Sri Lanka's Rivers (Sinhala: ශ්රී ලංකාවේ ගංගා; Tamil: இலங்கையின் ஆறுகள்) rise from the country's inland regions such as the Central Highlands and flow towards the sea. According to traditional classification, there are 103 rivers (basins) in Sri Lanka and 16 of them are longer than 100 km in length while 12 of them carry about 75% of the mean river discharge in the entire country (Katupotha & Gamage, 2020; Weerasinghe, 2008). Their basins cover 90% of the island.
A river is a ribbon-like body of water that flows downhill from the force of gravity representing different drainage patterns (Katupotha & Gamage, 2020). It can be wide, deep or shallow enough for a person to wade across (Katupotha & Gamage, 2020). A river with a regular discharge, throughout the year, is known in Sri Lanka as a Ganga while a smaller river that dries up during the dry season is called an Oya (De S. Hewavisenthi, 1997). Although there are 103 river basins in Sri Lanka, only 29 can be identified as rivers (Katupotha & Gamage, 2020).
Most rivers in Sri Lanka are short and less than 160 km in length, except the Mahaweli Ganga which is 335 km (Katupotha & Gamage, 2020; Vithanage, 1988). However, a few rivers rise in the Central Highlands, from 2,400 m or more elevation and reach the sea passing more than 100 km length (Katupotha & Gamage, 2020). Water from these rivers is utilized to fulfil the basic water requirements of the country.
Longest rivers in Sri Lanka (Vithanage, 1988)
-
1) Mahaweli Ganga (335 km)
2) Malwathu Oya (164 km)
3) Kala Oya (148 km)
4) Kelani Ganga (145 km)
5) Yan Oya (142 km)
6) Deduru Oya (142 km)
7) Walawe Ganga (138 km)
8) Maduru Oya (135 km)
-
9) Maha Oya (134 km)
10) Kalu Ganga (129 km)
11) Kirindi Oya (117 km)
12) Kumbukkan Oya (116 km)
13) Menik Ganga (114 km)
14) Gin Ganga (113 km)
15) Mi Oya (109 km)
16) Gal Oya (108 km)
.
River basins in Sri Lanka
A river basin is a natural unit and lends itself ideally for water resources studies concerning rainfall, streamflow water use, drainage etc (Arumugam, 1969). There are 103 river basins in Sri Lanka and many of them are located on the Intermediate, and Dry Zones below the 300 m and 150 m contour lines (Arumugam, 1969; Katupotha & Gamage, 2020; Hydrological Annual, 2011/2012). For the convenience of studies, each basin has been given a unique ID number ranging from 1 to 103.
Of the river basins, ID nos. 2 (Bolgoda Lake), 5 (Madu Ganga), 6 (Madampe Lagoon), 7 (Telwatta Ganga), 8 (Ratgama Lake) and 10 (Koggala Lagoon)) are water bodies located in back-barrier of the coastal area (Katupotha & Gamage, 2020). Also, the ID nos 24 (Mahasilawa Oya), 27 (Katupila Ara), 66 (Palakutti Ara) and 101 (Ratmal Oya) are not connected directly with the sea but to a major river or a marsh (Katupotha & Gamage, 2020). The Mahasilawa Oya flows into a salt marsh, while Katupila Ara is connected to Menik Ganga. Palakutti Ara is connected to a lagoon and Ratmal Oya flows into the Gin Oya (Katupotha & Gamage, 2020).
Of the 103 flows, 64 rivers flow at lagoons or lakes while 29 rivers directly flow to the sea (Katupotha & Gamage, 2020). Only 8 rivers (Kelani Ganga, Kalu Ganga, Walawe Ganga, Kirindi Oya, Menik Ganga, Kumbukkan Oya, Gal Oya and Mahaweli Ganga) start from the central highland and its adjacent areas [(>1,200 m contour line) Katupotha & Gamage, 2020]. Mahaweli Ganga is the longest river in the country and its headstreams start from Central Highland. The head-streams of the other 3 major rivers
namely Kelani, Kalu and Walawe begin from the western and southern flanks
of the Samanala Mountain Range (Katupotha & Gamage, 2020).
The list of river basins in Sri Lanka (103)
+ Rivers (29) * Water bodies (6)
# Not connected with the sea (4) ! Connect to either lagoons or lakes (64)
.
| Basin ID |
River name (category) |
Origin (elevation) |
Drainage area Sq. km |
Runoff (Annual total) 1000 Ac. ft. |
| 1 | Kelani Ganga (+) |
>2,400 m |
2,340 |
5,807 |
| 2 | Bolgoda Lake (*) |
<150 m |
396 |
669 |
| 3 | Kalu Ganga (+) |
1,200-2,400 m |
2,839 |
6,294 |
| 4 | Bentota Ganga (+) | 150-300 m |
667 |
1,427 |
| 5 | Madu Ganga (*) | 69 |
137 |
|
| 6 | Madampe Ganga (*) | 90 |
205 |
|
| 7 | Telwatta Ganga (*) | <150 m |
41 |
120 |
| 8 | Ratgama Lake (*) | <150 m |
13 |
23 |
| 9 | Gin Ganga (+) |
600-1,200 m |
915 |
1,550 |
| 10 | Koggala Lake (*) | <150 m |
55 |
137 |
| 11 | Polwatta Ganga (+) |
150-300 m |
232 |
255 |
| 12 | Nilwala Ganga (+) |
600-1,200 m |
1043 |
1,210 |
| 13 | Sinimodara Oya (+) |
<150 m |
35 |
46 |
| 14 | Kirama Oya (+) |
150-300 m |
183 |
168 |
| 15 | Rekawa Oya (!) |
<150 m |
70 |
55 |
| 16 | Urubokka Oya (!) |
300-600 m |
373 |
206 |
| 17 | Kachigal Ara (!) |
150-300 m |
208 |
100 |
| 18 | Walawe Ganga (+) |
>2,400 m | 2424 |
1,784 |
| 19 | Karagan Oya (!) |
<150 m |
60 |
20 |
| 20 | Malala Oya (!) |
150-300 m |
409 |
131 |
| 21 | Embilikala Oya (!) |
<150 m |
69 |
19 |
| 22 | Kirindi Oya (+) |
1,200-2,400 m |
1156 |
537 |
| 23 | Bambawe Ara (!) |
<150 m |
66 |
26 |
| 24 | Mahasilawa Oya (#) |
<150 m |
13 |
3 |
| 25 | Butawa Oya (!) |
<150 m |
37 |
14 |
| 26 | Menik Ganga (+) |
1,200-2,400 m |
1301 |
524 |
| 27 | Katupila Ara (#) | <150 m |
111 |
36 |
| 28 | Kurunda Ara (!) |
<150 m |
99 |
52 |
| 29 | Namadagas Ara (!) |
<150 m |
110 |
43 |
| 30 | Karambe Ara (!) |
<150 m |
54 |
33 |
| 31 | Kumbukkan Oya (+) |
1,200-2,400 m |
1,227 |
586 |
| 32 | Bagura Oya (!) |
<150 m |
93 |
55 |
| 33 | Girikula Oya (!) |
<150 m |
14 |
6 |
| 34 | Helawa Ara (!) |
<150 m |
38 |
8 |
| 35 | Wila Oya (!) |
150-300 m |
472 |
192 |
| 36 | Heda Oya (+) |
150-300 m |
615 |
302 |
| 37 | Karanda Oya (!) |
150-300 m |
425 |
196 |
| 38 | Seymena Ara (!) |
<150 m |
72 |
27 |
| 39 | Tandiadi Ara (!) |
<150 m |
20 |
14 |
| 40 | Kangikachchi Ara (!) |
<150 m |
78 |
27 |
| 41 | Rufus Kulam Aru (!) |
<150 m |
27 |
14 |
| 42 | Pannel Oya (!) |
<150 m |
195 |
116 |
| 43 | Ambalan Oya (!) |
150-300 m |
112 |
70 |
| 44 | Gal Oya (+) |
1,200-2,400 m |
1,911 |
1,418 |
| 45 | Andella Oya (!) |
300-600 m |
534 |
324 |
| 46 | Tumpan Keni Tank (!) | <150 m |
18 |
3 |
| 47 | Namakada Aru (!) | <150 m |
12 |
6 |
| 48 | Mandipattu Aru (!) | <150 m |
90 |
64 |
| 49 | Pathantoppu Aru (!) | <150 m |
101 |
64 |
| 50 | Vedi Aru (!) | <150 m |
22 |
21 |
| 51 | Magalavatavan Aru (!) | <150 m |
304 |
153 |
| 52 | Mundeni Aru (!) | 150-300 m |
1,373 |
609 |
| 53 | Miyangolla Ela (!) | <150 m |
228 |
101 |
| 54 | Maduru Oya (!) | 150-300 m |
1,439 |
1,133 |
| 55 | Pulliyanpota Aru (!) | <150 m |
87 |
27 |
| 56 | Kirimechchi Odai (!) | <150 m |
89 |
72 |
| 57 | Bodigoda Aru (!) | <150 m |
132 |
144 |
| 58 | Mandan Aru (!) | <150 m |
26 |
16 |
| 59 | Makarachchi Aru (!) | <150 m |
59 |
39 |
| 60 | Mahaweli Ganga (+) |
>2,400 m | 10,266 |
4,306 |
| 61 | Kantale Aru (!) | 150-300 m |
437 |
221 |
| 62 | Palapotta Ara (!) | <150 m |
97 |
49 |
| 63 | Panna Oya (!) | <150 m |
164 |
90 |
| 64 | Pankulam Aru (!) | 150-300 m |
377 |
223 |
| 65 | Kunchikumban Aru (!) | <150 m |
245 |
71 |
| 66 | Pulakutti Aru (#) | <150 m |
8 |
8 |
| 67 | Yan Oya (+) |
150-300 m |
1,518 |
636 |
| 68 | Mee Oya (!) | <150 m |
89 |
36 |
| 69 | Ma Oya (!) | <150 m |
1,042 |
384 |
| 70 | Churiyan Aru (!) | <150 m |
105 |
30 |
| 71 | Chavar Aru (!) | <150 m |
35 |
12 |
| 72 | Palladi Aru (!) | <150 m |
66 |
26 |
| 73 | Manal Aru (!) | <150 m |
194 |
90 |
| 74 | Kodalikallu Aru (!) | <150 m |
92 |
42 |
| 75 | Per Aru (!) | <150 m |
392 |
185 |
| 76 | Palu Aru (!) | <150 m |
70 |
44 |
| 77 | Maruthapillay Aru (!) | <150 m |
36 |
23 |
| 78 | Thoravil Aru (!) | <150 m |
104 |
39 |
| 79 | Piramanthal Aru (!) | <150 m |
91 |
41 |
| 80 | Netheli Aru (!) | <150 m |
114 |
51 |
| 81 | Kanakarayan Aru (!) | <150 m |
604 |
337 |
| 82 | Kalwalappu Aru (!) | <150 m |
68 |
34 |
| 83 | Akkarayan Aru (!) | <150 m |
244 |
107 |
| 84 | Mandekal Aru (+) |
<150 m |
208 |
121 |
| 85 | Pallavarayankaddu Aru (+) |
<150 m |
311 |
51 |
| 86 | Pali Aru (+) |
<150 m |
451 |
163 |
| 87 | Chippi Aru (+) |
<150 m |
79 |
18 |
| 88 | Parangi Aru (+) |
<150 m |
770 |
266 |
| 89 | Nay Aru (+) |
<150 m |
717 |
145 |
| 90 | Malwathu Oya (+) |
150-300 m |
3,291 |
1,004 |
| 91 | Kal Aru (+) |
<150 m |
210 |
94 |
| 92 | Moderagama Aru (!) |
<150 m |
1,001 |
252 |
| 93 | Kala Oya (+) |
300-600 m |
2,526 |
859 |
| 94 | Moongil Aru (!) | <150 m |
78 |
11 |
| 95 | Mi Oya (!) | <150 m |
1,555 |
121 |
| 96 | Madurankuli Aru (!) | <150 m |
128 |
7 |
| 97 | Kalagamu Oya (!) | <150 m |
169 |
12 |
| 98 | Rathambala Oya (!) | <150 m |
244 |
104 |
| 99 | Deduru Oya (+) |
600-1,200 m |
2,622 |
1,222 |
| 100 | Karambala Oya (+) |
<150 m |
693 |
292 |
| 101 | Ratmal Oya (#) |
<150 m |
341 |
143 |
| 102 | Maha Oya (+) | 600-1,200 m |
1,470 |
1,570 |
| 103 | Attanagalu Oya (+) |
150-300 m |
811 |
618 |
Attribution
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References
1) Arumugam, S., 1969. Water resources of Ceylon: its utilisation and development. Water Resources Board. pp.1-6.
2) De S. Hewavisenthi, A.C., 1997. Management of the Mahaweli, a river in Sri Lanka. Water international, 22(2), pp.98-107.
3) Hydrological Annual, 2011/2012. Hydrology Division. Irrigation Department. Ministry of Irrigation and Water Resources Department. pp.4-6.
4) Katupotha, J.; Gamage, S., 2020. Understanding the river basin classification of Sri Lanka. Wildlanka, 8 (4). Department of Wildlife Conservation, Sri Lanka. pp.175-197.
5) Vithanage, P.W., 1988. Relief and Drainage. The National Atlas of Sri Lanka. Survey Department of Sri Lanka. ISBN: 9559059009. pp.22-23.
6) Weerasinghe, S.M., 2008. North-Western Province Biodiversity Profile and Conservation Action Plan. The Biodiversity Secretariat. Ministry of Environment and Natural Resources. ISBN: 978-955-0033-01-0. p.30.
This page was last updated on 17 July 2023