About such concepts as flood and high water, many of you have heard. But not everything is known about what is a low water. This is one of the phases of the water regime of the river, which will be discussed in our article.
There are several million rivers in the world andrivulets. And each of them is unique in its own way! Each river has its own "character" and its own regime. Under the regime of the river means a complex of all seasonal changes in the state of the watercourse, which are due to the physical and geographical conditions of its basin (primarily the climate of the territory).
Seasonal climate changes are reflected in the state of almost all the rivers of the Earth. On some - stronger, on others - less noticeable.
In the summer, when in temperate latitudeshigh temperatures are set, water from the ground surface actively evaporates. Accordingly, all the rivers in these latitudes gradually become shallow, algae begin to actively propagate in them, coloring their channels in a bright green color. In the early spring, on the contrary, the rivers become deep-watered. First of all, due to the melting of ice in the riverbed and snow within its catchment areas.
The regime of any river includes three main phases. It:
What is the meadow? In geography, this is one of the phases of the watercourse regime. More details about the features of this phase will be discussed later.
So, we found out that each of the rivers has its own water regime. Now let's figure out what is the low water, what features are characteristic for this phase of the river regime.
Mezhen - this is the lowest level of water in the river, andalso a relatively long period of time at which this level is maintained. As a rule, this period is not less than 10 days. At this time, the river feeds mainly underground water.
In temperate as well as high latitudes of the Northernhemisphere, the low water begins at the end of the summer or in the autumn (less often in winter) and lasts until the start of the freeze-up. On mountain rivers, it can temporarily be interrupted by powerful floods, caused by heavy rainfall.
In order to better understand what is the middle of the river, it is necessary to find out from which factors it depends. Such factors include:
In general, the low - is rather unstable,the variable phase of the water regime, which is explained by the "fragility" of the river system itself. Even the most insignificant impact can significantly change the nature and duration of the river mezhdeni.
Why does water in the riverbed suddenly become smaller?The answer is simple: it occurs as a result of the restriction (or complete cessation) of the supply of a watercourse from a particular source. In the arid regions of the planet, the river bed during the intergrade can dry up completely. And sometimes it even manages to become covered with scanty vegetation.
What is a meadow from a philological point of view?
The origin of this scientific term is more likelyeverything, is connected with the word "boundary". This is the boundary between something. In this particular case we are talking about the boundary between the seasons of the year. Probably, in the olden times segregated precisely based on the water level in local rivers.
Mezhen can be different. Depending on the weather and climate conditions of the area, hydrologists singled out:
Summer-autumn low-water season starts right afterspring flood (in July-August) and continues until the period of autumn floods. If the latter are not observed, then this phase can continue throughout the winter, until the next spring high water (winter low water).
Depending on the time criterion, the river low-water can be:
But in most cases, the low water is broken in time, intermittent.
Immediately it is worth noting that the allocation of the middle ground (as well asany other phase in the river's water regime) is quite subjective. Especially when it comes to its time frame. That is, it is not possible to determine concretely and unambiguously when the onset of low water begins on a particular river.
The main criterion for determining the intergeneration isConsider a change in the volume of runoff in the riverbed. So, if at some period this indicator does not exceed 10-15% of the total annual flow, then we can talk about intergeneration in this particular period of time. An interesting fact: on large-scale topographic maps, the contours of river beds are depicted precisely according to their state during the period of intergeneration.
For most Russian rivers and streamsis characterized by summer-autumn low-water (from August to November). Summer showers on the territory of Russia, as a rule, are short-lived and can not significantly affect river floods. Exceptions are only the mountainous regions of the country, as well as the Far Eastern region, where on the rivers, the low water may not be observed at all.
