GEOSCIENCE FRONTIERS 2(4) (2011) 593e598
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China University of Geosciences (Beijing)
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ORIGINAL ARTICLE
Assessment of deep groundwater over-exploitation in the North China Plain Jiansheng Shi, Zhao Wang*, Zhaoji Zhang, Yuhong Fei, Yasong Li, Feng’e Zhang, Jingsheng Chen, Yong Qian Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shigang Street 406, Shijiazhuang, Hebei 050061, China Received 13 January 2011; accepted 17 May 2011 Available online 27 August 2011
KEYWORDS North China Plain; Deep groundwater; Assessment of over-exploitation; Land subsidence; Water table depression
Abstract A series of environmentalegeological problems have been caused by over-exploitation of deep groundwater (i.e., confined aquifer water) in the North China Plain. In order to better understand the status of deep groundwater over-exploitation and the resultant environmentalegeological problems on a regional scale, the over-exploitation of groundwater has been assessed by way of the groundwater exploitation potential coefficient (i.e., the ratio of exploitable amount of deep groundwater to current exploitation), cumulative land subsidence, and long-term average lowering rate of the groundwater table. There is a good correlation among the results calculated by the different methods. On a regional scale, deep groundwater has been over-exploited and there is no further exploitation potential under the current conditions. The groundwater exploitation degree index takes the exploitation in 2003 as the reference for the calculations, so the results mainly reflect the degree of current groundwater exploitation. The results of over-exploitation of deep groundwater obtained by land subsidence data and long-term average rate of depression of the water table mainly reflect environmentalegeological problems caused by exploitation of deep groundwater. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: þ86 311 88024953; fax: þ86 311 88024371. E-mail address:
[email protected] (Z. Wang). 1674-9871 ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved. Peer-review under responsibility of China University of Geosciences (Beijing). doi:10.1016/j.gsf.2011.07.002
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1. Introduction In the North China Plain, over-exploitation of deep groundwater has attracted the attention of several studies (Li et al., 2001; Hu et al., 2002). With the increasing demand, groundwater exploitation is also intensifying. As a result, a series of environmental and geological issues have arisen in the area, such as land subsidence, ground fissuring, seawater intrusion, lowering of the saline water interface and pollution of deep groundwater (Zhang et al., 1997, 2000; Xu et al., 2002; He et al., 2006; Dong et al., 2007; E and Sun, 2007). In order to more rationally exploit and utilize deep groundwater and minimize potential environmentalegeological problems, it is of paramount importance to assess the exploitation
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J. Shi et al. / Geoscience Frontiers 2(4) (2011) 593e598
Table 1
Classification of groundwater exploitation potential coefficient and potential status.a
Potential coefficient (P)
P 0.6
0.6 < P 0.8
0.8 < P 1.2
1.2 < P 1.4
P > 1.4
Exploitation degree
Seriously over-exploited No Exploitation controlled strictly
Over-exploited
Exploitation and recharge balance Low Maintaining present exploitation
Relatively low
Low
Relatively large Exploitation enlarged properly
Large Exploitation can be enlarged
Potential status Exploitation prospective a
No Exploitation controlled properly
Based on Zhang et al. (2009).
degree of deep groundwater in the North China Plain on a regional scale. Exploitation of deep groundwater in the North China Plain is mainly concentrated in the middle and eastern parts of the Hebei Province and Tianjin City (Li et al., 2001; Dong et al., 2007), whereas the degree of deep groundwater exploitation in most parts of Henan Province is rather low. Where groundwater is still in the state of its natural cycle, deep groundwater flows laterally and the composition of groundwater resources is relatively unchanged. An overall survey of land subsidence in the study area of Shandong Province has not yet been conducted, thus the balance calculation for deep groundwater in the whole area has also not been assessed. Based on monitoring data from early 1980s to 2003, the degree of deep groundwater exploitation is assessed in this study.
2. Selection of data and assessment methods to determine the degree of groundwater exploitation 2.1. Data selection and calculation methods Based on comprehensive analysis of previous exploration, monitoring data and research results, we use the latest information, including the water table, exploitation and utilization, water quality zonation and hydrogeological parameters, in order to
Table 2
ensure the validity of the data and calculation results. In accordance with comprehensive analysis of groundwater exploitation and utilization, and the environment, the period from 1991 to 2003 is used as the time interval (with 2003 as the status quo), for the calculation of groundwater sources and sinks. The land subsidence has been calculated using the data from 1984 to 2003. Assessment of deep groundwater resources has been conducted by the water balance method. Recharge items include lateral recharge and leakage recharge. Discharge items include lateral discharge, leakage discharge and artificial exploitation. Based primarily on the threshold of the deep groundwater environment, the usable amount has been assessed. Deep groundwater is characteristic of slow renewal and low recharge. The exploitation and utilization of deep confined groundwater in the North China Plain varies in different places; the degree of exploitation and utilization of deep, confined groundwater in Hebei, Tianjin and Shandong Province is high, whereas in Henan Province it is low. In the area where the degree of exploitation and utilization of deep groundwater is high, the release of confined groundwater by elastic reaction of the aquifer sediments has caused a decrease in the piezometric level. Usually elastically released water from these deep aquifers should not be further exploited. The usable amount of deep groundwater is the sum of leakage recharge and lateral runoff recharge. In the area where the degree of exploitation and
Assessment of the degree of deep groundwater exploitation in the North China Plain.
Province/ District City
Qrecharge Subsidence Qusable Qcurrent Over-exploitation degree Exploitation Over-exploitation (based on land subsidence) potential degree (based on (106 m3/a) amount amount exploitation (106 m3/a) (106 m3/a) coefficient potential coefficient) (mm/a)
Tianjin Hebei
233 088 146 24 140 162 261 270 154 235 1478 14 19
11.83 6.94 8.41 7.17 12.62 12.18 7.27 15.79 13.90 12.93 11.82 4.62 5.28
216 115 122 21 168 139 169 235 130 205 1306 59 97
309 198 206 38 235 249 235 393 223 351 2128 270 111
Seriously over-exploited Generally over-exploited Generally over-exploited Generally over-exploited Seriously over-exploited Seriously over-exploited Generally over-exploited Seriously over-exploited Seriously over-exploited Seriously over-exploited Seriously over-exploited Generally over-exploited Generally over-exploited
0.70 0.58 0.59 0.55 0.71 0.56 0.72 0.59 0.58 0.58 0.61 0.22 0.87
11 5 4 53 1764
3.85 2.68 4.48 4.45 8.15
44 17 20 237 1758
7 0 25 413 2850
Generally Generally Generally Generally Generally
5.57 e 0.79 0.53 0.61
Subtotal Shijiazhuang Tangshan Qinhuangdao Handan Xingtai Baoding Cangzhou Langfang Hengshui Subtotal Shandong Liaocheng Dezhou Binzhou Dongying Jinan Subtotal Total
over-exploited over-exploited over-exploited over-exploited over-exploited
Over-exploited Seriously over-exploited Seriously over-exploited Seriously over-exploited Over-exploited Seriously over-exploited Over-exploited Seriously over-exploited Seriously over-exploited Seriously over-exploited Over-exploited Seriously over-exploited Exploitation and recharge in balance Low e Over-exploited Seriously over-exploited Over-exploited
J. Shi et al. / Geoscience Frontiers 2(4) (2011) 593e598 Table 3
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Subarea statistics of deep groundwater exploitation potential in the North China Plain.
Province/City Potential grade
Area (km2) Area Availability Exploitation Surplus Exploitation Potential (106 m3/a) potential ratio (%) (106 m3/a) in 2003 modulus (106 m3/a) coefficient (103 m3/a km2)
Tianjin
2387 1047 1347 1416 3018 677 366 5053 9881 45353 15047 1172 3234 1047 11345 15351 2119 33462 2585 9634 12344 61836 119861
Hebei
Shandong
Henan North China Plain
With large potential With relatively large potential With general potential Over-exploited Seriously over-exploited With large potential With relatively large potential With general potential Over-exploited Seriously over-exploited With large potential With relatively large potential With general potential Over-exploited Seriously over-exploited With large potential Seriously over-exploited With large potential With relatively large potential With general potential Over-exploited Seriously over-exploited
Total
25.9 11.4 14.6 15.4 32.8 1.1 0.6 8.2 16.1 73.9 47.3 3.7 10.2 3.3 35.6 87.9 12.1 27.9 2.2 8.0 10.3 51.6 100
utilization of deep groundwater is low, the usable amount of deep groundwater includes leakage recharge and lateral runoff recharge, and elastically released water from the deep aquifer has also been taken into consideration under the current exploitation conditions. In some regions, the exploitable amount of groundwater in hidden karst areas has also been taken into consideration. In order to facilitate the appropriate use of planning departments concerned, groundwater resources have been assessed on the basis on county-level administrative units.
2.2. Assessment methods for degree of groundwater overexploitation 2.2.1. Groundwater exploitation potential coefficient method When the exploitation degree is calculated by the groundwater exploitation potential coefficient method, the relation between usable amount of groundwater and current groundwater exploitation is considered (China Geological Survey, 2004). The usable amount of groundwater means the amount of groundwater that can be continuously exploited under certain constrained conditions and that there are no environmentalegeological problems as a result of exploitation. Therefore, the usable amount of groundwater is related to the exploitation scheme and changes with technical and economic development. Based on the calculations of groundwater resources, a zonation assessment for the groundwater exploitation potential coefficient (P) has been conducted in the light of groundwater exploitation in 2003 of each county.
28 28 33 50 77 44 4 145 226 887 103 13 26 11 84 266 42 441 45 204 287 1089 2066
12 23 34 83 157 21 3 153 363 1587 28 10 27 15 332 13 82 75 36 214 462 2158 2945
16 6 2 33 80 22 1 7 138 700 75 3 1 4 249 253 40 366 9 10 175 1069 879
2.37 1.24 0.95 0.60 0.49 2.04 1.38 0.95 0.62 0.56 3.66 1.28 0.95 0.74 0.25 20.06 0.51 5.91 1.27 0.95 0.62 0.50 0.70
6.8 5.3 1.2 23.5 26.5 32.8 3.3 1.5 13.9 15.4 5 2.4 0.4 3.7 21.9 16.5 19 10.9 3.7 1.1 14.2 17.3 7.3
Deep groundwater in Beijing City has not been calculated due to the small extent of its distribution. The total usable amount of deep groundwater in other areas of the North China Plain has been estimated to be 2.066 109 m3/a. The groundwater potential can be graded and assessed based on the exploitation potential coefficient of groundwater (Table 1). Recharge (including lateral recharge and leakage recharge), discharge (including lateral discharge, leakage discharge and artificial exploitation), and storage variation (including elastically released water and released water from clayey soil compaction) were involved in the calculation of the usable amount of deep groundwater. Released water from clayey soil compaction (per year) was obtained from the calculated area of confined water multiplied by the annual average amount of land subsidence within the time period adopted in the calculation.
ð1Þ
2.2.2. Regional over-exploitation based on land subsidence and rate of water table lowering In order to more directly evaluate the environmentalegeological problems caused by groundwater over-exploitation, in accordance with guidelines developed by the Ministry of Water Resources,1 land subsidence and groundwater table data can be used. Namely, in the areas of various amounts of over-exploitation, areas with an annual average lowering of the groundwater table level of >2 m, or areas with an average annual land subsidence of more than 10 mm, are classified as a seriously over-exploited area; areas with no measurable annual average land subsidence or with the annual depression of groundwater table level of
