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In January 2022, the mainland announced for the first time the country's freshwater reserves of groundwater resources, but the results surprised many people.
Because of the stereotyped impression of the water-scarce north, groundwater reserves account for 95% of the country's reserves, while the south, which is relatively rich in precipitation, accounts for only 5%.
Since there is so much groundwater in the north, does it mean that there is no need for the south-to-north water diversion project? How can groundwater be exploited and utilized?
More groundwater in the north than in the south?
Groundwater refers to the water distributed below the surface of the earth, and can be divided into shallow groundwater and deep groundwater according to the depth of burial.
For example, in many rural areas, some wells use shallow groundwater, and deep groundwater usually refers to water 1 km underground, and the replacement cycle of these groundwater may reach more than 1,000 years.
Although it is difficult for us to see groundwater, it is a rare resource.
As early as July 2021, the China Geological Survey took the lead in investigating and assessing groundwater reserves across the country, which was the first time that the mainland had conducted a survey of groundwater reserves.
The results show that there are about 52.1 trillion cubic meters of groundwater in the country, but the distribution of groundwater is not the same as that of surface water.
The groundwater resources in the northern part of the mainland are 35.5 trillion cubic meters, accounting for 95% of the country's total, and most of the freshwater hidden in the ground is distributed in the North China Plain and the Northeast Plain.
In contrast, the reserves of underground freshwater resources in the southern part of the mainland are only 1.9 trillion cubic meters, accounting for 5% of the national total, mainly distributed in the Yangtze River Delta and Chengdu Plain.
In addition, there are 14.7 trillion cubic meters of saltwater buried in the mainland, most of which is distributed in the western basin.
However, why is there more groundwater in the north of the continent? Isn't there more precipitation in the south? This is mainly related to the difference in the environment between the north and the south.
First of all, most of the groundwater comes from above-ground precipitation, and some comes from lakes, alpine ice and snow meltwater, etc., and the source is basically surface water.
Secondly, the underground rock formation in the north is thicker, and the groundwater is less likely to infiltrate and drain downward, which is conducive to the accumulation of groundwater.
In the north, there is also a lot of glacial snow melt and precipitation in the mountains, so there is an abundance of groundwater.
As for the reason why there is less fresh groundwater in the south, it is because the rock fractures in the south are relatively large, and the loss of groundwater is relatively fast, so the reserves will naturally be less.
Finally, under the combined action of multiple factors, the distribution of groundwater in the mainland presents a situation of more in the north and less in the south.
According to the results of this survey, the reserves of groundwater resources in mainland China are in the stage of growth.
In addition, unlike surface water, groundwater is relatively stable, and in many cases, the amount of water does not fluctuate very much from year to year.
Over the years, groundwater has been used in many places by sinking wells, etc., which shows that it is not difficult for people to use groundwater.
Therefore, many people are curious, since there is so much groundwater in the north, it is enough to use groundwater directly, why do you need to divert water from the south to the north?
Is South-to-North Water Diversion Still Necessary?
In fact, whether the South-to-North Water Diversion Project should exist or not, to put it bluntly, is whether there is a shortage of water in the north, but the current water shortage problem in the north has not been solved by the large amount of groundwater.
First, groundwater in the north is not evenly distributed, just like surface water.
At present, groundwater in the north is mainly distributed in the Northeast Plain, North China Plain and other places, and there are still many places where there is a shortage of water, and there is also a lack of groundwater.
Secondly, groundwater cannot be exploited uncontrollably.
The mainland has evaluated the exploitation potential of groundwater resources in various places, which can be divided into over-exploitation areas, basic equilibrium areas, areas with low exploitation potential, areas with medium exploitation potential, areas with large exploitation potential, and areas with large exploitation potential.
Among these six grades, the overmining area covers Beijing, Tianjin, Shandong and other provinces and cities with large demand for water resources.
In other words, even in the North China Plain, where groundwater is relatively abundant, there are still many provinces and cities in overexploited areas, which shows that the potential for comprehensive groundwater exploitation in the north is relatively small.
However, the potential of groundwater exploitation in many provinces and cities in the north is relatively small, mainly related to the over-exploitation in the past.
As early as the 70s of the 20th century, groundwater exploitation on the mainland was small in scale and scattered.
However, after the 70s, the development and utilization of groundwater on the mainland accelerated rapidly.
By 2012, the amount of groundwater extracted by the mainland had risen from 20 billion cubic meters to 113.4 billion cubic meters per year.
In 2019, groundwater use in northern China accounted for more than 90% of the country's groundwater use.
The rapid expansion of groundwater extraction on the mainland is mainly related to industrial development and population, but if it continues unchecked, it will lead to more serious consequences.
First, the most intuitive problem caused by over-exploitation of groundwater is land subsidence.
For example, in the process of mining, many cities such as Beijing and Shanghai on the mainland have found different degrees of ground subsidence in some areas, among which the eastern suburbs of Beijing are about 600 square kilometers of subsidence of more than 550 millimeters.
Although this number in millimeters may seem insignificant, it can cause problems such as tilting of tall buildings, rainwater accumulation, and urban waterlogging.
If groundwater continues to be extracted in some areas with unstable geological structures, it may also cause surface subsidence, which may directly threaten the lives of local residents.
Second, much groundwater extraction takes place in coastal areas, which themselves have relatively few freshwater resources.
However, continued over-exploitation of groundwater can lead to an imbalance between freshwater and seawater pressure in the region, making it easier for seawater to inflow and damaging the local drinking environment.
Finally, in addition to satisfying living needs and industrial production, groundwater is exploited for agricultural production in many places.
In some places where water is scarce, crops rely on this groundwater to survive.
People continue to extract this groundwater, ostensibly to solve the problem of agricultural irrigation, but in fact, in the end, it will only lead to the real lack of groundwater for irrigation of these crops, and eventually the local ecological environment will be completely destroyed.
In other words, we can extract groundwater, but we can't allow it to extract more than it can recharge, or it will lead to a series of problems with incalculable consequences.
Therefore, all parts of the mainland are more cautious about the exploitation of groundwater, and the excessive exploitation of groundwater is also expressly prohibited.
Since groundwater is not able to meet the water needs of the north, the shortage of fresh water in the north still exists.
North China, for example, is one of the most densely populated and economically developed regions in the mainland, and occupies a pivotal position in the mainland.
North China accounts for a quarter of the country's population, which means that it needs to produce a quarter of the country's food without buying food.
But the real problem is that North China accounts for only 4% of the country's freshwater resources.
Over the past few years, water scarcity has been a major constraint on the development of North China, which has made the mainland more and more determined to implement the South-to-North Water Diversion Project.
The South-to-North Water Diversion Project is divided into three routes: eastern, central and western, and the eastern and central routes have been connected to water.
The eastern route project is to take water from the lower reaches of the Yangtze River, and then transfer the water to Shandong and Tianjin.
The middle route project is to take water from the middle reaches of the Yangtze River, divert water from the Danjiangkou Reservoir in the middle and upper reaches of the Han River, and transfer water to Henan, Hebei, Tianjin, and Beijing through the Huai River and the Yellow River.
The western route project is mainly to transfer water from the upper reaches of the Yangtze River to the Yellow River, and the environment here is relatively complex, so the western route project is still in the demonstration stage.
But what has the 500 billion yuan South-to-North Water Diversion Project brought to the north?
How big is the role of the South-to-North Water Diversion?
For many years, the annual scale of the South-to-North Water Transfer Project has been maintained at 38 billion to 4.8 billion cubic meters.
To put it simply, the South-to-North Water Diversion Project is equivalent to sending a Yellow River to the water-scarce north, which can basically alleviate the problem of water shortage in the north.
In addition, there is a lot of precipitation in the southern part of the continent, and flooding may occur in many cases.
However, the transfer of some water to the north through the South-to-North Water Transfer Project is sometimes conducive to alleviating flooding in the south, which is beneficial for both the north and the south.
Facts have once again proved that the South-to-North Water Diversion Project not only builds a water diversion line, but also constructs a lifeline, which is a utilitarian national plan!
Bibliography:
People's Daily Online: For the first time, China has identified about 52.1 trillion cubic meters of groundwater resources in the country