As a pioneer against internal competition in the late Ming Dynasty, Xu Xiake did not take the imperial examination or seek fame. Starting at the age of 20, she embarked on high-density "short distance trips" and "inter provincial trips" around Zhejiang, lasting for more than 30 years. Later, her travel mode gradually shifted from short distance trips to north-south travel, covering most of China. At the age of 49, he deeply felt that his old illness was approaching and it would be difficult to delay any longer. He resolutely embarked on the longest, most difficult, and most professional journey of his life, known as the "Southwest Thousand Mile Expedition" in history. As a famous tourist of the Ming Dynasty, he did not have a four-wheel drive car or GPS navigation, and often relied on "one slave or one monk, one cane and two blankets, no clothing, no food" (Qian Qianyi's "Biography of Xu Xiake"). Even entry-level backpackers find this equipment shabby today, but he relied on this outfit to expand his vast geographical territory and form a first-hand geographic information database. Because later on, a large number of his travelogues were lost and destroyed, "destroyed by war, fragmented and broken, not a single one exists" (Chen Hanhui's "Epitaph of Xu Xiake"), which prevented us from seeing the greater truth, it is truly regrettable. The 630000 word travelogue I read today is just a "post disaster recovery version" that later generations have collected and organized based on scattered and damaged manuscripts. In this remaining 'database', he mentioned 'Ningxia', which is my hometown and 'miniature bonsai of Chinese tourism'. From existing literature, it appears that Xu Xiake did not visit Ningxia before his death. However, based on his principle of "every day must be recorded" and the extent of destruction caused by the later travelogue "not one out of ten", it can be confirmed that his travelogue scale is very large, at least over a million words. The damage caused by the burning and loss of travelogues may be structural: Xu Xiake's complete records of his travels in the north, including crossing the Yellow River, climbing Taihua, and crossing the Bian River, have almost completely disappeared, leaving only fragments of words and phrases preserved in "Xu Xiake's Travels: Tracing the Origins of the Yangtze River". According to research, the "Tracing the Origins of the Yangtze River" has tens of thousands of words, but today there are only over a thousand words left. If these classics had not been burned or lost, future generations may have been able to see Xu Xiake's deeper understanding of the mountains and rivers in the northwest, the upper reaches of the Yellow River, the Hetao Plain, and the Helan Mountains from his complete travelogue. We may have seen a high-precision ecological map of the Ming Dynasty in the northwest. Nevertheless, from the surviving texts, we have seen Xu Xiake's astonishing judgment on the Yellow River and his precise confirmation of Ningxia. This is the result of his multiple investigations of the Yellow River, which also demonstrates the perspective of a traveler, the pattern of a geographer, and the sentiment of a literary figure. As early as 1609, Xu Xiake went north to Jizhou (present-day Hebei area), and I speculated that he should have conducted an investigation of the Yellow River, but unfortunately did not leave any travelogues. But in 1623, he entered Shaanxi from Henan and personally inspected the Yellow River. In 1633, he started his trip to the Qin and Jin Dynasties, visited Mount Wutai and Mount Hengshan, and his footprints ended in Guanzhong, Shaanxi. The origin of the Yellow River and the Yangtze River has been in his mind for a long time. In his diary "Journey to Mount Taihua", he outlined the grandeur of the Tongguan section of the Yellow River in minimalist language: "The Yellow River flows south from the Shuo Desert to Tongguan, then turns east. The pass is just a river and a mountain pass, overlooking the river to the north and connecting to Mount Hua to the south. However, this line is the east-west road, locked by a hundred pheasants." This is a very refined and majestic description of the geographical situation. Shuo is Shuofang, referring to the northern region. Ningxia has been known as Shuofang since the Book of Songs; Desert refers to the area north of the Hetao River in the upper reaches of the Yellow River. It can be seen that Xu Xiake's early exploration of the upper and middle reaches of the Yellow River laid the foundation for the later "Ningxia" in "Tracing the Source of the River". According to its source, the river originates from the north of Kunlun, and the river also originates from the south of Kunlun, and its distance is the same. The one originating from the north is called the Starry Sky Sea, while the Buddhist scriptures refer to it as the Migration River. The northward flow passes through Jishi, and then turns eastward into Ningxia, forming the Hetao River. The southward bend leads to the Longmen River, which merges with the Wei River "(" Tracing the Source of the River "). This is a chain of the Yellow River system from the source to the middle and upper reaches, which was collected by Xu Xiake in just a few crosses. It can be called the" one map reading the Yellow River "in the geographical version of the Ming Dynasty. Anyway, how can someone who has never been stuck in Ningxia write so accurately and concisely about the entire course of the Yellow River and its flow into Ningxia and around the river? I thought what I saw with my own eyes was the starting point of his cognition. In "Tracing the Origins of the Yangtze River", he described himself as "crossing the Huai River and crossing the Bian River, and then seeing the river flowing like a belt, with a width of less than one-third of the river". He also said, "From the Three Qins in the north to the Five Mountains in the south, from Shimen Jinsha in the west, I learned that the water entering the river in China is called the fifth province, and the water entering the river is called the eleventh province". He witnessed the true form of the Yellow River with his own eyes in North China, and based on what he saw, he judged that the Yellow River was far less wide than the Yangtze River. Why has the Yellow River, which has a much lower water volume than the Yangtze River, been considered a longer river for a long time? It was this question that drove him to start tracking the upstream direction of the Yellow River. Studying literature is the support of his cognition. Xu Xiake was particularly fond of strange books since childhood, and was well versed in ancient and modern historical records, geographical maps, and mountain and sea maps. His love for geographical maps gave him a solid knowledge reserve. Regarding the written records of the Yellow River source and the Ningxia Hetao, he can obtain them from at least three geographical classics: one is the "Yu Gong". This oldest geography book points out that the Yellow River "floats on Jishi, as for Longmen and Xihe". Jishi Mountain is one of the most iconic geographical nodes in the upper reaches of the Yellow River, and the spatial relationship from Jishi Mountain to Hetao can be deduced by any reader who is familiar with "Yu Gong". The second is the official river source investigation results of the Yuan Dynasty. In 1280, Kublai Khan ordered Dushi Peijin Hufu to explore the source of the Yellow River to the west, confirming that the source of the Yellow River came from Xingsu Sea. Pan Angxiao wrote the "Heyuan Chronicle" based on this. Xu Xiake explicitly mentioned in the article that 'there was a golden tiger talisman in Dushi', indicating that he not only read relevant literature, but also regarded it as an important source of information. The third is the "Da Ming Yi Tong Zhi" and a more specific Ming Dynasty Ningxia local chronicles and map system. The "Annals of the Great Ming Dynasty" is an essential "reference book" for Xu Xiake's long-term travels, which provides a detailed geographical framework of the northwest border including Ningxia. The four Ming Dynasty Ningxia Gazetteers, namely "Zhengtong Ningxia Gazetteer," "Hongzhi Ningxia New Gazetteer," "Jiajing Ningxia New Gazetteer," and "Wanli Shuofang New Gazetteer," all have categories such as "Shanchuan," "Hequ," and "Water Conservancy," detailing the flow direction, water situation, irrigation canal system, and border defense situation of the Yellow River in Ningxia. These local chronicles were compiled, printed, and circulated by the authorities, equivalent to the "White Paper on Local Government Affairs" of the Ming Dynasty. Hongzhi's "Ningxia Xinzhi" has published a map with geographical information of the Yellow River, and for the first time pointed out the number of acres of farmland irrigated by the Yellow River in Ningxia and the key role played by the Yellow River in the formation of the Hetao; The Wanli "Shuofang Xinzhi" first mentioned that the source of the Yellow River is Xingsuhai. It is reasonable for Xu Xiake to have read extensively on maps and maps throughout his life. Xu Xiake used the term "Ningxia" instead of old names such as "Shuofang" and "Xingqing" in the article, which indirectly proves his thinking quality as a first-class geographer. The establishment of the "Ningxia Guard" in the Ming Dynasty began during the Hongwu period and was under the jurisdiction of the Shaanxi Xingsi. The Wanli "Shuofang Xinzhi" specifically describes it under the name "Ningxia". The precision of this term itself indicates that Xu Xiake has a very clear understanding of Ningxia. Field investigation+systematic analysis "is the fundamental basis of his cognition. We can feel Xu Xiake's calmness and clear thinking just from 'Tracing the Origins of the Yangtze River'. Based on this understanding and perspective, a mistake that has been passed down for more than two thousand years - the statement in "Yu Gong" that "Minshan leads the river" will be corrected, and it is only natural. He adopted a comparative research method and for the first time compared the Yellow River and the Yangtze River in the same coordinate system. From the source, he combined previous records and his own investigation to determine that the river source is north of Kunlun and the river source is south of Kunlun, and that "their distance is the same". The river source is not shorter than the river source, and the river source is not longer than the river source. In terms of water volume, he first anchored the idea that "rivers are like belts, with a width less than one-third of the river" through field observations, and then counted the number of provinces that received water into the river and into the river one by one: the Yellow River received water from five provinces, and the Yangtze River gathered water from eleven provinces. "Counting its inflow, the river is twice as large as the river, and its size is also suitable" - this is a simple "audit" of water volume. From the flow direction, he defined the trends of the two rivers separately: the Yellow River flows northward, then turns eastward, and finally bends southward, while the Yangtze River flows southward, then turns eastward, and finally bends northward, forming a symmetrical geographical distribution, like the two arms of the earth, with equal lengths but vastly different water volumes. On this basis, he further questioned and introduced a crucial principle: "The source of the river has been searched for many times, so it is far away; the source of the river has never been inquired about, so it is only close." However, he believed that what truly determines the source should not be the distance of the road or the difficulty of exploration, but the actual length of the mountains and rivers. He proposed the famous principle of "the source of the Yangtze River is only far away" based on this, and concluded that the Jinsha River is the main source of the Yangtze River, pushing the source of the Yangtze River thousands of miles westward from the Minshan Mountains and directly pointing to the southern foot of the Kunlun Mountains. Until today, the preferred criterion for determining the source of rivers in the international geographical community is still the "farthest source" principle (i.e. length first), supplemented by comprehensive indicators such as watershed area, water volume, and flow consistency for correction. In the 17th century, Xu Xiake had no aerial photogrammetry, no high-altitude navigation, no remote sensing observation and other technical equipment, no official funding, no scientific research team, and relied solely on field surveys to propose the scientific conclusion that "the source of the river is only far away", which is highly consistent with the core principles of contemporary river source identification. This shows how broad Xu Xiake's geographical vision is, how clever his observation methods are, and how profound his academic realm is! Thank you to the international geography community for the 'dreamlike collaboration', which confirms the scientific insights of this walking 'fact checker' and 'master of fieldwork methodology'. In the scorching summer of Taiji Bay on the Yellow River in Qingshuihe County, Inner Mongolia, deep in my emotions, I would like to thank this great geographer as a traveler. In his most important "academic report" in his later years, he mentioned Ningxia and Hetao. Turning eastward into Ningxia, it becomes Hetao. Ningxia is the most agricultural and geographically dramatic area in the upper reaches of the Yellow River. From a modern geological perspective, the Yellow River cut through the Jishi Gorge and entered the Ningxia Basin about 1.2 million years ago, while the Helan Mountain is a product of the late Himalayan movement's fault block uplift, with its highest peak reaching an altitude of over 3500 meters and stretching for more than 200 kilometers, like a giant wall spanning between plains and deserts. The pattern of one mountain and one river forms the geological script of "Jiangnan on the Great Wall": the Yellow River rushes down from the Qinghai Tibet Plateau, passes through the Jishi Gorge, and enters the Ningxia Plain, where the water suddenly becomes gentle. Geographically speaking, the Hetao refers to the alluvial plain along the "Ji" bend of the Yellow River, which is divided into the Xitao, Houtao, and Qiantao. Among them, the Ningxia Plain is also known as the "Xitao", where the Yellow River travels 397 kilometers. The Yellow River splits the plain into two sections, the Weining Plain and the Yinchuan Plain, through the Qingtongxia. The Ningxia Plain is located deep inland, with an annual precipitation of less than 200 millimeters but an annual evaporation of over 1500 millimeters. According to common sense, it should be a desert. However, the Yellow River, on the edge of the desert, splits through layers of mountains and forcefully squeezes out a channel, sending water into this vast land; Helan Mountain rises from the ground, blocking the sandstorms in the northwest. Since the Qin and Han dynasties, our ancestors have been irrigating the Yellow River here, excavating ancient canals such as the Qin Canal, Han Canal, and Tang Lei Canal, and building the Great Wall from the Warring States Qin Great Wall to the Ming Dynasty Great Wall. Ningxia is therefore known as the "Museum of the Great Wall of China". Two thousand years of water diversion and cultivation have turned the barren land covered in gravel into a granary, giving birth to the saying 'the Yellow River is prosperous in the world'