Большинство людей представляет, что такое дельта rivers, but not all think about the role that it plays in the life of all representatives of the flora and fauna. What is it? The river delta is a lowland formed by the sediments of the river, located in its lower reaches. Most often it is strongly cut through by a network of ducts and sleeves. A special ecosystem is created on this lowland. The river delta received its name from one of the letters of the Greek alphabet, which in its form strongly resembled the triangular delta of the ancient Nile.
The river delta can begin hundreds of kilometersfrom its mouth. The deltas of some rivers are pushing into the seas or oceans, while others are not. Under the influence of tides and tides, rivers such as Amazon, Amur, Ob, Taza, and Pura have deltas that do not go beyond their indigenous shores.
Когда вода в реке имеет практически одинаковую density with sea water, the delta acquires a conical shape (for example, in the Nile). If the river water is rich in sediments, it becomes more dense than the sea, so under its influence, the delta acquires an elongated shape. With a reduced density of river water, deltas with a large number of branches and ducts (the Mississippi River) are formed.
Большинство рек мира имеют дельты с развитой alluvial activity. Such are the Volga, Lena, Terek, Northern Dvina, Kuban, Neva. Many southern rivers have developed "plavni" with rich vegetation and a diverse fauna. They have significant fish resources. Vegetation is represented by various herbs, thickets of reeds and reeds, shrubs and trees. They like to settle birds and different kinds of animals.
It is difficult to overestimate the importance of moisture andfertility of soils located in the delta of rivers. In many countries of the world they grow a significant part of agricultural crops. Juicy grasses on moist meadows located in the lower reaches of rivers, are an excellent food for livestock. The valleys of the Ganges, the Nile, the Yellow River, the Danube are areas with intensive farming.
The peculiar is the delta of the Neva River, whichflows through the marshy and flat Prinevskaya lowland. This river is conditionally divided into 2 parts (according to the nature of the regime): the upper (source - Ivanovo rapids), 30 km in length, and the lower (Ivanovskie rapids - a mouth), 44 km long. In the lower reaches (about 15 km from the mouth), the Neva forms a wide delta, full of canals, sleeves, islands and canals. It arose as a result of surges and drifts of water from the sea and under the influence of current waters. In the delta of the Neva, the largest islands are Krestovsky, Vasilievsky, Petrogradsky, Decembrists. Her sleeves are the Small and Big Neva, the Small, Middle and Large Nevki. The most famous channels are Obvodny, Morskoy, Kryukov, Griboyedov.
