Following services are provided by the Hydrology Division for the Citizens, Entrepreneurs, Researchers and other organizations.
- Management of island wide hydro-meteorological observation network including adding or removing stations as per the requirements and priorities.
- Management of hydro-meteorological database and information system with necessary improvements to meet the present and future requirements of the country.
- Flood mapping including collection of required data and information related to major floods.
Hydrometric Network of Sri Lanka
There are 103 major river basins in Sri Lanka which cover the 90 % of total land extent of the country as shown in Fig. 1. The remaining 10% which is situated along the coast and Jaffna peninsula is covered by small watersheds which are not much important in hydrological aspect.
About 24 major rivers (out of 103) convey the 80% of total flows generated within the Island and those are considered highly important in hydrological point of view. Our present hydrometric system is confined to those rivers. However there is a plan to expand and modernize the system in future under DSWRP (Dam Safety & Water Resources Planning Project).
The present hydrometric network of Hydrology Division comprises of 33 permanent stations and 40 peripheral stations covering 19 river basins. We are using manually operated instruments in all those stations except for few rain rainfall recorders and data loggers installed recently.
Thirty-three permanent stations, which record hourly water levels by the Department staff, are tabulated below (Table 1). Most of those stations are equipped with manual rain gauges which record rainfalls at 3 hr intervals.
|River Basin Number, Name & Drainage area km2||Hydrometric Station||Coordinates||Period of Operation (from)||Data Type|
|1||1. Kelani Ganga (2229)||Nagalagam Street||L/16(10.25*1.05)||1924||WL only|
|Hanwella||L/12(10.65*6.55)||1973||WL, Q & RF|
|Glencourse||L/8(4.15*2.2)||1948||WL, Q & RF|
|Holombuwa||L/14(9.70*8.42)||1962||WL, Q & RF|
|Deraniyagala||L/14(1.20*7.55)||1948||WL, Q & RF|
|Kithulgala||L/9(6.3*3.3)||1948||WL, Q & RF|
|Norwood||L/15(6.4*1.7)||1982||WL, Q & RF|
|2||3. Kalu Ganga (2719)||Putupaula||L/22(9.1*3)||1943||WL, Q & RF|
|Millakanda||L/23(4.6*5.1)||1990||WL & Q
|Ellegawa||L/18(6*3.15)||1956||WL, Q & RF|
|Ratnapura||L/24(5.5*8.15)||1995||WL, Q & RF|
|3||9. Ginganga (932)||Baddegama||O/13(3.5*0.15)||2006||WL, Q & RF|
|Tawalama||O/9(0.65*2.75)||1973||WL, Q & RF|
|4||12. Nilwala Ganga (971)||Panadugama||O/19(10.75*3.56)||2011||WL & RF|
|Pitabeddara||O/14(10.65*7.25)||1973||WL, Q & RF|
|Urawa||O/15(3.5*4.2)||1994||WL & RF|
|5||22. Kirindi Oya (1178)||Tanamalwila||P/3(0.9*2.1)||1987||WL, Q & RF|
|Wellawaya||M/17(13.5*1.6)||1956||WL, Q & RF|
|Kuda Oya||P/3(0.75*6.35)||1989||WL, Q & RF|
|6||31. Kumbukkan Oya (1293)||Nakkala||M/13(12.55*5.35)||1973||WL, Q & RF|
|7||36. Heda Oya (611)||Siyambalanduwa||M/15(2.35*6.25)||1991||WL, Q & RF|
|8||54. Maduru Oya (1559)||Padiyatalawa||J/18(5.4*3.9)||1984||WL, Q & RF|
|9||60. Mahaweli Ganga (14448)||Peradeniya||I/25(4.95*4.25)||1943||WL, Q & RF|
|Taldena||M/2(9.2*1.4)||1995||WL, Q & RF|
|Weragantota||J/22(4.96*8.17)||1945||WL, Q & RF|
|Manampitiya||G/22(11.5*5.11)||1953||WL, Q & RF|
|Nawalapitiya||L/10(1.1*7.2)||1989||WL, Q & RF|
|10||67. Yan Oya (1538)||Horowpathana||D/21(11.1*6.65)||1951||WL, Q & RF|
|11||90. Malwathu Oya (3284)||Tanthirimale||-||2007||WL, RF|
|12||95. Mee Oya (1533)||Galgamuwa||F/18(9.2*0.25)||1987||WL, Q & RF|
|13||102. Maha Oya (1528)||Badalgama||I/22(3.85*7)||1953||WL, Q & RF|
|Giriulla||I/22(13.13*8.7)||1962||WL, Q & RF|
|14||103. Aththanagalu Oya (736)||Dunamale||L/2(10.75*3.12)||2005||WL, Q & RF|
Table 1. Permanent Hydrometric Stations record hourly Water Levels and 3 hr Rainfalls
Eighteen rainfall stations are maintained by the department at the upper catchments crucial for monitoring floods (Table 2).
|River Basin Number, Name & Drainage area km2||Rainfall Station||Coordinates||Period of operation (from)|
||1. Kelani Ganga (2229)||Norton Bridge|
||3. Kalu Ganga (2719)||Dolabodakanda||2007|
|3.||12. Nilwala Ganga (971)||Talgahagoda||2003|
|4.||31. Kumbukkan Oya (1293)||Uwa-Karandagolla||2005|
|5.||99. Deduru Oya (2610)||Wijaya Katupotha||1989|
|6.||54. Maduru Oya (1559)||Akiriyankumbura||2007|
|7.||26. Menik ganga (1272)||Buttala||2003|
Table 2. Rainfall Stations maintained by Hydrology Division
Hydrology Division establishes temporary stations for Reservoir Panning and research works for the requirement of Irrigation Department and other Government Organizations on their request. Those stations are closed after the project period but records are available at the Hydrology Division for future uses.
Processed hydrological data and information are issued to outside agencies at standard rates approved by the Director General of Irrigation. Current rates are mentioned in Table 3.
|Data /Information Type||Rate|
|1||Daily average discharges (m3 / sec)||Rs 2500 per year per station|
|2||Monthly stream flow in MCM||Free of charge|
|3||Single Flood Event (WL & Q)||Rs 300|
|4||Annual maximum / minimum values||Rs 100 per year per station|
Table 3. Standard Rates for issuing Data and Information
In addition to above, hourly water levels and discharges at principal stations are being processed now and will be made available in near future.
Summary of important data and information are included in the ‘Hydrological Annual’ the annual bulletin published by Hydrology Division which is distributed among related Government Organizations. Private organizations and individuals also can purchase a copy from Hydrology Division.