Shallow groundwater dynamics in North China Plain

Transcription

1 J. Geogr. Sci. (2009) 19: DOI: /s Science in China Press Springer-Verlag Shallow groundwater dynamics in North China Plain WANG Shiqin 1, * SONG Xianfang 1, WANG Qinxue 2, XIAO Guoqiang 3, LIU Changming 1, LIU Jianrong 1 1. Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing , China; 2. National Institute for Environmental Studies, Tsukuba , Japan; 3. Tianjin Institute of Geology and Mineral Resources, Tianjin , China Abstract: The groundwater level of 39 observation wells including 35 unconfined wells and 4 confined wells from 2004 to 2006 in North China Plain (NCP) was monitored using automatic groundwater monitoring data loggers KADEC-MIZU II of Japan. The automatic groundwater sensors were installed for the corporation project between China and Japan. Combined with the monitoring results from 2004 to 2006 with the major factors affecting the dynamic patterns of groundwater, such as topography and landform, depth of groundwater level, exploitation or discharge extent, rivers and lakes, the dynamic regions of NCP groundwater were gotten. According to the dynamic features of groundwater in NCP, six dynamic patterns of groundwater level were identified, including discharge pattern in the piedmont plain, lateral recharge runoff discharge pattern in the piedmont plain, recharge discharge pattern in the central channel zone, precipitation infiltration evaporation pattern in the shallow groundwater region of the central plain, lateral recharge evaporation pattern in the recharge-affected area along the Yellow River and infiltration discharge evaporation pattern in the littoral plain. Based on this, the groundwater fluctuation features of various dynamic patterns were interpreted and the influencing factors of different dynamic patterns were compared. Keywords: North China Plain; shallow groundwater; dynamic region; dynamic feature of groundwater 1 Introduction The North China Plain (NCP) is located in the eastern part of China. The district of North China Plain includes all the plain area of Beijing, Tianjin and Hebei Province and the plain area of Henan and Shandong provinces to the north of the Yellow River, covering a total area of approximately 140,683 km 2. In NCP more and more serious water problems such as continuous decline of water table and worsening of water quality occurred (Liu et al., 2001; Received: Accepted: Foundation: National Natural Sciences Foundation of China, No ; No Author: Wang Shiqin (1981 ), Ph.D., specialized in hydrology and water resources, water cycle of watershed. wangsq.06b@igsnrr.ac.cn * Corresponding author: Song Xianfang, Professor, songxf@igsnrr.ac.cn

2 176 Journal of Geographical Sciences Jia and Liu, 2002). However, the water problems in NCP had a long history. In the 1960s, many reservoirs were built in the west mountain of NCP and drainage rivers were built in the east plain which led to the decline of water storage of NCP and the dry-up of rivers. Because the surface water had been depleted, groundwater began to be pumped. Since the 1970s, groundwater has been used as major water supply for agricultural, industrial and domestic needs because of the dry climate (Figure 1) and decreasing surface water. In NCP, the proportion of groundwater to total water supply had increased from 53.9% in 1997 to 58.9% in 2001 and the increasing rate was 1% per year (Liu, 2003). In recent years many environmental problems including water pollutions, land subsidence, land collapse and soil salinity have become much more serious than ever (Zhang et al., 1997; Fan, 1998; Xia et al., 2004). The natural groundwater flow system has been changed greatly due to over-exploitation of groundwater. In order to develop and utilize groundwater resources reasonably and formulate water managing and protecting policies for government, it is important to conduct research on groundwater resources evaluation and groundwater environmental protection. Groundwater dynamics is the reflection of a complex process of nature influenced by various influencing factors in certain environments (Chen et al., 1988). As a result, it is the basic work and the key point to monitor and research the groundwater dynamics. Figure 1 Trends of annual precipitation of weather stations of Beijing, Tianjin, Cangzhou, Qinhuangdao and Dezhou in NCP (Data are obtained from the China meteorological data sharing service system) The monitoring of the groundwater level in China began in the 1950s (Zhou and Li, 2007). The regional monitoring networks were put in place in the 1970s. These monitoring systems have provided much of the basic data for the evaluation and management of groundwater resources. However, over the long duration of the monitoring system there was incomplete data collected. During this period of time, observation wells were destroyed and the monitoring was infrequent. It did not benefit for monitoring the short trends of the groundwater. As a result the Institute of Geographic Sciences and Natural Resources Research of Chinese Academy of Sciences, National Institute for Environmental Studies of Japan and the Tianjin Institute of Geology and Mineral Resources of China cooperated to monitor the groundwater resources and construct the database of the evaluation of groundwater resources in the Yellow River basin including NCP. The automatic monitoring equipment (KADEC-MIZU II) of Japan was used to monitor the dynamics of groundwater in NCP. It is important to master the feature of groundwater dynamics and to resolve the key technical problems in the proc-

3 WANG Shiqin et al.: Shallow groundwater dynamics in North China Plain 177 ess of the groundwater resources evaluation. In this paper the data of shallow groundwater level in NCP were selected to research the dynamics of groundwater. The major influencing factors were considered to plot out the dynamic subregions of different patterns and the features of different regions were discussed in detail. 2 The study area and monitoring of groundwater level 2.1 Introduction of North China Plain The NCP reaches the Bohai Bay in the east and the Taihang Mountain in the west, lying between E and N. The northern boundary of the plain is the Yanshan Mountain and it reaches the Yellow River in the south. The landform is a typically plain landscape and the elevation is less than 100 m. Topography inclines from north, west and southwest to the Bohai Bay. The slope gradient is in the piedmont plain and in the coastal plain. From the foot of the mountains to the Bohai Bay, it can be divided into the alluvial flood plain of the western part, flood and lake sedimentary plain of middle part and the alluvial coast plain of the eastern part (Figure 2). Figure 2 Location of groundwater monitoring wells in NCP

4 178 Journal of Geographical Sciences The climate of NCP belongs to the continental climate. The perennial mean precipitation is about mm (Figure 3). The proportion of precipitation from June to September to precipitation of the full year is about 80%. And the transpiration is about mm. The proportion of evaporation from April to June to evaporation of the full year is about 45%. In this study area there are Haihe River catchment, Luan River catchment and Yellow River catchment (Figure 3). 2.2 Monitoring of groundwater level There are 39 observation wells which were selected from the end of 2003 to July 2004 when considering various Figure 3 Annual mean precipitation and rivers in NCP factors including the position in NCP or convenience of management and data collection (Figure 2 and Table 1). Of those wells two wells (No.29 and No.30) are located in the mountain areas in the Chongling experimental basin of Chinese Academy of Sciences (CAS) for researching the lateral recharge from mountain area to plain area. Others lie in the plain area of NCP. Except for wells of No.2, No.6, No.23 and No.25 which are used to monitor the confined aquifer, other wells are used to monitor the unconfined aquifer. These wells are used to collect and control data for research on the different groundwater problems: to control the leakage from surface water to groundwater; to control the lateral recharge from mountain area to plain area; to control the major groundwater cone; to control the seawater intrusion in the marine area; and to control Table 1 Information of groundwater monitoring wells in NCP Position of the monitoring wells No. District Position Longitude ( ) Latitude ( ) Type of aquifer Elevation (m) Well depth (m) Well diameter (cm) 1 Dahongmen, Fengtai District Unconfined Dahongmen, Fengtai District Confined The 4th water resources field Unconfined Shuguang Garden, Haidian Dsitrict Unconfined Banbi Dian, Daxing District Unconfined Banbi Dian, Daxing District Confined * South Mofang, Chaoyang District Unconfined Beijing

5 WANG Shiqin et al.: Shallow groundwater dynamics in North China Plain 179 Position of the monitoring wells No. Region Position Longitude ( ) Latitude ( ) Type of aquifer 8* 9* 10 South Mofang, Chaoyang District South Mofang, Chaoyang District Daheng Village, Jixian County Elevation (m) Well depth (m) Unconfined Unconfined Unconfined Wangbuzhuang, Baodi District Unconfined Daxin Station, Ninghe County Unconfined Cement Factory, Hangu District Unconfined Tianjin 14 Xiaobeibu County, Handan City Unconfined * Congtai Garden, Handan City Unconfined 16 Renxian County, Xingtai City Unconfined Shimen Garden, Shijiazhuang Unconfined Well diameter (cm) 18* Jiansheng Road, Shijiazhuang Unconfined Nanqi Village, Baoding Unconfined Biology Pharmacy Factory, Baoding Unconfined Xiaoxi Village, Baoding Unconfined The 1st group of Langfang Unconfined The 2nd group of Langfang Confined The 2nd group of Tangshan Unconfined The 3rd group of Tangshan Confined # Funing County, Qinhuangdao Unconfined Canghzou Experiment Site Unconfined Hengshui Experiment Site Unconfined 20.0 Hebei 29 Guoyuan, Chongling Basin, Yixian County Unconfined Yangshugou, Chongling Basin, Yixian County Unconfined Nayaogu Village, Huixian County Unconfined Songzhuang Village, Yanjin County Unconfined Laodianji, Huaxian County Unconfined Datun Village, Qingfeng County Unconfined No.203, Dezhou Unconfined Henan 36 No.805, Chengguan, Qihe County Unconfined Binzhou City Unconfined Shandong Lijin County, Dongying City Unconfined Liaocheng City Unconfined Note: Observation equipments were destroyed and monitoring was stopped later in wells with * upright (7, 8, 9, 15, 18); Observation equipments were newly set up and the data series were shot in wells with # upright (26); Others have been monitored for a long time.

6 180 Journal of Geographical Sciences the relationship between salinization and groundwater level in the saline areas. The KADEC-MIZU II groundwater monitoring data loggers were provided by National Institute for Environmental Studies of Japan to monitor the groundwater level. The monitoring frequency is 30 minutes or 1 hour. 3 Influencing factors of groundwater dynamics and dynamics subregion 3.1 Influencing factors of groundwater dynamics The influencing factors of groundwater dynamics can be divided into two types: One is caused by the change of water quantity of aquifer such as precipitation, evaporation, artificial discharge, river infiltration and irrigation infiltration. Another is caused by the change of aquifer stress such as the change of atmospheric pressure, the gravitation change of sun and moon, astronomical tide and earthquake (Godin, 1972; Shih, 2003; Dong et al., 2007). Except for the discharge of deep aquifer, the first type of influencing factors mainly affect the shallow groundwater and the groundwater level dynamics can reflect the influencing factors which are controlled by the topography and landform, rock property, depth of groundwater and hydrogeologic condition of aquifer. The confined aquifer is sensitive to the second type of influencing factors which can be analyzed by the high frequency groundwater level data and can be explained by the micro-dynamics feature (Bras and Rodrigues, 1985; Huang, 1983; Yang et al., 2005). In this paper only the macro-dynamics of groundwater were discussed. 3.2 Subregion of groundwater macro-dynamics The various factors which influence the groundwater dynamics were analyzed. The differences of geologic and hydrogeologic condition in NCP are large. As a result many factors can influence groundwater dynamics. What s more, these factors can interplay with each other, hence make the research of groundwater dynamics complex. For example, the factors of topography and landform, groundwater depth, rock property, storage of aquifer, river and lake were considered in this paper. The software of Arcview GIS 3.3 was used to overlap the subareas of these factors. There are 376 subregions which were got altogether. If more conditions were considered to plot the subregion plot of groundwater dynamics (Zhou and Li, 2007; Dong et al., 2007), the subregions would greatly exceed 376. Though the subregions can be obtained in detail, it would be more complex for our research because the groundwater data loggers were limited. In this paper the major factors which have large differences in the regional distribution were selected and overlapped to get the subregion plot which was referred as the base map to analyze the groundwater dynamics. These factors which can result in the obvious differences of groundwater dynamics include: Topography and landform condition which influence the runoff and recharge (Figure 2), groundwater depth which influence the infiltration and evaporation (Figure 4), discharge potential expressed by yield modulus and groundwater cone (Figure 5, in this figure, the shortname of Ning Bo Long groundwater cone refers to Ningjin Boxiang Longrao.), rivers and lakes (Figure 2). Each influencing factor was divided into different subareas and the score was given for each subarea with the expert scoring method (Huang, 1983), where different score delegates the different extents which influence the groundwater dynamics (Table 2). For example the score 1 means that it has large

7 WANG Shiqin et al.: Shallow groundwater dynamics in North China Plain 181 effects on the groundwater dynamics, the influence extent of score 2 is smaller than score 1 and the influence of score 3 is the smallest. The subareas of different factors were overlapped using Arcview GIS 3.3 software. Thus the overlapped subregion plot of the influencing factors of groundwater was got (Figure 6). Each subregion of Figure 6 delegates the in- Figure 4 Groundwater depth of NCP Figure 5 Groundwater yield modulus of NCP Figure 6 Subregion of dynamic patterns of groundwater in NCP

8 182 Journal of Geographical Sciences tegrated influencing factors. Combining the position of the monitoring wells with the time series of groundwater dynamics feature, six regional patterns of groundwater dynamics were obtained including discharge pattern in the piedmont plain (a), lateral recharge runoff discharge pattern in the piedmont plain (b), recharge discharge pattern in the central channel zone (c), precipitation infiltration evaporation pattern in the shallow groundwater region of the central plain (d), precipitation and river recharge evaporation pattern in the recharge-affected area along the Yellow River (e) and infiltration discharge evaporation pattern in the littoral plain (f) (Figure 6). Especially, the subregion (a) lies in the piedmont area inside the subregion (b). It is near to the city or town such as Beijing, Baoding and Shijiazhuang where the groundwater exploitation of industrial and agriculture is great. The groundwater dynamics of each observation well was affected by the actual discharge conditions to a large extent. For example, the groundwater of No.19 well, which lies in the Nanqi village of Baoding city, was recharged Table 2 Dynamic pattern subregions of groundwater and their effects on the dynamic change of groundwater in NCP Factors Subarea division Score Characteristics of regional hydrogeologic conditions Topography and landforms Depth of groundwater Discharge or exploitation degree Rivers Piedmont alluvial and flood plain (alluvial and flood fan, pluvial fan and internal terrace) Central alluvial and lake plain (alluvial plain) Eastern alluvial and littoral plain (alluvial plain and littoral plain) Depth of groundwater < 4 m 1 4 m < depth of groundwater <10 m) Depth of groundwater >10 m 3 Strong discharge (yield modulus > 30) Middle (10 < yield modulus < 30) Weak discharge or no discharge (0 < yield modulus < 10 or =0) Channel zone from upstream to downstream From channel zone to interchannel zone or depression Hydraulic gradient: , transmissibility: m 2 /d; grain of unsaturated and saturated zone is coarse in the piedmont plain and the thickness is large which is benefit for the precipitation infiltration and river leakage. Hydraulic gradient: , transmissibility: m 2 /d; grain of aquifer is coarse in the piedmont plain and became fine from east to west; runoff condition becomes weaker. Hydraulic gradient: , transmissibility: <50 m 2 /d; grain of aquifer is fine with silt sand, clay and silt interlay; runoff condition is the weakest. Strong evapotranspiration effect; sensitive response of groundwater level to precipiatation. Evaporation effect can be neglected except for the small porosity of clayed soil or clay; recharge rate of precipitation to groundwater is small. Evapotranspiration effect is very small or no evapotranspiration effect exists; lag time of precipitation recharging groundwater is long and it is related with the rock property of unsaturated zone. Exploitation leads to the decline of groundwater which makes the evaporation less and the infiltration recharge increased; Exploitation can affect the decline of groundwater obviously. The dynamics of water table has no relationship with the exploitation. From upstream to downstream of the channel the runoff intensity becomes weaker. Aquifer of channel is mainly composed of gravels and coarse sands with good permeability; the groundwater can be recharged by the surface water easily; transmissibility of aquifer is good; sands of aquifer in the channel zone become fine sands and clayed soil to the interchannel zone of depression.

9 WANG Shiqin et al.: Shallow groundwater dynamics in North China Plain 183 by the lateral runoff from piedmont area. So the range of groundwater level was large in each year. However, the water level declined continuously for several years. That is why the boundary between subregion (a) and subregion (b) was not made. 4 Groundwater dynamics in NCP According to the dynamic subregions of groundwater above, the position of the monitoring wells was considered. And the daily average value of groundwater level was calculated to analyze the feature of groundwater dynamics. Some typical observation wells were selected to discuss the dynamics of different dynamic patterns. 4.1 Discharge pattern in the piedmont plain The wells lie in the regions where the groundwater was greatly exploited. They are located close to cities or towns such as Beijing, Baoding and Shijiazhuang where the water use for industry and agriculture is large. Water level in these wells declined slowly and continuously. The effect of the precipitation was not obvious, that is, the water table did not increase in the rainy season and it did increase just during February and March when the exploitation was little. Of these wells shallow wells (No.1 in Beijing) declined to dry in For example, the water table decline rate of No.3 and No.5 wells near to Beijing groundwater cone from 1 January 2004 to 21 December 2006 are 0.58 m/a and 0.64 m/a respectively. Variance and variation coefficient of water table are small (Table 3). Besides these wells, some wells were recharged by the lateral recharge from the mountain area because of the large exploitation in the piedmont plain. Water table fluctuated greatly and declined continuously such as No. 19 in Baoding (Figure 7a). The groundwater dynamics is discharge pattern. 4.2 Lateral recharge runoff discharge pattern in the piedmont Wells lie in the alluvial and flood fan and plain of the piedmont where the slope is large and the permeability condition of aquifer is good. The water table from May to June each year was the lowest. The abundant precipitation in July and August infiltrated and recharged groundwater quickly which led to the abrupt increase of water table. The high water table can last until into March or April of the next year due to the good runoff condition in the piedmont plain. The range and variation of water table are large. For example, the range and variation of well No.32 in Henan province are 7.56 m and 4.51 respectively. The groundwater level of No.24 and No.25 in Tangshan city lie in the alluvial and flood fan of the Yanshan mountain front with strong permeability of aquifer, the deep depth of groundwater and the high discharge fluctuated greatly. Since some error with the data of shallow groundwater level, the groundwater level of confined aquifer at this site was selected to study the fluctuation of groundwater. The dynamic feature of groundwater level is similar to that of other shallow groundwater, which shows that the shallow and deep aquifers are all recharged by lateral recharge from mountain areas. The groundwater level fluctuated with large variation. However, the variation coefficient is different in different wells because of the different slopes or landforms (Table 3).

10 184 Journal of Geographical Sciences Table 3 Table of statistic parameters of the shallow groundwater monitoring wells in NCP Subregion No. Observation time (d) Range (m) Min. (m) Max. (m) Mean (m) Variance Variation coefficient a b c d e f >2.61 < Note: The groundwater of mountain area, the confined groundwater of the plain area (except No.25) and some equipment-broken wells were not listed here. The groundwater dynamics is lateral recharge runoff discharge pattern (Figure 7b). 4.3 Recharge discharge pattern in the channel zone of the central plain Wells lie in the channel zone of alluvial and flood plain in the central plain where the ancient Yellow River channel is distributed. The ancient channel is composed of sands of various size fractions with large porosity and good permeability, runoff and discharge conditions (Wu and Zhao, 1993; Wu et al., 1996). The obvious seasonal change of groundwater level existed. The lowest water table from March to June or July was caused by the pumping for spring irrigation. During that time the water table decreased obviously due to pumpage

11 WANG Shiqin et al.: Shallow groundwater dynamics in North China Plain 185 Figure 7 Curves of groundwater level in discharge pattern in the piedmont plain (a), lateral recharge runoff discharge pattern in the piedmont plain (b), recharge discharge pattern in the channel zone of the central plain (c), precipitation infiltration evaporation pattern in the shallow groundwater region of the central plain (d), precipitation and river recharge evaporation pattern in the recharge-affected area along the Yellow River (e) and infiltration discharge evaporation pattern in the littoral plain (f).

12 186 Journal of Geographical Sciences and recovered to increase after the irrigation due to the effect of return infiltration and recharge. The exploitation decreased after June or July so that the water table increased continuously until stabilized in February or March of the next year. For example, the fluctuation of water table of No.33 and No.34 of Henan province is similar, however, the difference of variance is very large. It means that the fluctuation of groundwater is not only related with the discharge and irrigation but also related with the aquifer property of the local river channel. The variation coefficient is small (Table 3). The groundwater dynamics is irrigation return and precipitation infiltration recharge discharge pattern (Figure 7c). 4.4 Precipitation infiltration evaporation pattern in the shallow groundwater region of the central plain Wells lie in the shallow groundwater region of the central alluvial and flood plain where saline water distribution is common and groundwater development degree is low. As a result, both the precipitation infiltration and evaporation influence groundwater dynamics. The lowest water table was in the dry season with strong evaporation and less precipitation. During spring and early summer, the water table increases rapidly due to recharge by precipitation. For example, the water table of well No.27 in Cangzhou City is the lowest in June or July each year and increases to the highest in August or September because of the precipitation recharge. The response of water table to the precipitation was sensitive. For example, the 109 mm rain on 30 July 2005 and the rain in later days made the groundwater increase up to 7.62 m. After which the water table decreased to 3.25 m by the end of May due to the dry weather. The water table of No.27 showed the decline trends during the three monitoring years which might be related with the enlargement of the deep groundwater cone areas. Similarly, groundwater fluctuation of well No.28 in Hengshui City had a close relationship with the change of precipitation. The water table in summer increased with the precipitation recharge and decreased to the lowest value in winter and spring of next year without precipitation but the largest evaporation. The range and variance of groundwater in Cangzhou are larger than that of Hengshui (Table 3). It is caused by the different properties of vadose zone. The soil of Cangzhou is composed of sand loam and silt loam, however, the soil of Hengshui is composed of sand loam. As a result, the infiltration rate at Hengshui observation site is larger than that in Cangzhou. The groundwater dynamics is precipitation infiltration evaporation pattern (Figure 7d). 4.5 Precipitation and river recharge evaporation pattern in the recharge-affected area along the Yellow River Wells lie in the recharge-affected area along the Yellow River. Because of the high water level of the Yellow River the surface water recharged groundwater and the water table changed with the surface water level. The water table of wells No.36 and No.37 near to the river with good permeability is low from March to May each year and fluctuates with the recharge of irrigation return of agriculture. During the flood season the water table showed the feature of abrupt increase and slow decrease. The ranges of wells No.36 and No.37 are 1.90 m and 0.92 m respectively with small variance and the variation coefficient. Figure 7e shows the recharge relationship between the river level of Luokou site and the groundwater

13 WANG Shiqin et al.: Shallow groundwater dynamics in North China Plain 187 level of No.36 and No.37. The groundwater dynamics is the precipitation infiltration and the Yellow River lateral recharge evaporation pattern Figure 7e. 4.6 Infiltration discharge evaporation pattern in the littoral plain area Large area of saline water is distributed in littoral plain where the degree of groundwater exploitation is low, even there is no development in some regions. The precipitation can recharge to groundwater quickly and the evaporation effect is strong because of shallow water table. Also the sea water may intrude to recharge the groundwater. So many factors might influence the dynamics of groundwater and it did not display obvious regular change in the limited observation wells. The variance and the variation coefficient are large. For example, the water table of well No.12 in Ninghe County of Tianjin City increased greatly after June 2004 which might be related with the precipitation recharge of summer. However, there were no obvious changes in 2005 which might be related with the countermeasure of restriction of exploitation. The reason was not analyzed for this paper because of lack of data. The groundwater dynamics is infiltration discharge evaporation pattern or the infiltration evaporation pattern (Figure 7f). 5 Conclusions The groundwater dynamics of NCP is influenced by the climate, geology, hydrology, hydrogeology and human activities etc. The regional dynamics of groundwater is in accordance with the water budget. As a whole, the groundwater dynamics displayed the infiltration runoff discharge pattern or the infiltration evaporation pattern. The major influencing factors are considered including the discharge, infiltration, runoff and evaporation conditions. So the subarea plots of topography and landform, groundwater depth, exploitation or discharge degree of groundwater, rivers, lakes and groundwater cone were selected to overlap using the Arcview GIS 3.3 software. Combing the synthesized plot of subregions with the position and the dynamic feature of the 39 observation wells in the research field, six regional patterns of groundwater dynamics were obtained, including discharge pattern in the piedmont plain, lateral recharge runoff discharge pattern in the piedmont plain, recharge discharge pattern in the central channel zone, precipitation infiltration evaporation pattern in the shallow groundwater region of the central plain, precipitation and river recharge evaporation pattern in the recharge-affected area along the Yellow River recharge, and infiltration discharge evaporation pattern in the littoral plain. Though the change of groundwater is similar in different regions, some obvious difference existed in the dynamics of different regions. As a result, to analyze the dynamic feature of different regions is very important to understand the evolution principle of groundwater resources from a large regional view. This work focused on the dynamic subregions from a large regional scale and the delegation was insufficient. That is why it is important to do more work on the groundwater monitoring. More monitoring wells will need to be set up to explain the dynamic feature from special and temporal scale in detail. To divide the subregion plot major conditions were considered without the rock property of vadose zone or aquifer and land use. These conditions will be considered in future research.

14 188 Journal of Geographical Sciences Acknowledgements The authors would like to thank Dr. Li Fadong of Chiba University of Japan for his help on setting the monitoring instruments at the experimental sites, thank Dr. Wang Zhiming, Mr. Liu Xin and Mr. Hou Shibin of Institute of Geographic Sciences and Natural Resources Research, CAS, who helped us collect the data, and thank the relevant institutions and persons in Beijing, Tianjin, Hebei Province, Shandong Province and Henan Province for providing data and help to this work. The authors would also like to thank Richard Graham from America who helped to check the English writing of this paper. References Bras R L, Rodriguez Iturbe I, Random Functions and Hydrology. Reading, Massachusetts: Addison Wesley. Chen Baoren, Hong Zaiji, Wang Fu et al., Groundwater Dynamic and Prediction. Beijing: Science Press, 382. (in Chinese) Dong Dianwei, Lin Pei, Yan Ying et al., Optimum design of groundwater level monitoring network of Beijing Plain. Hydrogeology and Engineering Geology, 34(1): (in Chinese) Fan Pengfei, Groundwater evolution and prediction in North China Plain. Acta Geographica Sinica, Bulletin of the Chinese Academy of Geological Sciences, 19(4): (in Chinese) Godin G, The Analysis of Tides. University of Toronto Press, Groundwater Research Group of Scientific Research Section, State Seismological Bureau. Identification of main disturbance factors for groundwater level and extraction of seismic information. Seismology and Geology, 5(4): (in Chinese) Huang Zhongshu, Spectrum Analysis Method and Its Application in Hydrology and Meteorology. Beijing: China Meteorological Press, (in Chinese) Jia Jinsheng, Liu Changming, Groundwater dynamic drift and response to different exploitation in the North China Plain: A case study of Luancheng County, Hebei Province. Acta Geographica Sinica, 57(2): (in Chinese) Liu Changming, Exploring an ecological benefit of South to North Transfers for rehabilitating groundwater systems in the North China Plain. South to North Water Transfers and Water Science & Technology, (1): (in Chinese) Liu Changming, Yu Jingjie, Kendy E, Groundwater exploitation and its impact on the environment in the North China Plain. Water Int., 26: (in Chinese) National Land Resources Survey Report, The sustainable development of groundwater in North China Plain, 10. Shih D C F, Lee C D, Chiou K F et al., Spectral analysis of tidal fluctuations in groundwater level. J. Amer. Water Resource Association, 6(5): Wu Cheng, Ma Yonghong, Zhang Xiuqing, Palaeochannel and palaeodrainage patterns in the North China Mountains. Geographical Research, 15(3): (in Chinese) Wu Cheng, Zhao Mingxuan, On explanation and utilization of ancient channel resources and relevant politics. Resources Development and Conservation, 9(1): (in Chinese) Xia Jun, Liu Mingyu, Jia Shaofeng et al., Water security problem and research perspective in North China. Journal of Natural Resources, 19(5): (in Chinese) Yang Zhongping, Lu Wenxi, Li Ping, Application of time-series model to predict groundwater regime. Journal of Hydraulic Engineering, 36(12): (in Chinese) Zhang Zonghu, Shi Dehong, Shen Zhaoli et a1., Evolution and development of groundwater environment in North China Plain under human activities. Acta Geoscientia Sinica: Bulletin of the Chinese Academy of Geological Sciences, 18(4): Zhou Yangxiao, Li Wenpeng, Design of regional groundwater level monitoring networks. Hydrogeology and Engineering Geology, 34(1): 1 9. (in Chinese) Zhu Shibin, Zhang Fengxiao, The application of investigation and expert marking method in risk assessment. Shanxi Architecture, 32(22): (in Chinese)