When Zhou Nan stepped on the Zhangjiawan Wharf, he really felt the former glory of the Empress Dowager Xiao.

On the wide river, occasionally a boat or two swim by; A straight wooden bridge is erected over the river, which can be crossed by horseback. On the shore, solid piers lined up, with only one large ship docked on the shore. It was the boat that Zhou Nan and they were on. Without the endless stream of cargo ships, the docks are also much deserted. In addition, both sides of the river are white sandy sandy beaches, and even a few broken wooden boats can be seen on the sand on the shore, which is even more desolate. On a high ground not far from the bank, a series of neat stone warehouses stand on the bank of the river, and the outside of the warehouses is fenced with a wooden fence, leaving only a tall gate, but it is unguarded and wide open. Presumably because there was nothing inside, there were no more guards.

Zhou Nan, Yu Shen and Xiao Jiu passed through Zhangjiawan by boat, and heard that this was the wharf where the goods were unloaded and transferred into the city in the past, so Zhou Nan specially asked to come down.

On the second day after the family banquet in Yufu, Zhou Nan took Yu Shen, Xiao Jiu, and the thirty farmers recruited, ten carpenters and blacksmiths who were rated as excellent as supervisors, and Zhou Nan's three hundred pro-army guards.

Zhou Nan and they set off from Yingchun Gate and went down the river by boat, the farmers and craftsmen followed Zhou Nan by boat, and the pro-army guards rode horses and escorted them along the banks of the river. The group first arrived at Shili Village, ten miles away from the east of the city, and Shili Village also has a wharf, but because of the river, it can't be too heavy, so it can only get on and off the boat, and can't unload the goods.

From Shili Village, turn southeast along the river, go down the river, and after more than 50 miles of road, it is Zhangjiawan where they are now.

"In the past, the transportation of grain and grass was through here, from Liaoyang Mansion in Tokyo to Beitang Haikou in Ninghe County, and then transferred to the river transport, first into the Bailong River, upstream into the Qili Sea, and then upward, into the Lu River, to this Zhangjiawan, or unloaded, or from here to the Empress Dowager Xiao River, directly to Nanjing City." Yu Shen introduced to Zhou Nan that although he was young, like last time, he must have done a lot of things to secretly run away from home, and he was clear about the situation up and down this river.

"At such a water level, I'm afraid that I can't carry a heavy ship, right?" Although the river is wide, the river is not deep, Zhou Nan asked suspiciously.

"It's not summer or autumn right now, and the river is naturally running low. This river is only at the turn of summer and autumn, when the rainfall is heavy, and those cargo ships can travel to Shili Village. Yu Shen explained.

Here in North China, it belongs to the continental monsoon climate, and the seasonal difference in precipitation is obvious, the winter is dry and rainy, and the summer is rainy, but it is a rainy summer, and the annual precipitation varies greatly. If there is no stable water source, then the river transportation is not very reliable.

"In winter and spring, the river is too little to sail, in summer and autumn there is more rain, but there are also more mountain floods, presumably in summer and autumn, this Lu River often bursts the embankment, right? The river is so swollen that I can't sail even if I'm afraid. Zhou Nan said casually.

Yu Shen looked at Zhou Nan with admiration and said, "What the horse said is extremely true. Not only do you know about the bursting of the embankment of the Lu River, but you can also tell the root cause - has the horse read the "General Discussion on River Defense"? ”

Zhou Nan said with a smile: "I'm a hunter, where can I read the "General Discussion of River Defense"? It's just that I see a lot and think a lot. Look," Zhou Nan said, pointing to the mountains in the northwest of Yanjing City with his hand, "The mountains in the northwest are high, and the source of the Lu River, as you just said, comes from the streams in the mountains. On weekdays, the size of mountain streams does not change much; Once the summer and autumn mountain torrent rushes down, the northwest terrain is high, the terrain here is low-lying, the mountain torrent rushes down from the high place, this river channel has no way to drain, the big water comes, naturally it can only break out of the embankment, flood irrigation flatland. ”

Yu Shen was overjoyed when he heard this, and saluted Zhou Nan again and again and said: "Listening to the words of the concubine, you know more than the villain himself reading a book for a year. I'm really a good one. ”

"If it weren't for your introduction, I wouldn't even know where the upper reaches of the Lu River are, let alone know the reason why the Lu River can't sail all the time in Xia Qiu." Although Zhou Nan said modestly, he was also a little complacent in his heart, with his own level of knowledge, he could explain most of the problems of this era, unless he encountered something like two children arguing about the day.

Xiao Jiu, who had been unable to interject, said at this time: "In the cottage, when the mountain flood comes down, it often washes down the fields and washes away the cattle and sheep, it seems that this mountain flood is really a scourge." ”

Yu Shen also nodded again and again, water and fire have always been ruthless, and what he said was fire and water, which were not at all something that people in this era could resist. Even in later generations, they can only minimize the harm of floods and fires, and they dare not say that they can guarantee that there will be no damage.

"Not really." Zhou Nantan came up, "If you can go upstream, choose a huge place to store water, let the river pass through the water storage place, and then intercept the sluice." In this way, when the flash flood falls, it can be stored here without harming the downstream; When the water is shallow downstream, or when the fields are dry and irrigation is urgently needed, the sluice gates are released to put the stored water down. This would kill two birds with one stone – no, three birds with one stone. ”

"Less water is released for watering fields and boats, and large water storage is used to prevent flooding, which is a double win. Why does the colt say it's three things? Yu Shen asked strangely.

"If a waterwheel, a waterwheel, a water mill, a water drain, etc., are built at the sluice, water power can also be used; According to this promotion, there can also be more sluices, water wheels, water mills, water mills, and water drains where there is a drop in the river section. The waterwheel can be used for irrigation; Water mills can grind rice grains; In addition to processing rice grain, it can also hammer pulp, gravel, etc., if it is used for papermaking, it greatly saves manpower; The water drain can be used to blow air and dust, and is used to smelt iron and blow air. All in all, this water power can replace manpower, and it can work without sleep, and I don't know how much it can be obtained. ”

Zhou Nan's words made Yu Shen and Xiao Jiu stunned. At first, Yu Shen stretched out his fingers to calculate for Zhou Nan, but after hearing it, Yu Shen also forgot to count and couldn't speak. Even a few craftsmen who were standing not far away who had been selected to be the prisoner heard it and approached it without knowing it.

"The king is a nobleman, and he even knows what we have done cheaply." One of the craftsmen said.

Yu Shen came back to his senses and ran towards the boat without saying a word. Everyone was puzzled, but Xiao Jiu said: "I must have gone back to the ship to find a pen and paper and take his notes." ”

Seeing that it was not early, Zhou Nan took everyone back to the boat and continued to move forward to see where the boat could go.

After Zhangjiawan, it is out of the Empress Dowager Xiao River and into the Lu River. It was only March, and the water in the river was obviously much shallower, and although the boat they were on did not carry any heavy objects, it only seemed to have a deep draft here.

On both sides of the river, it is no longer a piece of sand just now, but like entering the water town in the south of the Yangtze River, full of puddles and rivers, and on the ground at high places, it is also a white land.

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