Where is the most serious water shortage on earth? Why is there water shortage? (constituent materials)

As the seventh largest freshwater lake in China and the largest freshwater lake in Hubei Province, Honghu Lake has always been called the "water sac" in the middle reaches of the Yangtze River. This year, incredibly, the lake has dried up to the bottom. "The entire Jianghan Plain, Honghu Lake has the lowest terrain, and the surrounding water flows to Honghu Lake. Honghu Lake is a famous "water nest". How can you do it? " A person from the local meteorological bureau said.

A local reporter in Jingzhou lamented to the reporter of New Express that he used to come to Honghu almost every summer. Every time he goes to Honghu Lake, it is because it is waterlogged. Unexpectedly, because of the drought here, this is his first visit to Honghu this year.

Honghu Lake has less precipitation, rapid temperature rise and large evaporation.

Ceng Xiaodong is the director of the office of Honghu Wetland Nature Reserve Administration. Through years of research, he found that Honghu Lake is a "vegetable"-shaped lake. Its biggest feature is that the lake is shallow. "Even in the middle of the lake, there is no deep lake ditch, and the deepest part does not exceed 1.35 meters. This structure makes Honghu Lake not only unable to hold much water, but also unable to resist drought. "

Nevertheless, Honghu Lake releases some water to the Yangtze River every winter to welcome the rainy season next year. "This has become a routine." According to this practice, Honghu Lake also released water to the Yangtze River last winter. It was no problem to do this in previous years, but when the spring of 20 1 1 came, all Honghu people began to struggle with this behavior.

Honghu Lake encountered a drought that was almost difficult to encounter in the past! The source of Hong Hushui mainly depends on rain, but after the Spring Festival this year, there were only two Mao Mao rains in Honghu area, and even the ground was not wet. Until May 2 1 day, there was finally a moderate rain in the local area, but the only change brought by this rain was to turn the cracked lake bottom into boundless silt. The reporter learned that these three rainfalls belong to artificial rainfall!

Cheng Gang, chief engineer of honghu city Water Conservancy Bureau, told the reporter of New Express that from 1 month to May 20th this year, the accumulated rainfall in Honghu Lake was only 144.2 mm, which was the least since the local meteorological record, and 250 mm less than that in the driest time of Honghu Lake (1962).

Less precipitation and rapid temperature rise lead to large evaporation in Honghu wetland. In addition, farmers around Honghu Lake rushed to pump the lake after the drought appeared in April, which accelerated the decline of the water level in Honghu Lake.

The water level outside the drainage gate is too low to lead water into the lake.

Honghu Lake and the Yangtze River were once connected.

Yan Ruzhou, deputy director of Honghu Management Bureau in charge of wetland work, said that in the past, the Yangtze River levee was not strong, and Honghu and the Yangtze River were "integrated" during the flood season. After the founding of People's Republic of China (PRC), the Yangtze River levee has been strengthened day by day, and the number of floods hitting Jianghan Plain has been greatly reduced. However, "little brother" can't be separated from "big brother" after all. Later, the relevant departments built many culverts along the Yangtze River. In autumn and winter, the water level of Honghu Lake is high, and at the same time, in order to meet the next year's rainfall, the floodgate is opened to let excessive Hong Hushui flow into the Yangtze River. In April and May, in order to replenish Honghu Lake with rich fish from the Yangtze River, the culvert was lifted and the river entered the lake.

But this spring and summer, the water body replacement between the Yangtze River and Honghu Lake became difficult. Mainly because the water level of the Yangtze River has dropped significantly this year compared with previous years. According to the information provided by honghu city Water Conservancy Bureau, the water level of the Yangtze River this year is 2.5-5.6 meters lower than the same period of last year. On May 2 1 day, five days after the Three Gorges Reservoir increased the discharge, the water level outside the sluice gate of Honghu New Dike was still only 2 1. 19 m, which was 2.0 1 m lower than Honghu. According to Cheng Gang, the water surface is below the sluice bottom, so it is impossible to connect itself, and it is impossible to lead the Yangtze River to fill the lake.

Honghu Lake, which plays the role of regulation and storage, is overwhelmed.

The water system of Jianghan Plain is called the Four Lakes Basin, which consists of four lakes, namely, Changhu Lake, Sanhu Lake, Baihu Lake and Honghu Lake, and hundreds of small lakes. Among the four lakes, the long lake is above, the three lakes and the white lake are in the middle, and Honghu Lake is below. Honghu Lake has therefore become a gathering place for all kinds of water, thus becoming a water network area with regional characteristics in the south of the Yangtze River.

Ceng Xiaodong told the New Express reporter that the four lakes are responsible for water conservation in the middle reaches of the Yangtze River, and at the same time, they are also responsible for releasing water when there is water shortage, which plays an important role in alleviating the drought. Every summer, the lake evaporates seriously, and the interaction between the four lakes can produce many link effects.

At the same time, each lake has an important storage function: if there is more water, the large and small lakes will be accepted together; When there is little water, large and small lakes come out together to fight drought.

However, in the 1960s and 1970s, the local government shouted the slogan of "planting rice at the bottom of the lake and planting crops in the center of the lake", which led to the disappearance of Sanhu Lake and Bailu Lake in the "Four Great Lakes Basin" and turned them into farmland. In recent years, with the intensification of human activities, many small lakes in Jianghan Plain have also disappeared.

Honghu Lake also built dikes that year, with the area of 1.3 million mu changed to 600,000 mu.

Therefore, the water storage capacity of the four major lake basins is greatly reduced. Because the long lake is much smaller than Honghu Lake, Honghu Lake has a greater role in regulating and storing the whole basin, and it is becoming more and more overwhelmed every year. Ceng Xiaodong gave an example. A family used to have four water tanks, but now there are two. And the water tank is smaller and there is less water. However, there are still so many people drinking water, even more. Of course, problems will follow.

According to Cheng Gang, due to this year's drought, the "water bag" in Honghu Lake has dried up, the long lake in the "Four Lakes Basin" has also dried up, and the "Four Lakes Main Canal" has also dried up without water.

affect

water conservancy

The natural law was broken, and the "peach blossom flood" in the Yangtze River disappeared for the first time.

In fact, this year's drought is the second extreme weather phenomenon in Honghu area in a short time: in the summer of 20 10, Honghu area suffered the biggest rainstorm in history. According to the reporter's understanding from the honghu city Meteorological Bureau yesterday, the average continuous precipitation of this rainstorm was 566 mm, exceeding the maximum value in the same period in history, which led to a large-scale flood disaster in this area. Even the water in Honghu street is more than 1 m deep, causing losses to urban and rural people and Honghu fishermen.

The abnormal weather in Honghu area reminds people of the relationship between the drought in the middle and lower reaches of the Yangtze River and the Three Gorges Dam, which is hotly discussed on the Internet. Such voices have also appeared in local forums in Honghu.

The director of honghu city Meteorological Observatory claimed to be very concerned about the online debate on this topic, but he told reporters that the abnormal weather in Honghu Lake for two consecutive years should have nothing to do with the construction of the Three Gorges Dam. His reason is: "From 1998, judging from the local meteorological records in Honghu, it is normal that the disaster weather changes little." He supports the statement that "without the Three Gorges Dam, it may be drier this year". However, he also admitted that "there may be some laws that we haven't mastered yet."

Cheng Gang, chief engineer of honghu city Water Conservancy Bureau, also believes that the Three Gorges Project is beneficial to flood control. "It has little effect on this year's drought. After the Three Gorges Dam has increased the discharge, it should be said that the current river water is greater than the natural flow in previous years, and the storage function of the Three Gorges Dam is obvious. "

The only thing that makes Cheng Gang feel sorry is that this year's severe drought has caused the "peach blossom flood" that occurred in the Yangtze River every April to disappear. "The peach blossom flood season is a natural law in the middle and lower reaches of the Yangtze River and plays a vital role in replenishing fish in lakes along the Yangtze River. This is what the so-called' river irrigation and fish farming' means. But for the first time this year, there was no peach blossom water, and this natural law was broken. This has never happened before. I hope it won't be a memory. "

agriculture

Staring at a little water, farmers in towns along the lake build dams to grab the lake.

According to a government official in honghu city, local drought relief mainly depends on Honghu water source. However, as the bottom of Honghu Lake dries up, it has no ability to replenish water to other inland rivers in honghu city.

One alternative is to quote the Yangtze River water! Yejiabian Irrigation Station is the only irrigation station in honghu city that draws water from the Yangtze River, with a design flow of 3.6 cubic meters per hour. The four machines originally installed, if effective, can irrigate 40,000 to 50,000 mu of farmland. However, due to the low water level of the Yangtze River, the pumping pipes of irrigation stations can't reach the river. Even yesterday, despite the efforts of the local water conservancy department, two installed machines began to pump water from the Yangtze River, but it was still a drop in the bucket. Dongjing River is one of the main rivers flowing through Honghu area. According to the data provided by honghu city Water Conservancy Bureau, on May 2 1 day, the flow of Taomi Port in Dongjing River of Hanjiang River was 4.08 cubic meters per hour. Upstream counties and cities are also staring at this water. Due to the lack of coordination, counties and towns have built dams to grab water, and the water level of Dongjing River has dropped by 0.52 meters in one day. According to Cheng Gang, the water pumped by Honghu Lake from Dongjing River is stored in the river. Without effective rainfall, the Tokyo River may be cut off.

The serious shortage of drought-resistant water sources has led farmers in towns along Honghu Lake to rob the lake. "Some villagers fight with each other because of water intake and even attack grassroots cadres."

May is the critical period for mid-season rice planting. Due to the lack of water, farmers can only make the vacated land barren. According to the information provided by honghu city Flood Control and Drought Relief Headquarters, as of May 2 1 day, the drought-affected area in the city was 90 1 10,000 mu, including 550,000 mu of disaster-stricken area, 68,000 mu of crop failure area and 337,000 mu of transplanted upland rice, resulting in direct economic loss of 245 million yuan.