White-robed Minister

53. [Do you want to be Guangzhou's Li Bing?]

The sixth day of our journey into the mountains.

The scholars had become accustomed to surveying work and even had the leisure to pick flowers and pull weeds.

For these guys, wearing flowers in their hair has become an unconscious behavior; they pick wildflowers from the mountains and put them in their hair.

The group returned to the temple in the late afternoon. Each group cross-checked the calculation results, chatting and joking from time to time. After finishing the calculations, they sat there waiting for their vegetarian meal.

"This isn't right." Xu Lai stared at the set of data in front of him.

"Our team's calculations are definitely correct," Yang Shu retorted. "You're the one who's wrong. You even created your own arithmetic symbols, which are all crooked and twisted like earthworms."

Xu Lai ignored that sentence and pointed to a set of data, saying, "Where is Changyao Ridge? Why has the flow of this stream suddenly slowed down?"

Yang Shu said, "Changyao Ridge is at least eight or nine li away from the place you surveyed, by mountain road."

"You ran that far?" Xu Lai asked with amusement.

Yang Shu replied, "I measured it quickly. I heard from the monk guide that there are many springs in Changyao Ridge, and it is also a waterlogged area, so I went there to do a quick survey."

Xu Lai asked, "Why did the stream suddenly slow down?"

"Changyaoling is a watershed, with some streams flowing south into the Shahe River, which then flows directly south into the Pearl River," Yang Shu said.

The springs and streams of Pujian Mountain converge to form Ganxi, which flows eastward toward Guangzhou. Along the way, the streams continuously converge, and then split into two branches: one turns south into the Pearl River, and the other continues eastward into Juhu Lake.

Over the past few days, people have been calculating the water volume. It is difficult to meet the needs of the entire city by using bamboo pipes to draw water; it can only solve the water problem for a portion of the residents.

but……

Xu Lai suddenly had an idea: "Could we block the watershed? If we prevent the stream from flowing into the Shahe River and direct it all eastward into Juhu Lake, wouldn't that solve the drinking water problem?"

Ganxi and Juhu are also drinking water sources for Guangzhou residents.

This even gave rise to a profession – the water vendor.

Water vendors would go to Juhu and Ganxi every day to fetch water and transport it to Guangzhou for sale, where the water was not too severely affected by saltwater intrusion.

The downside is that the water level is often insufficient in winter, and Juhu Lake is often so shallow that it is impossible to navigate, so the sluice gates have to be opened to allow river water to flow in. Once the river water is used, the lake tastes salty and bitter.

Xu Lai wanted to directly replenish the water supply to Ganxi and Juhu!

"You've blocked the watershed, preventing the water from flowing into the Shahe River. What will happen to the people living along the Shahe River?" a student from the inner circle questioned.

Yang Shu laughed and said, "That's really feasible. The mountain pass where the river splits isn't wide; it can be easily blocked. I heard from the monk who led the way that the Shahe River has another source, so even if the watershed is blocked, there's no fear of the river drying up."

Everyone thought Xu Lai was being unrealistic; the bamboo pipe water diversion project was still uncertain, and now he was going to go and block some kind of diversion point.

Even Tsai Cheng-yu advised, "Naturally formed river channels should not be altered arbitrarily, otherwise it is difficult to predict what problems might arise."

"Regardless, let's go take a look tomorrow," Xu Lai asked. "Could Cai Dulu come with me?"

Tsai Cheng-yu nodded and said, "Okay!"

They had plenty of time to wander around and had already surveyed the area quite thoroughly, but the results were somewhat disappointing; the bamboo pipes could only supply water to a portion of the residents.

……

The next day, most of the scholars stayed in the temple, which gave them a good opportunity to rest and play.

They've been exhausted these past few days.

Xu Lai, Cai Chengyou, and a few others were led by Yang Shu to Changyao Ridge.

"Right there," Yang Shu said, pointing ahead, "that mountain ridge is called Changyao Ridge. The springs and streams in the mountain converge here and are then divided. Many streams are diverted to the Shahe River and cannot continue flowing eastward to Juhu Lake."

Before the diversion, Ganxi River would overflow its course during the high-water season, reaching a width of about 10 meters and a depth of about 4 meters. During the dry season, however, it was very poor, relying entirely on mountain springs and streams for replenishment, reaching a width of about 4 meters and a depth of about 0.6 meters.

After branching off at Changyaoling, the stream immediately becomes narrower and shallower!

If it weren't for other mountain springs and streams downstream replenishing the lake, Juhu Lake would have dried up long ago.

Xu Lai took off his shoes, rolled up his trousers, waded through the shallow, dry section of the stream after it split, and climbed up the opposite bank, Changyao Ridge, to survey the surrounding terrain.

Besides Yang Shu, who was in charge of leading the way, Ding Zhengchen, Liang Wensu, Wen Zhonghe, and Cai Chengyou also came today. They didn't take it seriously, just accompanying Xu Lai on his aimless wanderings, treating it as a sightseeing trip.

But Xu Lai vaguely sensed a familiar feeling.

He felt like he had seen this terrain somewhere before.

After observing and thinking for a long time, Xu Lai suddenly realized: Isn't this the Xidu River from my high school geography textbook?

It all fits together, everything fits together.

No wonder Su Shi was later forced to use bamboo pipes to draw water, and his solution was quickly adopted by the military governor at the time. It is highly likely that the Ganxi River dried up seasonally, and Juhu Lake also had difficulty supplying drinking water, so a way had to be found to alleviate the problem.

No wonder Juhu Lake dried up during the Southern Song Dynasty. It wasn't that the Yuan army maliciously filled it in; rather, by the time the Yuan Dynasty conquered Guangzhou, Juhu Lake had already dried up and become a useless shallow pond.

Indeed, we still need to conduct an on-site investigation. How can we connect the high school geography knowledge that we have forgotten with the water shortage problem in Guangzhou if we don't come here in person?

Xu Lai turned to the crowd and said, "That's not a normal watershed; it's a gap carved out by the river over millions of years. It's already formed a gulf at the watershed. If left unchecked, Ganxi will dry up and Juhu Lake will run dry within two hundred years!"

Everyone was taken aback and looked at each other in bewilderment.

Cai Chengyou was also full of questions. He had worked in water conservancy for most of his life, but he couldn't understand what Xu Xiucai was saying.

Could it be a record from some ancient book?

Cai Chengyou couldn't help but ask, "Scholar Xu, what does 'seizing the bay' mean?"

Xu Lai wanted to explain, but for a moment he forgot the reason for the formation of Xiduo Bay and couldn't remember how it was written in his high school geography textbook.

Therefore, Xu Lai could only explain simply: "The two rivers flow side by side across the mountains, and originally they did not interfere with each other. One of the rivers was more ferocious, and it eroded through the mountains, stealing the water source from the other river. It will become more and more aggressive as it erodes, and the breach it erodes will become bigger and bigger, eventually taking over the entire upstream of the other river."

Wen Zhonghe clicked his tongue in astonishment: "Ganxi isn't that big, how could it possibly rush through the mountains?"

Xu Lai shook his head and said, "The mountains were eroded by the Shahe River, and Ganxi was a victim of water theft."

When Juhu Lake was first excavated during the Three Kingdoms period, Ganxi River had not yet been seized by Shahe River. Therefore, the flow rate was particularly large at that time, and Juhu Lake also had abundant water, which was more than enough to supply the city's drinking water.

It is possible that starting from the Sui and Tang Dynasties, the upper reaches of Ganxi were gradually eroded, and the water volume of the lower reaches and Juhu Lake decreased year by year.

Ultimately, Chrysanthemum Lake dried up completely during the Southern Song Dynasty!

Xu Lai asked, "Cai Du, is it possible to plug that breach? How can we reinforce the riverbank to prevent further erosion by the flowing water?"

Cai Chengyou thought for a moment and said, "The water flow of the two rivers is not large, and the gap is not wide either. During the dry season, it is easy to build a dam to block it. However, the dam cannot be built too high, otherwise it will be easily washed away when there is a flash flood."

"That's no problem. We don't need to completely block it. Excess water can overflow the dam, as long as there's enough water flowing into Juhu Lake," Xu Lai asked. "How do we reinforce the riverbanks and slow down water erosion?"

Cai Chengyou said, "Wooden dragons protect the riverbank."

Xu Lai asked, "What is a wooden dragon embankment?"

Cai Chengyou explained, "The wooden dragon bank protection system was created decades ago, initially to resist the erosion of the Yellow River banks by the water flow. Now it has been implemented in all prefectures and counties across the country. It consists of horizontal beams for fixing and vertical beams that hang down to the bank. This slows down the flow and guides the main current."

"Using the methods for reinforcing the banks of the Yellow River to deal with this small river is like using a sledgehammer to crack a nut," Xu Lai couldn't help but laugh. "Let's go, we'll return to the city tomorrow and ask Minister Yu to recruit laborers to build the dike."

Ding Zhengchen asked, "Are we no longer using bamboo pipes to draw water?"

Xu Lai said, "Why bother with bamboo pipes? Just block that gap, and Ganxi and Juhu will have plenty of water. Even during the dry winter season, there will be enough water for the people to drink!"

"Then all the work we've done these past few days, even if we're exhausted, has been for nothing?" Liang Wensu was somewhat unwilling to have done useless work.

Xu Lai said, "It wasn't in vain. If Brother Jie hadn't surveyed this place, how could we have discovered why the water levels of Ganxi and Juhu Lake are decreasing?"

"If we don't use bamboo pipes to draw water, the well water will still be salty and bitter in winter." Ding Zhengchen wanted to drink good water all year round.

Xu Lai smiled and said, "With the water level of Juhu Lake rising, there will be no need to divert water from the Yangtze River to fill it in winter. At that time, the water from Juhu Lake will also be sweet, so you can just buy Juhu Lake water directly."

Ding Zhengchen muttered, "How can lake water be as sweet and refreshing as mountain spring water?"

Xu Lai's smile faded, and his expression turned serious. "Water pipes are only effective temporarily, and subsequent maintenance is extremely troublesome. If certain officials are in power, they might abolish this method to save expenses. Building a dam, on the other hand, is a one-time solution. As long as the dam is dredged regularly, it can last for a thousand years."

"Gentlemen, a thousand years from now, the people of Guangzhou will still remember our names and will still be drinking the water we brought. You know Li Bing of Dujiangyan, right? We are all Li Bing of Guangzhou."

"His name will be etched in history!"

go down in history?

Upon hearing these four words, Yang Shu was overjoyed, and the others reacted similarly.

Even Cai Chengyou was excited. He had spent half his life working in water conservancy, which was nothing more than monitoring and repairing the Guangzhou moat, all of which were repetitive technical tasks.

There are more than one or two people like him in Guangzhou.

Solving Guangzhou's drinking water problem would bring immense benefits, both before and after death!

He also wanted to be remembered in history, so that people hundreds of years later would read the record in the "Guangzhou Annals": "In a certain month of the eighth year of Jiayou, the chief craftsman Cai Chengyou was recruited by the military commissioner Yu Jing to serve as the commander of the moat..."

It would be worth dying for!