Do you understand the “blood” of the earth?

Do you understand the “blood” of the earth?

Question: How are rivers formed and what are their functions?

A: A river is composed of a river channel and the water flowing in the river channel. The water supply sources include rainwater, ice and snow meltwater, groundwater, etc. A large river can be divided into five parts: the source, upper reaches, middle reaches, lower reaches and estuary. From the source to the end of the river, it is winding. What we see is a certain section of the river, which is composed of the shore, river beach, river channel and water flow. Some rivers have built embankments, and the boundaries between the two banks are obvious. Some rivers have natural boundaries, and the width of the river changes with the amount of water flowing in the river channel.

Rivers are the "blood vessels" of the earth, and protecting them is everyone's responsibility. Rivers have many functions, including natural regulation, ecological support, and social service. The formation, development, and evolution of rivers are achieved through the movement of water. They are channels for floods, and flood control is the most important natural regulation function of rivers. Rivers also transport materials and adjust natural balance through the flow of water. Some rivers can also adjust microclimates.

The ecological support function of rivers is mainly reflected in two aspects. On the one hand, rivers are the habitats of animals and plants in the shore zone and water bodies, and the habitats of fish, some reptiles, birds, and microorganisms. On the other hand, rivers can also provide nutrients for these organisms, forming a relatively complete ecosystem.

The social service function of rivers, as the name implies, is the guarantee that rivers provide for human survival and development. One of the most important functions of rivers is to provide water for human survival. In addition, rivers also have delicious fish and shrimp for people to cook, and river water can also generate electricity and shipping. The beautiful scenery is a place for people to relax and entertain. Some rivers also have historical sites, carrying ancient stories, legends and ethnic customs. These are the social service functions of rivers.

Question: How many rivers are there in our country and what are their characteristics?

A: According to the first national water resources census, there are 45,203 rivers with a drainage area of ​​50 square kilometers or more, with a total length of 1.5085 million kilometers, of which 22,909 rivers have a drainage area of ​​100 square kilometers or more, with a total length of 1.1146 million kilometers. Since 2016, the central government has fully implemented the river chief system and lake chief system. my country has established more than 300,000 river and lake chiefs, who are the party and government leaders at the provincial, municipal, county and township levels, and are responsible for organizing and leading the management and protection of the corresponding rivers and lakes.

my country has many rivers, which are unevenly distributed across regions. The south has many rivers and large amounts of water. In some places, the river network is crisscrossed, with the charm of the Jiangnan water town. The north has few rivers and small amounts of water. There are many deserts and Gobi in the northwest, and few rivers. The water supply of my country's rivers, except for a few high mountain areas such as the Qinghai-Tibet Plateau, which are supplied by glacier melt, mainly relies on rainfall. my country's rainfall time is mainly concentrated in summer and autumn every year, when the rivers have a lot of water and are prone to floods. In winter and spring, there is little precipitation and the river water is small, so some places will suffer from drought and water shortage.

Q: How do you calculate the length of a river? How long are the seven major rivers in my country?

Answer: The length of a river refers to the length from the source to the mouth of the river, and is measured along the center line of the river. The seven major rivers are the Yangtze River, the Yellow River, the Huai River, the Haihe River, the Pearl River, the Liaohe River, and the Songhua River. The Yangtze River originates from the Geladandong Peak of the Tanggula Mountains in the eastern part of the Qinghai-Tibet Plateau and flows into the East China Sea in Shanghai. It is 6,397 kilometers long, the longest in Asia and the third longest in the world. The Yellow River originates from the Gadasuqilao Peak of the Bayankala Mountains in Qinghai Province and flows into the Bohai Sea in Dongying City, Shandong Province. It is 5,464 kilometers long and is the second longest river in my country. The lengths of the remaining rivers are: Huaihe River 1,000 kilometers, Haihe River 1,090 kilometers, Pearl River 2,214 kilometers, Liaohe River 1,390 kilometers, and Songhua River 2,308 kilometers.

Q: Why do rivers meander?

A: The rivers we see are all winding, which is the result of the interaction between water flow and riverbed over a long period of time. Under the action of gravity, water always flows toward the lowest point of the terrain to consume kinetic energy and potential energy, which is the saying "water flows to the lowest place".

Due to the different hardness and coagulation of the gravel on both sides of the river, the impact resistance is different. Under the impact of water flow, the river bank soil with weak impact resistance is easy to collapse, which will "attract" more water flow impact, and the bank slope soil is constantly washed away by the water flow to widen the river channel. Over time, a concave bank of the river channel will be formed. On the other side of the river channel, the impact resistance is strong, and the silt in the water flow is deposited. These sediments can block the water flow, and over time, a convex bank of the river channel will be formed. After long-term scouring by water flow and silt deposition, the river presents a tortuous and uneven appearance. For example, the Yellow River has formed the magnificent landscape of "Nine Bends and Eighteen Turns".

Question: Why do shoals and sandbars appear in the center of rivers?

Answer: Every river has a certain slope. The upper reaches of the river have a large slope and a turbulent flow. The river water constantly washes the riverbed, erodes the riverbank, and washes down a large amount of stones, gravel and silt. The slope of the middle and lower reaches of the river is small, the speed of the water slows down, and the ability of the water flow to carry silt is greatly reduced. The silt particles that were previously "mixed" in the water will fall to the bottom of the river and settle. Further downstream, the river channel is flatter, and some of the fine sand particles in the water are also deposited. Over the years, these sand and gravel accumulate more and more, and they will emerge from the water to form shoals or sandbars. It should be emphasized that these shoals and sandbars are important components of the river, and it is strictly forbidden to dig, exploit, occupy or use them indiscriminately.

Q: What is a seasonal river? Why are some rivers dry all year round?

Answer: Seasonal rivers, also known as intermittent rivers, only have water flowing in the river channel during the rainy season or after a heavy rain. In the northwest region of my country, precipitation is scarce and evaporation is strong. Usually there is no water flowing in the river channel. When there is a heavy rain, the water flow from the surrounding slopes quickly gathers and flows into the river channel, forming a seasonal river. Some places are particularly dry, and sometimes there is a heavy rain every few years. At this time, water flows in the river channel, and the rest of the time it is dry.

Q: Why is some river water so turbid? Where does the silt in the water come from?

Answer: my country's rivers are mainly replenished by natural precipitation. Since heavy rain or even torrential rain often occurs during the flood season, raindrops and the collected water will wash away the soil on the surface of the ground and bring it into the river, making the river water turbid. According to the above principle, the sediment in the river is mainly washed away from the surface of the land. In addition, some rivers, because the banks and bottom of the river are also loose soil, will collapse the bank and wash the river bottom under the impact of the water flow, which will also increase the sediment in the river. In order to reduce the sediment entering the river, we must do a good job in soil and water conservation.

Q: What is the "River of Happiness"?

Answer: In September 2019, General Secretary Xi Jinping presided over a symposium on ecological protection and high-quality development of the Yellow River Basin and delivered an important speech, proposing the concept of "Happy River" for the first time. He stressed the need to "strengthen ecological protection and governance, ensure long-term stability of the Yellow River, promote high-quality development of the entire basin, improve people's lives, protect, inherit and promote the Yellow River culture, and make the Yellow River a happy river that benefits the people". The "Happy River" is a healthy river with good functions that benefit mankind. The functions of the "Happy River" include at least: effectively storing and discharging flood water under natural conditions or human intervention, reducing losses caused by flood disasters, effectively serving as a carrier of material circulation and energy flow, supporting a good river ecosystem, and providing effective resource supply and cultural heritage for the development of human society.

Q: What should we do to build a “Happy River”?

Answer: To build a "happy river", we need to do a lot of things, mainly in five aspects. First, we must protect the river, treat the river as a "living body", adhere to the comprehensive management, systematic management, and source management of mountains, rivers, forests, fields, lakes, and grasslands, give play to the self-repairing role of nature, and maintain the healthy life of the river. Secondly, maintain the good regulation function of the river, unblock the water flow channel, combine flood storage, flood discharge, and flood retention, combine the engineering flood control and disaster reduction system with the prediction and early warning system, and combine daily defense with emergency dredging to protect the lives and property of the people. Third, according to the carrying capacity of the river, scientifically develop and utilize resources, adhere to the principle of determining cities, land, people, and production by water, and regard water resources as the greatest rigid constraint. Fourth, build a high-quality ecological space for the river, protect the water quality and biological habitat of the river, and maintain a good ecological system of the river. Fifth, inherit the long history and culture of the river, guard the precious heritage left by our ancestors, explore the contemporary value contained in the history of river management, promote traditional virtues, strengthen cultural confidence, and gather spiritual strength to realize the Chinese dream of the great rejuvenation of the Chinese nation.

Source: China Water Resources News, Issue 4640, July 9, 2020 Liu Xiaoyong (Director of the River Chief System Office, Development Research Center, Ministry of Water Resources)