The Venta (Latvian pronunciation , Lithuanian , , , Livonian VÃÂnta joug) is a river in north-western Lithuania and western Latvia. Its source is near Kurà ¡ÃÂnai in the Lithuanian à  iauliai County. It flows into the Baltic Sea at Ventspils in Latvia.
On the territory of Lithuania along the Venta are cities Uà ¾ventis, Kurà ¡ÃÂnai, Venta, Viekà ¡niai and Maà ¾eikiai. In Latvia, the cities of Skrunda, Kuldëga, Piltene and Ventspils are located on the Venta river. Venta Rapid, the widest waterfall in Europe, is on Venta river in Kuldëga, Latvia.
The river has only one tributary longer than 100 km, the Abava. Other major tributaries include the VirvyÃÂia (99.7 km) and the Varduva (96 km), which flows into the Venta at the LatviaâÂÂLithuania border.
Smaller tributaries include the Avià ¾lys, which runs for 20 kilometers and flows into the Venta River and the 30 kilometre Uogys which joins the Venta less than 1 km upstream of the Avià ¾lys at Akmenàdistrict municipality, à  iauliai County, northern Lithuania.
The Venta River valley exposes a record of Middle to Late Weichselian (ca 33,000 BP) environments beneath its modern floodplain. An area of roughly 80 km<sup>2</sup> in northwest Lithuania is underlain by up to 28 m of ancient lake sedimentsâÂÂbrown, grey and greenish-black clay, silt and fine sand with lenses of peatâÂÂburied beneath the uppermost Late Weichselian (Nemunas) till. At the Purviai outcrop, pollen analysis and radiocarbon dating (33,540 ñ 370 and 33,800 ñ 460 calibrated years before present) reveal initially cold, wet periglacial conditions dominated by open sedge (Cyperaceae) communities, followed by slight climatic amelioration marked by park-tundra vegetation of birch (Betula), pine (Pinus) and scattered spruce (Picea), showing that the climate warmed slightly from severe periglacial cold to a milder phase. Gravel layers within the sequence contain shells of the freshwater pearl mussel, Margaritifera margaritifera, signalling clean, fast-flowing stream channels feeding into the lake basin. Together, these data show that the Venta valley remained largely ice-free until at least 33,000 BP and that the main glacial advance over North Lithuania did not occur until after 25,000 BP.
Local water-quality surveys show that as the Venta flows through Kurà ¡ÃÂnai, soluble phosphorus roughly doublesâÂÂfrom about 0.069 milligrammes per litre (mg/L) upstream to 0.135 mg/L downstreamâÂÂexceeding national water-quality limits. This rise in phosphorus matches a 15 % increase in chlorophyll a (from 9.11 to 10.49 microgrammes per L), a standard indicator of algal biomass, and is accompanied by lush growth of duckweed species such as Lemna minor and Spirodela polyrhiza.
Nitrate concentrations also climb by roughly 50 %, from 2.27 mg/L upstream to 3.44 mg/L downstream, often exceeding the 2.3 mg/L guideline. Nitrite levels and organic pollution (measured as chemical oxygen demand) likewise regularly surpass safe thresholds. Although healthy aquatic ecosystems typically have a nitrogen-to-phosphorus ratio near 16:1, here the ratio is about 45:1 above the town and 27:1 below itâÂÂshowing that nitrogen remains in excess even as phosphorus spikes.
Investigation points to two main pollution pathways: insufficiently treated sewage entering via the Urdupis stream, and nutrient-rich runoff from the Pakulmuà ¡iai/Kumulà ¡a pond system. Together, these inputs fuel heavier algal blooms, dense water-plant cover and an overall decline in water quality downstream of Kurà ¡ÃÂnai.
A 2016 joint LatvianâÂÂLithuanian study applied WFD mixing-zone guidelines (rules under the EU Water Framework Directive that allow a defined stretch of river immediately below a discharge to temporarily exceed pollution limits before returning to standard levels) to twelve wastewater-discharge sites in the transboundary Venta River Basin. Under low-flow "worst-case" conditions they found that the river lengths needed to dilute total phosphorus and nitrogen discharges to EU standard levels varied from a few metres up to several hundred metresâÂÂand in small tributaries even became effectively "unlimited", meaning standards could not be met within the available channel. Of all the priority substances analysed, only nickel required a particularly long mixing zone (over 900 m) to meet the newer bioavailable-nickel standard.