Page 159 - Arabian Studies (II)

Effects of Irrigated Agriculture on Soil Characteristics 151

Evaporation (mm.)
Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jut. Aug. Sept.
8.0 6.1 4.2 4.0 4.3 7.2 8.2 10.5 11.9 13.1 12.0 10.0

In no month did rainfall exceed the evaporation as recorded by the
pan.
The average annual rainfall at Sharjah amounts to about 103 mm.
falling mainly in the months November to May. There are great
annual variations which have ranged from 0.3 mm. in 1961/2 to over
258 mms. in 1956/7. Much of this rain falls as localised showers and
a rainy day at Sharjah does not necessarily mean that rain will fall at
Digdaga. Furthermore, because of the localised nature of the rainfall,
there are considerable disparities in annual rainfall totals between the \
two stations (Table 1).
Sandstorms can also have an important effect on agriculture and
these mainly occur between January—March and August—October.
Hutton (1964) considered that when a windspeed exceeded 20 knots
then a true sandstorm developed. Such winds are most common in
March when the predominant wind direction is W or WNW and
consequently the agricultural areas of Ras al-Khaimah tend to be
affected by blown sand derived from the desert to the west.
The cultivated areas of Ras al-Khaimah is shown in Fig. 3. The
oldest forms of cultivation are the date gardens which are located
around the villages of Habhab, Khatt and Fahlain, and also in a

Table 1
ANNUAL RAINFALL, SHARJAH AND DIGDAGA

Annual rainfall (mm.)

Year Sharjah Digdaga
1959/60 47.6 138.0
1960/1 89.3 149.7
1961/2 0.3 51.7
1962/3 227.9 158.7
1963/4 127.6 195.5
1964/5 122.9 153.2
1965/6 60.8 61.0
1966/7 11.5 17.5
1967/8 81.8 66.6
1968/9 139.8 118.6
Sources: Trucial States Council data.