Project “Ecological flow estimation in Latvian – Lithuanian trans-boundary river basins” (ECOFLOW) that was led by Latvian Environment, Geology and Meteorology Centre, and participating Lithuanian Energy Institute, and Latvian Institute of Food Safety, Animal Health and Environment BIOR, after two years of implementation has been ended in March, 2019. In the Final seminar on 26th of February 2019, in Riga, Latvia, were presented main results and achievements of project for wider public. General conclusion was that small hydropower plants that are built on rivers in Lithuania and Latvia within the Venta and Lielupe river basin districts, significantly impacts the fauna (fish species) in rivers.

Main aim of project was to gather information necessary for river management of small rivers with obstacles (small hydropower plants (HPP)) on them, as well as using scientific approach to assess the impact of small hydropower plants on fish species in Venta and Lielupe river basin districts.

After intensive training led by Polish and Italian scientists, practical field works started in summer 2017. During field works each case study river below the small HPP in Latvia and Lithuania was monitored 4 times, depending on hydrological conditions – 3 times in low flow period, and once during mean discharge. Detailed monitoring of habitat areas was done, including river depth, flow velocity, bed substrate. Fish biodiversity assessment and definition of specific fish species in each river was done by fish experts.

In total during ECOFLOW project 12 rivers below small HPPs were monitored: in Latvia – Ciecere river (Pakuļu HPP), Ēda river (Šķēde HPP), Vanka river (Ēdole HPP), Auce river (Bēnes dzirnavu HPP), Bērze river (Bikstu-Palejas HPP), Īslīce river (Rundāle HPP), and in Lithuania – Venta river (Rudikiai and Kuodžiai HPP), Bartuva river (Skuodas HPP), Mūsa river (Dvariuku HPP), Lėvuo river (Akmeniju HPP) and Suosa river (Stirniškiai HPP).

Gathered results were analyzed and for each case study river were modelled habitat-flow rate curves, habitat suitability maps, fish “stress days” curves and other indicators characterizing ecological status of river. Common conclusion was that currently allowed minimal guaranteed flow (in some permits they are also incorrectly named as ecological flow) in most cases is too low for fish to survive, and there is need to make amendments and changes in national legislation in both countries to ensure good ecological quality and status in all waters – at least regarding ecological flows.