Download Discussion on Rainwater Utilization in Southern Mountain Area of Jinan

Discussion on Rainwater Utilization in Southern Mountain Area of
Jinan
LI Mei,WANG Hongbo,WANG Xin
School of Municipal and Environmental Engineering, Shandong Jianzhu University, P.R.China, 250101
limei0361@sina.com
：
Abstract The vast southern Mountain area of Jinan city, which have unique geographical environment
and abundant rainwater resources, are the groundwater recharge area of Jinan springs. The southern
mountain has obvious seasonal rainfall and its annual rainfall was between 450mm to 850mm which
mainly concentrated during June to August by statistics and analysis rainfall data of 50 years, and the
amount of 7.46 × 108 m3 rainwater can be used. Three patterns of rainwater utilization such as direct
utilization, indirect utilization and integrated utilization were also discussed. Integrated utilization of
rainwater is of great significance for resuming ecology environment in Southern Mountain area, keeping
groundwater level.
Keywords: South Mountain, Rainfall characteristics, rainwater resources, utilization
1 Instruction
The South Mountain area of Jinan city, with a total area of 1500 m2 and graphic lowering from south to
north, is located in southern region of Jinan. In rainy season, rainfall collected from the south Mountain
area is liable to form strong storm runoff and runs off from south to north. Rainfall is of significant part
in nature water cycle system, and it plays crucial role in improving the Jinan ecological environment and
making up and adjusting the water source. Because of unique hydro-geological conditions, Jinan has
four well-known spring groups including more than 150 famous springs within the scope of 2.6 km2 in
the urban district. The south Mountain area is the important conserve water area and supply area of
underground water source in Jinan. Utilization of rainwater resource in south Mountain area can
improve the ecological environment of south Mountain area and maintain springs spewing year by year.
The technologies of rainwater utilization have been widely researched in water-scarce countries and
regions [1]. The feature of rainwater utilization in China is for irrigation in arid regions; however, the
characteristic of rainwater utilization in other countries, such as Germany, Japan and England and so on
is for urban rainwater utilization. The coverage of vegetation in south Mountain area is less than 40
percent, which results in serious soil erosion and could easily lead to flash floods during heavy
rainstorms and deterioration of ecological environment within valleys. Sparse vegetation, cumulate
rubbish, land farming, road construction and housing make lots of leaky watercourse and valleys severe
siltation and reduced capacity of infiltration, resulting in poor water conservation conditions [2]. For
those characteristics of the south Mountain area, it is meaningful to study measures of rainwater
resource utilization in this region.
2 Overview of South Mountain
2.1 Situation of water resource
The south Mountain area of Jinan belongs to Taishan mountain range. The average annual precipitation
of the south Mountain area is 710 mm, 65 percent of annual precipitation occurred in the summer and it
is rich in rainwater resource. Limestone and fractured rock, which were formed in the south Mountain
area, absorbed large amount of atmospheric precipitation and surface runoff into underground to form a
wealth of fracture-karst water. The average annual groundwater recharge capacity of the natural
resources is 5.795 × 108 m3/a. The groundwater quality is better in this area. It is bicarbonate water and
the value of mineralization is less than 0.5 g/L, and the value of PH is about 7.4 and total hardness is
from 54 to 143 mg CaCO3/L, respectively. The general temperature is around 18 . Yufu River and
Beidasha River are the main rivers in the south Mountain area. The parameters of the two rivers are
℃
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showed in table1 [3].
River name
Drainage area
(km2)
Yufu river
Beidasha river
751
584
Table 1 Yufu River and Beidasha River
Annual runoff
Amount of available
(108m3)
storage( 108 m3)
1.3
0.78
0.75
0.21
Rate of available
storage (%)
57.7
27.7
Wohu and Jinxiu reservoirs are the main large reservoir in south Mountain area. Wohu reservoir belongs
to the Yellow River water system and the total reservoir capacity is 1.22 × 108 m3. Nowadays, Wohu
reservoir has become an important drinking water supply source for southern region of Jinan. Jinxiu
reservoir is located on the channel of Jinxiu River, which is a tributary river of Yufu river. The quality of
water is better and the total reservoir capacity is 0.41 × 108 m3. In rich water year, it supplies water to
urban region through Wohu reservoir.
2.2 Significance of rainwater utilization
Ecological environment of the south Mountain area has a direct effect on the changes of groundwater
quality and quantity in Jinan. Limestone and fractured rock formed in the south Mountain area, is liable
to the infiltration of atmospheric precipitation and groundwater savings, forming crevice-water. The
south Mountain area is the direct and indirect recharge area of Jinan springs groups. Therefore, the
protection of ecological environment in south Mountain area is an important guarantee for springs
spewing and water supply of Jinan. As the urban region moving towards to south, the area of water
recharge is continuously decreased and it causes varying levels of pollution of groundwater. In addition
to excessive exploitation of groundwater, the time on spring’s cutoff in Jinan is longer and longer in the
past years. Protecting water resource, strengthening the comprehensive management of the south
Mountain area, increasing the amount of infiltration and storage of surface water and making full use of
rainwater to recharge springs are of great significance to balance the water resource of Jinan.
3 Analysis of rainfall characteristics
3.1 Annual precipitation distribution
The average annual precipitation of the south Mountain area was 710mm. Figure1 showed the annual
precipitation of each year from 1956 to 2004. The value of annual precipitation was between 450 mm
and 850mm and the value of cumulative frequency was 72 percent. The cumulative frequency of annual
precipitation under 450mm was 14 percent; over 850mm was 14 percent. The maximal annual
precipitation occurred in 1964, was about 1075mm and the minimal occurred in 1968, was about
355mm. Fig.1 showed that the annual precipitation of the south Mountain area were widely changed
year by year, the value of maximum annual precipitation was about 3 times of the minimum annual
precipitation, there was no law of annual rainfall, but mostly concentrated between 500-800mm in
annual rainfall. Due to the impact of warm and humid air in summer, the season precipitation was over
400 mm, accounted for over 65 percent of the annual precipitation.
3.2 Characteristics of monthly precipitation distribution
According to the statistics for data of precipitation from 1956 to 2005, the amount of precipitation was
obviously seasonal; summer was a concentrated period of rainfall, while the remaining three quarters of
rainfall was in less. The data (figure 2) of average monthly precipitation in the south Mountain area
showed that rainfall mainly concentrated during June to August, the three months rainfall exceeded
420mm, accounted for more than 65% of the annual rainfall. The precipitation was less in month 12 to 3,
total amount of these four months were less than 40 mm which accounts for less than 6% of the annual
precipitation. The distribution of monthly precipitation in the south Mountain area was highly uneven.
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Amural precipitation(mm)
1200
1000
800
600
400
200
0
6
5
91
95
9
1
26
9
1
8
6
91
56
91
17
91
47
9
1
77
91
0
8
91
38
91
68
9
1
98
91
2
9
91
59
91
89
9
1
10
02
4
0
02
Year
Monthy precipitation(mm)
Figure 1
The average annual precipitation
250
200
150
100
50
0
1
2
3
4
5
6
7
8
Month
9
10
11
12
Figure 2 The average monthly precipitation
3.3 Analysis of rainfall characteristics
There exists an obvious seasonal characteristic of rainfall in the southern Mountain area. Flood was
easily happened in summer, and then large mounts of rainfall formed runoff and scoured channels of
urban region which made the downstream rivers and reservoir silt more seriously. This had a great
pressure on the spillway pipe network, threatened the life and property of urban residents such as that a
typical floods incident happened on the 18th, July in 2007. While the other three seasons rainwater
supply is in shortage result in serious water shortage. Local rivers become seasonal channels, resulting
in water and soil serious erosion and producing adverse effect on the life of residents and industrial
development of the south Mountain area. This feature has a negative impact to forest and vegetation
growth, and the living standard and food production and the ecological environment of the southern
mountain was also damaged in a certain extent. Meanwhile, this feature is not conducive to direct use of
rainwater, so certain measures to collect and store rain water will be taken to use storm water.
3.4 Analysis of potential rainwater utilization
Through analysis and comparison of theoretic and actual available rainwater utilization of the south
Mountain area in Jinan, the amount of theoretic rainwater resource of the south Mountain area was
1.065 × 109 m3 while the amount of the available rainwater resource utilization was 0.746 × 109m3 at
present which has relationship with technology and economic level of rainwater utilization, namely
rainfall factor. As the improvement of technology and economic levels, the amount of rainwater
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utilization of the south Mountain area will be maximally increased.
4 Measures of rainwater utilization
Rainwater saving and utilization, using rainwater to recharge groundwater, is an economic and practical
pony engineering technology and can bring great benefits for environment and ecology. So it is
applicable to rainwater utilization of the south Mountain area. It includes direct utilization, indirect
utilization and comprehensive utilization [3].
4.1 Direct utilization
Direct rainwater utilization is a technology of changing surface micro-relief to increase the capacity of
surface soil infiltration. Rainwater resource will be efficient utilized by the storage and adaption of “soil
reservoir”. The theoretical basis of this technology is that through reducing surface gradient, surface
runoff hydraulic gradient, to short the length and slow down migration velocity of the runoff, the surface
runoff detention time of a certain region will be prolonged and the amount of soil infiltration will be
increased. The soil infiltration amount increasing on the one hand can increase the soil water storage
capacity for absorption of surface vegetation and can also recharge groundwater reserves. Meanwhile
the slope runoff scouring force will be reduced, achieving to slow down the arable land water and soil
erosion. But in the south Mountain area of Jinan, the precipitation distribution is unevenly and the
annual precipitation is of great difference. When the heavy rain or rainstorm occurs, there are some
problems with direct rainwater utilization that the "soil reservoir" will be quickly washed easily to
destroy the water storage and resulted in soil erosion.
4.2 Indirect utilization
The technology of indirect rainwater utilization includes rainwater in-situ superposition utilization,
autumn plastic film covering soil and conserving moisture, plastic cover greenhouse efficient rainwater
utilization technology which combined with irrigation. The membrane covering and membrane-side
planting techniques named superposition of the southern mountain-site use of rainwater collection,
which are difficult to construct rainwater collection area and water storage cellar, by in situ rainwater
harvesting, in situ use to achieve the purpose of watershed, water retention and fighting drought.
Efficient rainwater utilization of plastic cover greenhouse is the technology of self irrigation. It includes
rainwater collection on the coverage, water storage by water cellar outside greenhouse and efficient
irrigation inside the greenhouse, which can be solved the crop canopy irrigation water problems inside,
and this technology application and popularization of the Mountain area will receive significant
economic benefits. It can increase crop yields, improve soil moisture, control drainage flood, and protect
water resources in the region by using indirect use of rainwater. Generally, the scale of indirect savings
of rainwater is not enough large and more decentralized, so it is difficult to solve the problems which
was caused by the heavy or torrential rain.
4.3 Comprehensive utilization
Rainwater comprehensive utilization is to combine direct utilization with indirect utilization. Based on
ecological conditions of south Mountain area in Jinan, the important things is of focusing on
eco-efficiency, combining ecological benefits with economic benefits and social combination,
combining greening with beautifying to build "eco-economy" comprehensive shelter forest with the aim
of preventing water and soil erosion. It will increase water storage capacity of 4 × 108 m3 per year after
the whole system of greening is built up for the region. It can improve the serious problems of soil
erosion and prevent the occurrence of floods, increase the rate of vegetation coverage and improve the
ecological environment in the south Mountain area by adopting water conservation measures, storing
surface flooding, artificially increasing the flood penetrate the surface to increase the amount of
underground runoff. The comprehensive utilization of rain water have greater advantages with less risk
and better effect comparing to the direct and/or indirect use of rainwater.
The comprehensive utilization is the measure of combining project storage with comprehensive shelter
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forest using rainwater to prevent soil erosion. Measures to save water such as reservoirs, ditches can
store surface water flooding to preventing large and urgent run-off when the rainfall is large and
concentrated. Meanwhile, the shelterbelts can store rainwater as well as maintaining water and soil [4].
Comprehensive utilization of rainwater reduces flood disaster while take advantage of rainwater
resources, protect the ecological environment of the southern Mountain area. Rainfall’s recharge into the
ground increase the groundwater level in Jinan city, and guarantee spring perennial normal spewing.
5 Conclusion
The following conclusions can be obtained in this study:
(1) Rainfall of the south Mountain area in Jinan was obviously seasonal. The annual precipitation was
mainly between 450 mm and 850 mm and the cumulative frequency was 72 percent. Most rainfall
occurred during June to August, the total precipitation of these three months was over 420mm which
accounted for more than 65 percent of the annual precipitation.
(2) Through the calculation of theoretic and available rainwater, the amount of potential theoretic
rainwater resource of the south Mountain area was 1.065 × 109 m3, but the amount of the realizable
rainwater resource utilization was 0.746 × 109 m3 at present. As the improvement of technology and
economic level, the amount of rainwater utilization of the south Mountain area will be maximally
increased.
(3) Comprehensive utilization includes direct utilization, indirect utilization and comprehensive
utilization. It is suited to the ecological conditions of the south Mountain area in Jinan and can reduce
flood disaster, protect ecological environment of the south Mountain area by utilizing rainwater resource,
elevate groundwater level by rainwater recharging groundwater, guarantee spring perennial normal
spewing.
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Acknowledgments
This study is supported by the Ministry of Science and Technology Plan Project (2008-K7-19) and
Shandong Resource-saving Society and Technology Support System Special Project of Construction
(2008JY01).
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