Information about water levels in rivers. River water levels, general concepts

Hydrological surveys include a large complex of field work such as monitoring water levels in rivers, lakes and artificial reservoirs, determining river slopes, living cross-sectional areas, flow velocities, water flow rates, studying river sediments and much more.

Observations of these elements of the water regime are carried out at specially arranged permanent or temporary water metering posts and hydrological stations. Depending on the tasks assigned, the timing of observations and the amount of information, stations and posts (in the GUGMS system) are divided into several categories. Hydrological stations are divided into two categories, river water-measuring stations - into three categories. At posts of the third category, observations are made of level fluctuations, water and air temperatures, and ice phenomena. At posts of categories II and I, the volume of observations is further increased by determining water flow rates, the flow rate of suspended and bottom sediments.

When conducting surveys for the construction of engineering structures, departmental organizations set up posts with a limited period of work, although this period can range from several months to several years. The composition and timing of observations at such posts are determined by the range of tasks solved during the design of an engineering structure. Therefore, in addition to their direct functions - providing information about the water regime of a watercourse, water-measuring posts play an important role in channel surveys, when carrying out work on compiling a longitudinal profile of a river, etc.

Water level is called the height of the position of the free surface of the water relative to a constant horizontal reference plane. Graphs of level fluctuations make it possible to judge the dynamics of hydrological phenomena and, accordingly, the long-term and intra-annual distribution of runoff, including during periods of high water and floods. To monitor water levels in the river, water measuring posts of various designs are used: rack, pile, mixed, self-registering.

Rack posts, as the name suggests, are a strip mounted on a pile securely driven into the ground, on a bridge abutment, embankment lining or natural vertical coastal rock. The length of the batten attached to the pile is 1¸2 m. The size of the divisions on the batten is 1¸2 cm. Water level readings along the batten are taken by eye, rounded to 1 cm (Fig. 1). It is difficult to record the level of a flowing, and often turbulent, water surface with higher accuracy; however, for most engineering tasks such accuracy is quite sufficient. If higher accuracy is required, then the rod is placed in a small backwater (bucket), located in the bank at the water's edge and connected by a ditch to the river.

Rice. 1. Rack water measuring station

Rack water gauges are primarily used for observing levels when their fluctuations are relatively small. On rivers with a large amplitude of level fluctuations or during periods of floods and floods, pile posts are used.

Pile water metering station(Fig. 2) consists of a number of piles located along the alignment perpendicular to the river flow. Piles made of pine, oak or reinforced concrete with a diameter of 15¸20 cm are driven into the soil of the banks and bottom of the river to a depth of about 1.5 m; the excess between the heads of adjacent piles should be about 0.5¸0.7 m, and if the coast is very flat, then 0.2¸0.5 m. At the ends of the piles, their numbers are signed with paint; the topmost pile is assigned the first number, subsequent numbers are assigned to the piles located below.

To fix the level on pile posts, use a small portable rail with divisions every 1¸2 cm; the cross section of the slats is rhombic, and the slats flow better around water; There is a metal frame on the bottom of the lath, which allows you to confidently fix the installation of the lath on the head of a forged nail driven into the end of the pile.

When reading the level, the observer places a portable staff on the pile closest to the shore, covered with water, and writes down the reading on the staff and the number of the pile in the journal.

Special means for measuring levels include maximum and minimum gauges, i.e. the simplest devices that allow you to record the highest or lowest levels for a certain period of time.

Rice. 2. Scheme of the observation tower and pile water metering post: 1 – tower; 2 – theodolite; 3 – rapper; 4 – pile; 5 – water measuring rod ( h– counting on the staff); 6 – float

Mixed water metering stations They are a combination of a rack and pile post. At such posts, fixation of high levels is done on piles, and low levels - by rails.

For continuous recording of level fluctuations, special devices- limnigraphs, which record all level changes on a tape driven by a clock mechanism. Water metering stations with water level recorders have a great advantage over simple water metering stations. They make it possible to record levels continuously, but installing a recorder requires the construction of special structures, which significantly increases the cost of their use.

To constantly monitor the stability of the slats or piles, a reference point is installed near the water-measuring station (Fig. 1), usually along the alignment of the piles of the water-measuring station, then it is also a permanent starting point (PO) for calculating distances, a kind of beginning of picketing.

The benchmark mark of the water-measuring station is established during leveling work from the benchmarks of the state leveling network. The benchmark of the water metering post is laid in the ground in compliance with the general rules for installing benchmarks, i.e. its monolith must be located below the depth of maximum soil freezing, in a place convenient for leveling, and always outside the flood zone, i.e. above the high water horizon (HWL).

As stated above, at most water measuring posts the height system is conditional. The starting point for counting heights is zero post graphics– an altitude mark that remains constant for the entire period of the post’s existence. This conditional horizontal plane is located at least 0.5 m below the lowest water level that can be expected at the post site. At slatted water-measuring posts, the zero of the graph is often combined with the zero of the water-measuring staff.

Measurements begin at the post after the zero mark of the post schedule has been assigned and the zero mark of the pile heads has been determined by leveling, and the difference between the zero marks of the post schedule and the marks of the pile heads has been determined. This difference in marks is called register.

The private height system at the water gauging station makes it possible to solve the overwhelming number of problems in studying the water regime of the river. However, for a number of structural design problems it is necessary to know not only conditional, but also absolute (Baltic) level heights. For this purpose, water-measuring posts, or rather benchmarks of water-gauging posts, are tied to the nearest benchmarks of the state leveling network.

Observations at the water gauging station, in addition to level observations, include visual observations of the state of the river (freeze up, ice drift, clear), weather conditions, water and air temperatures, precipitation, and ice thickness.

The thickness of the ice is measured with a special rod; air temperature with a sling thermometer, and water temperature with a water thermometer.

At permanent water-measuring posts, observations are carried out daily at 8 a.m. and 8 p.m. Average daily level is defined as the average of these observations. If level fluctuations are insignificant, then observations can be carried out once a day (8 hours). When solving special problems, as well as during periods of high water or high water, the level is fixed more often, sometimes after 2 hours.

The results of observations at the water gauge post are recorded in a journal.

The primary processing of water-gauge observations consists of bringing the readings on the staff to zero in the graph of the water-gauge post, compiling a summary showing daily average daily levels, and constructing a graph of daily levels, on which symbols show freeze-up, ice drift and other ice phenomena that took place on the river.

Systematized results of observations of levels at the entire network of water gauging posts of a given river basin are periodically published in hydrological yearbooks.

To obtain complete observation materials and guarantee the safety of the water metering post for the entire intended period of operation, it is recommended to specifically select a place to install the post. In this case, it is desirable that the river section be straight, the bed stable from erosion or alluvium, so that the bank has a moderate slope and is protected from ice drift; there should be no river piers nearby; the readings of the post should not be influenced by the backwater from the dam or a nearby tributary; It is more convenient to use a post if it is located near a populated area. There is no need to strictly align the water gauge with the axis of the future engineering structure.

At hydrological stations, water-measuring posts of categories I and II, as well as during departmental surveys, a hydrometric cross-section is laid out, which is used for regular determinations of flow velocities, water flows and sediments. In this section of the river, the flow of water should be parallel to the stream, which is ensured by its straightness and correct - trough-shaped bottom profile. If it is intended to conduct regular and long-term observations at a hydrometric site, then it will be equipped with walkways, hanging cradles, or equipped with floating facilities (ferries or boats).

The benchmark mark of the water-measuring station is established during leveling work from the benchmarks of the state leveling network, for periodic monitoring of the stability of the slats or piles of the water-measuring station, during measuring work, as well as when creating an altitude justification for surveying.

The benchmark of the water metering post is laid in the ground in compliance with the general rules for installing benchmarks, i.e. its monolith must be located below the depth of maximum soil freezing, in a place convenient for leveling, and always outside the flood zone, i.e. above the high water horizon.

On permanent watercourses, the most typical water levels are:

VIU– high historical level, i.e. the highest water level ever observed on a given river and established by surveys of old-timers or by visual traces on capital structures;

USVV– the highest water level for the entire observation period;

UVV– the level of high waters is the average of all high waters;

RUVV– the calculated level of high waters, which corresponds to the calculated water flow and is accepted as the main one when designing structures;

RSU– the calculated navigable level, which is the highest water level during the navigable period, is necessary when determining the altitude position of the bridge elements;

UMV– the level of low water corresponds to the water level during the period between floods;

USM– level of average low water;

UNM– low water level;

UL– level of freezing;

UPPL– level of the first ice movement;

UNL– the highest level of ice drift.

During surveys, fluctuations in water levels throughout the entire area can reach large values, therefore, to compare depths across cross-sections, enter cutting level– a single instantaneous level for the entire survey area. Usually, the instantaneous minimum level in the studied section of the river for the entire measurement time is taken as the cutoff level. To do this, it is necessary to determine the marks of the top of the edge stakes in each hydraulic gate using a leveling move.

All measurement results are reduced to a single position of the free surface of the river, which is subsequently considered zero for various constructions: transverse and longitudinal profiles, river plan in isobaths. It should be borne in mind that the adopted reference surface corresponding to the cutting level, like any free surface of the river, is not horizontal.

The water level in a reservoir is the height of the water surface relative to a conventional horizontal plane (that is, height above sea level).

The following water levels in the river are distinguished:

1. Flood is the highest of them. It is formed after the melting of snow and glaciers.
2. Flood is a high level of water formed after heavy, prolonged rainfall. A flood has a peak - a wave that moves along the river at the speed of the river flow. Before the flood peak, the water in the river rises, and after the peak it decreases.
3. Low water is the lowest natural and established level for a given reservoir.

Altai rivers mainly belong to the Ob river system. This river crosses the Altai region in its upper reaches. The Ob and its tributaries - Alei, Barnaulka, Chumysh, Bolshaya Rechka and others - have wide, well-developed valleys and a calm flow. The water level in the rivers of the region is defined as winter low water and summer high water. They have predominantly mixed nutrition: glacial, snow, rain and soil.

Water level in Altai rivers

The river network of the Altai Mountains is well developed (with the exception of the southeastern part). Rivers originate from glaciers, swamps and lakes. For example, on flat mountain ridges, a tributary of the Chulyshman River - Bashkaus - originates from a swamp, the Biya River flows from Lake Teletskoye, and the source of the Katun River is located at the Belukha Glacier.

The rivers of the Kulunda Lowland are predominantly fed by rain and snow with pronounced spring floods. In summer, very little precipitation falls in the region, and the water level in the rivers drops significantly, many of them become shallow, and in some areas even dry up. In winter they freeze, and freeze-up lasts from November to April.

Mountain rivers belong to the mixed Altai type of nutrition. They are rich in water and are fed by thawing glaciers, atmospheric precipitation and groundwater.

Snow melting in mountainous areas lasts from April to June. The snow melts gradually, starting from the north of the Altai Mountains, then in the low mountains, after which it begins to melt in the middle mountains and in the southern highlands. Glaciers begin to melt in July. In summer, rainy days alternate with clear and sunny ones. But prolonged downpours are quite common here, causing the water level in the rivers to rise sharply and quite strongly.

The rivers of the highlands are characterized by glacial and snow type of feeding. The summer flood is pronounced, although it also occurs in the fall.

For mid-mountain and low-mountain rivers, the regime is characterized by two high levels:

1. In spring and summer there is high water (from May to June).
2. In summer and autumn there are floods due to autumn rains and melting glaciers.

In autumn and winter, rivers are characterized by low water - the lowest water level in rivers.

In the mountains they become covered with ice much later than in the plains, but they usually freeze to the bottom. In some mountain rivers, ice formation occurs on the surface and along the bottom simultaneously. Freeze-over usually lasts about 6 months.

Mount Belukha is the most important source of nutrition for the rivers of the Altai region. The Belukha glaciers are very active, they go very low, melt a lot and receive a lot of precipitation.

From this melting process, the rivers receive approximately 400 million cubic meters. m. of water per year.

Water levels in the Ob River

Ob — a typical lowland river, but its sources and large tributaries are in the mountains. The Ob is characterized by two floods - in spring and summer. Spring occurs due to water from melting snow, summer - due to water from melting glaciers. Low water occurs in winter.

The river freezes for a long time. Freeze-up on the Ob lasts from November, and only in April does ice drift begin, when the river is freed from the ice layer.

Katun River

The Katun is a typical mountain river, its source is in the glaciers of Mount Belukha. The water supply of this waterway is mixed: from the melting of glaciers and from atmospheric precipitation. Water levels in the Katun River look like high water in summer and low water in winter. The flood period begins in May and lasts until September. In winter, the river freezes to the bottom.

Biya River

The Biya flows out of Lake Teletskoye. It is rich in water throughout its entire length. Biya is a river of both mountain and plain.

Water levels in the Biya River look like high water in spring, and low water in autumn and winter. The flood begins in the spring (starting in April), but in the summer the water level is also quite high, although at this time a gradual decline in water begins. In November, low water sets in on the river and freeze-up begins, which continues until April. Ice drift begins in April.

After filling out the table, be sure to indicate how you assess the general condition of the river and the quality of its water.

Please note that for convenience, the table can be turned over and the names of the columns can be written not in rows, but in columns. Then the sample descriptions will be arranged line by line. Draw and fill out the tables as you see fit, just remember that they should be understandable not only to you, but also to other researchers.

Hydrological regime

The type of river, the amount of water in it, and the speed of its flow changes significantly throughout the year. These changes are associated, first of all, with the change of seasons, with snow melting, droughts, rains - i.e. those natural factors that determine the flow of water that feeds it into the river. The characteristic features of changes in the state of a river over time are called its hydrological regime. The height of the water surface in centimeters, which is measured from some accepted constant elevation, is called water level. In the annual life cycle of a river, the following main periods are usually distinguished (they are called phases of the hydrological regime):

1. flood;

2. flood;

3. low water.

Flood is the time of the river's highest water content. In the European part of our country, high water usually occurs during the spring snowmelt, when streams of melt water from the entire catchment area rush to the bed of the main river and its tributaries. The amount of water in the river increases very quickly, the river literally “swells” and can overflow its banks and flood floodplain areas. Floods regularly recur every year, but can have varying intensity.

Floods are rapid and relatively short-term rises in the water level in a river. They usually occur as a result of rainfall, downpours in summer and autumn, or during thaws in winter. Floods usually occur every year, but, unlike floods, they are irregular.

Low water is the lowest water phase of the water regime. On our rivers there are two periods of low water - summer and winter. At this time, precipitation cannot provide sufficient nutrition to the river, the amount of water in it decreases significantly, a large river can turn into a small stream and life in it is supported mainly by underground sources of nutrition - springs and springs.

Human economic activity in the river catchment area and its banks also affects the hydrological regime. Drainage of swamps, water extraction for domestic and industrial needs, wastewater discharges, etc. lead to changes in the water content of the river. Particular attention should be paid to cases when water is withdrawn for economic needs from the catchment area of ​​one river, and water is used or returned to nature in the catchment area of ​​another. This greatly affects the natural distribution of water and can lead to drying out of some areas and swamping of others.

Ill-considered human actions can disrupt the natural course of changing phases of the water regime. There are cases when small rivers flowing within populated areas suddenly experience floods caused by large discharges of wastewater from industrial enterprises. Such changes affect the river's ability to

self-purification and affect the quality of water in it. Therefore, the study of water level fluctuations in rivers and lakes is of great scientific and practical importance.

Water level observations

Organizing level monitoring is quite simple and is within the capabilities of schoolchildren and students. Data on regular level measurements with precise indication of the location of the site, the time of observation and weather patterns are valuable information, and the larger the number of these observations becomes, the more valuable they become.

Government level observation posts consist of special devices for measuring levels, such as slats or piles. These slats and piles are securely anchored to withstand heavy seas and ice drift. Each post has its own exact topographical mark (height above sea level), which makes it possible to compare the readings of different posts with each other and assess the general situation in the catchment area, basin, etc. If there is no such state water metering post in your area, on your river or lake, you can organize your own temporary water metering post. Of course, its data cannot be compared with observational data from the state hydrometeorological service system, since this would require complex geodetic measurements. However, you will be able to track changes in the water level in the river from season to season and from year to year. The post can also be used as a sampling site for hydrochemical observations.

The most convenient way to set up a water gauge post is to use a permanent rail mounted on the support of the bridge over the river (Fig. 6b). Markings are applied to the rail, preferably with bright oil paint, so that they are not washed off with water and are clearly visible from afar. The batten is installed on the side of the bridge facing downstream so that during ice drift it will not be broken or torn off by passing ice floes.

Rice. 6. Construction of water measuring posts (a - pile, b - rack)

Level measurements must be carried out with an accuracy of one centimeter. The initial measurement mark is taken to be the mark below the lowest level. It is best celebrated at the end of summer, during the period of deep low water. This initial height is called the zero of the graph and all other levels are measured in excess of it.

The pile water metering post looks different (Fig. 6a). First, one pile is installed at the zero level of the graph (5th in Figure 6a). Then, above it, at a certain height (0.5 m, 1 m), other piles are installed using a level. To prevent the piles from rotting longer, they can be burned over a fire or coated several times with vegetable oil and allowed to soak in the oil. It’s even better to drive scraps of metal pipes into the ground, and

strengthen them with wooden piles. On the upper end of the pile you can put a nozzle cut from used polyethylene dishes. It turns out beautiful and durable, and most importantly, such piles are clearly visible. The piles are then numbered in order from top to bottom, and for each, its height relative to the zero of the graph is noted. To determine the level, a water gauge (you can use a simple ruler) is placed on the pile immersed in water closest to the shore, and the water level mark is noted. The measured height of water above the pile is added to the relative height of the pile and the water level mark is obtained. For example, pile No. 4 is at a height of 100 cm above the zero of the graph and is hidden under water by 12 cm. Therefore, the water level is at H = 100 + 12 = 112 cm.

Observations of the water level at hydrological posts are usually carried out twice a day - at 8 and 20 o'clock, but you can limit yourself to a one-time observation in the morning. If you do not have the opportunity to measure the water level exactly at this time, it does not matter, measure when you can, just do not forget to indicate the time and date of observation. In cases where you may be taking readings over several days, try to do so at the same time.

The received data is recorded in the journal in the form of table 5. During the flood period, when the water in the river rises especially quickly, observations are carried out more often - every 3-6 hours. The same applies to periods of heavy rain and floods on the river.

Table 5. Results of observations of water level in the river

Name of the river........................................

Location of the post......................

Time (h, min)

Water level above zero of graph H, cm

Level change ± h, cm*

FULL NAME. observer

* change in level compared to the previous observation.

Based on the data obtained, it is possible to construct a graph of water level fluctuations over the observation period. Then it will be easier for the interested person to navigate your results, and besides, graphs are clearer than numbers.

Measuring the depth and width of a river

To determine the depth of the river and the features of the topography of its bottom, measurements of the river bed are taken. Based on the results of measuring work, it is possible to obtain plans of the river bed in lines of equal depths - isobaths, and also to determine the areas of river water sections.

Necessary equipment:

rope with markings;

strip with markings;

journal for recording.

The depth of the river can only be determined by direct measurements using water measuring rod or lot. On large rivers with depths of up to 25 m, a lot is used - a metal weight weighing from 2 to 5 kg, attached to a strong cable with appropriate markings. IN

When studying small rivers, a water gauge is sufficient. It is a wooden pole with a diameter of 4-5 cm with centimeter markings applied to it, and the zero division should coincide with one of the ends of the pole. When measuring depth, the staff is lowered with the zero mark down. The length of the rod can be selected based on the expected depths of the rivers being studied, but usually it is made no longer than 1.5-2 m. If the river is shallow, then the depth can be measured by wading the river. If the river is deep, then measurements must be taken from a boat. The easiest way to determine the depth is from a bridge hanging over the river, if there is one nearby.

Attention! Allow young explorers to measure the depth of the river themselves only in those places where the water is no higher than their rubber boots! Reassure them that this can only be done under the supervision of the group leader or his adult assistants. The depth of an unfamiliar bottom can be determined by measuring the bottom of the river in front of you using a water gauge and moving slowly, step by step, following it. You should be very careful, as there may be unexpected holes and cliffs in the river bottom

In addition to the slats, for carrying out measuring work you will need marked rope to determine the width of the river and the location of measuring points and special journal for entries. The rope is usually marked in advance, before work is carried out. The easiest way to do this is with ordinary threads of different colors, for example red and blue - each ten-centimeter division should be marked with blue threads, and each meter division with red threads. You can also highlight every 0.5 m, for example, with red and blue threads at the same time, this will make it possible not to make mistakes when measuring the distance between measuring points. Instead of threads, you can use multi-colored ribbons, cords, permanent marker or oil paint - the main thing is that the marks on the rope are clearly visible, easy to notice when taking measurements and are securely fastened.

The points on the target at which the depth of the river is measured are called measuring points. The number of measuring points for the river under study should be determined as follows: on rivers with a width of 10-50 m they are assigned every 1 m, on rivers with a width of 1-10 m - after 0.5 m, for a river or stream up to 1 m wide, 2-3 measuring points are sufficient points.

How to take measurements of river depth and width:

At the selected section of the river under study, a marked rope is pulled across the flow (this is important!), and the width of the river is determined from it.

In accordance with the measured width, the number of measuring points and their position on the alignment are determined. It must be remembered that the first and last points must be located directly at the water's edge.

Moving along the rope at the designated points, lower the measuring rod to the bottom (try to keep the rod vertical!) and fix the division at the level of which the water is located - this is the depth of the river in this place.

Measurement data is recorded in a log in the form tables 6. At the same time, data on the date and time of measurements and the location of the target must be entered into the log. It is also necessary to note the nature of the soil (silty, sandy, rocky), as well as the presence and nature of vegetation in the riverbed (“no vegetation”, “vegetation in the coastal zone”, vegetation along the entire riverbed”, dense or sparse vegetation).

Distance from the beginning of the alignment,

Distance between points, m

Depth, m

Nature of the soil

Vegetation

Who did the work......................

Based on the measurement data, it is possible to construct a transverse profile of the river bed and calculate the water cross-sectional area, i.e. cross-section of the river flow by an imaginary plane at the location of the measuring section (Fig. 7). The area of ​​this section can be found as the sum of the areas of simple geometric figures formed by the measuring verticals. These figures can be rectangular trapezoids (S2, S3 and S5) rotated at 90 degrees, rectangles (S4) or right triangles (S1), the area of ​​which is determined according to well-known rules - the area of ​​a rectangular trapezoid is equal to the product of half the sum of the bases (in the example - h1 and h2) by height, the area of ​​a right triangle is equal to half the product of the legs, and the area of ​​the rectangle is equal to the product of its two sides. In our case, the bases, legs and sides of the figures will be the measured depths and distances between measuring points. The resulting cross-sectional area must be recorded in the journal in Table 7.

Rice. 7. Determination of the cross-sectional area of ​​the river bed w (m2)

S1 = h1 * b1 / 2 w = S1 + S2 + S3 + S4 + S5

S2 = (h1 + h2 ) / 2 * b2

S3 = (h2 + h3) / 2 * b3

S4 = h3 * b4 = h4 * b4

S5 = (h4 + h5) / 2 * b5

Dividing the resulting cross-sectional area (w, m2) by the measured width of the river (B, m), we obtain the value of the average depth of the river at the site: hav = w/B.