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The Dviete River Case Study

The Dviete River is a mid-sized left-bank tributary of the Daugava River, located downstream from Ilūkste town in southeastern Latvia. Its catchment area covers 254 km², with a total river length of 37 km. The average annual runoff is 0.057 km³, while the peak flood discharge reaches 70 m³/s. The slope of the riverbed varies significantly, from 4 m/km in the upland section to 0.2 m/km in the lowland reach.

Photo 1: A river flows through fields and farmland (Sebastian Piękoś)

The catchment is divided into two contrasting landscapes. The left-bank tributaries drain predominantly wet mixed forests of the East Latvian Lowland, while the right-bank tributaries flow through the deforested and intensively farmed hills of the Augšzeme Upland. Forests cover between 25% and 75% of the catchment, depending on location. Two small villages are located in the drainage area: Bebrene and Dviete, each with approximately 500–600 inhabitants.

The river originates in the Augšzeme Upland and flows rapidly northward before entering the broad Dviete floodplain, where its course slows and meanders southeastward for about 20 km before joining the Daugava River near Dviete village. The floodplain is flat, composed of late Holocene alluvial deposits (sand, silt, and peat) overlain by eutrophic Gleysols and Histosols. The meadows of the floodplain have high ecological value but were subject to large-scale drainage (melioration) during the 20th century. In its lower reaches, the Dviete flows through two large eutrophic floodplain lakes of glacial origin, Skuku and Dvietes, both dominated by dense reed stands (Phragmites australis). Shortly before its confluence with the Daugava, the river also joins the Ilūkste River, which passes through Ilūkste town (approx. 2,500 inhabitants).

Climate in the catchment is temperate, lying in a transitional zone between maritime and continental influences. Mean monthly temperatures range from –6.7 °C in winter to 16.9 °C in summer. Mean monthly precipitation varies from 30–40 mm in spring to 60–70 mm in summer, with an annual average of 530–540 mm, which is relatively low compared to the Latvian average.

Hydrology of the Dviete River reflects both natural conditions and long-term human interventions, including drainage, deforestation, and agriculture. Snowmelt accounts for approximately 50% of the annual runoff. The Daugava River exerts a strong influence on the Dviete floodplain: each spring, its floodwaters backflow into the valley, inundating it for 2–3 months. At Dviete village, the inflows from the Daugava can exceed 400 m³/s, creating a reverse flow in the lower reach of the Dviete and extending flooding up to 15 km upstream.

Photo 2: Floodplain forest (Tom Fisk)

Nature values of the floodplain are recognized through the designation of the Dviete Floodplain Nature Park, a Natura 2000 site established in 2004, covering almost 5,000 hectares. The park protects species-rich eutrophic floodplain meadows that provide breeding grounds for the corncrake (Crex crex) and other rare bird species during summer low-water periods. It is also an internationally significant resting site for migratory waterfowl during spring floods.

Photo 3: A herd of cattle grazing on a lush green field next to a river (Philipp Deus)

In 2008, the Dviete Primeval Valley Information Centre “Gulbji” was established on Putnu Island in Bebrene parish. The Centre promotes the natural and cultural values of the Dviete valley, offers guidance on the management of biologically valuable grasslands and nature conservation, and provides advice on sustainable grazing practices. The Union of Dviete Valley Municipalities (DSPA), founded by five parishes (Bebrene, Dviete, Eglaine, Pilskalne, and Sedere), plays an important role in maintaining the area and works in close cooperation with Daugavpils University on conservation and development projects.

Stakeholder engagement has been fostered through the Multi-Actor Reference Group (MARG), with all meetings held at the “Gulbji” Information Centre. These meetings have engaged a broad range of local stakeholders. During MARG 2, three Environmental Performance Indicators (EPIs) were identified as most important at the farm scale: soil moisture, groundwater level, and flooding duration. These priorities reflect the contrasting hydrological challenges in the basin – declining soil moisture and groundwater levels in upland areas, alongside permanent flooding of some floodplain meadows and pastures, exacerbated by beaver dams on the Dviete and its tributaries. At the catchment scale, nutrient concentrations and loads were highlighted as the most important EPI due to persistent water quality problems at the river mouth, particularly during summer and winter low-flow periods. These issues are likely linked to diffuse agricultural pollution and pressures from nearby settlements.

Authors: Artūrs Škute and Raimonds Ernšteins