At Wiluna we have a departure from the moan of 
-f- 201 per cent, and — ■ 79 per cent., whereas at Katanning similar figures over 
the same period are H- 45 per cent, and — 26 per cent. 
ANNUAL RAINFALL AT WILUNA, 1899-1942, SHOWING ANNUAL VARIATION. 
(Annual average 
rainfall. 
00 
'.O 
1 
931 points. 
Year. 
Annual 
Total. 
De[:>arture 
from Mean. 
Year. 
Annual 
Total. 
D(' part lire 
from Mean. 
1899 .... 
855 
— 
8 
1922 .... 
691 
— 
26 
1900 .... 
2,803 
_L 
( 
201 
1923 .... 
742 
— 
20 
1901 ... 
875 
— 
18 
1924 .... 
506 
— 
46 
1902 .... 
1,366 
-L 
47 
1925 .... 
K430 
-f 
54 
1903 .... 
737 
— 
21 
1926 .... 
633 
— 
29 
1904 .... 
1,077 
16 
1927 .... 
1.034 
1 
~r 
11 
1905 ... 
617 
— 
34 
1928 .... 
460 
— 
50 
1906 .... 
780 
— 
16 
1929 .... 
805 
— 
13 
1907 .... 
804 
— 
24 
1930 .... 
1,564 
-h 
68 
1908 .... 
1,019 
+ 
9 
1931 .... 
1,374 
49 
1909 .... 
1,334 
+ 
43 
1932 .... 
654 
— 
29 
1910 ... 
192 
— 
79 
1933 .... 
1,032 
11 
1911 ... 
676 
— 
27 
1934 .... 
1,412 
+ 
52 
1912 .... 
745 
— 
20 
1935 ... 
363 
— 
62 
1913 ... 
1,396 
+ 
50 
1936 ... 
271 
— 
71 
1914 ... 
790 
— 
15 
1937 .... 
804 
— 
14 
1915 .... 
1,693 
-L 
82 
1938 .... 
812 
— 
12 
1916 .... 
1,061 
14 
1939 .... 
778 
— 
16 
1917 .... 
1,086 
17 
1940 .... 
346 
— 
62 
1918 .... 
987 
+ 
(i 
1941 ... 
1,100 
+ 
IS 
1919 .... 
935 
0 
1942 .... 
2,770 
1 
147 
1920 .... 
847 
— 
4 
1921 .... 
729 
— 
22 
