Hydrography. – By far the most important river is the Nemunas (German Memel ; Russian Niemen) which has a course of 889 km. (936 with Rusnė), of which only 477 in Lithuanian territory or on the state border; the basin is 91,915 sq km. (98.102 with Rusnė), of which 38 thousand belong to Lithuania and the rest to Poland and the USSR It arises from the Rokitno marshes and enters Lithuania just downstream from Grodno; up to Kaunas it maintains a south-north direction, then it receives the Nėris (or Vilija) and with a rather wide valley then turns to the West to build its delta, enclosed between two main branches, in the Kurisches Haff south of Memel. The major tributaries are those on the right; the Nėris has only 122 km. of course in Lithuanian territory (on 510 km.), but it is important because, by means of one of its tributaries (Šventoji), it drains the waters of eastern Lithuania. The range of the Nemunas is in Kaunas, after the confluence of the Něris, of 450 cubic meters. per second (5000 in full and 135 in lean); in Jurbarkas (after it has received the waters of the Nevėzis and Dubysa tributaries) the average flow rises to 510 cubic meters; in Tilsit (after receiving the Šešupė), it is 580 cubic meters (6320 in flood and 170 in lean). In general, the runoff coefficient is limited and the river drains only one third of the water that falls into the basin. The maximum flows occur in April and May, at the time of the melting of the snow, the minimum in July. A part of western Lithuania is tributary to the Baltic through direct courses (the main one is the Venta, 352 km long and with a basin of 11,888), while a large area also sends its waters to the Gulf of Riga via the Mūša river (280 km long. ). Characteristic of Samogitia is the radial arrangement of the rivers. while a large area also sends the waters to the Gulf of Riga through the Mūša river (280 km long). Characteristic of Samogitia is the radial arrangement of the rivers. while a large area also sends the waters to the Gulf of Riga through the Mūša river (280 km long). Characteristic of Samogitia is the radial arrangement of the rivers.
There are also numerous lakes, especially in the Baltic Ridge. Those with an area greater than 0.02 sq km. there are 1305 in all, of which 1078 between 0.02 and 0.5, 205 with an area between 0.5 and 5.22 with an area greater than 5 sq km. The largest are Lake Dusios (23.3 sq km) and Meteliai (12.8). Lithuania also has 405 sq km. of Kurisches Haff (about a quarter of the entire lagoon), separated from the Baltic by a sandbar (lit. Kur š iu Kopos) only 500 m wide. to N. of Sarkau and 5 km. about N. di Nida, which is partly occupied by mobile dunes of white sand, without any vegetation, 70-80 m high. (so-called Lithuanian Sahara), pushed by the wind towards E. in order to sometimes cover the villages, which then reappear on the opposite side after passing under the dunes. Elsewhere there are vast marshy lowlands, poorly drained, which especially during the spring, being the ground impermeable, are completely submerged.
Climate. – Lithuania is located in a transition zone, on the border between the sub-Atlantic and sub-continental climatic regions, where the sea only partially mitigates the imbalances between the extreme seasons. Proceeding inwards, the winters become more rigid, the summers warmer and the precipitations, generally connected to the relief, become less abundant. The alternating vicissitudes of the seasons, subject to very considerable differences, which make the value of the averages very uncertain, is in relation to the high pressures that cover Russia in winter, causing cold and dry east winds, while in summer they send from the Atlantic wet winds. The whole state is included between the annual isotherms of 6 ° and 7 °, which have a course from NO. to SE. The monthly excursion, which along the sea is about 20 °, rises to 24 ° in the Vilnȧ area, where January averages are lower than −5 °. Everywhere in the country the thermometer drops to average values below 0 ° for four months.
Precipitation, which is maximum in Samogitia (700-800 mm) and minimum in the region between Šiauliai and Kaunas, is more than sufficient for agricultural needs and, if anything, it is more excessive than short. Memel has an average of 684 mm., Kaunas of 617 mm, with maximum values during the summer and minimum values in winter and spring. The ground is covered with snow on average for 83 days each year in Kaunas and 69 in Memel; Nemunas is frozen in Jurbarkas (125 km. from the mouth) for an average of 79 days and in Kaunas (216 km. from the mouth) for 77 (from 26 December to 13 March). A certain influence on the climate is also exerted by the vegetal mantle which attenuates the speed of the wind and the daily imbalances.
Vegetation and flora. – Lithuania, which belongs to the Sarmatic province of Central Europe, is at the limit of many characteristic species; thus, among the best-known plants, for example, the beech tree is missing, which only reaches the southern slope of the Baltic Hill. On the whole, unlike what is now observed in the rest of central Europe, it preserves the vegetal mantle intact in several places, and therefore presents a landscape only partially modified by man. The woods, which occupy less than a fifth of the country and therefore a considerably smaller extension than that of the neighboring states, are made up of 68% coniferous trees (often having juniper bushes as undergrowth) and the rest of broad-leaved trees: the the former prevail in the hilly areas, the latter in the more humid parts, without, however, there is a clear separation, so much so that birches and alders often mix with pines. Among the different species, fir trees (40%), pines (28%), poplars (13%), then birches, alders, oaks prevail. The numerous marshes usually have a vegetation of Carex, and of Hypnum ; sometimes they also host trees and, when the ground is dry, they have steppe vegetation. Where sands exist and beneath these impermeable soils, bushy meadows predominate. The largest forests are found in the Marijampolė and Vilkaviškis districts; vast sandy surfaces also cover the sparsely populated regions of Lavena Nevėžis and the sandy surfaces around Kaunas, while the upper Samogitia, where the settlement is long-standing, retains below-average extensions.
Fauna. – The fauna of Lithuania does not have its own character but is part of the Baltic fauna as a whole. Among the Mammals there are various flying animals, insectivores, the wild cat, the lynx, the wolf, various martens, the otter, the elk, various gnawing animals. There are numerous birds, few reptiles and amphibians. There are also various species of fish that populate fresh waters. Among the most frequent insects are beetles, especially carabids. Various spiders, myriapods and terrestrial molluscs complete this fauna complex. For Lithuania geography, please check franciscogardening.com.