River feeding types. Water feeding of rivers and its types Which rivers are fed by snow
Lecture No. 2
Rivers are fed by surface and groundwater. Surface nutrition, in turn, is divided into snow, rain and glacier.
Snegovoe The rivers are fed by the melting of snow in the spring, which accumulated during the winter. For the majority of lowland rivers of the Unified National System of the Russian Federation, the spring flood flow is more than 50% of the total annual flow.
Rivers are fed by rain mainly due to heavy rainfall and downpours. Characterized by significant fluctuations throughout the year. For rivers in the south of the Russian Federation and Far East rainfall nutrition can reach 70...80% or more of the annual runoff.
Glacial nutrition occurs as a result of the melting of glaciers and eternal snow in high mountain areas. The greatest glacial runoff is observed during the hottest summer months of the year.
River feeding groundwater most steadily and evenly throughout the year. Almost all rivers have it. The share of underground recharge in the annual runoff varies within a very wide range: from 10 to 50...60% and depends on geological conditions and the degree of drainage of the catchment.
Most widespread It has mixed water nutrition.
Depending on the nutritional conditions, it is formed hydrological regimewater body, which is understood as a set of naturally repeating states of a water body that are inherent to it and distinguish it from others water bodies. It manifests itself in long-term, seasonal, monthly and daily fluctuations: water level, river water content, water temperature, ice phenomena, solid sediment runoff, composition and concentration chemical substances and etc.
IN hydrological regime allocate three phases of water regime (WWR): high water, floods and low water.
High water– FWR of a river, which is repeated annually under given climatic conditions in the same season, characterized by the highest water content, a high and long-term rise in water level. It is caused on lowland rivers by snowmelt (spring flood), on high mountain rivers by the melting of snow and glaciers (summer flood), the fall of summer rains in the monsoon and tropical zones(for example, summer floods on the rivers of the Far East).
Flood– The FWR of a river, which can be repeated many times in different seasons of the year, is characterized by an intense, usually short-term increase in flow rates and water levels caused by rain or snowmelt during thaws.
Low water– FWR of the river, which repeats annually in the same seasons and is characterized by low water content, long-term low water levels and resulting from a decrease in the river’s nutrition. Underground feeding predominates. The summer (summer-autumn) low water period includes the period from the end of the flood to the autumn floods, and in their absence, until the beginning of the winter period. Winter low water usually coincides with the period of freeze-up. Water flows from the beginning of freezing of rivers gradually decrease, reaching a minimum before opening, which is associated with the depletion of groundwater reserves.
A general idea of the change in river FVR is given by flow hydrographs– a chronological graph of changes in water flows during the year or season at a given specific watercourse site. In hydrological calculations, they usually operate with a typical runoff hydrograph, i.e. with a hydrograph reflecting common features hydrographs over a number of years. Establishing patterns in the distribution of runoff within a year is important practical significance for various water management purposes, for example, to determine the basic parameters of reservoirs and hydraulic structures.
A typical runoff hydrograph for lowland rivers of the Russian Federation is shown in Fig. 5. It is possible to highlight the volumes of drainage generated from various power sources.
River feeding
River nutrition
entry and influx of water of various origins into the river. It can be rain, snow, underground, glacial. Usually it is mixed with a predominance of one type of nutrition. During the spring floods Snow feeding of rivers clearly predominates, during low water– underground.
Of particular interest for various branches of water management is the ratio of surface and underground recharge, since the underground component of river flow is stable over time and practically does not require regulation. For Russian rivers, underground recharge amounts to slightly more than 20% of river flow, while for rivers globe this share in avg. exceeds 30%.
Determination of the contribution of various sources of river nutrition is carried out on the basis of the division of river flow hydrographs, i.e. graphs characterizing the change in time of water flow for a year or part of the year (season, high water, flood or low water).
The hydrograph is constructed based on observational data at hydrological stations and posts. The hydrograph is divided based on general characteristics flow of water coming from various food sources, manifesting itself, in particular, in different speeds water movement. During the onset of max. water flows, when its level in the river can be higher than the water level in individual underground horizons, it is possible to replenish them from the river. Then, as the water levels in the river decrease, this water is returned to it. This process is called “shore regulation”.
Geography. Modern illustrated encyclopedia. - M.: Rosman. Edited by prof. A. P. Gorkina. 2006 .
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Types of river nutrition. The nature of river water supply is determined by the complex natural conditions. There are the following types of river feeding: rain, snow, glacial and groundwater.
R ain nourishment occurs either from periodic rains in certain seasons of the year, or from short-term heavy rains. This type of food is predominant on the rivers of the southwestern part of the Caucasus, Crimea, Carpathians and some other areas of the southern part of the European territory of the CIS. Periodic summer rains play a significant role in feeding many rivers of Eastern Siberia and the Far East (Amur, Zeya, etc.).
Heavy rains are observed in summer and autumn in various regions of the European part of the CIS. Due to their high intensity, they are capable of causing rises in water levels in rivers of small basins that exceed spring levels.
Snow feeding is predominant on most rivers. The basins of these rivers occupy more than ¾ of the territory of the CIS. Despite the relatively short duration of snow melting, snow-fed rivers receive up to 60–80% of the total volume of water flowing through them during the spring flood period.
Glacial feeding is typical for rivers in the high mountain regions of the Caucasus and Central Asia. It comes from the melting of glaciers and eternal snow in the mountains. Glacier-fed rivers have summer floods, often with pronounced daily fluctuations in levels due to temperature changes during the day.
Soil recharge occurs either due to shallow groundwater or due to groundwater located at significant depths. In its pure form, ground nutrition is very rare. As a rule, soil and The groundwater serve as a source of river nutrition during periods of decreased or absent surface flow.
Many lowland rivers are fed primarily by groundwater in the summer, and in winter this type of nutrition is the only one for them.
Different types of nutrition are involved in the formation of river flow in different periods of the year. For example, R. In the spring, Kuban is fed by snow due to snow melting in the right-bank flat part of the basin; in the summer months - glacial feeding from the Caucasus Mountains; in autumn - rain nutrition from intense downpours and in winter - ground nutrition.
Mode of levels and expenses. The water level in a river is the elevation of the water surface above a certain conventional horizontal plane.
Water levels in rivers are constantly changing. The main reason for the fluctuation in levels is the difference in the amount of water entering the rivers at different times of the year. In addition to the amount of water flow, a number of other factors can influence the height of the level: the presence of ice cover, erosion of the riverbed and sediment deposition, sea tides at the mouths of rivers, natural backwater from another river, artificial backwater from hydraulic structures, etc.
The annual graph of water level fluctuations throughout the year is compiled based on actual observation data (Fig. 8.3).
To analyze long-term level fluctuations, several lines are plotted on one graph, characterizing the change in level in different years. The nature of level fluctuations depends primarily on the river’s feeding regime.
Lowland rivers with predominant snow feeding are characterized by a large rise in levels in the spring from snow melting and relatively low water levels the rest of the year. Many of them experience rises in levels in the autumn due to rainfall, and on the small rivers of this group there are rises in levels caused by rains in the summer months.
Rice. 8.3. Annual graph of water level fluctuations
Large rivers with predominant rain or glacier feeding are characterized by an extended period of high levels in summer and autumn months. Small mountain rivers With rain or glacier feeding, sharp short-term rises in levels from rainfall and snow melting in the mountains are characteristic at different periods of the year. These rivers often experience intense daily fluctuations in levels.
Rivers flowing from lakes or swamps have smooth levels. Thanks to the regulating role of lakes and swamps, the rise in levels caused by the spring flood extends on these rivers until mid-summer.
The most important characteristic river level regime is the amplitude of oscillations, i.e. the difference between highest and lowest levels for a certain period of time. There are amplitudes of fluctuations in annual levels, long-term and individual periods of the year. The amplitude of long-term fluctuations in levels at large rivers reaches 15–20 m or more.
Fluctuations in river water levels are caused by changes in flow rates. A graph depicting the relationship between flow rate and level at a certain river section is called flow rate curve.
Having an annual graph of level fluctuations in the river section under consideration and a flow curve, it is easy to establish the average daily flow rates for all days of the year. Based on the found values of average daily flow rates, an annual graph of their changes is constructed, which is called a h ydro graph. Since there is a direct connection between the flow rate and the level, the hydrograph has an outline similar to the graph of level fluctuations.
Phases in rec mode. Characteristic water levels and flow rates. In the water regime of rivers, a number of characteristic phases can be distinguished, each of which is characterized by certain characteristics.
On rivers with a predominant snow supply, such phases are: spring flood, summer low water, summer-autumn rain floods and winter low water.
The spring flood is the main phase in the water regime of most rivers. It is characterized by a sharp rise in water level and a less steep decline. On large rivers, spring flood lasts from 1.5 to 3 months, and on small and medium rivers - from 10–15 to 30–45 days.
The summer low water begins after the end of the spring flood and lasts until the onset of autumn rains. This phase is characterized by low and stable levels in most rivers. Some small rivers of the southern and southeastern regions of the European part of the CIS in summer period dry out.
Autumn rain floods are observed on many rivers of the European part of the CIS, western and eastern Siberia. They are caused by an increase in precipitation and a simultaneous decrease in evaporation from the surface of river basins.
The winter low-water period coincides with the freeze-up period on most lowland rivers. The lowest water consumption is observed at the end of winter. Small northern rivers in winter they sometimes freeze to the bottom.
The main characteristics of each of the listed phases in the river regime are: its duration, the magnitude of characteristic levels and flow rates, the dates of the onset and end of the phase. Along with the average values of these characteristics, it is often necessary to know their possible fluctuations over time. multi-year period.
The water regime of the river in each year and over a long-term period is characterized by the following basic levels:
the highest level of spring flood;
the highest and lowest levels of spring ice drift;
the highest and lowest levels of river ice clearance;
the lowest and average low-water levels;
the highest and lowest levels of summer and autumn floods;
average winter level.
The main characteristic river flows include: average annual flow, maximum flows during spring floods and summer-autumn floods, minimum flows during summer and winter low water periods.
Winter regime of rivers. With the onset of cold weather, rivers freeze in most parts of the CIS. The duration of freezing depends on the intensity of the cold snap and the speed of the current. On small rivers it is 3–7 days, and on large rivers – 8–15 days. Often the freezing process of rivers is accompanied by autumn ice drift.
During the winter, the ice thickness gradually increases, reaching 0.6–1.0 m on the rivers of the central and northern regions the European part of the CIS and 1.0–1.5 m on the rivers of Siberia.
In the spring, as a result of snow melting, the opening of the rivers begins, followed by ice drift. The latter lasts from 1–3 days on small rivers, to 8–10 days on large rivers. The nature of the opening of rivers by spring ice drift depends primarily on geographical location rivers. On rivers flowing from north to south, the lower reaches are first cleared of ice cover, which ensures the unhindered movement of ice from the upstream areas. Therefore, ice drift on these rivers is relatively calm. On rivers flowing north, ice conditions are very difficult. Later, the opening of the lower sections of these rivers prevents ice flow and ice jams form in the higher sections, causing significant rises in water levels, often leading to floods.
River feeding - flow of water into rivers.
There are four sources of river nutrition (table).
Their water content, seasonal distribution of flow, water regime . Rivers often have mixed nutrition.
In this case, the source that provides the majority of the river flow is considered predominant. It is he who determines the regime of the river.
River mode — intra-annual distribution of flow, characterizing the life of the river.
In Russia, rivers predominate snow fed. They have clearly expressed seasonal fluctuations in the level and water content of the river.
A friendly spring contributes to the rapid melting of snow, rising water in the river and flooding of the floodplain - it is coming flood In summer, during the dry period, summer low water is observed.
Summer low water — stable low water level and flow rate.
In winter, rivers freeze and become the main source of food. groundwater. As a result, the runoff is reduced and winter low water.
Most of the lowland rivers of the East European Plain, the West Siberian Lowland, and the Central Siberian Plateau belong to the type of predominantly snow-fed rivers with spring floods.
On rivers with predominance rain power supply develops flood regime.
Flood is a sharp short-term rise in water in a river, most often due to heavy rains.
If floods are typical for spring, then floods can occur at any time of the year. Thus, on the Black Sea coast, in the northern foothills of the Caucasus, short-term high floods occur as a result of heavy rains, both in summer and winter time.
| Rice. 137. Mountain river |
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| Rice. 138. Plain river |
The river regime of some areas (for example, in Russia - Primorye and Amur region) is formed under the influence monsoon climate. Heavy rains cause high and prolonged floods in late summer and early autumn. There is little snowfall, so high spring floods are not observed; low winter low water is typical.
High floods often take on the character of catastrophic floods. Significant areas of land are flooded, causing great damage to the population, economy, and natural environment.
Melting glaciers ( glacial feeding ) causes summer floods on mountain rivers (for example, in Russia - the Baikal region, Transbaikalia, Altai).
Ground nutrition Most rivers do not play a decisive role, but serve as an important addition to the main ones - snow, rain, and glaciers.
With the onset of autumn, the rivers begin to freeze and become covered with ice. The duration of freeze-up on rivers generally decreases from north to south and southwest from approximately 8 to 2-3 months. Material from the site
In the spring, as the temperature rises and the snow melts, ice begins to flow. It flows especially violently on rivers flowing from south to north (in Russia, for example, the Northern Dvina, Lena), since here the melting of snow begins in the upper reaches, and the ice in the lower reaches of the river restrains the pressure spring waters. As soon as it breaks, a powerful wave of flood begins.
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| Rice. 140. Ice drift |
Some rivers experience constant spring floods due to heavy snow melting. These include almost all watercourses of the former Soviet Union. They, in turn, are divided into several more types. The most common types of river regime: Kazakhstan, West Siberian, Altai, East European, East Siberian.
River feeding
Even in elementary school, they learn that the nutrition of rivers is explained by the water cycle in nature. However, this formulation is general; In order to fully understand this issue and understand where and what method will be appropriate, it is necessary to study everything in more detail. There is rain, glacier, snow and underground nutrition. Both the river regime and the replenishment of stream waters depend mainly on climatic conditions. For example, in countries with hot weather, the snow type of nutrition is practically absent. In cold conditions main role melt and groundwater play. IN temperate climate mixed nutrition predominates.
Rain and snow feeding of rivers
The regime of the river, which is fed by rain, has such a feature as the occurrence of frequent floods. Unlike floods, they occur at absolutely any time of the year. Floods occur where it rains quite often, and in winter the temperature is so favorable that the water flow is not covered with ice. Some mountain rivers are fed exclusively by rain. These are watercourses of the Baikal region, Kamchatka, Altai, etc.
Snow-fed streams are characterized by soft water and low salt levels. Most of Rivers of this type are practically not replenished in summer. Mixed-mode water flows are also common here. The most favorable location for rivers of this type of feeding is in the mountains, which are annually covered with thick layers of snow.
Underground and glacial feeding of rivers
In countries that are located on mountains and at their foot, the rivers are fed by glaciers. IN summer time maximum replenishment of water flows occurs as a result of the melting of many large glaciers. This type of food is the most dangerous, especially in combination with snow. Often there is too much meltwater (this depends on the size of the glaciers), which allows the river to overflow its banks. That is why the lands located near watercourses with such nutrition are sparsely populated and can rarely be cultivated, since the damage caused by floods is too great.
The underground (or ground) regime of the river is less common than the types of nutrition already described. This type is being studied by the State Hydrological Institute of Russia. The regime itself is divided into ground and artesian feeding. However, the main source of river replenishment is still groundwater. In the course of research, scientists have discovered the fact that this type of nutrition is excellent for small water flows, but it is absolutely not typical for large ones.
Rivers with Altai, East Siberian and West Siberian regimes
Low, extended flood, low water level in winter, increased flow in summer and autumn season- features of the Altai type. This river regime differs from others in that the main food source is not only melt water, but also rainfall. The flood is prolonged with a low level of water rise. Snow, melting from different sides, falls into the rivers evenly - this explains this phenomenon.
The East Siberian type is characterized by such features as high floods in summer and autumn, as well as increased flood levels in spring. Kolyma, Aldan, Tunguska are rivers belonging to this regime. In winter they often freeze completely due to low flow. This can be explained by the fact that the watercourses are fed primarily from groundwater, and in winter it is reduced to a minimum.
Such a water regime of rivers as the West Siberian one is found in the forest zone. The spring flood is blurred, extended, no different high levels rising water. In summer and autumn, the flow is increased; in winter, low water is typical. This “behavior” of rivers is due to the flat terrain and swampiness of the lowlands on which they are located.
Rivers with Eastern European and Kazakh regimes
The characteristic high spring flood, increased flow level in autumn (due to heavy precipitation) and low water in the summer and winter clearly define the Eastern European regime of the river. Autumn floods are quite pronounced in all regions except the southern one. Small rivers, with an area of no more than 300 km2, are prone to drying out and freezing in summer and winter. For large watercourses, such phenomena are very rare.
Rivers of the Kazakhstan type are characterized by high spring floods, while in summer, winter and autumn they are very low in water and most often dry up. Such flows occur in Kazakhstan, the Volga region, and in the area of the Aral-Caspian Lowland. In fact, they are common in places where there is only snow.
