Thematic Group Leader Ainis Lagzdiņš, Latvia University of Life Sciences and Technologies
The activities implemented by the thematic group of diffuse pollution are related to determination and assessment of the state of water quality in the areas affected by agricultural and forestry activities, paying increased attention to potential sources of losses of nitrogen and phosphorus compounds in the selected riverine water bodies at risk (Age, Slocene, Auce and Eda). In addition, the activities implemented by the thematic group are related to the complex research of Lake Sauka, which includes determination and analysis of hydrobiological, hydrochemical and hydromorphological indicators of water quality. Based on the results of comprehensive assessment, the project partners have developed recommendations and will practically implement measures aiming to improve the ecological quality of riverine and lake water bodies at risk.
As part of the preparatory activities carried out within Action A1, the water courses with increased concentrations of nitrogen and phosphorus compounds in their waters are identified in the selected waterbodies at risk including Age, Slocene, Auce and Eda. Determination of the existing water quality status is based on water quality monitoring activities carried out during the implementation of the project. The monitoring activities have been started in May 2020 and consists of targeted, continuous, systematic and regular water sampling at 57 selected locations. The water samples were collected in the upper, middle and lower parts of the Age, Slocene, Auce and Eda rivers, as well as in the main tributaries of these rivers. In order to characterize the impact of agricultural activities on water quality, water samples were collected in subsurface drainage systems and agricultural ditches established in agricultural lands and in water courses before and after livestock facilities, which are characterized by an increased number of livestock in the area. In addition, water samples were collected in water courses before and after wastewater treatment plants of small villages and industrial facilities in order to get an overview of the efficiency of the plant’s operation.
The practical recommendations and technical solutions for implementation of measures aiming to improve water quality were elaborated for the catchments of water courses in which increased concentrations of nitrogen and phosphorus compounds were observed. Depending on site-specific conditions, it was recommended to establish practices of sustainable and environmentally friendly land drainage systems (sedimentation ponds, two-stage ditches, bottom dams, meandering, controlled drainage and constructed wetlands) and practices of green infrastructure (buffer strips, intelligent buffer strips, saturated buffer strips, woodchip bioreactors, sediment traps, grassed waterways, swales with vegetation, infiltration trenches, barriers/traps in ditches and swales, infiltration basins and surface runoff inlets). In addition, within the framework of Action A1, the assessment of environmental effectiveness and economic aspects of implementation of practices of green infrastructure was carried out, as well as the evaluation of the administration system for implementation of practices of green infrastructure was prepared including legal relations with landowners, compensations, permits, approvals.
Based on the results obtained during implementation of the preparatory activities within Action A1, the following measures have been practically constructed within the scope of the demonstration activities carried out in Action C5:
- In the water body of G264 Age – restoration of the Mazupite water course in a 3.5 km long section of the water course, construction of three sedimentation ponds, creation of two cow watering places and water course crossings, establishment of three fish spawning areas and rapids;
- In the water body of V093 Slocene – restoration of the Slocene River in an 8.26 km long section of the river, construction of one surface flow constructed wetland in the Slocene River (440/35 – 441/35), construction of sedimentation ponds in five agricultural ditches before the water inflows in the Slocene River, construction of one surface flow constructed wetland in the Vasleja River (70/70 – 73/00).
The aim of these measures is to reduce concentrations of nitrogen and phosphorus compounds along with suspended solids (particles of soil and organic matter) in the water, while at the same time reducing negative effects of hydromorphological transformations (beaver dams, human-made obstacles, riverbed siltation, bank deformations).
As part of the preparatory activities implemented within Action A2, the potential risks of water pollution from forest areas have been assessed in the water body of Age by paying attention to concentrations of nitrogen and phosphorus compounds, as well as suspended solids in the water. Targeted water quality monitoring activities have been carried out at 16 locations since May 2020. For the planning and practical implementation of practices of green infrastructure a regulated section of the Tora River, which is a tributary of the Age River, has been selected. The most important planned activity in the selected section of the Tora River is diversification of the composition of tree species in the riparian zone by reducing the proportion of spruce trees and promoting introduction of deciduous trees in order to improve the ecological functionality of the riparian zone. In addition, removal of excess debris from the riverbed, removal of sloping and unstable trees without reducing biodiversity associated with dead wood, control of beaver activity and strengthening of river banks are also planned. As part of this activity, the technical recommendations for establishment of green infrastructure in forest land have been prepared.
The demonstration activities of Action C6 are content wise related with the results obtained and recommendation prepared in Action A2. The practical activities in the context of implementation of green infrastructure include diversification of the composition of tree species in a 50 m wide and a two kilometres long section of the Tora River, in a total area of 20 hectares. As part of this activity, the number of spruce trees was reduced and growth of deciduous trees in the riparian zone of the river was facilitated, which in the long term will increase the amount of deciduous tree litter that is useful for aquatic organisms entering the river. The opening of large and old oak trees was carried out so that they would receive enough sunlight and could provide habitats for rare and protected species of mosses, lichen and insects. In 2024, as part of the implementation of green infrastructure, the planting of deciduous trees and construction of a walking trail are planned. The establishment of the walking trail will provide an opportunity for anyone interested in nature to see the solutions already implemented and learn about their importance in improving water quality. Information boards with explanations of the work performed will be placed along with the walking trail thus educating and inspiring others to use environmentally friendly solutions in forest and water management.
As part of Action C6 two detailed technical design projects have been prepared and construction of blue infrastructure in the water body of Age has been started. In the forest drainage system “Toras Dambis”, one sedimentation pond with a peak flow control structure (a dam with overflow pipes) is created on the existing forest ditch that flows into the Tora River. In the forest drainage system “Vidrizu garsa”, three different types of sedimentation ponds are created on the existing forest ditches, which all flow into the Age River – one sedimentation pond of a non-standard shape (crescent shape), one sedimentation pond of a standard shape (the technical parameters for this sedimentation pond are determined by taking into consideration the area of catchment for the specific ditch) and one sedimentation pond filled with a filtration material (woodchips or other material). The purpose of creating sedimentation ponds is to reduce losses of sediments and nutrients from forest lands. The construction works of the blue infrastructure are planned to be completed in 2024.
The purpose of implementation of the preparatory activities within Action A4 is to develop research based recommendations to recover the ecosystem and improve the ecological conditions in Lake Sauka. As part of these activities, the anthropogenic pressures have been investigated in the context of present and historical pressures by evaluating biotic and abiotic factors, which leads to a negative impact and hinder to achieve a good ecological status in the lake. The assessment of the current ecological status of Lake Sauka was carried out based on the results of complex and comprehensive monitoring of hydrobiological, hydrochemical and hydromorphological parameters. Since May 2020, intensive monitoring of hydrobiological parameters took place for two years –samples of phytoplankton and zooplankton were collected every month, samples of benthic invertebrates (zoobenthos) were collected once a season, while samples of higher aquatic plants (macrophytes) were collected once in a vegetation season. In addition, a study trip was made to investigate the fish fauna and develop the bathymetric map for Lake Sauka. Regular and systematic water level and flow measurements were carried out in Lake Sauka, several inflowing water courses and one outflowing water course (Dunupite), as well as water samples were collected, which were necessary to characterize hydrological conditions and physical and chemical water quality parameters in the study area. The results of the above-mentioned activities were applied for development and approbation of the food web model for the Lake Sauka’s ecosystem – the recommendations to improve the ecological conditions in Lake Sauka were prepared.
In order to reduce inflow of nitrogen and phosphorus compounds into Lake Sauka, targeted implementation of practices of sustainable and environmentally friendly land drainage systems is planned within the framework of demonstration activities carried out in Action C8. The results of water quality monitoring show that increased concentrations of nitrogen and phosphorus compounds have been observed in one of agricultural ditches, which collects and drains water from agricultural lands in the catchment area of Lake Sauka. In 2024, preparation of documentation and construction of a surface flow constructed wetland or a sedimentation pond in the selected agricultural ditch is planned.