What Are the Different Types of Hydrographic Surveyor Jobs?

A collection of water-related data. It is based on observations of various hydrological elements of rivers, rivers, lakes, and seas. The hydrological elements of rivers and lakes include water depth, water level, flow direction, velocity, flow rate, water temperature, ice condition, specific gravity, sand content, precipitation, evaporation, water color, transparency, and chemical composition of water, etc .; marine hydrological elements include tides, currents, Waves, currents, sea temperature, salinity, sea air temperature, air pressure, wind direction, wind speed, plankton, etc. Hydrological observing stations are usually set up at certain locations or sections of rivers, lakes and seas under certain conditions for long-term uninterrupted hydrological observations. After sorting and analyzing various hydrological observation data, it is not only the basis for various hydrological predictions, but also the research sea. Important materials such as riverbeds, riverbeds, riparian changes, ocean currents, runoff laws, various water conservancy projects, coastal engineering design calculations, and navigation guides. ^[1]

A collection of water-related data. It is based on observations of various hydrological elements of rivers, rivers, lakes, and seas. The hydrological elements of rivers and lakes include water depth, water level, flow direction, velocity, flow rate, water temperature, ice condition, specific gravity, sand content, precipitation, evaporation, water color, transparency, and chemical composition of water, etc .; marine hydrological elements include tides, currents, Waves, currents, sea temperature, salinity, sea air temperature, air pressure, wind direction, wind speed, plankton, etc. Hydrological observing stations are usually set up at certain locations or sections of rivers, lakes and seas under certain conditions for long-term uninterrupted hydrological observations. After sorting and analyzing various hydrological observation data, it is not only the basis for various hydrological predictions, but also the research sea Important materials such as riverbeds, riverbeds, riparian changes, ocean currents, runoff laws, various water conservancy projects, coastal engineering design calculations, and navigation guides. ^[1]

Chinese name: Hydrological observation

Foreign name: hydrometry

Hydrological observations of precipitation and evaporation

Hydrological Observation of Precipitation

The precipitation observation site should be selected in the open and flat surroundings to avoid the influence of local terrain and terrain. The instruments used to observe precipitation generally use 20cra caliber rain gauges and self-recording rain gauges.

(1) Artificial rain measuring cylinder observation

The artificial rain cylinder is a cylindrical metal cylinder, as shown in Figure 3-2. During the rain, the rainwater enters the water storage bottle from the funnel. After the rainfall, the special measuring cup that pours the rainfall in the water storage bottle can directly read the rainfall depth and record it.

Rain measurement using artificial rain gauges generally uses segmented timing observations. Two-segment system (8 o'clock and 20 o'clock daily) is commonly used for observation. The four-segment system (daily 8:00, 14; 00, 20:00, and the following day) is used in the rainy season. 2:00), eight-segment system (8: 00, 11:00, 14:00, 17:00, 20:00, 23:00, and 2:00, 5:00 the next day) Need to increase the number of observations. If you use an artificial rain measuring cylinder to observe snowfall, you can take out the funnel and water storage bottle, leaving only the outer cylinder as the snow-bearing device.

(2) Observation by self-recording rain gauge

Self-recording rain gauges mostly use siphon-type self-recording rain gauges or dump bucket-type self-recording rain gauges. The working principle of the commonly used siphon-type self-recording rain gauge is that after the rainwater enters the float chamber from the rain bearing device, the float is raised and the self-writing pen is driven to record on the recording paper on the periphery of the self-recording clock. When the rainwater in the floater's room is full, the rainwater is discharged to the water storage bottle through the siphon, at the same time the self-writing pen drops to the starting point, and continues to rise with the increase of rainfall. In this way, the rainfall process is drawn on the self-recording paper.

Self-recording rain gauge

From the recording paper of the self-recording rain gauge, the start and end time of the rainfall, the cumulative change of the rainfall over time can be determined, and the rainfall intensity at different periods can be extracted from the recording paper. But the self-recording rain gauge cannot be used directly to measure the snowfall process.

(3) Collation of precipitation data

After obtaining the precipitation data, the data should be collated. The main contents include: compiling excerpts of precipitation during the flood season; counting the maximum precipitation in different periods; calculating the daily, monthly, and annual precipitation. Yesterday's daily rainfall.

According to research, the precipitation measured by current rain gauges or gages is relatively small due to the influence of wind, evaporation, and wall adhesion, and related observation work is being carried out.

Hydrological observations of evaporation

There are three types of evaporation: surface evaporation, soil evaporation, and plant emission.

(1) Water surface evaporation observation

Water surface evaporation is divided into two types: onshore water surface evaporation field and floating water surface evaporation field. The water surface evaporation observation instruments include E-601 evaporator, an evaporator with a sleeve of 80 cm in diameter and a evaporator with a diameter of 20 cm. Others include FFH-3000 evaporator, floating evaporator on water, large evaporation ponds of 20m and 100m, etc.

The structure of the evaporator with a sleeve of 80cm in diameter is divided into an inner basin and an outer basin. The inner basin is an evaporation barrel that directly observes the amount of evaporation. It is placed in an outer basin with a larger diameter. The influence of ambient temperature on the temperature of water in the evaporation bucket.

The E-601 evaporator is an evaporator with a set of basins buried under the ground. The inner basin (area 3000cm) contains water. When it is installed, it is flat on the ground. The mouth of the evaporator should be flush with the ground. Set of water circles.

The evaporation is observed at 8 o'clock every day, and the previous day's evaporation is measured. The observed evaporation is calculated based on the amount of change in water level indicated by the stylus in the evaporator and the daily rainfall.

The above-mentioned evaporator or evaporation pond is a water surface evaporation observation device installed on land. Another type of floating evaporator is to place the evaporator on a raft floating on the water surface. In this way, the environmental conditions of the evaporator are closer to the natural water body, and the observed evaporation is more representative of the evaporation of the natural water body. However, some studies have shown that due to conditions and wind and waves, the observation accuracy of floating evaporators is not high. The observation data of floating evaporators can only be used when the actual measurement data of evaporation ponds are lacking.

(2) Observation of soil evaporation

The soil evaporation observation is more complicated than the water surface evaporation observation. Currently, weighing soil evaporator is commonly used. It is based on measuring the weight change of the soil mass in the evaporator within a certain period (usually 1 day), and taking into account the precipitation during the observation period. And the amount of water leaking from the soil, the principle of water balance is used to derive the amount of soil evaporation. At present, the commonly used instruments in China are -500 soil evaporator and large lysimeter. Among them, -500 soil evaporator has a simple structure, is convenient to install and observe, and is widely used.

-500 soil evaporator includes two iron cylinders inside and outside. The inner cylinder is used to cut and fill soil samples. The inner diameter is 25.2cm, the depth is 50cm, and the caliber area is 500cm. The inner diameter of the outer tube is 26.7cm and the depth is 60cm. It is used as the holder of the inner tube for the inner tube. In addition, there is a water collector under the inner cylinder to bear the amount of water leaking from the soil sample in the evaporator. A drainage pipe is connected to the inner cylinder to connect to the runoff cylinder to collect the runoff generated by the soil surface of the evaporator.

(3) Plant emission observation

Plant emission is that the water in the soil is absorbed by the roots of the plant and transported to the leaf surface, and then the stomata of the leaf surface cells escape into the atmosphere, and the stomata have the ability to scale with changes in external conditions, and can adjust the intensity of water dispersion. Plant emission is not only a physical process of water, but also a physiological process of plants. Direct observation is difficult. Even the study of small samples under experimental station conditions has only theoretical value and is difficult to directly quote.

(5) Sorting of evaporation data

The collation of evaporation data refers to the calculation of daily, monthly, and annual evaporation of observed values and statistics of relevant characteristic values. For water surface evaporation measured with an evaporator, due to the significant difference between the hydrothermal conditions and wind force of the evaporator and natural water bodies, the measured evaporation is too large, so the observation results of the evaporator cannot be directly used as the evaporation value of the natural water body. The research of relevant units shows that the relationship between evaporation intensity and the area of the evaporation pool becomes smaller after the diameter of the evaporation pool is larger than 3.5m, so it is believed that its evaporation can represent the natural evaporation. For this reason, the data observed for a large number of small evaporators needs to be multiplied by a conversion factor to be more realistic.

Hydrological observation of water level and discharge

Calculation of Hydrological Observation Water Level

The elevation of the free water surface of a body of water such as oceans, rivers, lakes, swamps, reservoirs at a certain moment relative to a fixed base is called the water level, and the unit is m.

The starting plane for calculating water levels and elevations is called the base plane; this base plane can take the multi-year average sea level or assumed plane somewhere on the seashore. The bases involved in the hydrological data are: absolute bases (standard bases), hypothetical bases, bases of stations, and frozen bases.

Water level is an important basis for water conservancy construction, flood prevention and drought resistance. It is directly applied to the design of dykes, reservoirs, weirs, irrigation, drainage and other projects, and is used for hydrological forecasting.

Water level is another basic information for national economic construction services such as river shipping, timber rafting, and urban water use. In the construction of navigation channels, bridges, ports, water supply and drainage, it is also necessary to understand the water level.

In the hydrological test, when performing other tests such as flow, sediment, and water temperature, it is also necessary to observe the water level at the same time, as an important indicator of the flow situation.

There are two types of observation equipment commonly used in water level observation: artificial water ruler and self-recording water level gauge.

(1) Observation with artificial water ruler. Water ruler is a scale for observing the water level of rivers or other bodies of water. It is the basic facility for observing the water level at stations. It can be divided into 4 types: vertical, inclined, cantilever and low pile. An upright water rule is a fixed water rule perpendicular to the horizontal plane. An inclined water rule is a type of water rule that is set along the slope of a stable bank or the side wall of a hydraulic structure. Its scale directly indicates the vertical height relative to the zero point of the water rule. Cantilever water ruler is a water ruler composed of a rope or chain with a heavy hammer. It is used to calculate the water level by measuring the vertical height difference from the water surface at a fixed point with a known elevation above the water surface. The short pile water ruler is a water ruler composed of a set of short piles and a portable measuring ruler arranged on the observation section. A measuring ruler is set upright on the top of a pile below the water surface, and the water level is determined based on its known pile top elevation and the water surface reading on the measuring ruler. Among them, the vertical water ruler has a simple structure and convenient observation, and is generally used by general stations. It is made of hard, straight slats or enamel, and is placed on an upright pile for easy observation on the shore or nailed to a bridge pillar or brake wall. If the water level changes greatly, a set of water rulers should be set up. Inclined water ruler is to paint the water ruler directly on a special slope or the inclined wall of a hydraulic structure, such as a reservoir's facing slope or a protected canal slope. When observing the water level, the reading on the water surface plus the zero elevation of the water surface is the water level.

The time and number of water level observations are based on the principle that a complete water level change process can be measured. When the water level is stable or slowly changing in a day, you can observe it at 8 o'clock daily or at 8 o'clock and 20 o'clock regularly; when the water level changes a lot, it can be at 2 o'clock, 8 o'clock, and 14 o'clock every day. Observe 4 times at 20 o'clock; when the water level changes sharply during the flood period, you should increase the measurement as needed to enable the measurement of the flood peak, valley water level and flood process. When observing, pay attention to the level of sight, pay attention to the effects of waves and backwater, and the reading should be accurate and accurate to 0.5cm.

(2) Observe by self-recording water level gauge. Self-recording water level gauge is an instrument that automatically records the process of water level change. It has the advantages of complete recording, continuous, and saving manpower. At present, a variety of methods for sensing the water level have been developed at home and abroad. The method includes a method of measuring a water surface, a method of measuring a water pressure, and a method of estimating a water level from an ultrasonic wave propagation time. At present, the more commonly used types of self-recording water level gauges are buoy type self-recording water level gauges, hydraulic pressure self-recording water level gauges, ultrasonic water level gauges and the like.

Calculation of Hydrological Observation Flow

Flow is the volume of water flowing through a cross section of a river channel or pipeline per unit of time, measured in m / s. Flow is the basic information reflecting the change of river water resources and water quantity, and it is of great significance in the planning, design and management of water conservancy and hydropower projects. The method of flow measurement by flow velocity area method is introduced below.

The method of estimating the flow rate by measuring the velocity of the cross section and the area of the cross section is called the velocity area method. The principle of measuring flow is: from hydraulics, flow is equal to the product of the average cross-sectional flow velocity and the cross-sectional area of the water flow. Natural rivers are affected by boundary conditions, and the velocity distribution in the section is very uneven. The velocity varies with different positions in the horizontal and vertical directions. Therefore, the water flow section is divided into several sections by vertical lines, and then the partial velocity and area are measured. The product of is the flow through the area of the part; and finally the flow across the cross section is obtained.

Hydrological Observation and Hydrological Automatic Forecasting System

Hydrological automatic measurement and reporting system is a general term for various sensors, communication equipment and receiving and processing devices provided for collecting, transmitting and processing real-time hydrological data. It usually consists of three parts: telemetry station, channel and receiving processing center. Before the automatic forecasting technology was put into use, the collection of hydrological data relied on a small amount of manual observation, and hydrological stations and rainfall stations transmitted information by telegraph or wired telephone. This is not only due to the limitation of manpower and natural environment, the number of observation sites is sparse, and the amount of information is small. At the time, due to the backward communication methods and poor timeliness of information transmission, it could not meet the requirements of applications such as flood control and water resources management.

The United States and Japan are the first countries in the world to attach importance to the development and application of automatic forecasting technology. With the acceleration of industrialization, Japan and the United States have begun research and development of automatic hydrological forecasting technology in the 1960s, and their products gradually matured and entered the international market in the late 1970s. In 1976, a set of automatic hydrological forecasting equipment developed by the United States SM Company under the funding of the United States Army Engineering Corps and the US Weather Service was a representative product of this period.

Since the 1980s, due to the continuous improvement of automatic measurement and reporting equipment, the diversification of data transmission methods and the increase in their reliability, and the further development of microcomputer technology, forecasting and dispatching theory and software, automatic hydrological forecasting and flood control and dispatching automation technology Widely used worldwide.

The development of hydrological automatic forecasting technology in China began in the mid-1970s. In the past 30 years, the construction and technology of China's automatic hydrological forecasting system have made great progress. In different historical periods, the data collected by the system quickly provided a basis and reference for flood control decision-making and water resource management, and played a very good role.

In the mid-1990s, the Ministry of Water Resources began planning and constructing the national flood control command system project, and successively organized and compiled the "National Flood Control Information System Planning Essentials" (1992), "National Flood Control Information System Construction Planning" (1993), and " National Defense Flood Computer Wide Area Network Construction Plan (1993), National Central Flood Station Hydrological Testing Facilities Construction Plan (1994), National Flood Control and Drought Control Command System Construction Plan (1995), National Flood Control Command System Project Project Proposal (1995), "Overall Design of National Flood Control Command System Project" (1998) and "Feasibility Study Report of National Flood Control Command System Project" (1998). In May 2003, the National Development and Reform Commission formally approved the comprehensive summary of the experiences and lessons of the construction of China's automatic hydrological forecasting system in the construction of the National Flood Control Command System Hydrological Information Center, and based on the careful analysis of the development trend of the forecasting technology, the application of advanced electronic communication Sensor, communication, computer, network and other technologies for automatic collection, transmission, processing and application of hydrological information. In order to adapt to the new situation and new requirements of the rapid development of information technology, on the basis of summing up the construction and operation experience of the demonstration area and the new technologies and new experiences of hydrological automatic measurement and reporting systems in recent years at home and abroad, the 1994 version of the specification was revised to form The 2003 new regulations were issued and implemented. The 2003 version of the specification has made major adjustments and additions in all aspects. ^[2]