Qingyong Liu, Baoxiang Zhang, Xin Zhang

Water Conservancy Research Institute of Shandong Province, Jinan，Shandong ,250013,China

Abstract: Several coastal ground water reservoirs have been built since 80’ in 20 century in order to utilization of storm and flood water. Achievements of construction of ground reservoir in Shandong were introduced and the potential of building ground reservoirs in Shandong peninsula as well as advances on ground water reservoir research were analyzed . Problem on environment protection for ground water reservoir was pointed at last.

Key Words: Ground water reservoir , advance , ground dam.

1 Introduction

 

Fig1. Sea Water Intrusion and ground water reservoir distributing drawing in Shandong Peninsula

2 Achievements of Construction of Underground Reservoir in Shandong
        There are 62 monitoring points and stations in the area of reservoir and 13 underground water extraction wells. A pond with a size 150×60×6 m³ is built 10 meter in front of the dam, and the motor pump equipments are also installed. After the construction of the underground reservoir, the water amount in the pond is increased obviously and this helps to concentrate the water extraction. The villages around the reservoir profit a lot from this.

        The water Bureau of Longkou planed and started the early preparation for Huangshuihe reservoir during these research works of Bali shahe river. Since the cooperation with Shandong former university to develop remote sensor for planning the Huangshui River reservoir in 1987, the local water bureau has invested more than 67.32 million Yuan in the past decade. The system of water projects include surface reservoirs at the upper reach, retention at the middle reach and downstream underground reservoir. The model of integrated water management of surface and ground water is realized.

        2.2 Ground water reservoir at Huangshuihe river

        The ground reservoir at Huangshuihe river is situated at the middle and lower reach of the Huangshuihe in the city of Longkou. The north of the reservoir is Bohai. The eastern and west side of the reservoir is hilly. The landform of site of reservoir is flat and open. Eastern and southern parts are higher than the western and northern parts. This landform can be divided into the following five types: tectonic denudation, denudation pile, eroded pile, sea pile and wind formed landform.The ground water reservoir at the Huangshuihe river was completed in 1995 and contains the following projects:

    (1)Ground Water Recharge Project: The aim is to increase the surface runoff, especially the transformation from flood to ground water. Major measures are infiltration trench along the river bed, infiltration ditches, infiltration wells which are connected with aquifer. To determine the recharge amount, ground recharge experiments were done in 1990. Simulations (35h) of the infiltration through infiltration wells and the infiltration combined with artificial recharge wells in the wet season were completed. The steady infiltration capacity was calculated through the simulation. The turbidity of the simulation was similar to the actual state during the flood. The results showed that the infiltration capacity of a single well was 404 m³/d, and that of an artificial recharge well was 76 m³/d. Clay and sandy clay were 2 meters underneath the river bed at the middle and lower reach of the Huangshuihe river. They makes 61% of the whole size of the river bed. This weakens the ability to turn surface water into ground water, therefore 2218 artificial wells, 300 motor drilled infiltration wells, 773 infiltration swales were built. The artificial well and motor drilled infiltration wells, infiltration swales and trenches were combined, in order to promote recharge.

    (2)Surface water storage project: One or several storage dams were built along the river, in order to prolong the hold-up time and the infiltration time and in order to increase the recharge amount and reduce the water amount discharged into the ocean. Four large sized automatic ferro-concrete trap dams were built at Cegao, Ximiao jia, Miaoguo, Huanghe ying along the main river course at the middle and lower reach of the Yellow river. They hold back the runoff with as a step. Ground water will be recharged by the combination of recharge wells. The barrage is a turn over barrage with ten holes. Each hole is 20 m and 2.5 m tall. A lift valve with two holes (2 m long) was installed on the left bank of the river. When the water is 2.6~2.8m deep, the ferro-concrete retention board will automatically turn over and let water flow out. The storage volume of the retention valve is 2795 thousand m³. The cumulated storage volume is 7960 thousand m³.

    (3) Underground barrier project: It is an important part of the rground reservoir. It works with the surface storage dam together. The last storage and ground barrier hold back water resource together. Surface runoff will be hold back within the dam, the sea wave will be stopped outside of the dam, so that the river valley became a site for storing fresh water. An underground retention dam is built 1.2 km away from the beach at the lower reach of the river. The length of the cross-section is 5996 m, the height of the average dam is 26.7m. The largest height is 40.1m, the maximum depth of the dam is 43.4m. The total size of the cross section is 160000 m². This dam has the double function of ground water storage and salt water intrusion. The total volume of the ground reservoir in front of the dam is 53.59 million m³, the maximum regulation volume is 39.29 million m³.

    (4)Water lifting projects: These projects are combined with the infiltration projects and use watergathering gallery and wells to transport water to water supply network by pumps.

    (5)Water supply projects: The extracted groundwater will be transported to the pipe lines or will be used on site. The water will be delivered to users after treatment. Beside the decentral water extraction, there are four central water supply sources: the water source of Longkou power station (22 production wells), urban water supply source (seven pumping wells), water source for thermal power station (four pumping wells) and water source for paper mill (four pumping wells).

    (6)Drainage projects: To prevent the groundwater pollution in the river valley, the waste water in the river valley is drained through a closed network to areas outside for treatment. Water supply industry is developed at the lower reach of the Huangshuihe river. There are many small industries in country towns which cause serious pollution. Therefore, pipeline are installed along the right bank of thehuangshuihe river. The industrial waste water is transported to the sea side and drained after treatment. The total length of the pipelines is 38.6 km, the diameter of the main truck is 0.5m. The drainage is done by gravity. The diameter of the side pipe is 0.35 m. Water in the side pipe is drained through by pressure. The drainage capacity is 3.74 million t/a. This measure reduces the groundwater pollution caused by waste water.

    (7) Monitoring project: Monitoring of the dynamics of the ground water, providing information and using this information for management, decision and control help to achieve the long term steady operation. There are six groups of altogether 12 monitoring holes on both sides of the underground dam. There are 55 monitoring points scattering in the area of the reservoir. Beside monitoring the water level, water samples are taken every two months. Water quality is controlled and that of the important sects of the river course is intensively controlled.

        2.3 Ground water reservoir at Daguhe river in Qingdao city

        Daguhe river with a total length of 179 km is one of the major rivers on Shandong peninsula. The practices of the water extraction during 1982~1989 at Dagu river: to prevent the salt water intrusion at the lower reach of the Dagu river, an underground anti-infiltration wall is installed at the northern part of the underground reservoir. The wall is 3.4 km long and was finished in 1998. Research results showed that the adjusting function of the underground reservoir with artificial infiltration is obviously larger than the case without artificial recharge. The difference between the averages of many years is 26 million m³.

        2.4 Ground Water reservoir at Wanghe river in Laizhou city

        Wanghe river is situated in the north east of Laizhou. The length of Wang river in Laizhou is 50 km, the total area is 326.8 km². The continuous draught since 1977 caused serious salt water intrusion. The intruded area is 250 km², which is 32.7% of the whole area of Laizhou. The ground reservoir project includesground storage wall, artificial recharge and storage project at Guitai in shanshanwa.

        2.5 Ground reservoir at Jiahe river in Yantai city

        Jiahe river with two branches is a major river in Shandong peninsula. The total area of the river valley is 1224 km². The Menlou reservoir is built at the middle reach of the river. Its design volume is 126 million m³. The ground wall with a length of 4030 m was started to be built in 2000. The total length of the project is 4030 m. The volume of the underground reservoir is 205 million m³. The regulation capacity is 60 million m³.

        The main technical parameter of the above mentioned reservoirs is listed in table1.

 

Table 1: Main technical parameter of the main underground reservoirs in Shandong

Name	Area of the river valley (km²)	Total area of the reservoir (km²)	Average thickness of the aquifer (m)	Length of the underground dam (m)	Surface retention project	Total volume of the underground reservoir (104 m³)
Bali sha River at Longkou	47.75	14.7	4-6	756	Barrage dam	42.97
Yellow river at Longkou	1034	51.82	2-5	5996	Barrage dam	5359
Dagu river in Qingdao	4631	421.7	5.19	2600	Rubber dam	38400
Wang river in Qingdao	326.8	70	6-36	West 5608 east: 8520	Barrage dam	5326
Jia river in Yantai	2296	65	5-30	3890	Barrage dam	20500

 

2 The potential of building underground reservoirs on Shandong peninsula

        Building ground reservoir is the major method to adjust the water resources. It has the functions of water supply and environmental protection. Shandong has optimal natural conditions for building ground water reservoirs. There are already systematical technique for the construction.

    2.1 Optimal water resources

        The average precipitation of many years (1956-1998) in Shandong is 756 mm. Apart from water used for surface water, recharged into ground and retained by plants, 4215 million m³ water flows into sea. For example, the average water flowing into sea amounts to 226 million m³. Therefore, the main water resource for the underground reservoir shall be the water flowing into the sea. The alluvial deposit at the lower reach of the river valley and alluvial plain in front of the hills get precipitation, river water and rock groundwater. There is also foreign water for groundwater supplement.

    2.2 Water resource with good quality

        Expect the water at Tangduan shan of Zhulong river, Weifang of Bailang river, Jiutai duan of Wei river, Gejis shan of Lichun river, Tuanwan of dongwu ling river, other rivers at other places have water with good quality which can be used for groundwater recharge.

    2.3 Large storage volume

        Alluvial deposit and alluvial plain in Shandong were formed by many rivers and distributed in large area. Aquifer is thick and the grid is large. The sealing function of the bottom is also good. The conditions for underground storage is optimal. For example, the area of the sand layer formed by alluvial deposit at the middle and lower reach of Dagu river in Qingdao is 293.24 km², the average thickness of the sand layer is 6.16 m, the total volume is 1806 million m³, 309 millions m³ water can be used for storage which almost amounts to the volume of three surface reservoirs with an individual volume of 100 million m³.

    2.4 Optimal infiltration conditions:

        The alluvial layer and the alluvial plain in front of the mountain is influenced by the deposit of the earth. Apart from some parts, the vadose zone is thick, the deposited grid is large and has loose structure. This is positive for infiltration. Especially, aquifer in the alluvial layer in the river valley is covered with sandy clay, and there is passage between river bed and sand layer under the river bed, part of the sand layer is situated on the ground surface. This is easies surface infiltration.

3 Major techniques for the building of ground water reservoir

        The ground reservoir is divided into ground reservoir with and with out ground dyke.

    3.1 Ground water reservoir with ground dyke

        Ground reservoirs with dyke is constituted mainly with runoff regulation system and infiltration system. The retention system includes retention dyke on the river bed and underground dyke. The formal one retains river runoff and infiltrate ground water and also prevent the back sea water. The later retains the ground water flowing to downstream and prevents the underground salt water intrusion. The infiltration system includes the infiltration wells, infiltration trench and infiltration ditches.

        Regulation dyke is normally built on the part of river bed which is relatively steady. The form of the upstream river bed should be straight and regular. The upstream river bed and river bank should be flat and wide. The downstream river bed should not get back storm. To minimize the investment and construction work, the site should be chosen at the narrow sect of the river bed. The rubber dam at Jai river in Yantai with a span of 200 m was built in 1988. 2.5 miliion m³ water can be stored.

        The ground regulation and infiltration dyke is the major part of the ground reservoir. Normally people distinguish between complete ground dyke (the body of dyke goes through the aquifer and reach the top of the imperious layer) from uncomplete ground dyke (the body of the dyke penetrates through the aquifer, but it does not reach the imperious layer). The donwstream at east basin of Shandong peninsula is suitable for complete ground dyke.

        Table 2 lists the underground reservoirs which are designed and constructed by our institute.

Table 2 Ground reservoirs designed and constructed by Shandong water research institute

    3.2 Underground reservoir without dyke

        When the hydraulic slope of aquifer and the pervious property do not meet the requirements for building underground reservoirs with dyke, or although the aquifer is relatively thick, but impossible for building underground dyke to retain undercurrent, it is recommended to build reservoir without dyke. Ground water reservoirs without dyke makes use of the characters of ground water flow which is flat and slow. The water level will be increased through recharging surface water into the ground. Water hills can be formed and water can be easily extracted. Underground storage can be formed even without infiltration and storage dyke. The alluvial plain in form of the hills in Shandong is flat and have thick and widely distributed aquifer. The conditions for ground water run off are poor and secondary. These sects are suitable for building ground reservoirs without dyke. For example, Zhouping area which gets the water form Yellow river, and Guangrao, etc.

        On the whole, the construction of rground reservoirs is possible form the view of techniques and natural conditions. The potential is great. The several ground water reservoir already built have all obvious positive effects.

4 The achievements of the research of ground reservoirs in Shandong province

        The achievements of the project “the techniques of ground reservoirs to regulate ground water and to prevent sea water intrusion” conducted by our institute with the focus on Bali sha river and Huangshuihe river reservoirs are:

                (1) The research on the parameters of the planning for building of ground water reservoir.

                (2) Methods for selection of the thickness of the high pressure jet grouting wall and the distance between the holes .

                (3)Calculation methods of theregulation capacity.

                (4)Research of recharge measures on ground water reservoir.

                (5) Methods for ground wall detective.

                (6) Research of economic benefit calculation

        These results provide valuable scientific and complete data for developing water resources in coastal regions and prevention of sea water intrusion. This project won the third award of national scientific and technology advancement.

        After three years research, in the year of 2003, the project “ Research and demonstration of the models of ground water recharge” of our institute achieved the adavances:

               (1) Techniques for retention and infiltration and the techniques for underground reservoir

               (2) Engineering techniques of surface water storage and recharge for prevention of sea water intrusion in the Wanghe valley in Laizhou.

               (3) The development and use of Wanghe river ground reservoir and recharge engineering

               (4) Underground reservoir engineering and models of operation and management

               (4)Modeling of the Yellow water river underground reservoir

               (5) Real time adjustment and management system of the Wang river underground reservoir based on the GIS system

              (6) The construction and management of underground water without dyke in the area which gets water form the Yellow water river

              (7) Sea water prevention techniques with artificial adjustment of ground water in Guangrao

              (8) Ground water regulation techniques in Zhouping county where gets water from Huanghe river

This project won the third award of the scientific development in Shandong province .

Perspectives of the study and construction on ground reservoirs

        The Huangshuihe river ground reservoir in Longkou greatly eased the drought during 1989~2000. It has a great demonstration value. The Dagu underground reservoir in Qingdao (beginning in 1999) and Jia river underground reservoir in Yantai (beginning in 2000) as well as Wang river underground reservoir in Laizhou will bring great social economic and ecological benefits. It is predicted that more than 50 underground reservoirs can be built in Shandong. The total size of underground reservoirs is 8000 km². The total adjusting volume underground reservoir is 400 million m³. The increased water extraction amount can be 1500 million m³ (almost of the tapping amount of two periods of the eastern line of the South-North water transfer project). It is estimated that the annual economic benefit will be 1515 million yuan. Take apart of the operational costs, the pure benefits is 1399 million yuan per year.

        At present some reservoirs were built and put into operation. However, the pollution of water stored in underground reservoir is obvious, for example the nitrate concentrates rashly. Underground reservoir is a complicated system engineering. Problems about planning and operation must be further studied. The sources of ground water pollution and the cut off hydraulic connections between river courses must be studied by experiments. Besides, the calculation methods of the increased usable water resource retained by underground reservoir, the recovery of the salt water body at the upper reach of the underground dyke, the assessment of the weakness of the ground water in costal region, the pollution and control of nitrate, surface reservoir and ground reservoir in cast region should be researched.

Reference