The research necessary for the restoration of the Salaca rapids was carried out this summer.

Work planned for this year

In the LIFE IS SALACA project, it is planned to start the restoration works in the next few weeks in three sections of the Salaca river, in a total area of 6.43 ha – upstream of the Korģe intake in an area of 1.22 ha, in the section near “Atpūtas” 0.58 ha and near “Brūveļi” 4.63 ha. In general, during the LIFE IS SALACA project, it is planned to implement measures to restore the rapid flow of the Salaca river on an area of 16 ha. The sections of the Salaca where the rapids restoration works will be carried out in the following years will be identified later, after all the field studies carried out in 2024 and the analysis of the data collected.

Why is this work necessary?

In the sections of the Salaca where work is planned to be carried out in 2024, there is a large overgrowth of aquatic vegetation, the majority of which is lake sedum. In rivers rich in plant nutrients, the root system of sedges and other above-water plants creates a sod up to 30 cm thick above the bottom that covers areas of fast flowing water, destroying the coarse sandy habitats and spawning grounds of salmonid fish. The salmon population in Salaca is entirely natural, so the area and quality of salmon spawning habitat, which has been reduced by the overgrowth of the riverbed, is of great importance. Given the shallow depth of the rapids sections, the overgrowth of the riverbed occurs directly in the rapids. In some places, the overgrowth is so extensive that the characteristic substrate and velocity of the rapids have been partially lost.

Therefore, the planned restoration of the rapids by removing the turf of the sedge roots will, in the long term, improve the quality of the habitat of EU importance 3260 Rapids of rivers and natural river sections, as well as the overall ecological quality of the river, and will also increase the area of the rapids.

Salaca’s values and necessary reviews
Salaca is the most important salmon river in Latvia. Eight species of fish and lamprey found in the Salaca rapids in 2024 or in previous years in different sections of the Salaca inventory – rockfish, salmon, pike, broadhead, spidiľľki, taiminš, river lamprey and stream lamprey – are protected by national and international legislation. But fish is not the only value of Salaca. Salaca is a part of the “Salacas velėja” Nature Park, which is an important area for the protection of several habitats of the EU Habitats Directive – sandstone outcrops, undisturbed caves, hillside forests, oak forests, fast-flowing rivers, etc., with excellent scenic value. The stages in which the cleaning of the Salaca bed is planned to be carried out in 2024 are fast-flowing stages (flow rate greater than 0.2 m/s), but the river’s belonging to the habitat variant is determined on a wider scale, so in general Salaca corresponds to the 2nd variant of habitat 3260, which are natural, slow-flowing rivers. On the banks of the Salaca, near the sections where bed cleaning is planned, there are three protected forest habitats of EU importance – 9010* Old or natural boreal forests, 9180* Forests of slopes and ravines and 91F0 Mixed oak, elm, ash forests along large rivers, as well as two grassland habitats – 6450 Floodplain grasslands and 6410 Wet grasslands on periodically drying soils. Three specially protected vascular plant species have been found in the coastal areas of the Salacas River – Baltic Cuckoo (Dactylorhiza baltica), Dactylorhiza incarnata and Fragrant Nightshade (Platanthera bifolia). It is therefore important to plan the work carefully so that the fish are not harmed in the process.

In order to obtain the technical regulations issued by the State Environmental Service for the execution of the works, an expert opinion was prepared with the aim of evaluating the planned activity, in this case the impact of the Salaca riverbed cleaning works on specially protected natural areas, specially protected species and specially protected biotopes, and to determine measures to mitigate the consequences of the activity. In June and July, nature surveys were carried out and expert opinions prepared on the impact of the planned works on fish, invertebrates, plants and habitats of EU importance – not only freshwater, but also the forests and grasslands on the banks of the Salaca.

Research and data-driven work
For the restoration of the rapids to be successful, time-consuming preparatory work is required, which began in winter – data collection, research into cartographic material, identification of different methods and experiences already implemented, and many discussions between theorists and practitioners, as well as representatives of various industries. The seminar “With heavy equipment in the river – challenges, benefits (and losses?) in cleaning and restoring watercourses” was also held and met with an unexpectedly high level of interest. The main lesson that can be learnt from all parties involved in river management and from foreign experience is that careful planning is needed to achieve the best possible results in river restoration. It is important to do this in a targeted and planned way, based on data and the best available knowledge. In order to assess the success of the management measures, monitoring is required after the work has been carried out in order to evaluate the actual benefits.

This is why the data collection this summer is so important, to ensure that any action taken is data-based and scientifically justified, and to have complete data on the situation in the river before work starts, so that comparisons can be made. The project involves a diverse team of experts – specialists in ecological quality of habitats, fish, water, invertebrates, etc. This is also one of the great advantages of the LIFE IS SALACA project, as the practitioners will be working side by side with the experts throughout the project.

Potential rapids restoration sites have been jointly surveyed several times. It is not always possible to implement what is planned in nature, because access and the specificity of the river banks have to be taken into account. However, it is very important not to damage valuable species or habitats. Then you have to rethink, plan, discuss and look for other solutions together to find the best possible common denominator. It is not only focused, but also quite challenging. Before the actual work starts, the planned work sites are surveyed again and the boundaries of the habitats of EU importance found on the coast are marked.

What are the expected negative and positive impacts of the work?
In the short term, during the course of the works, it is impossible to avoid negative impacts. It is expected that the removal of aquatic plants and their root systems will contribute to increased sedimentation and leaching of nutrients into the river, but the impact on species and habitats will be temporary. As the restoration works will be carried out in the fast-flowing sections of the Salaca, it is predicted that sediment and suspended matter will be dispersed relatively quickly under the influence of current velocity. When moving along the river bed with tractor equipment, some of the mussels and other aquatic invertebrates inhabiting the river bed will be mechanically compressed, and some of the aquatic organisms will be thrown to the bank together with the bottom substrate and macrophytes. However, it should be taken into account that in the rapids where the works are planned, the most important species for fishing is salmon, for which the parts of the rapids currently overgrown with aquatic plants are not suitable at the moment.

However, by following all the recommendations of species and habitat experts, and by carrying out these works in an environmentally responsible manner, no long-term negative impacts are expected on the protected habitats of EU importance in the Salacas River and adjacent areas. The aim of the measures implemented is to increase the area and quality of spawning grounds for the most important fishery species – salmon. As a result of habitat restoration, salmon spawning success in the Salaca is expected to improve. To a lesser extent, the spawning success of sea trout and both lamprey species is also expected to improve. Following the works, the ecological condition of the river itself is expected to improve – together with aquatic plants and their root systems, nutrients will be removed from the river, rapid flows will be restored, the self-purification capacity of the river will be increased and the quality of the river as a biotope of EU importance will also be improved.

It should be noted that the river may not look attractive during the works, but it is similar to road repairs – it is worth being patient so that it will be better afterwards. And we should not forget the positive impact in another respect – the river will be more accessible to boaters and other active recreationists, and the cleaned-up sections of the rapids will regain their scenic appeal.