Water shortage and needs for wastewater re-use in the north china X C Wang and P.K. Jin School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, No 13 Yanta Road, Xi'an 710055, China(E-mail: xcwang @auat edu cn) 98→8 Abstract This paper analyses the present condition of the water shortage in north China where annual rainfall is low and per capita water resource is below the line of regular water stress, or even the line of absolute water scarcity Of the available water resources, the percentge of water withdrawal in all the north basins is high the Yellow River and Huai River basins being greater than 80%6 and the Hai River basin mainly depending on interbasin water transfer. Over-withdrawal of water also results in serious water environmental problems including" flow cut-off"of the Yellow River main channel and water pollution of many rivers. The paper also analyses the potential of wastewater as a resource and the demand for treated wastewater re-use. In north China, due to low rainfall and high potential evaporation environmental re-use, gardening, afforestation, etc is considered as the main usage of the treated wastewater. Considering the economic restrictions in the less developed area, a decentralised system can be taken as an important option in formulating water re-use strategies. Keywords Annual rainfall; decentralisation; north China; potential evaporation; water shortage Introduction According to the latest statistical data, the total renewable water resources in the world amount to 4. x 10 m /year(Water Resources Institute, 2003).Considering the total world population of 6,301,463,000(United Nation Population Division, 2003), the per capita water resource can be calculated as 6, 859 m/person/year. However, due to an uneven distribution of rainfall, and uneven distribution of the population, the actual per capita water resource differs extensively region by region and country by country. Among the major watersheds of the world, the Thelon River basin in Canada's North West Territories has the highest per capita water resource at 14, 641, 336 m/person/year while the Yaqui River in Sonora, Mexico has the lowest per capita water resource as only 173 m/person/year(Water Resources Institute, 2001). The Yellow River basin in China is also the watersheds with very low per capita water resource at 361m/ person/year (Water Resources Institute, 2001). Regarding water resource by countries, Iceland has the highest per capita water resource at 599,944 m/person/year, while the United Arab Emirates have the lowest per capita water resource at only 55.5 m/person/ (Water Resources Institute, 2001). An uneven distribution of water one country exists according to its geographical, meteorological and demographical conditions It is widely accepted that the per capita water resource can be used as a parameter for reasonable evaluation of water supply conditions. Once a countrys available water resources drop below 1, 700 m per person per year, the country can be expected perience regular water stress -a situation in which disruptive water shortages ca frequently occur; if the available water resource drops below 1,000 m"/person/year. evere and lead to problems with food production and econ- the amount of water available per capita drops below doi:10.2166/wst2006.267
Water shortage and needs for wastewater re-use in the north China X.C. Wang and P.K. Jin School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, No 13 Yanta Road, Xi’an 710055, China (E-mail: xcwang@xauat.edu.cn) Abstract This paper analyses the present condition of the water shortage in north China where annual rainfall is low and per capita water resource is below the line of regular water stress, or even the line of absolute water scarcity. Of the available water resources, the percentge of water withdrawal in all the north basins is high – the Yellow River and Huai River basins being greater than 80% and the Hai River basin mainly depending on interbasin water transfer. Over-withdrawal of water also results in serious water environmental problems including “flow cut-off” of the Yellow River main channel and water pollution of many rivers. The paper also analyses the potential of wastewater as a resource and the demand for treated wastewater re-use. In north China, due to low rainfall and high potential evaporation environmental re-use, gardening, afforestation, etc. is considered as the main usage of the treated wastewater. Considering the economic restrictions in the less developed area, a decentralised system can be taken as an important option in formulating water re-use strategies. Keywords Annual rainfall; decentralisation; north China; potential evaporation; water shortage Introduction According to the latest statistical data, the total renewable water resources in the world amount to 4.3219 £ 1013 m3 /year (Water Resources Institute, 2003). Considering the total world population of 6,301,463,000 (United Nation Population Division, 2003), the per capita water resource can be calculated as 6,859 m3 /person/year. However, due to an uneven distribution of rainfall, and uneven distribution of the population, the actual per capita water resource differs extensively region by region and country by country. Among the major watersheds of the world, the Thelon River basin in Canada’s North West Territories has the highest per capita water resource at 14,641,336 m3 /person/year, while the Yaqui River in Sonora, Mexico has the lowest per capita water resource as only 173 m3 /person/year (Water Resources Institute, 2001). The Yellow River basin in China is also among the watersheds with very low per capita water resource at 361 m3 / person/year (Water Resources Institute, 2001). Regarding water resource by countries, Iceland has the highest per capita water resource at 599,944 m3 /person/year, while the United Arab Emirates have the lowest per capita water resource at only 55.5 m3 /person/ year (Water Resources Institute, 2001). An uneven distribution of water resource within one country exists according to its geographical, meteorological and demographical conditions. It is widely accepted that the per capita water resource can be used as a parameter for a reasonable evaluation of water supply conditions. Once a country’s available water resources drop below 1,700 m3 per person per year, the country can be expected to experience regular water stress – a situation in which disruptive water shortages can frequently occur; if the available water resource drops below 1,000 m3 /person/year, the consequences can be more severe and lead to problems with food production and economic development; and if the amount of water available per capita drops below Water Science & Technology Vol 53 No 9 pp 35–44 Q IWA Publishing 2006 doi: 10.2166/wst.2006.267 35
500 m/person/year, countries face conditions of absolute water scarcity(Engelman and Leroy, 1993; Falkenmark and widstrand, 1992; United Nations Population Fund, 1997) According to the Water Resources Institute (2000), in 1995 approximately 41% of the orld's population, or 2.3 billion people, lived in river basins under water stress, with a water supply below 1, 700 m/person/year. Of these, approximately 1.7 billion people resided in highly stressed river basins where water supply fell below 1,000 m/person/ year. By 2025, it is projected that, assuming current consumption patterns continue, at least 3.5 billion people or 48% of the world,s population -will live in water-stressed river basins. Of these, 2.4 billion will live under high water stress conditions To meet the present and future needs of water supply, various measures have to be aken into consideration. Many countries that are water scarce are dealing with the water shortage problem by investing in inter-basin water transfer, saline water desalination and wastewater reclamation and re-use(International Hydrological Programme, 1999; Minton et aL., 2003: Asano and Levine, 1996). Among these options, inter-basin water transfer, i.e. to transfer water from a water rich basin to a water scarce basin. and saline water desalination are not very practicable and/or feasible to many countries or regions due to the limitation of locations and economic factors but wastewater reclamation and re-use can be practiced in various ways. Therefore, priority has begun to be placed on waste water re-use in selection of measures to solve the water shortage problem. As will be described in the following sections, China, as a vast country with a large population, facing this problem and is at the beginning of practicing wastewater reclamation and re- use. In this paper, the author intends to analyse the present condition of the available water resource in north China, to discuss its water shortage problem and needs for waste- water re-use, and to suggest a strategy of wastewater re-use in the urban area of this region, taking into account the regional, environmental and economical factors Water resource in north china Distribution of water resources at the national level China has a total renewable water resource of 2, 8255x 10m(Ministry of Water Resource, 2002). This perhaps ranks as number 6 in the world following Brazil, Rus sia, United States, Canada and Indonesia (Water Resources Institute, 2003). However, due to its large population of 1. 29227 billion(National Bureau of Statistics, 2004), the per capita water resource is only 2, 130 m/person/year which is less than 1/3 of the world average and ranks number 118 among the 154 countries in the world where data are available (Water Resources Institute, 2003). China possesses a large territory with its geographical and meteorological conditions varying from the north to the south and from the east to the west. As can be seen in Figure 1. there is gradual decrease of average annual rainfall from the southeast to the northwest. In the south provinces, such as Guangdong and Fujian, the annual rainfall can be high as 2, 000mm, while in the northwest provinces, such as Xinjiang Uygur Auton omous Region, where desert and Gobi areas occupy a large portion of the territory. the annual rainfall drops to less than 50 mm. The whole country can be divided into 10 hydrological zones or large river basins, as shown in Figure 2. The basic data of each basin related to the renewable water resource and water withdrawals are sum- marised in Tables I and 2, based on the 2002 national annual report on water resources(Ministry of Water Resource, 2002 It is clear from Table 1 that the 10 hydrological and three are below 500 m/person/year, the level of absolute water scarcity. All these water scarce zones are in the north part of China. Among them, the Hai r
500 m3 /person/year, countries face conditions of absolute water scarcity (Engelman and Leroy, 1993; Falkenmark and Widstrand, 1992; United Nations Population Fund, 1997). According to the Water Resources Institute (2000), in 1995 approximately 41% of the world’s population, or 2.3 billion people, lived in river basins under water stress, with a water supply below 1,700 m3 /person/year. Of these, approximately 1.7 billion people resided in highly stressed river basins where water supply fell below 1,000 m3 /person/ year. By 2025, it is projected that, assuming current consumption patterns continue, at least 3.5 billion people – or 48% of the world’s population – will live in water-stressed river basins. Of these, 2.4 billion will live under high water stress conditions. To meet the present and future needs of water supply, various measures have to be taken into consideration. Many countries that are water scarce are dealing with the water shortage problem by investing in inter-basin water transfer, saline water desalination and wastewater reclamation and re-use (International Hydrological Programme, 1999; Minton et al., 2003; Asano and Levine, 1996). Among these options, inter-basin water transfer, i.e. to transfer water from a water rich basin to a water scarce basin, and saline water desalination are not very practicable and/or feasible to many countries or regions due to the limitation of locations and economic factors, but wastewater reclamation and re-use can be practiced in various ways. Therefore, priority has begun to be placed on wastewater re-use in selection of measures to solve the water shortage problem. As will be described in the following sections, China, as a vast country with a large population, is facing this problem and is at the beginning of practicing wastewater reclamation and reuse. In this paper, the author intends to analyse the present condition of the available water resource in north China, to discuss its water shortage problem and needs for wastewater re-use, and to suggest a strategy of wastewater re-use in the urban area of this region, taking into account the regional, environmental and economical factors. Water resource in north China Distribution of water resources at the national level China has a total renewable water resource of 2,825.5 £ 109 m3 (Ministry of Water Resource, 2002). This perhaps ranks as number 6 in the world following Brazil, Russia, United States, Canada and Indonesia (Water Resources Institute, 2003). However, due to its large population of 1.29227 billion (National Bureau of Statistics, 2004), the per capita water resource is only 2,130 m3 /person/year which is less than 1/3 of the world average and ranks number 118 among the 154 countries in the world where data are available (Water Resources Institute, 2003). China possesses a large territory with its geographical and meteorological conditions varying from the north to the south and from the east to the west. As can be seen in Figure 1, there is a gradual decrease of average annual rainfall from the southeast to the northwest. In the south provinces, such as Guangdong and Fujian, the annual rainfall can be as high as 2,000 mm, while in the northwest provinces, such as Xinjiang Uygur Autonomous Region, where desert and Gobi areas occupy a large portion of the territory, the annual rainfall drops to less than 50 mm. The whole country can be divided into 10 hydrological zones or large river basins, as shown in Figure 2. The basic data of each basin related to the renewable water resource and water withdrawals are summarised in Tables 1 and 2, based on the 2002 national annual report on water resources (Ministry of Water Resource, 2002). It is clear from Table 1 that among the 10 hydrological zones, five are with per capita water resources below 1,700 m3 /person/year, the level of regular water stress, and three are below 500 m3 /person/year, the level of absolute water scarcity. All these water scarce zones are in the north part of China. Among them, the Hai River X.C. Wang and P.K. Jin 36
×≤ Figure 1 Average annual rainfall in China (as of average from 1956 to 1979)(source: Liu and Chen, 2001) Basin(Zone III) has a per capita water resource as low as 123.78 m/person/year. It is the water scarcest region in China and nowadays people depend on water trans- ferred from other basins, such as the Yangtze River Basin (Zone vD) through the South-to-North Diversion Project(Pan and Zhang, 2001), so the water withdrawal in this region is 251.57% of the internal water resource, as shown in Table 2. The per capita water resources in the Huai River Basin (Zone V) and Yellow River Basil (Zone IV) are also extremely low, and the water withdrawals take 88 and 82% of the internal water resources in the two basin igure 2 Main hydrological zones in China(source: Liu and Chen, 2001)
Basin (Zone III) has a per capita water resource as low as 123.78 m3 /person/year. It is the water scarcest region in China and nowadays people depend on water transferred from other basins, such as the Yangtze River Basin (Zone VI) through the South-to-North Diversion Project (Pan and Zhang, 2001), so the water withdrawal in this region is 251.57% of the internal water resource, as shown in Table 2. The per capita water resources in the Huai River Basin (Zone V) and Yellow River Basin (Zone IV) are also extremely low, and the water withdrawals take 88 and 82% of the internal water resources in the two basins, respectively. Figure 2 Main hydrological zones in China (source: Liu and Chen, 2001) Figure 1 Average annual rainfall in China (as of average from 1956 to 1979) (source: Liu and Chen, 2001) X.C. Wang and P.K. Jin 37
Table 1 Water resources in the main hydrological zones in China (as of 2002) Basin Main river(s) Basin area Population Annual Water resources 1,2484512331 (billion m) Per capita 000 m per and l Heilongjiang 31113.4145.34 ver. Liao river 318.1612845 400 15.9 123.78 125.72 474 48.95 185. ver1,808.50440.591,1761,089.12471.899301 Zhu river 58064155431,708 525.1 146.5 VIll Southeast rivers 239.80 71.93 1,862 2314 133.03 Southwest rivers 851,41 20.55 564.127 3.374442698 187 145.7 17.04 Table 2 Water withdrawals in the main hydrological zones in China (as of 2002) tal(billion m) Domestic (96) Industry (96) Agriculture (96) I and Il 18.6 72.1 41.22 129 38.9 769 8207 612 73.1 168.2 28 555 15.44 645 16.21 X 10.3 1.83 75 93.9 3946 Low annual rainfall. As can be seen from Table l, all the north river basins(Zones IV and X) have very low annual rainfall. The inland rivers basin(Zone X), which covers the desert and Gobi area at the far northwest region, has the lowest annual rainfall at only 187 mm, but because of the vast basin area and relatively small population, the calculated per capita water resource is not low. Another parameter to affect the accessibility of water resource is water resource in unit area. From the last column of Table I it can be seen that the water resource per km- in the inland rivers basin is only approximately 17, 000 m, showing the difficulty in access for wate Uneven distribution of daily rainfall. Another important feature of rainfall in north China is the uneven distribution of daily rainfall within I year. Figure 3 is an example of distribution of recorded daily rainfall in 2002 at Xi'an, a central city in the Yellow River basin. The total annual rainfall in 2002 was 406 mm and the number of days with measurable rainfall(daily rainfall larger or equal to 0. I mm) was 76 days. Among them, the largest daily rainfall was recorded as 75.2 mm on the 9th of June, which was 18.5% of the annual rainfall. The days with rainfall larger than 20 mm were 5 days with a total of 183. 5 mm or 45.2% of the annual rainfall, those with rainfall larger than 10 mm were 12 days with a total of 280.5 mm or 69% of the total annual rainfall, and those with total annual rainfall. The other 43 rainy days were all with a rainfall of less than 2 mm. Such types of uneven distribution may result in intermittently concentrated runoff during
Characteristics of annual rainfall in north China Low annual rainfall. As can be seen from Table 1, all the north river basins (Zones I– IV and X) have very low annual rainfall. The inland rivers basin (Zone X), which covers the desert and Gobi area at the far northwest region, has the lowest annual rainfall at only 187 mm, but because of the vast basin area and relatively small population, the calculated per capita water resource is not low. Another parameter to affect the accessibility of water resource is water resource in unit area. From the last column of Table 1 it can be seen that the water resource per km2 in the inland rivers basin is only approximately 17,000 m3 , showing the difficulty in access for water. Uneven distribution of daily rainfall. Another important feature of rainfall in north China is the uneven distribution of daily rainfall within 1 year. Figure 3 is an example of distribution of recorded daily rainfall in 2002 at Xi’an, a central city in the Yellow River basin. The total annual rainfall in 2002 was 406 mm and the number of days with measurable rainfall (daily rainfall larger or equal to 0.1 mm) was 76 days. Among them, the largest daily rainfall was recorded as 75.2 mm on the 9th of June, which was 18.5% of the annual rainfall. The days with rainfall larger than 20 mm were 5 days with a total of 183.5 mm or 45.2% of the annual rainfall, those with rainfall larger than 10 mm were 12 days with a total of 280.5 mm or 69% of the total annual rainfall, and those with rainfall larger or equal to 2 mm were 33 days with a total of 376 mm or 92.4% of the total annual rainfall. The other 43 rainy days were all with a rainfall of less than 2 mm. Such types of uneven distribution may result in intermittently concentrated runoff during Table 1 Water resources in the main hydrological zones in China (as of 2002) Basin Main river(s) Basin area (000 km2 ) Population (million) Annual rainfall (mm) Water resources Total (billion m3 ) Per capita (m3 /person) 000 m3 per km2 I and II Heilongjiang River, Liao River 1,248.45 123.31 460 137.3 1113.41 45.34 III Hai River 318.16 128.45 400 15.9 123.78 125.72 IV Yellow River 794.71 109.19 404 47.4 434.13 48.95 V Huai River 329.21 208.09 726 69.5 333.98 185.90 VI Yangtze River 1,808.50 440.59 1,176 1,089.1 2,471.89 93.01 VII Zhu River 580.64 155.43 1,708 525.1 3,378.41 146.56 VIII Southeast rivers 239.80 71.93 1,862 231.4 3,216.85 133.03 IX Southwest rivers 851.41 20.55 1,073 564.1 27,446.81 12.10 X Inland rivers 3,374.44 26.98 187 145.7 5,401.27 17.04 Table 2 Water withdrawals in the main hydrological zones in China (as of 2002) Basin Water withdrawals Total (billion m3 ) Domestic (%) Industry (%) Agriculture (%) as a % of water resource I and II 56.6 9.3 18.6 72.1 41.22 III 40 12.9 15.5 71.6 251.57 IV 38.9 9 14.1 76.9 82.07 V 61.2 11.7 15.2 73.1 88.06 VI 168.2 12.8 31.7 55.5 15.44 VII 85.1 14 21.5 64.5 16.21 VIII 31.9 14 28.2 57.8 13.79 IX 10.3 9 6.2 84.8 1.83 X 57.5 3.4 2.7 93.9 39.46 X.C. Wang and P.K. Jin 38
100[ Annual rainfal 406 mm in 2002 in Xi'an EE四 与皇身与{8豆邕 ×≤ Figure 3 Distribution of daily rainfall in Xi'an in 2002(data source: Meteorological Bureau of Shaanxi Province, 2002) heavy rain while in the other days with light rain, there would be no runoff at all. Consequently, water harvest becomes difficult. This is another reason for the low quantity of available water resource. High potential evaporation. Potential evaporation is defined as the amount of water that could be evaporated if it were available. Figure 4 shows the relationship between the average annual rainfall and the average potential evaporation based on the long term measurement data of 140 meteorological stations in the five northwest provinces (Shaanxi, Gansu, Ningxia, Qinghai and Xinjiang). The potential evaporation ranges from 1, 100 to 4,100 mm in this region and there is an apparent trend that the potential evaporation increases as the annual rainfall decreases. The ratio of potential evaporation/annual rainfall can be as high as more than 180, indicating very difficult conditions for the recharge of surface water or groundwater through the rainfall Present condition of water use As shown in Table 2. water withdrawal in the total available water resource from each of the water basins in north China is extremely high. Even in the inland rivers basin(Zone X), where the water resource per km- is very low, the percent of water withdrawal is as high as approximately 40%. The composition of water use in the six water basins in north China(Zones I-V and X) in 2002 is shown in Figure 5. Water for agriculture takes 5 4000 3000 8 1000 1000 Annual rainfall/ mm Figure 4 Relation between annual rainfall and potential evaporation( data source: Institute of Geographic Science and Resources, 2004)
heavy rain while in the other days with light rain, there would be no runoff at all. Consequently, water harvest becomes difficult. This is another reason for the low quantity of available water resource. High potential evaporation. Potential evaporation is defined as the amount of water that could be evaporated if it were available. Figure 4 shows the relationship between the average annual rainfall and the average potential evaporation based on the long term measurement data of 140 meteorological stations in the five northwest provinces (Shaanxi, Gansu, Ningxia, Qinghai and Xinjiang). The potential evaporation ranges from 1,100 to 4,100 mm in this region and there is an apparent trend that the potential evaporation increases as the annual rainfall decreases. The ratio of potential evaporation/annual rainfall can be as high as more than 180, indicating very difficult conditions for the recharge of surface water or groundwater through the rainfall. Present condition of water use As shown in Table 2, water withdrawal in the total available water resource from each of the water basins in north China is extremely high. Even in the inland rivers basin (Zone X), where the water resource per km2 is very low, the percent of water withdrawal is as high as approximately 40%. The composition of water use in the six water basins in north China (Zones I–V and X) in 2002 is shown in Figure 5. Water for agriculture takes Figure 3 Distribution of daily rainfall in Xi’an in 2002 (data source: Meteorological Bureau of Shaanxi Province, 2002) Figure 4 Relation between annual rainfall and potential evaporation (data source: Institute of Geographic Science and Resources, 2004) X.C. Wang and P.K. Jin 39