August 12, Shanghai Institute of Urban Planning Link:

0.1 SpongeBob City hundred of controversies

0.2 SpongeBob City is a basket?

1.1 Special planning index control

1.2 Annual runoff control rate?

The State Council Document No. 75 requires that in 2020 it is more than 20%, and in 2030 it should be more than 80% of the built-up area to achieve 70% of the rainwater on-site absorption, can it be done?

There is so much debate about the total annual runoff control rate target, this is the "Sponge Club Sponge Cities and Watersheds Group", a WeChat group set up by Prof. Guo Qizhong from the US, which has the most heated debates.

Cheng Xiaotao is the deputy chief engineer of the Chinese Academy of Water Sciences, and he @Che Wu feels "confused" about the total annual runoff control rate, meaning that some people don't understand basic hydrology, and those who engage in municipal drainage don't understand hydrology. Then he talked about "small rain to stay, big rain fast drainage", is the concept of the problem, 70% of the small rain to stay, it may mean more than 90% of the time, the river did not converge .......

The discussion was intense, 5:30 a.m. on July 22, up so early to discuss it, and it's nighttime in the U.S. time because it's exactly 12 hours difference, it's evening time.

Is it a problem that the drizzle didn't stay? I studied water conservancy origin, and then engaged in water, and with urban planning, close cooperation, understanding of the water-related professions and relationships; I came to answer Mr. Cheng's question:

In fact, the small rain to stay no problem, small sponge to stay in the small rain, you said to stay in the rainwater to where to go? In fact, most of the infiltration, infiltration increases the ecological base flow, how can more than 90% of the time there is no ecological base flow?

Secondly, the retention of rain will increase evaporation, and I will use a diagram to show that rain returns to the earth.

Thirdly, after the small rain is retained, even if it is used, then you used the rainwater and where did it go? Used you are not discharged again? The water did not diminish because the substance does not perish.

I said to him at the time, some water conservancy projects such as large reservoirs to retain small rain, that greatly reduces the ecological base flow. This is a separate issue, including the current debate over the Three Gorges and the South-North Water Diversion, which is not being discussed here today.

Heavy rain all fast drain down the line? I ask the question in turn. What is the reason for the serious flooding in Wuhan this year?

To quote part of the point of view of the director of the Chinese Academy of Planning Wang Jiazhuo, Wuhan flooding is first because of continuous heavy rain,

which June 30 to July 6, 1 week Wuhan rainfall totaled 576 millimeters, more than 98 floods of 539 millimeters:

The second is due to the flood flooding because of the Yangtze River water level raised,

The Yangtze River, the water level of the Hankou than the surface of the ground of Wuhan 5 to 6 meters higher,

Wuhan's water can not be discharged, only by the pumping station discharge.

The third reason is that Wuhan's massive filling of the lake, resulting in a serious shortage of stagnation,

The fourth reason is that the drainage is ineffective. the Wuhan Drainage Three-Year Action Plan, released in 2013, with an investment of $13 billion, but by the end of 2015 only $4 billion, Wuhan's planning to increase the number of pumping stations most of them were not built,

This year, the middle and lower reaches of the Yangtze River cities are seriously flooded, with the

This year, the city of the middle reaches of the Yangtze River is seriously flooded, compared with the "98" flood, the maximum intensity of rainfall for a week is more than 98 flood, but the total amount of rainfall for a month is not as large as the 98 flood.

Why is the water level in the middle and lower reaches of the Yangtze River this year more than the level of the same period of the 98 flood? The first is a natural disaster or a man-made disaster?

Man-made disasters are greater than natural disasters. 98 floods, the upper reaches of the Yangtze River soil and water conservation is still effective, so the main cause is "too much concrete", along the Yangtze River towns and cities, "the water to the high side of the strong row", the entire middle and lower reaches of the Yangtze River water level raised. This is the problem of the entire Yangtze River Basin, so the construction of the Yangtze River Basin sponge.

August 4 "Southern Weekend" "a thousand pieces of a green" column:

I quote from the article "a pot of porridge":

"Even the most basic parameters - annual runoff total annual runoff control rate are arguing", Cheng's opinion is: sponge city to retain 20 millimeters of light rain, only a small-scale solution to "light rain does not stagnate", but for "heavy rain does not flooding" and "water bodies do not stink". "The water body is not black odor" not only can not be solved, but also blocked the urban river base flow, resulting in the drying of the river.

Excerpts from various opinions are as follows:

What does Prof. Chew say?

There was a bit of disdain from Prof. Che, who said that after two years he is still obsessed with this? We are in the meeting, the meeting, face to face I do not know how many times with them, there is a little arrogance, in fact, did not make it clear, otherwise it will not be argued to the present.

I agree with Prof. Che's later statement that "sponges can store, stagnate, and retain water, recharge groundwater, and provide the necessary base flow for rivers and lakes", which is true, but he should make the whole condition clear.

I use Mr. Che's chart below to say that Mr. Che has been involved in rainwater harvesting and utilization to rainwater management for 20 to 30 years, and is indeed a senior.

This is Mr. Che's water cycle diagram, from his paper, a comparison of natural drainage, gray drainage and LID water cycle:

What is the consequence of traditional urbanization? When it rains 55% of the rainwater drains out, and it drains black, only 15% infiltrates and 30% evaporates back into the sky.

Through the sponge city LID after the transformation, can be from 55% of the discharge reduced to 20%, and the water quality has become better.

Infiltration increased from 15% to 35%; evaporation increased from 30% to 45%, an increase of 50%.

But sponge city transformation, it is impossible to go back to a purely natural water cycle:

The natural water cycle is that after it rains, only 10% of the rain produces runoff, 40% infiltrates, and 50% evaporates back to the cycle again.

I've been talking about water and municipal drainage and urban planning, and they're not talking about the same thing.

So the first question is: the object of sponge city are not clear? The object is a big sponge, medium sponge, or small sponge?

In fact, the municipal drainage because of professional constraints, consider the small sponge, up to the pipe network, bring in the sponge.

Water is a big sponge concept, is the watershed water cycle considerations, in fact, water basin is not a complete watershed, because the water basin generally did not take into account the urban small sponge, and rainwater infiltration and evaporation, the ground and the underground and even the atmosphere is a whole.

There is a Tsinghua Professor of Water Resources think: control and use of the atmospheric water cycle, the design of a water vapor transport "sky road" to replace the "South-to-North Water Diversion" and "West-to-East Water Transfer" project!

The second problem is that the three professional goals are not clear. We engage in sponge city or, engage in water conservancy project or, what is our purpose? Is the amount of water? Water quality? Or ecological? The goal is not clear.

The third problem, the conditions are not clear. Each is not the same boundary conditions:

The first condition of rainfall, is it a small rain or heavy rain? Is it a point storm or surface storm? Is it a short or long calendar rainfall? It is not clear.

The second condition soil, how about the infiltration of soil? There is no saturation in the front? In fact, the key to sponge city in the lower part of the rain garden below the soil to be replaced, the permeability than the original soil increased dozens of times more. So the United States requires rain gardens in the water must be 24 hours to infiltrate the completion of the rain garden, so the rain garden to change the soil.

The third condition is vertical, sponge city is the most important vertical design. In the first half of the section, I quoted Xiaoguang: "LID design without vertical professional depth participation is bound to fail".

If the object, goal and conditions of the sponge city are not clearly stated, the various families are not on a platform and a channel to talk, the chicken and the duck, so noisy into a pot of porridge.

It is recommended to use big data virtual reality, now is not VR? It is entirely possible to rely on big data mathematical models to simulate the entire water cycle on the surface, underground and in the atmosphere, and then we all look at the virtual reality animation of the model calculations, so we know the whole process, just as I lectured today, talking with diagrams and figures.

I'll talk with another diagram, this is a diagram of the Earth's water cycle, the land and ocean water cycle:

100 millimeters of rainfall on land, of which 39 millimeters come from the ocean, and the remaining 61 millimeters is the land's own evaporation, including the plants and the soil evaporation, transpiration, so 61% of the rain is self-cycling.

Of course back to the ocean is 39 millimeters, because the water is balanced, of which 38 millimeters into the sea through runoff, there is 1 millimeter is returned to the ocean through groundwater, is so a water cycle.

Water Cycle Source: Gleick, P.H., 1996 : Water Resources, Encyclopedia of Weather and Climate, edited by S.H. Schneider , Harvard University Press, New York, Volume 2:

Only 3% of the Earth's water is freshwater, and surface freshwater, such as rivers, freshwater lakes, and freshwater marshes, make up only 0.3% of the Earth's freshwater.

But 20% of the world's surface freshwater is concentrated in Lake Baikal, and another 20% is stored in the Great Lakes of the United States (Lakes Huron, Michigan, and Superior).

Rivers hold only 0.006% of the world's freshwater; thus life on Earth depends on a "drop in the ocean" of the planet's total water supply.

Why do rivers, which account for only 0.006% of the world's fresh water, support billions of people around the globe?

Because water circulates!

We then look at the water cycle from the basin, which is the entire catchment area of the Yangtze River Basin,

This is the average annual rainfall in the Yangtze River Basin in different parts of the distribution of the largest place is the Sichuan Basin, an average of 1,200 to 2,000 millimeters of rainfall per year (gray, local blue); Taihu Lake to the mouth of the Yangtze River in Shanghai is green, 1,000 to 1,200 millimeters of rainfall per year.

The average annual rainfall of the entire Yangtze River Basin is 1067 millimeters, and because the Yangtze River Basin covers an area of 1.8 million square kilometers, the total rainfall is 1.92 trillion cubic meters of water.

How much runoff is there from the mouth of the Yangtze River into the East China Sea? It is 951.3 billion cubic meters, accounting for 49% of the total precipitation. What does that mean? According to the algorithm that rainwater can be self-absorbed in the basin and not discharged, the annual runoff control rate of the entire Yangtze River basin is 51%?

This 51% is similar to Mr. Che's natural water cycle diagram, where evaporation accounts for 50%, because it is a global average, and after reviewing a lot of hydrological and meteorological data, an average of 50% of the rainfall is evaporated back, because the material is indestructible, and the water is constantly in the cycle.

Another example is the Yellow River Basin, where there are several months a year when the flow is cut off because the amount of water discharged into the sea is very small, and the annual runoff control rate of the Yellow River has reached more than 90%.

So the total annual runoff control rate indicator, can be applied to the big sponge?

Back to the small and medium-sized sponge of the annual runoff control rate indicator discussion. in November 2015, in foreign countries engaged in water supply and drainage Xiaoguang wrote an article, caused by the discussion of the annual runoff control rate is a misinterpretation of the annual runoff control rate can not be used for many years the average rate of natural runoff, because sponge city is mainly for the city in the middle of the small block,

The second is the adaptability of the indicator: it should be a water quality Control indicators, rather than water control indicators, but the country is now mainly for water quantity.

The third is the scope of application of the indicators, mainly applicable to land parcels, building blocks, etc., not applicable to urban areas containing water systems.

Because the Ministry of Housing and Construction's sponge city indicator system is not clearly defined, so each family said. For example, how to say Shanghai? How to deal with the problem of meeting the total annual runoff control rate?

Shanghai has also come up with a set of sponge city indicator system, seven units *** with the preparation,

less than nine dragons to rule the water two dragons, housing and construction, planning, development and reform, water, transportation, environmental protection plus landscaping, a *** seven dragons *** with the rule of water.

Shanghai's total annual runoff control rate, if the control 75% corresponds to 22 millimeters, 80% corresponds to 26.7 millimeters.

Shanghai's indicator system has a terminology to explain the rainwater storage capacity:

Then Shanghai has a very interesting explanation: because according to the requirements, Shanghai is not able to achieve 80% of the total annual runoff control rate, why?

Because Shanghai's so-called "three highs and one low": high water table, high coverage, high development intensity, and low infiltration rate, so you have the Ministry of Housing and Construction has a target assessment of the policy, then I have a countermeasure in Shanghai. Shanghai with what countermeasures? With the river to bottom:

If Shanghai's annual runoff control rate did not meet the standard, then I through the river storage, even through the deep storage, as long as the river storage later even. I last talked to the Ministry of Housing and Construction to develop the 70% standard, I said you did not make it clear, that can not be helped, you have a policy we have a countermeasure in Shanghai.

The fight to fight, explaining the total annual runoff control rate is not clearly defined, and do not say clearly the scope of application, not to mention for what? Instead, it causes misunderstanding, so that hydrologists misunderstand sponge city to make the river cut off! In fact, foreign countries are not too concerned about the issue of water quantity, mainly concerned about water quality, and the water cycle mentioned earlier.

Inside the Guide, there is a partition on the total annual runoff control rate, the Guide's Exhibit F2-1, the average of the country's four municipalities and provincial capitals, 80% of the runoff control rate corresponds to 24.9 millimeters, or 25 millimeters.

Shanghai, according to the statistical analysis of tens of thousands of rainfalls in the last hundred years, each time the control of 26.7 millimeters of rainfall is equivalent to the control of 80% of the total annual rainfall runoff.

And then back to the water cycle map, this is the global water cycle map, the 25 millimeters mentioned earlier, a few years ago with foreign experts have been discussing, they have been saying that the foreign LID design of rainfall runoff and pollution control, generally 20 millimeters to 30 millimeters, the average is 25 millimeters an inch, they will control an inch of rainfall. At first I couldn't understand, I said why just one inch, not two inches, not half an inch, they said just control so much.

Now I found the answer, this is the Harvard University publication of the nature of the encyclopedia of an article inside the introduction, about the global water cycle, do you know? How much water is in the Earth's atmosphere? It's 12,900 cubic kilometers, and there are 12.9 trillion tons of rain, which is the water vapor in the atmosphere.

These water and gas if a one-time rainfall to the ground, spread evenly over the surface of the Earth, the entire surface of the Earth on average how much rain?

25 millimeters, 2.5 centimeters, one inch! This is the law of nature, the Tao. That means the moisture in our air, the global average is 25 millimeters an inch, so you see it's in a constant cycle, it's an average of one complete rainfall, which is 25 millimeters.

For example, Shanghai, because of the relative humidity, a little bit bigger than average, is 26.7 millimeters, which corresponds to an 80% control rate. So behind this one-inch number is the law of nature aka the Tao, which is very interesting.

This is Shanghai, the Xujiahui weather station here,

the earliest weather station in China, with more than a hundred years of weather records.

According to the statistical analysis of tens of thousands of rainfalls in the last hundred years, the cumulative probability distribution of rainfall events and rainfall totals at the Xujiahui station is as follows:

You can see that the different rainfalls, 5 millimeters, 10 millimeters, and 27 (26.7) millimeters, there is a statistical analysis of the number of rainfalls, because it rained more than a little bit of rain, and the number of rainfalls less than 27 millimeters almost accounted for 95% of the rainfalls, because there are a small number of heavy rainfalls. there were also a handful of a few heavy rainfall events.

The rainfall less than 27 millimeters cumulative, that is to say, control 27 millimeters, how much cumulative rainfall was controlled? About 82% to 83% of the total rainfall was controlled. Such a value is based on the statistical analysis of tens of thousands of rainfalls in the last hundred years, but behind it is the law of the natural water cycle.

So I'm talking about, this is a water cycle problem, it can be seen that we engage in sponge city, you have to know astronomy, geography, you have to understand these to know what the inner law.

I'm going to go a little deeper and talk about the underground water cycle. This is a diagram of the underground water cycle,

After the rainwater infiltrates, there is a water barrier and a pressure layer below the surface, and this water can be evaporated through the plants and the soil, evaporation, and return to the atmosphere.

10% of the water in the atmosphere comes from plant transpiration, a large oak tree transpiration 151 tons of water a year:

July 30, in Shanghai, "sponge city planning, design and construction management" training, I spoke of "Zhouyi Tuangua sponge":

Later organized into a series of Zhouyi sponge!

Tuen Gua is the top of a water below a thunder,