自然資源部巖巖溶動力學重點實驗室

Part IV Environmental Problems and Rehabilitation of karst

1999-07-10KDL 1747

Part IV??? Environmental Problems and Rehabilitation of karst

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Road Construction Plan in the Kamenca Valley ,Slovenia

Andrej Seliskar (Natural History Society of Slovenia)

The Kamenca valley, the most southern glacially shaped valley in Slovenia near the border with Italy is endangered by a project planning construction of a new road on the northern very steep slope of the valley between the Volce village in the Soca valley and the Solarji pass on the border with Italy.

NATURAL CHARACTERISTICS

The Kamenca valley is a typical glacially shaped valley which has developed in the south-eastern part of the Kolovrat pre-alpine massif.

The basic form was made by the Soca glacier some 25.000 years ago. At that time, the glacier ablation went far southwards and the Kamenca valley is the most southern Slovene glacial valley and lies at the lowest altitude. Due to the geomorphologic processes the bottom of the valley is very dissected. It lies at the altitudes between 220 meters and 550 meters, while the rim ranges between 300 meters and 1115 meters above sea level. The Kamenca brook has cut its bed into glacial sediments, screes and hard bedrock. The water flows over the grey layers of 'volcanski ploscati apnenec' (flat limestone of Volce), differently coloured sandstones, rockfalls and other rock formations. Small waterfalls, rapids, pools and other hydrologic phenomena in the colourful brook-bed, abundant vegetation and numerous animal species are the most important components of the rich natural environment.

The whole valley and the Kamenca brook are still very natural. There is hardly any disturbance resulting from human activities. The slopes and the valley bottom are mostly covered by woods, only the pastures around the abandoned Kamenca farmstead are grazed about four to five months per year.

The whole valley is listed as a natural heritage site of exceptional importance for the Republic of Slovenia. Since 1986, the valley and the brook are inccluded in the inventory of th 'Obcina Tolmin' (the Commune of Tolmin), which was prepared for the needs of the long-term land-use/regional plan.

PROJECT

The construction of a new road on the northern extremely steep slope of the valley would cause an enormous interference with the natural environment, destroy the ecological balance which is hard to maintain in these harsh conditions and represent a considerable encroachment upon the Slovenian natural heritage.

The consequences of the construction works, which would completely change the slope by digging and depositing the bedrock material, would destroy the present natural landscape in the upper and middle parts of the valley. This degradation could have been softened by extremely expensive reconstruction of the slopes, but the biological and landscape values would have been lost for good. The fact is that the slopes are too steep, differences between the altitudes too big and the distance too short to enable establishment of any effective reconstruction.

In such a small glacially shaped valley the planned construction simply could not be carried out. The road would cause additional impacts and new pressures on the natural environment.

In spite of the strong opposition of the institutions for conservation of nature and natural heritage the Council of the Commune of Tolmin has approved changes to the communal land-use plan in order to carry out the project. The prepared project documentation has not been approved and the location permission twice refused, because it has been incomplete and the comprehensive EIA has never been done. Yet, all the professional arguments could not stop the political decisions. This project will cost over a million ECU and it is co-financed by the EU funds. The professional and non-governmental organisations for conservation of nature and natural heritage understand that at this point only international pressure on the investors, i.e. the Slovenian Ministry of Economic Relations and Development and the EU Commission who allocated an enormous amount of money through PHARE, could stop this destructive investment.

The construction of new road at the Kamenca valley would be an expensive mistake, because there is an existing road between the Volce village and the Solarji pass going through the settlement of Volcanski Ruti. This road is in bad condition and due to this and other reasons, the area along the border is increasingly being depopulated. Reconstruction of this road (a few kms longer than the planned one) would be a more reasonable and better solution for reaching the Solarji pass on the border with Italy and additionally, also for improving the living conditions on this depopulated border area. And consequently, this alternative maintains the natural heritage of the Kamenca valley which is an important objective in safeguarding the Slovenian biological and landscape diversity.

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LUOTA, AN EXAMPLE OF SUCCESS IN
REHABILITATION OF A
ROCK-DESERTIFIED KARSTLAND

Rock desertification is a serious ecological geological problem in the broad karst area of southwest China, which covers about 540,000 km2. It brings about poverty to local people. The rehabilitation of such poor region is one of the major target in China’s ?Jà Agenda 21?J?, and a part of the governmental drive to develop middle-west part of the country.

During 1978-1982, a research group of the Institute of Karst Geology, Chinese Academy of Geological Sciences went to a typical site of rock desertification, the Luota township of Longshan county, Hunan province (Fig.1) to carry out karst hydrogeological survey, and look for rehabilitation measures. The township had a population of about 10 thousand living under the state poverty line. It covers 119.07 km2?underlain by Permian and Triassic carbonate rocks. The area is on the transitional slope zone between Guizhou plateau (1200m asl in general) and Hunan Basin( 100m asl in general), and characterized by multi-level plateaus dissected by deep gorges. There are 737 hectares of terraced farmland scattered on slopes 1000m-600m asl, which suffered from drought because of leakage in the underlying intensively karstified carbonate rocks, even though there are remarkable rainfall of about 1400mm annually.

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Fig.1, The location of Luota township

Through systematic geological and hydrogeological mapping, caving, tracing test, hydrological and meteorological monitoring works, 51 underground streams larger or smaller with a total length of 82 km were identified. The total karst water resources are estimated to be 120 million m3/a. Moreover, the area is found to be rich in coal, limestone and hydropower resources. The latter is also related to karst underground streams.

The rehabilitation works in the past 15 years turned out to be successful. It started from re-arrangement of land use, i.e, plantation on the slope above 1000m asl (Fig.2) for ecological rehabilitation, and building reservoirs in dolines(Fig.3) in this zone for irrigating the terraced ricefield below 1000m asl. The harvest from the ricefield grows up remarkably after the irrigation system putting into use, and provides food for local peopple more than enough. After irrigation use, the water returns to the underground stream again in a lower level. There, the hydraulic gradience is still high, and hydropower station was built to provide electricity not only for their own use , but also for neighbouring township and making money. Besides, Luota people take the advantages of their coal and limestone resources to develop cement and coal industry. On plateaus with different elevations, fruits and some herb medicines(such as Eucommia Ulmoides) are planted in accordance with the local climate and soil conditions.
The comprehensive developments have not only helped Luota people overcoming proverty problems, but also changed Luota’s ecological system into a more rational cycle.

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Fig.2, Aqueduct on 1000m asl, Luota,Hunan, above it is the plantation and?
doline-reservoir building zone, below it is the terraced farmland

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Fig.3, The Baxiandong doline-reservoir constructed by damming a swallet?
hole, showing low water level in dry season. The water is conducted into
the aqueduct in Fig.2 through a natural underground course

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A KARST GEOLOGICAL HAZARD INCIDENT OF
NOV.11,1997 IN ZHEMU VILLAGE, GUILIN

A new case of karst collapse ( or called as sinkhole in USA) happened 11:50, Nov.11, 1997 in Zhemu village on the west bank of Lijiang River, and 10km southeast of downtown Guilin, the well-known scenic city in South China’s Guangxi province.

The incident was considered to be related to engineering works carrying out on the Lijiang River, whcih was aimed at improving navigation channel for tourism boats. However, no problem had happened since the engineering work started on Nov.9 until the incident took place. It is said that 15 dynamite explosions had already been made before the collapse, but the amount of dynamite used for each explosion was limited under 2 kg.

On Nov.11,11:30, a stronger explosion was made with more dynamite (Fig.1).

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Fig.1, The distribution of collapse pits around Zhemu village ,Guilin


Anyway, it was only 12.8 kg, but disastrous problems followed : on 11:50, namely, 20 minutes after the explosion, a NW oriented collapse 10m long, 2-3m deep took place 25 m away northwest from the explosion point( point 1 in Fig.1, and Fig.2). It was dry at first, but inundated on 16:00pm. Soon after the No.1 collapse, a "geyser" with a mixture of sand, mud, and water bursted out in the living room of a farmer’s house(Fig.1,point 2), and then the room was subsided. A new house under construction in the village was destroyed by another collapse(Point 3 in Fig.1, and Fig.3). Until Nov.13, the far most collapse took place 500m away to the northwest of the explosion point. A spring with mudy water was found flowing out under Lijiang River near the explosion point(point 4 in Fig.1). No casualty was reported because the incident was taking place in daytime. Investigation and remedation measures are still under way.

Fig.2, A big karst collapse pit on the sand beach, with the engineering?
explosion point near the boat on the background(No.1 point in Fig.1)

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Fig.3, A new house under construction was destroyed (point 3 in Fig.1)

In a Sino-US Workshop on "Natural Disaster Mitigation and Remedation" (Nov.19-21,1997, Diaoyutai Hotel,Beijing), Yuan Daoxian reported this incident and brought about hot discussions. It was believed that the engineering explosion had activated an underground stream, and a sort of resonance process happened in the underground karst course to make the incident lasting a longer time. According to previous similar experience in other region, the process may last as long as 5 months.

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Lesson from 1998 Flood on Yangtze River:
Karst Engineering Problem Emphasized

In view of the serious flood of 1998 Summer on Yangtze River and Songhuajiang River, especially several accidents of embankment breach, the Ministry of Land and Resources(MLR) has called on attention to the engineering geological problems of dyke foundation. It is recalled in a recent circular of the Ministry that since 1950's,86 events of collapses totalling 22.2km have happened on the dyke along the Yangtze River in its section of Jiangxi Province. One of the most important causes of the collapses is that parts of the embankments are underlain by covered karst with caves and soil cavities well-developed. According to geological survey, covered karst shares more than 80km out of the 152km along the Southern bank of Yangtze River in Jiangxi Province. Shallow karsts are intensively developed in the Jiujiang section of the major dyke of Yangtze River. Karst caves are hitted in all the 10 preliminary exploration boreholes. Three caves with total length of 10.32m are encountered in each borehole in average. The biggest cave under the dyke as revealed by exploration works is 13.63m high. The MLR will take immediate action for an overall engineering geological survey on the foundation of dykes along the Yangtze, Yellow and other major rivers in China. Emphasis will be to make clear the distribution of caves and soil cavities that may underly dykes in the section of covered karst. Engineering countermeasures will be taken immediately to ensure the dyke no danger of anything going wrong.

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Karst Waters Help Resolving Drought
in Northwest China’s Arid Region

Major breakthrough have achieved in finding deep buried karst water in a Northwest China’s Special Program of Groundwater Resources. The Program started two years ago was carried out by the former Ministry of Geology and is now succeeded by the Ministry of Land and Resources. It is supported directly by the State Council.

The findings are at the eastern part of Northwest China’s Arid Region. It is in the neighbouring areas of Ningxia, Nei Mongol , Shaanxi, Gansu Provinces (or Autonomous Regions), and characterized by extensive Loess cover hundreds meters thick (Fig.1). It is thus called as Loess Plateau covering some 200,000 km2, and is the broadest of this kind of landscape in the world. In the north of the Great Wall, there is a 20,000 km2?Mu Us Desert. Geotectonically, it is underlain by the Ordos platform, where Lower Paleozoic carbonate rocks (Cambrian and Ordovician) are overlain disconformably by Permo-Carboniferous Coal measures , followed by Mesozoic Red Beds, Neogene Red Clay and Quaternary loess. The paleokarst on the surface of lower Paleozoic carbonate rocks is one of the most important natural gas reservoirs in China .

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Fig.1 Location of exploration wells with high yield karst water

The southern part of the Loess Plateau is bordered by the active Wei River Graben, where geothermal springs are often seen, and frequented by earthquake. The Wei River Plain is the cradle of ancient China’s culture, with its Xian city as the historical capital of many Dynasties.

The Loess Plateau has long suffered from water shortage because of low annual rainfall ranging between 500mm at South (Xian) and less than 200mm at the North (Mu Us Desert), and bad water quality of shallow aquifers.

The first breakthrough happened in early 1997, when the Y1?exploration well completed in Fuping County at the southern part of the Loess Plateau(Fig.1). It is 778m deep, but 200m are in Loess, with an addition of 300m in Neogene clay and gravel. 238m of the lower part in the well are in Ordovician Limestone Karst Aquifer (Fig.2). Pumping test gives a discharge of 5320m3?per day, with a drawdown of only 1.89m (Fig.3). The potential yield of the well is estimated to be 13300m3?per day. The TDS is 1.18g/L, while the water temperature is 43°JHC, obviously related to geothermal.

The second well (Y2) was completed early 1998, near Qianxian county, also at the southern part of the Loess Plateau (Fig.1). It is 800.03m deep with a potential yield of 5000m3/D. The water temperature is 22?°JHC.

In July 1, 1998, rich karst water was also found in the northern part of the Loess Plateau. The 175m deep No.107 well at Qipanjing Region, Otog Qi, Nei Mongol Autonomous Region (Fig.1), is on the northwest part of Mu Us Desert. Its potential yield is 10,000m3/D. Moreover, it contains some trace elements (Sr,Se etc.) which meet the National Standard of Mineral Water.

The findings of deep karst water are highly praised by local residents. The Northwest China’s Special Program of Groundwater is still making Headway. According to tectonic background, hydrogeologists believe that it is also possible to find deep karst water in Ningxia Hui Autonomous Region and Gansu Province.

Fig.2 Hydrogeological cross section of Well No.Y1,Fuping, Shaanxi

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Fig.3 Pumping test at Y1 well of? Fuping county, Shaanxi Province

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