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Towards the north of Tongguan, there are two passes that can be praised: one is Pujin Pass and the other is Longmen Pass. There are still relics to be found in Pujin Pass. Longmen Pass should be next to Longmen Mountain on the side of the Yellow River between Hancheng City and Hejin City. However, searching on the east and west hills of Longmen, there is nothing to find. Shi Congwen's second stop is here. Although the gate city needs to be found, the river water at the foot of the mountain is turbulent and it is difficult to cross the boat, but it is a dangerous place to go.

The only traffic here is the iron cable pontoon bridge. The bridge can be laid on it, so you can walk by pedestrians. When you encounter a strong wind, you will be removed. Shi Congwen is not lucky. He happened to encounter a strong wind that day, so he had to take the risk of stepping over the iron cable. There are blue sky above and frozen silver sea below, with layers of sand waves floating, with eyes dazzled, and there are many gods, and he is almost unable to move.

When I arrived south of Yulin, I still couldn't find the Longmen Pass ruins after searching for more than ten days. The county towns used to search and locate were no longer verified. In the long-standing era, the mountains and the original had changed, and the original had changed particularly prominently. Some county towns on the original had to migrate again, especially Luochuan County.

Luochuan County is on the Luochuan Plain. Luochuan Plain is still the Dayuan in northern Shaanxi. Its old city is in the northeast of the current county town, which is close to the original edge. When the old city was first built, historical records were recorded as Yuanshan. Because the nearby ditch extended, it became a ravine. In the end, it had to migrate separately. However, looking for Longmen Pass based on Luochuan County town became a carving boat and asking for swords. Shi Congwen had to return in disappointment.

The erosion of the Loess Plateau is a long-standing phenomenon. There are many gullies on the Loess Plateau, which is the specific manifestation of erosion. Shi Congwen has been in the Loess Plateau for a long time and is not unfamiliar with gullies.

But even so, the gullies on the Loess Plateau would still arouse his amazement, so he saw that there were countless gullies in the past. When he went to the high mountains, he wandered and looked far away. He looked at the ravines and saw that there were ravines and ravines. It was rare to see a flat river. Not only did there be no trees, but there were almost no green grass.

This is the special thing about the Loess Plateau! The number of places Shi Congwen went to later continued to increase. Every time he went to a place, he first noticed the gully, observed its width and depth, and explored the location of the gully head. The gully was everywhere, as if it had become a normal phenomenon. The Loess Plateau was originally full of place. It was originally a high and flat terrain. This should be a major feature of the Loess Plateau. However, such characteristics have been reduced and no longer have characteristics.

Because there are already gullies on the land, some of them have more than one, and even the original surface is cut by many gullies, it is no longer the original. As mentioned earlier, Dayuan, Pengyuan, Liangyuan and Dong Zhiyuan have all experienced such changes and were damaged. The Loess Plateau has also established many counties, like other regions. The county has county seats.

In the past, the county capitals were built with city walls and were quite large. The cutting of gullies made it difficult to have a foothold inside and outside the county town. The county towns had to move new places without moving. There are many examples of this. Shi Congwen has also seen the abandoned county towns many times. It is so common for county towns to move capital, and it is hard to say about towns and villages. Many villages were destroyed by gullies, so local people had to live on the edge of the gullies or on the top of the ramps.

Erosion on the Loess Plateau is a common phenomenon. The migration of county towns and towns and villages is only more significant. It should be said that as long as the ground has an inclination, erosion will occur. The loess tissue is loose and easy to be eroded. The ground has an inclination, which will appear even more low and concave after erosion. If it is not remediated, it will gradually develop into a gully.

Not only will the ground not be cultivated or engaged in related construction, the eroded soil will inevitably pass through streams and tributaries of the Yellow River, gathering into the Yellow River, causing the riverbed to rise in the lower reaches of the Yellow River, and even causing the overflow of breaches, and even causing disasters such as diversion. This is not only not a trivial matter, but it is related to the important matters of national economy and people's livelihood.

In his diary, he gave a certain recognition of the construction of silt dams in Yulin area. These silt dams were built in a relatively regular manner and had obvious siltation. Some small gullies had traces of bridging. In the long run, the yellow soil in Yulin area will become a plain earlier. Shi Congwen also noticed that trees were planted in some places, and in order to prevent cold, these trees were tightly wrapped with straw.

Some counties in northern Shaanxi are bordered by the Yellow River, and their settings are exquisite. Most of them are to make it easy to utilize the geographical situation. Wubao, Jiaxian is the most unique. So we take a detour on the way to find out. Wubao County is located at the original head of the riverside, with a towering original head and a steep river bank. The road is on the edge of the river bank, and it is narrow and difficult to walk. If a war breaks out, it is indeed a fortress that is easy to defend and difficult to attack. Wubao County is located between Fuzhou and Linzhou.

There are gullies in Fuzhou and Linzhou, but the specific situation is different. Linzhou's capital is now Yangjiacheng, with gullies everywhere. Fuzhou's capital is tall and the original head is not as good as this phenomenon. There are several river roads in Fugu County today, among which the rising water of Qingshui River is particularly noticeable. The river is named after the clear water, and I want to see the clear water flowing in the river. When there is no rain, the name is consistent.

When it rained heavily, the mud and sand carried the most. The water head was like a wall, and the water flow was not smooth. This was rare on the Loess Plateau. Shi Congwen went to Fugu and glared for half a month before seeing such a spectacle. It was really a wall, which was unbelievable. Shi Congwen took the photo in the rain and received a reward of 1,000 yuan from a newspaper!

The county travels north to Dianta Town, and goes northwest to Hongjianao and Dos Plateau. There are few rivers on the Ordos Plateau and lacks water sources, but there are also lakes. Most of the lakes are concentrated in the middle of the plateau, but they are rare in the southern edge. What can be mentioned should be counted as Hongjianao. Hongjianao is a freshwater lake, with fish in it. The water beside the lake was licorice and fat. In the Ming Dynasty, Tatars invaded the south, and they also used the way here to prepare for war.

However, the battle site in the past has now become a large construction site, with hundreds of thousands of people working day and night, and the huge water pipes come from afar and winding away. After Shi Congwen revealed his identity, he was prepared to allow him to enter the construction site. In his impression, this place was originally a lush white bone land, but now it has become a forest of willow trees. Under the explanation of an official, Shi Congwen knew that billions of cubic meters of fresh water were received from Baikal every year, and then it was continuously transmitted to the Three Norths, mainly Mongolia and Guanzhong.

Although it was only one year, Shi Congwen could see that these people were also very troubled to manage. Recently, I was surprised to see the photos taken by tourists in the local area. In the desert outside the city of the ancient battlefield ruins, trees were planted, and they were lined up, with green shade and yellow sand coexisting. Although it was extremely uneven, it seemed to be emerging. If you could continue, the trees would become shades within ten years, and the desert would become a forest!

Shi Congwen continued to travel westward until Dingbian County. The Great Wall in northern Shaanxi has been destroyed, and Dingbian is still slightly intact. The Great Wall has gone from the south of Dingbian County and turns northward. According to the current situation, it seems that the Great Wall passes through Dingbian County. In fact, when the Great Wall was first built, Dingbian County did not have a county. At that time, Dingbian Camp was only set up under the Great Wall. Dingbian Camp would not be located outside the Great Wall.

Dingbian is a county with many lakes, and is unique in northern Shaanxi. These lakes are all salt water lakes that can dry salt. Dingbian County was used to be the capital of Yanzhou. Yanzhou was first established in the Western Wei Dynasty. It can be seen that salt water lakes here could be made here. Among them, the Salt Lake was the larger. The Salt Lake was the white pond of the Tang Dynasty. Tang and Song coins were found in the surrounding sand from time to time, which shows that it was an important place at that time.

Such itineraries can be said to be a circumference of northern Shaanxi. In the past, northern Shaanxi had many battlefields and passes between the ethnic groups operating agriculture and the ethnic groups engaged in animal husbandry. They walked along the way and looked everywhere, as if they were counting the routine. The roads they walked were mainly thoroughfares, and sometimes they could not help but go astray.

Shortly after leaving Guyuan, he entered the saline-alkali area. The saline-alkali area was quite large, until near the head of the Tianshuigou, not far from Huanxian County. The saline-alkali area was full of saline-alkali, and it looked white everywhere, as if it was boundless. In some places, even weeds were difficult to grow. It can be seen that the Great Wall built by King Zhaoxiang of Qin was deeply restricted by the natural environment. King Zhaoxiang of Qin moved the Great Wall to build the Great Wall, and this saline-alkali area was naturally ruling from the Huns. If the Huns could not capture the Great Wall, it would be difficult for them to stay here for a long time. Although King Zhaoxiang of Qin was restricted by the natural environment when he built the Great Wall, it also showed that he was good at using the natural environment at that time.

What impressed Shi Congwen the most during this implementation of Shanxi was the ditch control project that could be seen everywhere in Shaanxi at that time. This project had been completed and achieved commendable achievements. The designer was Mr. Li Yi. He was the director of the Comprehensive Management Office of the Loess Plateau of the Ministry of Water Resources.

His design for ditches was to build a dam at the mouth of the ditch to store water. The soil for the dam was taken from the highlands on both sides of the ditches. This was to extract soil and also the land at flat heights. When I went to visit, I saw with my own eyes a pool of autumn water stored in the dam. The seedlings outside the dam were green and green. The highlands on both sides of the tches were flat and turned into flat fertile fields, planted with apple trees, and the apples on the trees drooped, red and beautiful.

Local farmers all praised that wealth is just around the corner. The water stored in the ditch dam is flowing down from the ditch head during precipitation. Naturally, it is inevitable that there will be washed away soil. After a little longer, it will be deposited in the reservoir in the dam. Once the silt is flat, it will no longer be stored.

There will always be this day: I hope that this day will be when the dam is silted and you can go up the ditches and build a new dam. It turns out that the dam will become a new field, which is a layer of terraces in the future. If the new dam is silted and flat, it will have to be built up again. In this way, dams will be built layer by layer and all the dam will be built to the end of the ditch. Every time a new dam is built, there will be another layer of terraces under the dam. When it is built to the end of the ditch, the entire dam will be converted into terraces.

Terraced fields can store water in every layer. The water does not flow out or drought, and they become fertile land. They can not only sow grains, but also cultivate fruit trees, which can not only cure gullies, but also increase fertile fields, which will make farmers rich accordingly. Shi Congwen believes that this is the most effective method to control gullies on the Loess Plateau, so it is called a model, and it is always in my heart. I hope it can be promoted so that the gullies on the Loess Plateau can be managed. The erosion is reduced, the Loess Plateau will no longer be broken, and the mud and sand will no longer flow with the water, so it will no longer affect the stability of the Yellow River. This is a major event that benefits the country and the people. Even if you spend more money, you have to continue.
Chapter completed!