Case study:Onga River
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- 1 Project overview
- 2 Image gallery
- 3 Catchment and subcatchment
- 4 Site
- 5 Project background
- 6 Reasons for river restoration
- 7 Measures
- 8 Monitoring
- 9 Additional documents and videos
- 10 Additional links and references
- 11 Supplementary Information
|Project web site|
|Themes||Fisheries, Habitat and biodiversity, Hydropower, Water quality|
|Main contact forename||Kesler|
|Main contact surname||Martin|
|Main contact user ID||User:Kasvio|
|Contact organisation web site|
|Parent multi-site project|
| This is a parent project
encompassing the following
The Onga River is the biggest tributary of the Pedja River in the upper course. It is located in Lääne-Viru and Jõgeva counties. The length of this river is 30 km and its catchment area is 109 km2. The upper course of the river is located on the Pandivere Highlands, the middle course on the Alutaguse lowlands and the lower course is located in the north of Vooremaa.
In the summers of 1988 and 1994, The Onga Rivers water was slightly alkaline: in 1988, the pH value was 7,8 in the middle course of the river and 8,0 in the lower course of the river, and in 1994, the pH value was 7,7. There is no data about the mineral content of the water. The total content of organic matter in the water was low in Juny 1988 in the middle course of the river and medium in the lower course. In July 1994, the same figure was very low in the lower course of the river.
There is no literature data regarding which fish species can be found in the Onga River. Results for test catches in 1988 showed 6 different fish species. These species were: minnow, bullhead catfish, pike, burbot, loach and stickleback. The Onga River with its cold water which mostly comes from springs, is considered a trout river.
Recent work that has been done on the river: the clearing of sediments from the Onga River, the construction of sedimentation tanks on the river and bigger dicthes, the clearing of shores from fallen trees, if necessary, opening old river beds, fixing up drain oulets, slope fixing with rocks, fixing up a bridge, rapids in the streambed, placing rocks and groups of rocks, spawning beds for brown trots, construction of fish ladder and extension of the river bed for the dam at the Selli mill, construction of winter areas for fish and bringing the Selli biological treatment plant into order.
The construction took place on a 15,5 km distance on the Onga River. It started in October 2010, ended in October 2011 and the cost of it was 326 000 euros.
Monitoring surveys and results
Catchment and subcatchment
Cost for project phases
Reasons for river restoration
Hydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Additional documents and videos