Drainage
Nearly all of the precipitation that falls on Albania drains into the rivers and reaches the coast without even leaving the country. In the north, only one small stream escapes Albania. In the south, an even smaller rivulet drains into Greece. Because the topographical divide is east of the Albanian border with its neighbors, a considerable amount of water from other countries drains through Albania. An extensive portion of the basin of the White Drin river (Drini i Bardhë), basin is in the Rrafshi i Dukagjinit area, across Albania's northeastern border. The three eastern lakes that Albania shares with its neighboring countries, as well as the streams that flow into them, drain into the Black Drin river (Drini i Zi). The watershed divide in the south also dips nearly 75 km (47 mi) into Greece at one point. Several tributaries of the Vjosa River rise in that area.
With the exception of the Black Drin, which flows northward and drains nearly the entire eastern border region before it turns westward to the sea, most of the rivers in northern and central Albania flow fairly directly westward to the sea. In the process, they cut through the ridges rather than flow around them. This apparent geological impossibility occurs because the highlands originally were lifted without much folding. The streams came into existence at that time. The compression and folding of the plateau into ridges occurred later. The folding process was rapid enough in many instances to dam the rivers temporarily. The resulting lakes existed until their downstream channels became wide enough to drain them. This sequence created the many interior basins that are typically a part of the Albanian landform. During the lifetime of the temporary lakes, enough sediment was deposited in them to form the basis for fertile soils. Folding was rarely rapid enough to force the streams into radically different channels.
The precipitous fall from higher elevations and the highly irregular seasonal flow patterns that are characteristic of nearly all streams in the country reduce the economic value of the streams. They erode the mountains and deposit the sediment that created the lowlands and continues to augment them, but the rivers flood when there is local rainfall. When the lands are parched and need irrigation, the rivers usually are dry. Their violence when they are full makes them difficult to control, and they are unnavigable. The Buna River is an exception. It is dredged between Shkodër River and the Adriatic Sea and can be navigated by small ships. In contrast to their history of holding fast to their courses in the mountains, the rivers constantly change channels on the lower plains, making waste of much of the land they create.
The Drin River is the largest and most constant stream. Fed by melting snows from the northern and eastern mountains and by the more evenly distributed seasonal precipitation of that area, its flow does not have the extreme variations characteristic of nearly all other rivers in the country. Its normal flow varies seasonally by only about one-third. Along its length of about 282 km (175 mi), it drains nearly 5,957 km2 (2,300 sq mi) within Albania. As it also collects from the Adriatic portion of Kosovo's watersheds and the three border lakes (Big Lake Prespa drains to Lake Ohrid via an underground stream), its total basin encompasses about 15,540 km2 (6,000 sq mi).
The Semani and Vjosa are the only other rivers that are more than 160 km (99 mi) long and have basins larger than 2,600 km2 (1,004 sq mi). These rivers drain the southern regions and, reflecting the seasonal distribution of rainfall, are torrents in winter and nearly dry in the summer, in spite of their length. This variable nature also characterizes the many shorter streams. In the summer, most of them carry less than a tenth of their winter averages, if they are not altogether dry.
Although the sediment carried by the mountain torrents continues to be deposited, new deposits delay exploitation. Stream channels rise as silt is deposited in them and eventually become higher than the surrounding terrain. Shifting channels frustrate development in many areas. Old channels become barriers to proper drainage and create swamps or marshlands. It is difficult to build roads or railroads across the lowlands or otherwise use the land.
Read more about this topic: Geography Of Albania