What Lake Peipus is
Lake Peipus is the English name commonly used for the connected Peipsi–Pihkva lake system. It consists of three unequal sections: Lake Peipsi proper in the north, the strait-like Lake Lämmijärv in the center, and Lake Pihkva in the south. Russian names for the same sections include Chudskoye, Teploye, and Pskovskoye.
The entire system covers about 3,555 square kilometers and contains roughly 25 cubic kilometers of water. It is broad but shallow: the mean depth is about 7.1 meters, and the deepest measured hollow reaches about 15.3 meters. That shape gives wind, waves, river inflow, and seasonal ice a strong influence over conditions across much of the lake.
Between the Baltic lowlands and the Russian Plain
The lake lies in northeastern Europe, with Estonia along the western side and Russia along the eastern side and most of the southern basin. Its long axis runs roughly north–south. Low plains, wetlands, moraine terrain, and gently rolling uplands surround the water rather than a high mountain rim.
The drainage basin covers about 47,800 square kilometers. It extends west into the Emajõgi system of Estonia, south and east across the Velikaya basin in Russia, and into northeastern Latvia through headwater catchments. Piirissaar, a low island near the junction of the northern and central basins, helps divide the connecting flow into eastern and western passages.
A glacial depression divided into three reaches
The basin occupies an older lowland depression that was repeatedly reworked by Pleistocene ice. Glacial erosion modified the floor and margins, while meltwater and later rivers redistributed sand, silt, clay, and till. After the ice retreated, changing outlets and uneven land uplift helped shape the connected lake system and its low surrounding terraces.
Shore form varies around the basin. Sandy beaches and low bluffs are common along parts of the northern lake, while flat peaty, silty, and reed-fringed margins occur widely along the west and around river mouths. The Velikaya delta spreads into the southern basin, and broad shallows allow water levels to shift the shoreline noticeably over low-gradient ground.
Broad northern basin
At about 2,611 square kilometers, the northern section holds most of the system's area and volume and has a mean depth near 8.3 meters.
Narrow central link
This roughly 236-square-kilometer passage is shallow overall but contains the system's deepest hollow, near 15.3 meters.
Shallow southern basin
The approximately 708-square-kilometer southern lake receives the Velikaya and averages only about 3.8 meters deep.
River water moving north toward the Baltic
About 240 rivers and streams enter the lake system. The Velikaya reaches Lake Pihkva from the south after draining the largest sub-basin. The Emajõgi enters Lake Peipsi from the west and links the lake to Lake Võrtsjärv and much of southern Estonia. The Võhandu, Zhelcha, and many shorter streams add runoff from the surrounding lowlands. Together, the Velikaya and Emajõgi provide most of the river inflow.
Water moves from the southern basin through Lake Lämmijärv into the northern basin, although wind can complicate local currents in the narrow connecting reaches. The only main outlet is the Narva River at the northeastern end of Lake Peipsi. From there, water flows north for about 77 kilometers to Narva Bay in the Gulf of Finland.
The lake is not a terminal basin. Its average water residence time is about two years, and levels respond directly to precipitation, snow storage, thaw, evaporation, and river discharge across the catchment. Spring snowmelt commonly raises the lake and inundates low shoreline wetlands; levels then recede as inflow falls and evaporation increases through the warmer season.
Continental seasons, wind mixing, and winter ice
Lake Peipus lies in a cool, humid continental setting influenced by both Atlantic weather and the stronger seasonal temperature range of the Eurasian interior. Snow accumulates across the basin in winter, and thaw-driven runoff is an important control on spring river discharge and lake level. Rainfall through the ice-free season maintains inflow from the lowland catchment.
The lake is ordinarily ice-covered from about December into April, though freeze and breakup dates vary from year to year and across the three basins. During the open-water season, winds crossing the broad northern lake build short, steep waves. Because the water is shallow, wind-driven circulation can reach much of the lakebed and repeatedly disturb stable temperature layering that develops during calm, warm periods.
From interior lowlands to the Gulf of Finland
Lake Peipus is the main storage basin in the Narva drainage network. Upstream, its tributaries connect broad lowlands, peatlands, smaller lakes, and river valleys across three countries. Downstream, the Narva provides a short route to the Gulf of Finland, placing the lake within the Baltic Sea catchment despite its inland position.
In atlas terms, Lake Peipus belongs with the lake hub because its identity rests on connected basins, shallow-water form, shoreline materials, river inflow, seasonal ice, and a defined outlet. It also connects to the river hub through the Velikaya, Emajõgi, and Narva systems and to the terrain index as a glacially reshaped lowland basin.