Emergency water supply capacity analysis of major cities in Hebei

CUI Qiu-ping, LIU Zhi-gang, LIU Li-jun, ZHANG Shao-cai, CHEN Yun-qian

1 Hydrogeology & Engineering Geology Institute of Hebei Bureau of Geology and Mineral Resources Exploration, Shijiazhuang 050021, China.

2 Hebei Bureau of Geology and Mineral Resources Exploration, Shijiazhuang 050021, China.

Abstract: In order to prevent the catastrophic events such as extreme drought, continuous drought and source-water quality pollution, 15 groundwater emergency water sources are to be selected in 11 important cities in Hebei, and the evaluation of allowable emergency exploitation quantity is 180.19×104 m3/d. Under the current conditions, the water supply quantity of emergency water sources and the total emergency water supply quantity will meet the emergency water demand with the guarantee rate of 65.79% to 377.78% and 90.35% to 270.51% respectively. By 2020, the water supply quantity of emergency water source places and the total emergency water supply quantity will meet the emergency water demand with the guarantee rate of 22.08% to 74.49% and 82.65% to 144.08% in the benefited areas of South-to-North water diversion (SNWDP); and for non-SNWDP areas, the guarantee rate will be 74.64% to 337.78% and 74.64% to 377.78%.

Keywords: Emergency water sources; Emergency water demand; Water supply capacity;Analysis

Water sources of centralized water supply in most cities of Hebei Province relies on groundwater exploitation; a small number of cities relies on surface water, or are jointly supplied by surface water and groundwater, and the current water supply capacity can meet the water demand basically. However, as most cities are lack of emergency reserve water sources, especially some cities depend on surface water in higher degree, so once the water sources suffer sudden pollution, the normal life and production order of city will be seriously affected, causing social panic. On December 31, 2012, aniline leakage incident happened in the Zhanghe River section, and the water of the downstream Yuecheng Reservoir in Handan City was polluted, causing the drinking problem for 600 000 people in the city. In order to prevent the catastrophic events such as extreme drought, continuous drought and source-water quality pollution, groundwater emergency water sources of city are required to improve riskresistance level of city water supply system (SUN Jin-wei et al. 2013). It is also required to carry out analysis of emergency water supply capacity, and take pertinence measures to improve the bearing capacity of city water supply system on coping with the extreme circumstances and emergencies,ensuring the security of city emergency water supply (XIE Zhi-gao et al. 2014).

1 Water source structure and the current situation of water supply in major cities

In 11 major cities in Hebei, water sources of centralized water supply include surface water,which is mainly extracted from upstream reservoir,and ground water, the water extraction layer of which is mainly shallow groundwater on piedmont plain, deep ground water on the middle east plain,and karst water or valley Quaternary groundwater in mountain and basin areas (CUI Qiu-ping et al.2010).

Up to the end of 2012, water sources number of centralized water supply in 11 cities was 50 in total,and the actual total volume of water supply was 181.61×104m3/d. The water sources included 12 surface water sources, the water supply of which account for 46.8% of the total; and also 38 groundwater sources, accounting for 53.2% of the total (Table 1).

2 Emergency water demand quantity and calculation principle

2.1 Planning period of emergency water supply and emergency water supply period

Considering the population growth of city,“Twelfth Five Year Plan” and ten-year plan (2010-2020) of national economy, the planning period of emergency water supply is determined to last for 7 years (2013-2020), and the emergency water supply period is determined to last 6 months (180 days) (YE Yong et al. 2010).

2.2 Emergency water demand quantity of major cities in Hebei under the current conditions

Under the current conditions, the major cities with surface water sources take the water supply quantity of surface water source with the highest water flow rate as the emergency water demand quantity of the city.

For the cities solely utilizing groundwater,alternative water source is demanded to make up the emergency water supply source of groundwater.Emergency water demand quantity is determined according to the current groundwater sources distribution, vulnerable degree to pollution and actual water supply quantity.

In Hengshui City, the actual water supply quantity of current centralized groundwater is 6.0×104m3/d, and is determined as emergency water demand quantity; in Langfang City, the water supply quantity of current groundwater sources is 10.4×104m3/d in total, and as the new airport of the capital will occupy the Baijiawu water source, new water source with the water supply of 9.0×104m3/d needs to be exploited;located in Qinghe River channel, three of the five groundwater sources in Zhangjiakou City are the riverside water sources, which are vulnerable to be polluted by surface waste water, and as for the close distance, the upstream water source pollution will affect the downstream, so the current total water supply quantity (4.5×104m3/d) of the three water sources is determined as the emergency water demand quantity of the city; there are six groundwater sources in Chengde City, and four of them are located in the Wulie River channel and the Luanhe River channel, which have similar characteristics to those of Zhangjiakou, so the current total water supply quantity (4.69×104m3/d)of the four water sources are determined as the emergency water demand quantity of the city(Table 2).

Table 2 Emergency water demand quantity of the major cities in Hebei under the current conditions

2.3 Emergency water demand quantity of major cities in 2020

2.3.1 Emergency water demand quantity of major cities in the SNWDP benefited areas

In Hebei Province, Handan, Xingtai,Shijiazhuang, Baoding, Hengshui, Cangzhou and Langfang are the cities in the SNWDP benefited areas. After the project has been put into operation,the water will become the major supply of the city water, and also the largest surface water source.The current water sources will be regarded as water reserve. According to water allocation of first-stage project of SNWDP middle-line, the allocated water quantity of the major cities in benefited area can reach 416.4×104m3/d.

For the instability that the SNWDP project has,50% of the project water is determined as the stable water supply quantity of the major cities.Once the project water suffers pollution, water supply of the current water sources and the standby water sources will be started. If the emergency demand could not be met, the emergency water sources will be started. Therefore, the emergency water supply quantity of emergency water sources shall be the gap of the stable project water after subtracting the available water supply of the current water sources and standby water sources.With Shijiazhuang as an example, the stable water supply quantity of SNWDP project is 67.67×104m3/d, the water quantity of the current water sources is 47.5×104m3/d, and emergency water demand gap is 20.17×104m3/d. Through utilizing this method, emergency water demand gaps of Baoding, Handan, Xingtai and Langfang are 12.37×104m3/d, 16.98×104m3/d, 7.51×104m3/d and 10.38×104m3/d respectively.

The stable water supply quantity of SNWDP project in Hengshui is 18.90×104m3/d, and the water supply quantity of the current groundwater sources is 6.00×104m3/d. Surface water source of Hengshui Lake, which designed water supply capacity is 10×104m3/d , will soon be completed.Then the total emergency water supply quantity will reach 16.0×104m3/d, and emergency water demand gap will be 2.9×104m3/d; the stable water supply quantity of SNWDP project in Cangzhou is 19.25×104m3/d; the available water supply quantity of Dalangdian reservoir is 6.46×104m3/d currently, two groundwater sources of which have been stopped producing can supply water for 5.20×104m3/d, and till then the total emergency water supply quantity will reach 11.66×104m3/d,and emergency water demand gap will be 7.59×104m3/d (Table 3).

Table 3 Analysis sheet of emergency water demand in major cities of SNWDP benefited areas in Hebei in 2020

2.3.2 Emergency water demand quantity of major cities in non-SNWDP areas

Tangshan, Qinhuangdao, Zhangjiakou and Chengde are cities in non-SNWDP areas of Hebei province. According to the actual situation of water supply in Tangshan and Qinhuangdao, water supply quantity of the planning surface water source with the highest water flow rate is determined as the emergency water demand quantity. In 2020, the Douhe Reservoir, which is the largest surface water source in Tangshan, will supply water for 6 500×104a (17.8×104m3/d) to the city,and is regarded as emergency water demand quantity of Tangshan; the Taolinkou reservoir,which is the largest surface water source in Qinhuangdao, will supply water for 5 000×104a(13.8×104m3/d) to the city, and is regarded as emergency water demand quantity of Qinhuangdao.

In 2020, groundwater will still be the major water supply source in Zhangjiakou and Chengde,and the water supply capacity of the current water sources will meet the designed capacity. Therefore,the emergency water demand quantity of Zhangjiakou is the total designed water supply capacity (4.5×104m3/d) of the three riverside water sources; and the emergency water demand quantity of Chengde is the total designed water supply capacity (9.18×104m3/d) of the four riverside water sources.

3 Allowable exploitation quantities of emergency groundwater sources

3.1 Advantages of emergency groundwater sources

In the North China Plain, especially in Quatenary aquifer in piedmont plain area, water storage space is considerable, with years of runoff regulation capacity. Aquifer medium and the overlying strata in the vadose zone has a natural function of filtration protection, providing the stability of water supply, quantity and quality of the groundwater, and making the groundwater environment less susceptible to external pollution.At the same time, groundwater facilities are difficult to suffer from destroys caused by sudden disasters like earthquakes and wars. Compared with surface water source, groundwater source has obvious advantage in emergency water supply(DAI Chang-lei et al. 2008). The common method at home and abroad is taking advantage of groundwater and set emergency groundwater source.

3.2 Hydrogeology of emergency water sources

According to the selecting principle and emergency exploration constraints of emergency water sources, 15 emergency water sources are selected in Hebei, including 3 in Shijiazhuang and Langfang respectively, and each other major city has 1 emergency water source. And then the target strata (CUI Qiu-ping et al. 2010), types of emergency water source (CHEN Wang-he et al. 1999)and hydrogeology conditions (FENG Chuang-ye and CUI Qiu-ping, 2004) of groundwater emergency exploitation are determined (Table 4).

3.3 Allowable exploitation quantities of emergency groundwater sources

3.3.1 Evaluation principle

Emergency water sources are exploited for high strength in the period of emergency water supply, forming a certain scale of water supply to meet the emergency water demand or to solve the supply problems. Therefore, in the period of emergency exploitation, the water yield shall be kept stable and drawdown be kept under the constraints.With no disastrous environment geology, overall consider the water source area, aquifer thickness,the maximum drawdown of groundwater level,water yield of single well and emergency water demand quantity etc., and preliminarily design exploitation conditions like well depth, well number, well spacing and well location, then carry out the allowable exploitation evaluation of emergency water sources (water supply quantity of emergency water sources) (CUI Qiu-ping et al.2010).

3.3.2 Evaluation method

Interference with the Wells Group Method is utilized in emergency water sources of plain areas;phreatic unsteady constant flow interference with the Wells Group Method is utilized in shallowdeep groundwater evaluation; unsteady constant flow interference with the Wells Group Method of confined aquifer or big well method is utilized in karst water evaluation; recharge method or discharge method is utilized in intermontane valley and basin area, and the allowable emergency water exploitation is evaluated under the condition that the guarantee rate p is equal to 95% or 97%(Hydrogeological manual of water supply, 1977).

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Table 5 Allowable exploitation of emergency water sources selected in the major cities of Hebei

3.3.3 Evaluation result

Through calculating and evaluating, the allowable exploitation quantity of the 15 emergency water sources selected is 180.19×104m3/d(Table 5).

4 Analysis of emergency water supply capacity

4.1 Emergency water supply capacities under the current conditions

Under the current conditions, the water supply quantity of emergency water sources in the 11 major cities meets the emergency water demand with the guarantee rate of 65.79% to 377.78%.Besides Cangzhou and Qinhuangdao with the guarantee rate of 65.79% and 81.68% respectively,the guarantee rate of other 9 cities are all above 100%. Presently, the living water quantity of the city is 120 L/d per capita, and according to this data, the living water guarantee rate of emergency water sources is 77.27% to 222.86%, besides Cangzhou and Handan with the guarantee rate of 77.27% and 85.63% respectively, the rate of other 9 cities are all above 100%. During emergency period, water supply of the current groundwater sources will be centralized, and the water supply of emergency water sources will be started, and the guarantee rate of the total emergency water supply will be kept between 90.35% and 270.51%. Each of other 10 cities has the guarantee rate above 100%, except Qinhuangdao, which guarantee rate is 90.35% (Table 6).

4.2 Emergency water supply capacity by 2020

4.2.1 Emergency water supply capacity of the major cities in SNWDP benefited areas in 2020

In 2020, under the condition that 50% of the SNWDP cities' water allocation will be determined as the emergency water demand quantity by SNWDP benefited area, water supply quantity of emergency water sources in the 7 major cities will meet the emergency water demand with the guarantee rate of 22.08% to 74.49%. The guarantee rates of Cangzhou, Handan and Hengshui are below 50%, while other four cities' guarantee rates are above 50%. Calculated on the basis of urban planning population and living water quantity (150 L/d per capita) in 2020, water supply quantity of emergency water sources will meet living water demand with the guarantee rate of 33.33% to 111.11%, among which, Cangzhou's guarantee rate is 33.33%, which is the lowest, and Handan's is 38.53%. Only Shijiazhuang and Langfang have the guarantee rate above 100%.

During emergency period, water sources for reserve and emergency will all be started, and the emergency water supply quantity will meet the emergency water demand with the guarantee rate of 82.65% to 144.08%. The guarantee rates of the 5 cities are all above 100%, except that Cangzhou and Handan, which guarantee rates are 82.65% and 84.05% respectively. The total emergency water supply quantity will meet living water demand with the guarantee rate of 95.2% to 226.67%, and the guarantee rates of 6 cities are all above 100%except Handan, which guarantee rate is 95.2%(Table 7).

4.2.2 Emergency water supply capacity of the major cities in non-SNWDP areas in 2020

In 2020, emergency water supply quantity of the 4 major cities in non-SNWDP areas will meet the emergency water demand with the guarantee rates of 74.64% to 337.38%, and the guarantee rates of the 3 cities are above 100%, except Qinhuangdao, which guarantee rate is 74.64%; the water supply quantity will meet the living water demand with the guarantee rates of 62.42% to 103.03%, and only Zhangjiakou has the guarantee rate above 100%. During the emergency period,the total emergency water supply quantity will meet the emergency water demand with the guarantee rate of 74.64% to 377.78% under the condition that the emergency water sources and the current water sources are exploited simultaneously.The guarantee rates of the three cities are above 100%, except Qinhuangdao, which guarantee rate is 74.64%. The emergency water supply will meet the living water demand with the guarantee rate of 62.42% to 131.73%, the guarantee rates of Qinghuangdao and Chengde are 62.42% and 86.67% respectively, and Tangshan and Zhangjiakou have the guarantee rate above 100%,see Table 7.

5 Conclusions

(1) Fifteen groundwater sources are selected for 11 major cities in Hebei according to the construction and situation of current water supply source construction, city planning, and selected principle of emergency groundwater source; and on the basis of emergency exploitation constraints,the allowable emergency exploitation of evaluating water sources is 180.19×104m3/d.

(2) Under the current conditions, water supply of the emergency water sources in the 11 major cities will meet the emergency water demand with the guarantee rate of 65.79% to 377.78%, and all other 9 cities can meet the emergency water demand except Cangzhou and Qinhuangdao; the emergency water supply will meet the living water demand with the guarantee rate of 77.27 and 222.86%, and 9 cities can meet living water demand except Handan and Cangzhou. During the emergency period, the total emergency water supply quantity will meet the emergency water demand with the guarantee rate of 90.35% and 270.51%, and 10 cities can meet the living water demand except Qinhuangdao.

(3) In 2020, water supply of the emergency water sources of the 7 cities in SNWDP area will meet the emergency water demand with the guarantee rate of 22.08% to 74.49%; meet the living water demand with the guarantee rate of 33.33% to 111.11%, which only Shijiazhuang and Langfang can meet the demand. During the emergency period, the total emergency water supply quantity will meet the emergency water demand with the guarantee rate of 82.65% and 144.08%, and 5 cities can meet the demand except Cangzhou and Handan; meet the living water demand with the guarantee rate of 95.2% to 226.67%, and 6 cities can meet the demand except Handan.

(4) In 2020, water supply of emergency water sources of the 4 cities in non-SNWDP area will meet the emergency water demand with the guarantee rate of 74.64% to 337.78%, and 3 cities can meet the demand except Qinhuangdao; meet the living water demand with the guarantee rate of 62.42% to 103.03%, which only Zhangjiakou can meet the demand. During the emergency period,the total emergency water supply quantity will meet the emergency water demand with the guarantee rate of 74.64% to 377.78%, and 3 cities can meet the demand except Qinhuangdao; meet the living water demand with the guarantee rate of 62.42% to 131.73%, which Tangshan and Zhangjiakou can meet the demand.

Acknowledgements

Study on emergency water supply capacity of groundwater and water research for drought relief in Hebei Province (No. 201208).