Sinharajaya - Climate

• Climate
The Sinharaja lies within a rainfall range of 3,000 to 6,000 millimeters. Rainfall figures available for the last 60 years show values ranging from 3,614 to 5,006 millimeters in places, in and around the Sinharaja (Table 1). The mean monthly rainfall data for the year 1981 to 1984 given in Figure 6 indicates the general pattern of rainfall with a minimum of 50 millimeters even during the driest month and two distinct monsoonal peaks.

Table 1. Mean annual rainfall data available for locations in and around Sinharaja

Location Elevation (m) Time Period Mean Annual
Rainfall
(MAR) in mm.
Source
Beverly Estate
(South-eastern
boundary of reserve)
635 1925 - 1935 4054 Baker (1937)
Weddagala
( North-western boundary)
275 1948-1970 3691 Maheswaran (1982)
Kudawa
(North-western boundary)
340 1980-1981 1614 Maheswaran (1982)
Sinharaja field station
(3km within the North-western end of reserve)
380 1981-1984 5006 March of Conservation (1986)

The high annual temperature of the Sinharaja is typical of the tropics, recording little seasonal variation, but with marked daily ranges. The lowest mean monthly temperature has been abserved during the wettest season and the highest during the driest season. Conventional temperature patterns however change during long periods of drought or excessive rainfall. Some details of temperature and relative humidity recorded during the last 60 years are presented in Table 2.

Figure 6. Monthly distribution of rainfall and temperature from 1981 - 1989,
recorded at the Field Research Station in Sinharaja.



Table 2. Temperature and relative humidity data available for Sinharaja

Climate Elevation Within or outside forest Time of day Relative humidity Temperature C0 Source
Hapugoda Banks of Napala dola 570 within 2400
1400
93
83
21.0a
24.4b
Baker (1937)
Kumburugoda Banks of Napala dola 390 outside 700
1500
95
59
19.4a
31.1b
Merritt & Gunatilleke (1981)
Kudawa 340 outside - - 22.5a
34.1b
Gunatillake & Gunatilleke (1981)
Sinharaja 600 within - - 20.2a
25.2b

Sinharaja 600 within 1200 87 24.0 Maheswaran (1982)
Waturawa 510 within 1335 80 25.5
Waturawa 530 within 19.5a
24.0b

19.5a
23.5b
20.0a
24.0b

March for Consevation (1984)


A typical nature rivulet emerging from the dense forest of Sinharaja A common sight all over the wooded area with crystal clear water draining into the various waterways which makes the forest the most important watershed. This tropical humid rain forest plays a vital role in maintaining the quality and regulating the continuous supply of water. A numerous network of such rivulets found within the forest, feed the popular rivers Kalu Ganga to north and Gin Ganga to the south of Sinharaja.