LU researchers assess the elements of biological quality in the Lake Sauka and six rivers

Since the end of May, researchers from the Hydrobiology Laboratory of the Institute of Biology of the University of Latvia have been researching biological quality elements in the Lake Sauka and six demonstration rivers of the LIFE GOODWATER IP project. In total, the work is taking place in the lake and in 12 river sections – in Mergupe, Zana, Ēda, Slocene, Age and Auce, in order to find out the ecological status of the Lake Sauka and the mentioned rivers.

The ecological quality assessment of the Lake Sauka will be determined on the basis of a detailed assessment of samples of benthic aquatic invertebrates (zoobenthos), phytoplankton and higher aquatic plants (macrophytes), while the ecological quality of rivers will be assessed on the basis of macrophyte and zoobenthos samples. Intensive sampling of biological quality elements will take place for two years from May 2020 – phytoplankton and zooplankton samples are collected monthly, benthic invertebrates once a season and macrophytes once during a vegetation season. This is necessary for the development of the Sauka Lake food chain model, which will be launched in 2021.

The protection of water resources is one of the main priorities of the European Union’s environmental policy, as evidenced by the many pieces of legislation adopted, the most important of which is the Water Framework Directive 2000/60 / EC of the European Parliament and of the Council, which aims to achieve at least good ecological quality for surface water and groundwater within the territory of the European Union.

The Water Framework Directive stipulates that the ecological quality of river and lake water bodies is determined on the basis of three groups of quality elements: biological, general physico-chemical and hydromorphological quality elements, of which biological quality elements are given the highest importance.

There are currently 164 risk water bodies in Latvia (89 rivers and 75 lakes), including Lake Sauka and six project demonstration rivers. The main problems that have led to these water bodies being identified as being at risk are related to increased nutrient inputs and various hydromorphological changes. The Life GoodWater IP project aims to improve the water quality of approximately 30% of risk water bodies in the long term, including in the Lake Sauka and the project demonstration rivers.

Below we provide some general descriptions of research objects:

Lake Sauka is a public lake located in Sauka Parish, Viesīte District. The lake is located in the Lielupe catchment area. The area of ​​Lake Sauka is 718.2 ha, its maximum depth reaches 9.5 m, but the average depth is 5.1 m. Lake Sauka can be described as a shallow clear water lake with high water hardness.

Aģe is a 43 km long river with a catchment area of ​​215 km2 and a slope of 51.4 m (1.3 m / km). It flows out of Lake Aģe in the Idumeja plateau and flows along the northern part of Saulkrasti municipality, the southern part of Limbaži municipality and Krimulda municipality.

Mergupe is a tributary of the left bank of the Great Jugla in Amata, Sigulda, Mālpils and Ogre counties. It flows out of a small lake Būnēni in Nītaure parish. The length of the river is 64 km, but the catchment area is 316 km2.

Slocene is a river in Tukums and Engure counties, which belongs to the hydrological district of Western Latvia. The area of ​​the Slocene basin is 315 km2, the length is 44 km, the annual runoff is 0.06 km3 and the slope is 58 m (1.3 m / km).

Auce is a tributary of the left bank of the Svēte, which flows through the counties of Auce, Dobele, Tērvete and Jelgava. The river flows from Lake Lielauce in the Lielauce hills. The length of the Auce is 92 km, but the catchment area is 392 km2.

Zaņa is a tributary of the right bank of the Venta in Saldus municipality. The total length of the river is 53 km and the catchment area is 257 km2. The annual runoff of the Zana River is 0.06 km2, but the fall of the river is 75 meters (1.4 m / km).

Ēda is a tributary of the right bank of the Venta in Saldus and Kuldiga counties. From Jaunlutriņi to Šķēde it is also called Lukāčupe, but from Šķēde village to Vārme estuary – Šķēde. The length of the river is almost 50 km, but the catchment area is 305 km2.

The ecological quality assessment of Lake Sauka and six rivers takes place within the framework of the Life Goodwater IP project. The project is implemented by 19 Latvian organizations related to environmental issues in the period from 2020 to 2027, the leading partner is the Latvian Center for Environment, Geology and Meteorology. Information prepared by: Linda Uzule, researcher at the Institute of Biology, University of Latvia.