自然資源部巖巖溶動力學重點實驗室

KARST HYDROGEOLOGY

2002-07-10KDL 2750

KARST HYDROGEOLOGY

10

Tectonic Control on the Waters of Vratza Karst System?(Western Balkan, Bulgaria)

Shanov S., Benderev A.
Geological Institute, Bulgarian Academy of Sciences,
Acad. G. Bonchev Street, bl. 24, 1113 Sofia, Bulgaria

Abstract

Vratsa Karst System, situated in Western Balkan Mountain is developed in deformed limestone layers of Jurassic and Lower Cretaceous age. The faults have been of important role for the development and the evolution of the karst system. The reconstruction of the tectonic stress fields using conjugated tectonic shear joints and strea on slickensides, as well the studies of the electrical rock anisotropy, compared to the fault-plane solutions from local earthquakes, has permitted to detect 5 phases of tectonic deformations from the Triassic to now. Especially for the North-West part of the area, the Pyrenean Tectonic Phase initiated the formation of open joints with direction NE-SW. These joints are controlling the principal direction of the karst galleries and the draining of the ground waters. The fast neotectonic mountain elevation predestined, in general, the predominating formation of vertical karst cavities.

The ground water flow is discharged by several relatively big karst springs. Up to now the utilization of karst water is ineffective due to the important variation of the discharge rate. Because of the fact that the ground karst water flow is of type "rivers" or "channels" the water retention and accumulation inside the karst system is not possible. Only 20 % of the available natural water resources are effectively exploited.

Introduction

The water permeability of the rocks is strongly depending of the system of fractures. Widely used practice in karst region is to study the relationship between the fracturing and the direction of the main karst hollows. The most elementary approach is to make rose-diagrams of the joints and to expect to find out some relation between the maximum on the diagrams and the local tectonic conditions, or with the karst processes, as secondary imposed phenomenon. But this method does not take sufficiently information about the tectonic stress fields, controlling in great level the karst processes. The maximum on the rose-diagrams can reflect shear joints concentrations, but the most important conducting water way in carbonate rocks could be the tensile fractures. Their plain is orthogonal to the minimum tectonic stress axis and, consequently these fractures are the most open and accessible for the water. Normally, the tensile axis of the youngest tectonic stress field is determining the direction of the recent active karst processes.

Fig. 1 The Balkan Peninsula with the situation of the studied region

?

Studies on the tectonic stress fields in the Western Balkan Mountain, Bulgaria (Fig. 1) were performed principally on Vratsa Block during speleological expeditions in 1985 and 1986 (analyses of the fracturing) and they were published later (Chanov, 1988). Some new data were included in the present study on the striae on slickensides, as well as fault plane solution from an earthquake near the studied area (Georgiev, Shanov, 1991). Vratsa Karst System is developed in deformed limestone layers of Jurassic and Lower Cretaceous age. The faults have been of important role for the development and the evolution of the karst system (Fig. 2).

Methods of investigation

The reconstruction of the tectonic stress fields that have deformed the rocks is one very important tool for determining of the direction of the most opened fractures during a given geological time. These fractures (tensional fractures) are the least resistant to the water current and they are most effectively widened when dissolution of the limestone is going on. The fractures having orthogonal plane of breaking to the minimum tectonic stress axis (tectonic extension) are the most convenient for the development of the karst process. Two?methodologies were used for reconstruction of the tectonic stress axes.

20150206-part3-2-3.gif

Fig. 2 Geological schematic map of the Vratsa Block of the Western Balkan
(according to Tronkov, 1965) with the points of tectonic stress field
reconstruction and the principal karst springs.

1 - Early Cretaceous; 2 - Late Jurassic; 3 - Middle Jurassic; 4 - Early Jurassic; 5 - Rhaetian; 6 - Norian and Carnian; 7 - Ladinian; 8 - Anisian; 9 - R?th; 10 - Early Triassic; 11 - young Paleozoic volcanic rocks; 12 - Permian and the upper part of Stephanien; 13 - flexure; 14 - fault; 15 - principal caves with general trend of the galleries; 16 - point of tectonic stress reconstructions; 17 - main springs: I - Matnitsa; II - Beli Izvor; III - Spring near Saint Ivan Pousti Monastery; IV - Bistretz; V - Chigoril.

Analyses on the shear fractures

The first one is based on a special analysis of the conjugated shear joints systems. The method is based on the observation, that the maximums of the conjugated systems of shear joints have expressed asymmetry on the diagrams of their density. The elongation of the maximums is towards axis of the minimum tectonic stress field??(?s?3). This idea was developed and published by P.N.Nikolaev (1977). Mass measurements of the space elements of joints (dip direction and dip angle) in different outcrops of the rock massif are the bases of this method (normally at least 50 measurements are necessary for non-biased statistics). After special mathematical processing of the data (Shanov, Stoyanov, 1986) and analysis of the dissipation direction and the angle between the conjugate shear joint systems, they can be reconstructed the axes of the tectonic stress fields that have acted on and deformed the rock massif in different geological times.

Analysis of relative movements on fracture and fault planes - striae on slickensides

The second method is based on the kinematics characteristics of the movements on the rock block bounding surfaces - striae on slickensides. They could be manifested in a moment of the fracturing or faulting. But, the older rupture orientations can facilitate the relative movements of the adjacent blocks at conditions of younger tectonic stress field, i.e. the resulting striae can be detected on the surface of the older joints. The principal tectonic stress axes could be reconstructed by analysis, which is based on a conception about the relation between movement on shear cracks, and tectonic stresses (Ramsay, 1980; Gamond, 1983).

The program FAULT (Caputo, 1989) works in DOS and allows performing the analysis by using PC-AT and more modern compatible systems. There are tree possible procedures for principal stress axes reconstruction by using the data from measurements of the space orientation of the striations on slickensides and the type of the movement along them.

Right Dihedron Method (RDM)

This method assumes that the rock material is previously cracked (before the movement) and the rate of movement realized on each single surface is smaller than the sizes of the studied rock body. The plane, which is orthogonal to the striae on the fault surface, is defined as an additional plane. These two planes divide the space around for the fault surface into 4 rectangular dihedra. Each two conjugated dihedra contain axes?s?1?and?s3, which can be presented in a stereographic projection. If there is a group of measurements, then the sectors are defined as zones of action of axes?s?1?and?s?3.

Method of P and T axes (P/T)

It is based on the assumption that the rock material is homogenous and isotropic, as well as the axis of the maximal extension is oriented at 45° to the fault surface and to the movement direction. I.e., the axis of maximum compression is at 90° to the fault surface.

The Least Square Method (LS)

The LS method is additional one for the procedures for spatial assessment of the main axes of the stress field. This method is used for finalizing the obtained results. The reconstructed principal axes of the tectonic stress field have to be orthogonal, but due to the data, they could be inside of zone of variation around a pole. Namely, the LS method gives this pole for every principal stress axis keeping the orthogonality between them.

Results from the tectonic stress fields reconstructions

Vratsa Block is a integral part of the big Berkovitsa Block-Anticlinorium structure (after Tronkov, 1965). The northern border of the block is one remarkable flexure, built by the

20150206-fig3-2-3.jpg?
Fig. 3??Reconstruction of the tectonic stress field orientation since the Middle Triassic?till now for the studied area.

sediment layers of Triassic, Jurassic and Early Cretaceous age. The flexure is discussed as the ductile effect of the movements along a big fault, disposed northwards from the flexure, and covered now by younger sediments (Fig. 2). An important role during the tectonic evolution of Vratsa Block has been attributed to the longitudinal and transversal faults. According to Tronkov (1965), the analyses of the all tectonic structures of Vratsa Block show their genetic relationship to the lateral strain acting with direction NNE - SSW (N30-400?- N210-2200). This is the direction of the short deformation axis the long axis being directed N120-1300. The faults in this situation appear as shear planes.

The reconstruction of the tectonic stress fields using the above mentioned methods was the first step of the study. The second one was to adjust the received solutions in tectonically logic scheme for the time of manifestation of given tectonic strain. This scheme (Fig. 3) reflects the possible evolution in the time of the tectonic stress axes orientation for the area of Vratsa Block.

Looking at the performed reconstruction of the tectonic stress fields (Fig. 3), the most coinciding with the described above tectonic deformations in macro scale are these from the method using the shear joints. We suppose this tectonic stress field to be related to the Sub-Hercinian Tectonic Phase. In the studied region they exist a second group of clearly expressed systems of joints, assumed as a result of the Pyrenean Tectonic Phase. Only one of the site of the measurements (No 6) has shown deformations that could be reported, with some level of probability, to the neotectonic stage. The argument for this is the similarity of the reconstructed tectonic stress axes directions to the result of the fault-plane solution from the earthquake with magnitude M=3.3 northwards from the studied area. But, the all proceeded data do not show evidence for cardinal changes of the tectonic strain principal directions after the Pyrenean Tectonic Phase.

This fact is reflected in the general NE-SW orientation of the karst galleries of the region. Analyzing the principal stress axes changes from the Sub-Hercinian to the Pyrenean Phase it is possible to deduce left rotation of the structures. For the most recent processes such a deformation was not established. The karst systems of the area are of precipice type, actually active, and draining the superficial and underground waters towards northeast. The contemporary configuration of the karst systems is possible only when the minimum tectonic stress axis?s?3?is sub-vertical.

Characteristics of the karst of Vratsa Karst Systhem

The rainfalls are one of the most important factors determining the active development of the karst processes in the region. Their average quantity is above 1000 mm/m2, when the average value for the territory of Bulgaria is 618??mm/m2?(Spasov et al.,?in press). The classic type of karst is presented at the upper part of the mountain (Skorpil H, K.Skorpil, 1895, 1898; Radev, 1915; Mishev, Popov; 1958,??Markovicz at all, 1972; Kostov ,1997). Its formation is also controlled by the tectonics, as well as by the geomorphological evolution of the area (Ilieva et al., 1979; Angelova et al., 1995, 1999). The complicated geological and tectonic situation of the area, and the relief features predestinated the formation of a number of karst regions (Boyadjiev, 1964; Antonov, Danchev, 1980; Benderev et al., 1987, Spasov et al., 1998 and Spasov et al.,?in press).

The discussed in the present work karst system is situated inside the so called Bistretz-Matnitsa Karst Basin at the north-western part of Vratsa Mountain. It represents a plateau with steep, even vertical slopes, except the narrow band from the south relating it to the neighbor karst basin. It is built by dipping towards north - north-east monoclyne of limestone layers of Late Jurassic and Early Cretaceous age. They are separated from the underlying Iskar Carbonate Formation by a thin layer of no karstified rocks of Early-Middle Cretaceous age. The principal erosion basis is at the north-eastern part of the plateau. The principal karst springs appear at that place. But, as a general rule for the all area, the border between the karstified and no karstified rocks is above the level of the local river network.

The principal part of the basin is characterized by discovered at the surface karst abounding of karst forms. Some of the dolines are with dimensions 1 to 2 km2, the biggest one attends to 2-2,2 km2.?The underground karst forms are predominant.?More than 70 caves and precipices are known in this area, most of them are in the limestones of Late Jurassic-Early Cretaceous age. Some zoning can be followed from south-west to north-east. The south-western part contains relatively little horizontal caves. Above them, near the Streshero Pick and Ostria Pick, they exist considerable and complicated as morphology precipices. Here are the deepest Bulgarian cave Barkite 14, the caves Beliar, Barkite 8, Mijishnitsa. All of them begin from dolines and continue as a system of steps or dipping generally towards northwest segments, following the upper boundary of the underlying karst resisting rocks. Little water streams exist in every one of the caves, their discharges are depending directly from the atmospheric precipitation.

Typical precipices of different depths characterize the next zone. The deeper one is Haydoushka Precipice, near the Ivan Pousti Monastery. It entrance begins with 108 m deep well. Other important precipices in the area are Nevestina - 76 m, Kalnata - 85 m, and Zmeyova Dupka - 65 m.

Along the north-east border of the plateau some little precipices and horizontal caves are known, some of them with springs. These ones are grouped near the Saint Ivan Pousti Monastery, the longest cave being of 546 m, and with a water stream inside.

Only a few caves have been discovered in the Triassic limestones and dolomites. The most important of them is Gardiova Dupka with a length of 510 m. The stream inside this cave is discharging its water trough the spring Tzonovoto near the village of Zgorigrad.

The 7 longest caves of the region contain 75% of the total length of the galleries. The ratio between the total vertical to the total horizontal lengths shows the domination of the vertical karstification on the horizontal.

The karst formation began at Early Miocene and had continued during the Pontian and Pliocene time. When Popov (1964) studied the genesis of Ledenika Cave, he showed that its formation date from the beginning of the Dacian time, and it is related to the Pontian level of denudation. The same period of formation can be attributed to the caves and the precipices of the high parts of the plateau. The most recent caves, as Beliar and Barkite appeared when was discovered at the surface the narrow band of unable to be karstified rocks with Middle Jurassic age.

Table 1. Length of the caves

Length

bellow 50 m

50 - 100 m

100 - 500 m?????

500 - 1000 m

above 1000 m

Quantity

52

9

3

3

4

?

Table 2. The longest caves of the region

N

Name

Situated at the vicinity of:

Length, m

1

Barkite 14

Gorno Ozirovo

2600

2

Beliar

Gorno Ozirovo

2500

3

Toshova Dupka

Stoyanovo

1302

4

Barkite 8

Gorno Ozirovo

more than 1000

5

Mijishnitsa

Ledenika

855

6

Chernia Izvor

Matnitsa Monastery

546

7

Gardiova Dupka

Zgoridrad

510

?

Table 3. Depth of the caves

Depth

bellow 10 m

10 - 50 m

50 -100 m

more than 100 m

Quantity

19

40

7

4

?

Table 4. The deepest precipices and caves

N

Name

Situated at the vicinity of:

Depth, in m

1

Barkite 14

Gorno Ozirovo

-356

2

Beliar

Gorno Ozirovo

-282

3

Barkite 8

Gorno Ozirovo

- 208

4

Haydoushka

Saint Ivan Pousti Monastery

-108

?

Hydrogeological characteristics

From hydrogeological point of view, the regional geological, tectonic, physical and geographical conditions has predestined the presence of totally drained monoclyne slope dipping towards north with two principal karst aquifers - Triassic and Middle Jurassic. Relatively thin terrigenous rock complex (Lower and Middle Jurassic) is dividing the two aquifers. The common regional water basis is formed by the Lower Triassic sandstones. These rocks are relatively high elevated towards the local erosion basis. The northern basis of erosion is the Vratsa Plane, separated from the studied karst area by the Kostelevo Fault.

There is now enough data for the Lower Triassic aquifer. It is presented by a few outcrops at the northern and the eastern peripheries of the basin. The rocks are weekly karstified. The aquifer receives its water from the atmospheric precipitation, as well as by infiltration from the upper lying karstic aquifer. A few springs are draining it, the biggest of them is Chigoril with discharge rate of 7 to 11l/s (Antonov, Danchev, 1980).

The principal aquifer (Upper Jurassic - Lower Cretaceous) is totally discovered at the surface. This fact predestines the high level of karstification related to the possibility of intensive feeding from the atmospheric precipitation. According to Spassov et al. (1998) more than 54% of the atmospheric precipitation (in average 1000 mm/m2?per year) are feeding the underground waters. Part of the water forms temporal streams on the surface, but they are loosing quickly their water in the dolines. The karst springs situated at the northern part of the Vratsa Mountain are draining the aquifer. Most of them are of ascending type. The tectonic predestination of their situation is clear. Important springs in the area are situated near the village of Bistretz, two springs are near the Matnitsa Monastery, and one is near the village of Stoyanovo. Some amount of the water is passing towards Vratsa Plane, and there is the spring Beli Izvor. During the period from 1995 to1996 regime studies were performed (Table 5 - unpublished data from Spasov et al. 1996).

Table 5 Results from the water regime monitoring on the principal springs from Bistretz-Matnitsa Karst Basin.

Site

Discharge, l/s

Temperature,?°?С

Specific electrical conductivity,?m?s/cm2

?

Number of the records

Qmax

Qmin

Qav

s?Q%

Tmax

Tmin

Ecmax

Ecmin

Bistretz

12

776

127

458

52

12.4

10.3

444

328

Monastery –

upper spring

12

270

17

105

87

11.8

?8.7

364

309

Monastery –

lower spring

13

158

0.8

33

142

11.8

8.7

414

276

Village of

Stoyanovo

12

391

78

160

54

15.8

7.7

336

192

Beli Izvor

14

317

96

170

47

13.7

7.7

573

432

?

They exist also other less important springs that have not been monitored. The spring near the Saint Ivan Pousti Monastery has discharge rate of about 5-20 l/s. It is draining some of the longest caves of the region.

For the most important spring of the region, the spring of Bistrtz, there are data from long term monitoring from the National Institute for Meteorology and Hydrography on its discharge ratio. According this data the discharge ratio is changing within large limits - from a few l/s till more than 5 m3/s (Machkova, Dimitrov, 1999). This dynamics of the qantitative and the qualitative parameters confirms the peculiarities of the karst system - the dominanr movement of the karst waters as underground streams in large cave galleries with relatively steep slope, insignificant zone of saturation, and the important role of the atmospheric precipitation. These peculiarities are reflected on the intensity of the karst processes. Accordimg to Marcovicz et al.(1972) the denudation in the region, determined on the base of studies of separeted sites is 38.4-45 m3/a.km2. Using the new obtained data for the quality and the quantity of the karst waters, the data from the water regime monitoring included (Spasov et al., 1998 - unpublished), it was shown that the total denudation for the area is more intensive - 87 m3/a.km2.

Conclusion

The karst waters have one very important potential for supplying potable and industrial water for the region. Due to the unstable and changing discharge ratio of the springs only 20% of the natural resources of the karst basin are used. The low retention capabilities of the karst system do not permit the effective using of the karst waters, and considerable quantities run off freely during spring-summer season. In autumn the people of the region usually suffer for potable water (Molov, Spasov, 1994; Spasov et al.,?in press). Besides the high level of karstification the waters are normally not polluted and they meet the Bulgarian National Standard. This can be explained with the fact that the zone of feeding of the karst springs is situated inside the park “Vratsa Karst” and the human activities are minimized.

References

Angelova, D., A.Benderev,?G.Baltakov, I.Ilieva, T.Nenov. 1995. On the evolution of the karst in Stara Planina Gorge - Journal of Bulgarian Geological Society, v. 3, 111-124 (in Bulgarian).

Angelova, D., A.Benderev,?K.Kostov. 1999. On the age of the caves in the Stara Planina Iskar gorge, NW Bulgaria. European Conference “Karst 99”, 10-15 sept., 1999, Grands Causses –Vercors, 25-35

Antonov, H., D. Danchev. 1980. Ground waters in Bulgaria. Sofia, Tehnika, 360 p. (in Bulgarian).

Benderev A., Shanov S., Ilieva I., 1987. Characteristics of the formation of karst in the Western Stara Planina Mountains. Proceedings of the Conference “The problems of the complex study of the karst of mountain areas”, Tbilisi-Tzhaltubo-Suhumi, 5.12.1987,??5-12.10.1987, 94-97 (in Russian).

Boiadjiev N. 1964. Karst basins in Bulgaria and their ground waters. Proceedings of the Institute of Hydrology and Meteorology, BAS, Sofia, 45-96. (in Bulgarian).

Caputo R., 1989. FAULT. A programme for structural analysis. Department of Earth Sciences, University of Florence. Manual, 55 p.

Chanov S. 1988. Conditions géologiques et tectoniques de la formation des cavités karstiques dans la région de "Barkité" et de "Béliar", montagne de Stara Planina près de Vratza /Bulgarie/. Dans "Récit d'une amitié", Saint Herblain, 12-14.

Gamond J.F., 1983. Displacement features associated with fault zones: a comparison between observed examples and experimental models. J. Struct. Geol., 5, pp. 33-45.

Georgiev, Tz., S.Shanov 1991. Contemporary geodynamics of the western part of the Moesian Platform (Lom Depression). Bulgarian Geophysical Journal, v.LXVII, N? 3, 3-9 (in Bulgarian).

Ilieva I, I., I.Zdravkov, à.Benderev. 1981. The role of the tectonic movements for the development of the karst at the area or Cherepish Railway Station. - In: Proceedings “Scientific and Practical Conference on Tourism, Alpinism, Caving and Environment Protection”, Rousse, May 4-6 1979, Sofia, 207-214. (in Bulgarian).

Kostov, K. 1997. Karst morphology in Bazovski part of Vratsa mountain (Stara planina, NW Bulgaria). Procc. 12th?Intern. Congr. of Speleology, La Chaux-de-Fonds (Newchatel, Switzerland), August 10-17, 1997, v.1, 409-412.

Machkova, M., D.Dimitrov. 1999. Handbook for the quantitative characteristics of the ground waters for the period 1980-1996. Sofia, MOSV-NIMH, 376 p. (in Bulgarian).

Markowicz,M., V.Popov, M.Pulina. 1972. Coments of Karst denudation in Bulgdria. - Geogr. polonica, 23, 118-139

Mishev, D., V.Popov. 1958. The karst of Vratsa Mountain.??- Nature, Sofia, 7, 7-13 (in Bulgarian).

Molov, D., V.Spasov. 1994. Perspectives for exploiting of the underground waters for resolving the problem of water supply for the town of Vratsa and the surrounding settlements. In: Proceedings “Water supply for the town of Vratsa”, Vratsa, 23-27 (in Bulgarian).

Nikolaev P.N., 1977. Method for statistical analysis of joints and the reconstruction of the tectonic stress field. Bull. of High Schools, Geology and Prospecting, Moscow, No 12, 103-115 (in Russian).

Popov,V. 1964.??Morphology and genesis of Ledenika Cave. - Bull. of the Geographical Institute, BAS, 8, 77-87 (in Bulgarian).

Radev,J. 1915. Karst forms in Western Stara Planina. - Ann. Of Sofia University, Historical and Philological Fac., v. 10-11, 149 p.(in Bulgarian).

Ramsay J.G., 1980. Shear zone geometry; a review. J.Struct.Geol., 2, pp.83-99.

Shanov S., Stoyanov S., 1986 On a method for treatment and dynamic interpretation of joints. Rew. of Bulg.Geol.Soc., vol.57, part 1, p. 64-73, (in Bulgarian with an Abstract in English).

Scorpil,H., K. Scorpil. 1895. O kraskych zjevech v Bulharsku. - Rozpr. Ceske Akad., 4, 2, 1-35.

Scorpil,H., K. Scorpil. 1898. Sources et pertes des eaux en Bulgarie.??- Mem. Soc. speleol., 15, 99-139.

Spasov, V., à.Benderev, D.Gabeva. 1998. Perspectives for more effective using of the underground karst waters of the region of the town of Vratsa. Proceedings of the National Conference “Water resources - usage and preservation”, Sofia, 23-25 September, 1998, 47-51, (in Bulgarian).

Spasov, V., A.Benderev, D.Gabeva (in press). Karst waters in the Vratza mountain (Bulgaria).??Geologica Balcanica, Sofia.

Tronkov D., 1965. Tectonics and analysis of the structures in the Vratza Block of Western Stara Planina. Plastic deformations near the fault planes. Studies on the geology of Bulgaria, Series “Stratigraphy and Tectonics”,6, 217 - 257 (in Bulgarian).

11

Karst Analysis through the Chemical Analyses of Water?in Ghir Dam Site

?

R. Ajalloeian and M. Salehi
Department of Geology, Isfahan University, Isfahan-Iran

Abstract???There are two primary reasons that can be concerned with fractured and karst rock, First one is structural integrity (which may be lead to rock failure and collapse); and the second one is ground water flow (which may be of concern as a ground water resource or as a pathway for contaminant transport, or in the case of an earthen dam may affect structural integrity of a site). Generally the karst includes surface and subsurface features which are the result of dissolution enlargement of soluble rocks (and also mechanical enlargement by erosion and strain). Caves, sinkholes, sinking streams, springs and the rapid movement of ground water are common example of karst. Underground cavities may range from less than 1foot to more than a few hundred feet in diameter. Their depths may vary over the same range, while their position and length may extend over an area of considerable extent.

Present paper is dealing to analysis the karst condition in Ghir dam site which is located in 180km of southeast of Shiraz province in southeast of Iran. Regarding to the geological view point, this site is located on north flank of Changal anticline and the Ghareghag river passed from there. Water of river and springs and also artesian borehole in site has been analyzed.??The amount of cations such as Ca2+, Ca2+, K+?and Na+?and anions such as SO42-,Cl-?and HCO3-?and also pH has been measured. Based on common classification, each sample was studied individually. It is concluded that some of them includes the high amount of Na+?which means the water passed through the saline layer or salt domes. Some others possess high percent of Ca2+?and Na+. It shows that they passed through the limy formations. These results will be discussed in detail full paper.

12

Dynamics Freatures of the Epikarst Zone and Their Significance in Environments and Resources

Jiang Zhongcheng???Yuan Daoxian
(Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004)

Abstract

The epikarst zone is in the convergence zone of atmosphere, lithosphere biosphere and hydrosphere. It is widespread in South China, but its sizes, landforms and locations are influenced by geological and climatic factors. The tropical and subtropical monsoon climate in South China can create such strong karst dynamic conditions as the mean annual between 1000 to 2000mm, high average air temperature 14-21℃, and high soil air CO2content from 3000×10-6??up to 50000×10-6; therefore the carbon –water-calcium cycle is active and rapid. The karst dynamic processes in the epikarst zone are much stronger than the deep karst part, which result in high solution rate and hardness of water. As a result, high CO2?flux sinks in karst water. The karst dynamic processes in the epikarst zone are sensitive to environmental changes, and hence can provide environmental information in a short time scale. Due to the development of the epikarst zone, the water cycle in kasrt mountain area can be divided into two parts: shallow water flow in epikarst zone and conduit flow in the deep karst zone. In addition, the shallow water cycle is very important for water supply in karst mountains where the underground karst water in deep.

Key words???epikarst zone, karst dynamics, global environmental change

13

Discussion of Shanxi Karst Water

Guo??Zhengzhong?
Shanxi prospecting and developing bureau of geology and mineral resources

Abstract:?Through the brief introduction of Shanxi karst water we brief analyzed the environment geological problem of Shanxi karst water, process the proofing suggestion, discuss the resources problem of Shanxi karst water, and have the description to the advantage of each kind of broadcast patterns of water fluid. And at the same time discuss the loss of water discharge, point out the great potentialities of Shanxi karst water.

Key words:??karst water???problem??discuss

14

Hydrogeological Characteristics of a Karst Mountainous Catchment?
in the Northwest of Vietnam

??V. T. Tam1,2, Vu T.M.N2, O. Batelaan3

1Corresponding author. Email:?[email protected]; Tel: 84-4-8543107;?
Fax: 84-4-8542125?
2?Research Institute of Geology and Mineral Resources, Ministry of Industry, Vietnam?
3?Department of Hydrology and Hydraulic Engineering, Free University Brussels, Belgium

Abstract

This paper presents a preliminary assessment of the hydrogeological characteristics of a karst mountainous catchment, the Suoi Muoi River catchment, in the Northwest of Vietnam. The catchment is located at 600 – 1700m a.s.l and covers an area of 284 km2. Exposed limestone occupies 32% of the total catchment area. Various types of assessments have been carried out, including geological and hydrogeological field surveys, cave surveys, dye-tracer tests, meteorological and surface water monitoring.??Geological studies and cave surveys have identified the most important active cave/conduit systems within the catchment. Although these data are essential, they are insufficient to make a comprehensive appraisal of the hydrologic nature of the catchment under interest. An attempt was made to calculate a global water balance of the catchment, based on short-term (15 months) meteorological and streamflow records. The results show that, despite the existence of a number of substantial cavern conduit systems, the groundwater system of the catchment is governed by the fracture/fissure matrix. The cavern conduit systems only collect groundwater from the adjacent fracture matrix and/or connect topographically isolated surface watercourses. The groundwater storage of the cavern conduit systems appears to be regionally insignificant in comparison with the governed fracture matrix groundwater system.

Keywords:??Karst hydrology; Geology; Lowflow

Introduction

Approximately twenty percent of the landmass of Vietnam is covered by tropical mountainous karst (Tuyet, 1998). Within the Suoi Muoi catchment, approximately 32% of the landmass is occupied by exposed karstified carbonate rocks, which form a landscape characterized by sinkholes, sinking streams, caves and karstic springs. Although various geological, hydrogeological and karst geological studies have been carried out in the area, very few studies have profoundly documented the karst hydrology. None of these studies has so far assessed, at a regional scale, the nature of the groundwater system of the catchment area of interest.

It is often argued that the study of karst hydrology is particularly difficult due to the lack of necessary input data and poorly developed mathematical descriptions/theory of water flow in karst aquifers. The theory and methods developed on the basis of the Representative Elementary Volume (REV) concept are sometimes applied to karst aquifers when baseline data is limited. Under certain assumptions, various hydrological models developed for porous media have been successfully applied in karst areas, thereby rendering insight into the hydrological situation at a regional scale. There is a common conviction though that the validity of such models is limited by the great complexity and discontinuity of the karst medium. The data most commonly available for karst areas are time series of streamflow discharge and/or spring discharge, because they are relatively cheap and easy to collect. Therefore, most studies about the functioning and hydrodynamics of karst aquifers have been based on analyzing hydrographs (depletion and/or recession; Felton and Currens, 1994; Bonacci, 1988, 1993; Eisenlohr, 1997; Bent, 1999) or on the cross-spectral analysis of time series data of streamflow and rainfall (Labat, 2000; Lacey, 1998; Larocque, 1998; Padilla, 1995).

The overall objective of this study is to identify the functioning and hydrodynamics of the karst aquifers of the Suoi Muoi River catchment based on analyzing the hydrograph of the Suoi Muoi River streamflow. A simple monthly water balance model was subsequently calculated to estimate the storage surplus/deficit of the soil layer and the underlying karst aquifer. The outcomes of the model, together with the results of geological and hydrogeological studies, cave surveys and dye-tracer experiments, yield an initial understanding on the nature of the karst groundwater system of the catchment.

Geological and hydrogeological setting

The Suoi Muoi River catchment is situated in the mountainous Da River basin, more specifically to the southwest of this river, between eastern longitudes 103°35'5” and 103°51'33” and northern latitudes 21°20'03” and 21°33'53”. The catchment is located at an altitude of 600 – 1700m a.s.l and encompasses approximately 284 km2?(in this study, the Suoi Muoi sinkhole was determined as the catchment outlet). The administrative and geographic center of the area is Thuan Chau District, located northwest of Son La town. The area is characterized by a humid subtropical climate with extensive summer rainfall; the yearly mean temperature is 21.1°C and the mean total yearly precipitation is 1450 mm. About 20% of the catchment area is covered with forest. The surface drainage density is 0.66 km/km2.

The catchment is confined by two regional deep fault systems trending in NW–SE direction, the Son La Fault on the east and the Da River Fault on the west. Within the catchment a range of non-limestone and limestone rocks of different ages are exposed (see figure 1). In the southwestern part the non-limestone rocks consist of Proterozoic - Ordovician quartzite/sericite schists and sandstones intercalated with thin-bedded limestone; the central part is covered by Permian basalts; late Triassic thin-bedded siltstones and shales and Jurassic – Cretaceous medium - thick bedded gravelstones, sandstones and conglomerates crop out in the northeasternpart. The limestone rocks, which constitute the main geological object of this study, are confined within the two fault systems as shown in figure 1. The rocks are regionally dipping to the southwest.

The most perspective groundwater is located within karstified carbonate rocks outcropping in the area between the two regional deep fault systems. The karst area consists mainly of two sub-areas: the central part is composed of karst water bearing carbonate rocks of Early Permian-Carboniferous and Middle Devonian ages, the eastern part is of Middle Triassic age. The limestone rocks are cut by southeast-northwest and northeast-southwest trending faults. Many different tectonic phases and neotectonic movements have affected these rocks. The activation of the Son La fault system has resulted in a relative subsidence of the right-side block. The neo-tectonic movements have led to the formation of mainly peak forest landscapes in the limestone, with residual karst peaks and towers, which emerge here and there above the dissolution-erosion valleys. Here, the groundwater occurs at great depth and the land is dry.

20150206-fig1.jpg

Figure 1. Geological map of Suoi Muoi Catchment

The movement of karst groundwater is closely controlled by these tectonic deformations. The groundwater is mainly stored in fractures, crushed zones and caves and circulates in consistence with the hydrodynamic variation.

Between?the central and eastern sub-areas exist many karst springs at the lithologic contact between the extremely karstified Triassic, the highly karstified Early Permian-Carboniferous and the semi-impervious, non-karstic formations of different ages.?Karst springs also exist along the surface watercourses and at the western limit of the central sub-area near the lithologic contact between the highly karstified limestone and the semi-impervious, non-karstic rocks. Most of the karst springs are permanently active, only a few of them stop flowing during the dry season.

The Suoi Muoi River system is the main surface drainage system in the Thuan Chau area, which is underlain in great part by the above-said limestone units. A narrow area of clayey Quaternary alluvium is present along the Suoi Muoi River and its tributaries.??Along the river course there exist a number of karst springs/resurgences and sinkholes, which interact with the karst groundwater aquifers.

The karst aquifers receive water, mainly by the regional groundwater flow, with additional important in-situ recharge by rainfall, surface water and exotic water from higher-lying non-karstic areas. Discharge of the groundwater takes place in the river valleys and depressions. A comprehensive discussion of the geology, including tectonic history and stratigraphy of the region is provided by Tuyet (1998).

Hydrogeological studies and tracer experiments

Three karstic groundwater units were identified within the catchment territory: the Middle Devonian formation, the Early Permian-Carboniferous formation and Middle Triassic formation, all being medium – highly karstified limestone rocks. These karstic groundwater units were hypothetically defined on the basis of the geological stratification and fracture/karstification degree of the outcropped rocks. The non-limestone formations are much less permeable than the limestone formations (Xuyen, 1998; Hop, 1996). No strong evidences exist to argue whether the groundwater units are indeed hydrologically dissimilar. The study of the results of the seven existing pumping tests (Xuyen, 1998) could not help to validate the delineation of these units since the boreholes were limited to a depth of around 100m, which is much shallower than the presumed 400 – 1000m thickness of the limestone formations and is also shallower than the local karstification depth (Tuyet, 1998). A detailed study of the lineament scheme developed from satellite images (the result is not shown here) and of the geo-structural map of the area showed that the fractured and crushed zones prolong in two main directions, namely NW-SE and NE-SW. A very rough estimation, based on the density of estimated fractures at regional scale, of the groundwater conductivity is 100 times higher in the NW-SE direction in comparison with the NE-SW direction.

A river discharge monitoring survey carried out during the dry season has shown that the total discharge of the Suoi Muoi River tributaries located in the non-limestone area west of the Son La Fault contribute only 7% - 10% of the total river discharge measured at the catchment outlet. Their discharge contribution can rise up to 25% of the total river discharge during storms. It is believed that this increase is mainly due to surface runoff, which is much more generated by the steeper terrain (altitude changing from 1700m to 800m) of the non-limestone rocks in comparison with the more flatten terrain (altitude changing from 800m to 600m) of the limestone rocks.

Since 1993 a number of caving - expeditions have been carried out, primarily focusing on active cavern conduits existing in the study area. It was found that the development of the cavern conduits mainly coincides with the development direction of geological faults and fractured zones (November, 1999). The cavern conduits range from a few hundred meters to a few kilometers in length. Their starting point is in most cases the end of a surface watercourse in a blind valley or in a depression. Their endpoint is generally a resurgence located at an elevation more or less equal to that of the surface watercourses where the karst groundwater discharges. A tracer experiment was carried out in the largest cavern conduit (approximate length of 2.5 km) between the Suoi Muoi River sinkhole and resurgence. Uranine was used as tracer dye, the tracer-breakthrough curve is shown in Fig 2. Analysis of this curve using the software QTRACER showed that the mean tracer transit time is around 28 hours and that the estimated karst conduit volume is 43,000 m3?(Vu, 2000). Another tracer experiment was carried out in a cave conduit with an approximate length of 2 km, located in the southeastern part of the catchment. The mean tracer transit time was 10.4 hours and the estimated conduit volume was 13,796 m3. Based on these results it is believed that the storage of the cavern conduits is regionally insignificant. The conduits play only the role of conveyers between surface water bodies or of galleries collecting karst groundwater from the adjacent fracture/fissure media.

20150206-fig2.jpg

Figure 2. Tracer breakthrough curve of uranine??at the Suoi Muoi River resurgence.

Much of the sinkholes and dolines are covered with a layer of Quaternary alluvium, consisting of clay, sand and gravel. The soil thickness is up to 17 m near the Suoi Muoi sinkhole and gradually diminishes along the Suoi Muoi watercourse and its tributaries. In a borehole very close to the Suoi Muoi sinkhole, no groundwater was found at the depth of 17m. In another borehole about 3 km upstream of the sinkhole, groundwater was found at the same level as the river water and as the groundwater level observed in a nearby cavern conduit. A number of karst springs/sinkholes can be found along the Suoi Muoi River course. They play the role of interaction between karst groundwater and surface water. The interaction can be direct or indirect through the soil cover layer. In dolines and closed karst valleys the soil thickness can be up to 3-5 m, below which a blind system of shaft/open fracture exists and therefore the surface water find the way to percolate deeper to the groundwater system.

Hydrograph analysis

Hydrograph analysis has proven to be a useful technique in a variety of water-resources investigations. Quantitative analysis of streamflow recession is of considerable importance to many aspects of water resource management such as water allocation, irrigation, flow requirements for aquatic ecosystems, hydroelectricity generation, wastewater disposal and dilution of contaminant discharges. Separation of streamflow hydrographs into base-flow and surface-runoff components is used to estimate the groundwater contribution to streamflow. Hydrograph-separation techniques also have been used to quantify the groundwater component of hydrologic budgets and to aid in the estimation of recharge rates. In addition, base-flow characteristics determined by separation of hydrographs from streams draining different geologic areas have been used to show the effect of geology on base flow (Lacey, 1998; Bent, 1999).

Three USGS computer programs (RECESS, PART and HYSEP) were used in this study to analyze the streamflow record of the Suoi Muoi River. The river streamflow hydrograph, covering a period of 15 months, was constructed on the basis of the data recorded by an automatic waterlevel logger (pressure-transducer type) installed at the outlet of the catchment, i.e. the Suoi Muoi River sinkhole. A rating curve of the formpart3-6.gif?, with Q being the river discharge and h the river waterlevel, was constructed to convert the recorded waterlevel to discharge. The original data were recorded on a 10 minutes basis, but they were averaged and converted to a daily basis in the hydrograph analysis.

The RECESS program (Rutledge, 1998) was used to determine the streamflow master recession curve (MRC) during times when all flow can be considered to be groundwater discharge. The program uses a repetitive interactive procedure for selecting several periods of continuous recession. Consequently it determines a best-fit equation for the rate of recession as a function of the logarithm of flow. Finally the coefficients of this equation are used to derive the MRC, which is an equation of time as a function of the logarithm of flow. The program thus allows for the?possibility of?nonlinearity?in the relation between time and the logarithm of flow. In the application to the streamflow of the Suoi Muoi River, only recession periods of at least 6 continuous recession days in rainless wintertime were selected for the determination of the MRC.

The PART program (Rutledge, 1998) was used to estimate a daily record of baseflow under the streamflow record. The program scans the record for days that fit a requirement of antecedent recession, designates baseflow to be equal to streamflow on these days, then linearly interpolates the daily record of baseflow for days that do not fit the requirement of antecedent recession. The program was applied to a long period of Suoi Muoi River streamflow record to give an estimate of the mean rate of groundwater discharge. The calculated result was compared against the one simulated by the HYSEP program (Eaton, 1996), which operates on the principal of systematically drawing connecting lines between the low points of the streamflow hydrograph. With the streamflow data of the Suoi Muoi River catchment, the computed groundwater discharge by the two programs shows a small discrepancy (3%).

20150206-fig3.jpg

Figure 3.??Total streamflow and groundwater discharge calculated by PART program

Results of the hydrograph analysis are shown in Fig. 3 and Table 1. It is calculated that the baseflow index (i.e., the ratio of groundwater discharge volume over total streamflow volume) of the Suoi Muoi Catchment is 0.86. This high value of the baseflow index shows that a major portion of the streamflow of the Suoi Muoi River comes from the groundwater. According to literature, the baseflow index is a good indicator of the effects of geology on low-flows (Smakhtin, 2001) and can give an indication of the percentage of carbonate bedrock area (Bent, 1999). The high baseflow index is often associated with high primary porosity – deep permeable soils or highly fractured bedrocks (Lacey, 1998). Analysis of an hourly basis hydrograph (data not shown here) shows that the surface runoff generated by a storm terminates within 32 hours after the end of the event. The short life of the surface runoff is assumed to be due to extreme differentiation of the terrain and the heavy deforestation of the catchment. The recession index, interpreted in literature as a?representative of the residence time or the turnover time?of the groundwater??(Wittenberg, 1999) is for the Suoi Muoi River catchment 55.4 days. Comparing with the common values of 10 - 140 days found for other catchments (Nathan, 1990), the Suoi Muoi groundwater system is considerable.

An analysis of the auto-correlation of the time series streamflow record and cross-correlation of the streamflow and rainfall was made with the catchment data (Fig. 4). One can apparently see the existence of two distinguished storages in the cross correlation function (fig. 4a) of Suoi Muoi catchment: the first sharp peak at time lag Tlag?= 1day representing the quick flow storage (which could be of surface runoff or highly transmissive conduit system or both) and a series of top - flat peaks at a much longer time lag representing the slower depletion storage, the baseflow. Time response to rainfall of Suoi Muoi streamflow is quite long, about 100 days. The quick response to rainfall at Suoi Muoi sinkhole is 1 day.?One can consider the time to centroids of the quick flow component (first peak) and baseflow component (series of top – flat peaks) as the mean resident time of these components; for Suoi Muoi catchment Tq?= 1 day and Tb?= 50 days, where Tq?and Tb?are mean resident time of quick flow and baseflow, respectively. The series of top – flat peaks of the cross correlation function were explained by the notable periodic components occurring in the input rainfall time series. The long residence time of the groundwater, together with the high baseflow index value, suggest that the karst groundwater system of the Suoi Muoi catchment is governed by a fracture and fissure media.

?20150206-fig4-a.jpg???????????20150206-fig4-b.jpg

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?(a) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?(b)

Fig 4. Cross-correlation (a) and autocorrelation (b) analysis of Suoi Muoi River

Global water balance of the catchment

Quantitative assessment of the catchment water balance can provide useful information about the seasonal variation of different hydrological fluxes. A simple monthly based water balance model for the catchment was therefore built. It accounts for rainfall input, evapotranspiration, groundwater recharge, groundwater discharge and surface runoff components. In this model, the catchment was considered as a lumped and spatially homogeneous hydrological entity with two layers. The lower layer represents the karstic groundwater aquifers and the upper represents the topsoil layer and/or the epikarst zone. The water balance for the model is described by the following equations:

-????????Equations for the epikarst zone:

20150206-part3-3.gif???????????????????????????????(1)

-????????Equation for the karst aquifers

20150206-part3-4.gif??????????????????????????????????????(2)

Where?DS and?DGW are monthly soil storage deficit and groundwater storage deficit, respectively; St+1, St, GWt+1?and GWt?are respectively monthly soil storage and groundwater storage; It+1, ETt+1, GWRt+1, SRt+1, GWRt+1?and BFt+1?are respectively monthly rainfall, evapotranspiration, groundwater recharge, surface runoff and groundwater discharge; t is time.

Table 1. Global water balance of the Suoi Muoi Catchment

Month

I (mm)

ET (mm)

GWR (mm)

BF (mm)

SR (mm)

DS

(mm)

DGW (mm)

Jan-2000

1.20

71.50

6.60

12.68

0.28

-77.18

-6.07

Feb-2000

86.30

79.40

10.54

15.16

1.80

-5.44

-4.62

Mar-2000

21.10

100.80

28.02

16.96

2.49

-110.21

11.06

Apr-2000

71.10

112.40

13.92

15.58

1.22

-56.44

-1.66

May-2000

287.08

71.80

50.47

23.57

11.61

153.20

26.90

Jun-2000

167.82

60.30

60.17

48.18

13.97

33.38

11.99

Jul-2000

248.65

64.30

185.24

115.10

28.10

-28.99

70.14

Aug-2000

226.13

61.80

67.61

108.23

16.54

80.18

-40.62

Sep-2000

36.30

62.40

60.58

62.45

7.08

-93.76

-1.87

Oct-2000

105.59

56.20

78.89

59.28

10.13

-39.63

19.62

Nov-2000

1.80

69.10

51.64

47.60

0.92

-119.86

4.04

Dec-2000

7.50

68.30

46.63

40.22

0.95

-108.38

6.41

Jan-2001

18.30

81.00

33.68

34.79

1.54

-97.92

-1.11

Feb-2001

1.80

74.40

27.41

29.12

1.18

-101.19

-1.72

Mar-2001

128.96

86.60

26.80

31.83

4.84

10.73

-5.04

The parameter values, necessary to calculate the monthly storage deficit, were derived from the above-described hydrograph analysis i.e. the surface runoff and groundwater discharge. The monthly groundwater recharge value was calculated by the USGS computer program RORA (Rutledge, 1998), under the assumption that the groundwater recharge arealy diffuse. The evapotranspiration was determined using a reference crop evapotranspiration measured at a nearby hydrometeorological station. Result of the water balance calculation is shown in Fig. 5 and Table 1.

During period January 2000 – March 2001, the groundwater system received a surplus storage (deficit = 87.45 mm). This is evidenced by the higher groundwater discharge at the end of dry season of the year 2001 in comparison with the one of the preceding year (Fig. 3). In contrary, the topsoil layer received a negative deficit of storage (-561.5 mm). This could be explained by the fact that the total rainfall volume of the year 2000 is about 250 mm less than a normal year, the rainy season started earlier and the rainfall was more intensive. Another possible explanation, which could not be tested here, is that the years before 2000 were relatively dry. Clear is that the epikarst zone plays the important role of buffering and transfering rainwater to the groundwater system. During rain events, the zone stores infiltrated rainwater and later replenishes the groundwater in dry season, which starts from September till April.

20150206-fig5.jpg

Fig. 5: Monthly soil storage and groundwater storage deficit

Conclusion

A multi-thematic analysis was carried out to identify hydrogeological characteristics of the Suoi Moi Catchment. The study showed that the karst groundwater aquifers are determined by fractured/fissured media whilst the cavern conduits, although abundant occuring in the region, act as groundwater galleries and/or conveyers. At regional scale, such a conclusion is very important with respect to later applications of the hydrological models, which have been developed on the basis of the REV concept. A simple model to estimate the catchment global water balance was developed to estimate seasonal change of the hydrological components in the catchment. It is believed that with a longer data record the model can explain better the functioning and hydrodynamics of the karst aquifers under interest.??

Acknowledgements

This work has been carried out within the project A3210 “Rural development in the mountain karst area of NW VietnamVietnamese-Belgian Karst Project (VIBEKAP) funded by the Flemish University Council (VLIR). The authors are grateful to all VIBEKAP’s participants for their contributions. Koen Van Keer and Do Tuyet are acknowledged for their helpful reviewing and commenting of this paper.

References

Bent, G.C., 1999. Streamflow, baseflow, and groundwater recharge in the housatonic river basin, Western Massachusetts and parts of Eastern New York and Northwestern Connecticut.?USGS, WRIR 98-4232.

Bonacci, O., 1988. Determination of the catchment areas in karst.?IAH 21st?Congress. 10-15 October 1988 Guilin, China.

Bonacci, O., 1993. Karst springs hydrographs as indicators of karst aquifers.?Hydrol. Sci, 38: 51-62.

Eaton, G.P., 1996. Hysep: a computer program for streamflow hydrograph separation and analysis.?USGS, WRIR 96-4040.

Eisenlohr, L., 1997.?Numerical simulation as tool for checking the interpretation of karst spring hydrographs.?J. Hydrol., 193: 306-315.

Felton, G. K., Currens, J.C., 1994. Peak flow rate and recession-curve characteristics of a karst spring in the Inner Bluegrass, central Kentucky.?J. Hydrol., 162: 99-118.

Hop, N.D., 1996. Report on Geological Mapping scaled 1:50000, Thuan Chau Area,?Research Institute of Geology and Mineral Resources of Vietnam, 178 pp.

Labat, M., Ababou, R. and Mangin, A., 2000. Rainfall-runoff relations for karstic springs. Part I: convolution and spectral analyses.?J. Hydrol., 238: 123-148.

Lacey, G.C., Grayson, R.B., 1998. Relating baseflow to catchment properties in south-eastern Australia.?J. Hydrol., 204: 231-250.

?Larocque, M., Mangin, A., Razack, M. and Banton, O., 1998. Contribution of correlation and spectral analyses to the regional study of a large karst aquifer (Charente, France).?J. Hydrol., 205: 217-231.

Nathan, R.J., McMahon, T.A., 1990. Evaluation of Automated Techniques for Baseflow and Recession Analyses.?Water Resour. Res., 26(7):1465-1473.

November, J., 1999. Karstgeologisch onderzoek in het gebied van Son La en Thuan Chau (NW-Vietnam).?KULeuven, dissertation (unpubl.), 135 pp.

Padilla, A., 1995. Study of hydrographs of karstic aquifers by means of correlation and cross-spectral analysis.?J. Hydrol., 168: 73-89.

Rutledge, A.T., 1998. Computer programs for describing the recession of groundwater discharge and for estimating mean groundwater recharge and discharge from streamflow records – update.?USGS, WRIR 98-4148.

Smakhtin, V.U., 2001. Low flow hydrology: a review.?J. Hydrol., 240: 147-186.

Tuyet, D., 1998.?Overview on Karst of Vietnam. In: Daoxian (ed),?Global Karst Correlation, Final Report of International Geological Correlation Program. Science Press Beijing, 179-191.

Tuyet, D., 1998. Karst geology investigation of the Northwest region.?Research Institute of Geology and Mineral Resources, Hanoi., 250.

Xuyen, C.X., 1998. Report on Hydrogeological Mapping scaled 1:200000, Dien Bien Yen Bai Area.?Geological Survey of Vietnam, 202 pp.

Wittenberg, H., 1999. Baseflow recession and recharge as nonlinear storage processes.?Hydrol. Process.,?13: 715-726.

Vu, T.M.N., 2000. Design of Karst Web-based Database and Hydrological Analysis for Thuan Chau – Son La Catchment, VN. Master dissertation,?Free University Brussels., 88.

15

Sudan, Strengthening Community Water Management and Striving for Improved Sanitation

Abdeen Mustafa Omer?
( 231 Denman Street Nottingham NG7 3PS Nottinghamshire, UK)

Abstract-?Although the amount of water on our planet is a relatively fixed, it remains essential for all living things (hydropower generation, navigation, industrial use etc.). It is also becoming increasing necessary for the growth and economic well being of industry. It is vital therefore, that this scarce resource is well managed so as to meet the needs of a growing future population as well as the demands of increased industrialisation throughout Sudan. Water and raw materials may be transported for long distances to reach domestic consumers and industries. Domestic and industrial wastes however to be dealt with where they are generated. In large cities, domestic wastes and waste management has been difficult because of rapid urban growth. Environmental pollution is now a major concern all over Sudan. An integrated approach to tackle pollution issues should be adopted by industries, communities, local authorities, central governments and professionals working in the sector. Most polluters give little or no attention to the control and proper management of the polluting effluents. This may be due to lack of enforceable legislation and/or the fear of spending money on the treatment of their effluent prior to discharge. Furthermore, the fines imposed on offenders are generally too low and therefore do not deter would be offenders.

Introduction

Sudan is geo-politically well located bridging the Arab world to Africa. Its large size and extension from south to north provide for several agro-ecological zones with a variety of climatic conditions, rainfall, soils and vegetation. Water resources available to Sudan from Nile system and the under groundwater resources provide a potential for three fold increase in the irrigated sub-sector. There are also opportunities for increased hydropower generation. The strategy of Sudan at the national level aims at the multi-purpose use of the water resources to ensure water security for attaining food security, drinking water security, fibre-security, hydro-energy security, industrial security, navigation, waste disposal and the security at the regional levels within an environmentally sustainable development context and in harmony with the promotion of basin-wide integrated development of the shared water resources.

Government has continued to pay for the development and operation of water systems, and this is not sustainable. Ways and means are being sought to get the user communities to pay for water charges. Funds not only needed for water supply development, but also for operation, maintenance and environmental protection measures. In order to ensure the sustainability of the water supplies, an adequate institutional and legal framework is needed. Funds must be generated for production, environmental protection to ensure water quality and to ensure that water abstraction remains below the annual groundwater recharge. At present, there are private sector providers who do not have an enabling environment to offer the services adequately.

There is needed for the government to have mechanisms in force to help regulate and harmonize the private sector providers. Privatisation is a part of solution to improve services delivery in water and sanitation sector. Presently, there is a transitional situation characterised by:

  • Resistance to charge
  • Insufficient suitable law/law enforcement
  • Insufficient capacities
  • Inadequate interaction between actors Government to withdraw from implementation in water and sanitation sector and remain at:
  • Policy making level, and?Supervision level

There are certainly proponents of private sector engagement who do not support unfettered exploitation of the consumer in the interests of private capital Again, my concern is "what works?" Efficient, sustainable water and sanitation services are notoriously difficult to achieve, particularly in poor communities. After decades of work we are still not getting it right and countless thousands of people have died as result. Whilst we have to guard against the excesses, which are inherent in any system, do we have the luxury to sit on opposite sides of the ideological fence and score points which are in our interests but not the interests of the un-served? Until we utilise resources at the optimum point in the present, consideration for future sustainability is simply a paradox or riddle!

Community Water Quality and Sanitation Management:

Community water supply and sanitation management is a new form of co-operation between support agencies in the water and sanitation sector and communities. It involves a common search to identify problems with the local water supply and sanitation systems, and the possibilities for, and constraints on, management by communities, as well as possible solutions that may be tested. Some fundamental principles of community water and sanitation management are that:

  • Increased management capacities are the basis for improved water and sanitation systems and that each community develops its own specific management systems.
  • Communities own the process of charge; facilitators and local researchers participate in the community's projects, not the other way around.

Through this approach, the support agency is no longer the provider of technical goods or solutions, but the facilitator of process to enhance the capacity of the community to manage its own water and sanitation systems.

Communities are no longer the passive receivers of technical goods, but are active participants, knowledgeable and accountable for their actions. At the core of this co-operation are partnerships and ownership based in the community. Community management stimulates thinking and debate about relationships between support agencies and communities, about the capacities of communities to manage their own systems, about the attitudes of field staff working with communities and about sustainable water and sanitation management. The objective is to get the process of strengthening management capacity moving, creating opportunities for communities to debate and reflect on their abilities to manage their own systems. However, community management is not a 'magic wand' for solving problems in water and sanitation sector, or for governments who are keen to decentralise or privatise water provision. Neither is it a recipe that can be replicated wholesale as a blueprint.

Constraints to achieve Environmentally Sound Water and Sanitation Management: Thirty four million Sudanese-nearly 75% of them-do not have access to sanitation or clean, healthy living environments. 90% of rural and peri-urban sanitation is completely inadequate. There are many constraints, which inhabiting environmentally sound water and sanitation management in Sudan:

(1)?????Debits and financial deterioration; lack of funds or substantial delays in allocating funds for essential requirements such as operation and maintenance of irrigation and drainage projects, deterioration in data collection activities, etc.

(2)?????Lack of appropriate and consistent policies for water development for both large-and small-projects.

(3)?????Serious delays in completing water projects after major investments like dams, and other hydraulic structures, and main secondary canals are not being completed. Thus potential benefits arc not fully realised.

(4)?????Absence or inadequacy of monitoring, evaluation, and feedback at both national and international levels.

(5)?????Lack of proper policies on cost recovery, and water pricing or, if policies exist, absence of their implementation.

(6)?????Shortage of professional and technical manpower, and training facilities.

(7)?????Lack of beneficiary participation in planning, implementation, and operation of projects.

(8)?????Inadequacy of knowledge, and absence of appropriate research to develop new technologies and approaches, and absence of incentives to adopt them.

(9)??????General institutional weaknesses and lack of coordination between various ministries such as irrigation, agriculture, energy, healthy, environment, planning, economic, etc.

(10)??Inappropriate project development by donor agencies chg., irrigation development with drainage, supporting projects which should not have been supported.

(11)??Lack of donor coordination resulting in differing approaches, and methodologies, and thus conflicting advice.

Control of Environmental Pollution

Water is the single most important natural resource and means of livelihood. It is also the most expensive resource to manufacture unlike all others, because the technology to combine hydrogen and oxygen molecules to form water H2O) would be an impossible expense. It is therefore, very important to protect and control water and environmental pollution in our day-to-day activities. The huge volume of water used in homes ends up as sewage or in open drains as wastewater toxicated with chemicals and irritating odours not even suitable for irrigation.

Needless to say God had control for every creation including wastes, hence the reason why natural occurring microorganisms biodegrade small amount of wastes. Population increase, own inventions, and behavioural changes have however inhibited these natural processes through toxication, accumulation, and inappropriate methods of disposal and poor attitudes malting waste disposal and environmental pollution an additional headache especially to most urban settlements. Scientific advances have approached the use of natural methods to deal with water cleaning, control of water and environmental pollution. Products containing billions of very aggressive but dormant environmental friendly and specifically selected micro-organisms to biodegrade different types of wastes ranging from hydrocarbons tike oil, grease, fats, proteins starch, paper, etc. when introduced to the wet wastes. 1 litre of the products contains 18.5 billion microbes?each bacteria dividing every 20 minutes and multiplying to 33 million in about 8 hours when introduced to wet waste matter. The process of breaking down and digestion is therefore fast or and more effective than the natural process. Bad odours and files are and also eradicated. Handling is easy and harmless unlike toxic detergents and can be used universally in kitchen, toilets, bath-rooms to clean and remove sludge build up in piping without side effects like rusting, poisoning or itching. The wash off end up in septic tank or sewage to continue with the process without dilution and the end product is clean water which can be collected and recycled for irrigation, natural gases that can be trapped for lighting or cooking and small amount of pleasant smelling sludge. Goals and Challenges: Sudan faces daunting problems in dealing with water quality issues. The main obstacle is obviously a lack of adequate financial and trained manpower resources. Alternative technologies should help alleviate some of the pressure. Sudan like many developing countries classified as water scarce, or is rapidly moving in that direction, so that little dilution capacity is available; informal settlements are spreading rapidly, seriously adding to pollution from storm water runoff. In Sudan, an increasingly holistic approach to water resources management has become apparent over the lost two decades. This trend was clearly recognised in the concept of integrated water resources management, which emerged from the Earth Summit Conference in Rio de Janeiro in 1992. It is an approach, which involves people from all levels in water resources management, including those who have previously stood completely outside the process. Sudan needs assistance in developing and implementing the fallowing approaches:

  • River basin management
  • Diffuse source pollution
  • Environmental restoration
  • Urban storm drainage

At present the international, bilateral donor agencies, and relevant United Nations bodies mainly provide such assistance. The international associations constitute an additional, but as yet largely untapped, source of assistance. The solution, which should be seriously explored, is the forging of partnerships with bodies such as the World Bank(WB) and the appropriate UN agencies. Advanced research and technology could serve a lot in resolving water shortage and sanitation problems. Non-conventional reliable water supplies cannot be obtained, provided unless the environmental impacts have to be taken into consideration. Sudan is dependent upon surface and ground aquifers for its supply of water both for human consumption and irrigation. However, these have not been managed well Present resources must be strictly monitored and managed effectively if further deterioration is to be avoided. Looking forward to the future, Sudan has a set of priorities for water resource research and development till the year 2020:

(1) Raise the overall water use efficiency to the ms, mum limit. This could be achieved through:

  • Improve the irrigation system and assure its flexibility to cope with modern farm irrigation system.
  • Develop on the farm system.
  • Draw up a proper mechanism for water charges.

(2) Modify the cropping pattern considering the following:

  • Plan the different cropping pattern according to water quality.

·????????Replace sugar cane by sugar beats gradually.

  • Use genetic engineering and tissue culture to develop salt tolerance crops.
  • Reduce the area of clover (Berseem).

(3) Reuse all the possible amount of agricultural drainage water using proper technological means in the time and space to deal with its quality, especially after implementing the irrigation development program.

(4) Plan properly the reuse of sewage water after drawing up guidelines for their use.

(5) Research agreements of losses and suggest conservation projects.

(6) The conjunctive use and management of the reservoirs and the underground water reservoirs il the Nile valley with consideration to drought conditions.

(7) Developing non-renewable groundwater resources in the deserts on a sustainable basis.

(8) Water harvesting of rainfall in desert areas and make full use of torrential streams and flash floods.

(9) Use new economical technology of seawater desalination.

(10) Raise public awareness about water resource scarcity and??government management plans.

(11) Laws should be considered to match with the required development and existing scarcity.

Although, we enjoy safe drinking water we must continually safeguard this precious resource and seek ways to provide the best water quality possible. Safe drinking water and the willingness to pay for it must be a national priority.

Remedial Measures

From visual and analytical investigation of the Nile river (Table.1), the major sources of pollution were identified as:

·??????Industrial effluents

·??????Raw sewage from blocked, broken or overloaded sewers

·??????Sewage from informal sectors e.g., sewered or unsewered areas

·??????Effluents from public and private sewage works

·??????Surface runoff, and

·??????Solid wastes dumped into the river

Some remedial and improvement measures must be taken before the environment becomes further polluted and the natural resources are completely over-exploited. The challenges fusing and enhancing the ecology in the 21st century are the following:

?

Table (1) Wastes in the Nile water

Materials

Percent (%)

Papers, woods

50%

Ferrous residues

12.5%

Glasses

11%

Organic wastes

10%

Plastics

5%

Non-ferrous residues

1.5%

Others

10%

?

?

  • Water sources for drinking should be treated with chemicals from a sanitation point of view.
  • Suitable places for toilet facilities should be provided along the main tracks and halting places to minimise the pollution.
  • Proper arrangements for litter dumping and waste disposal should be made.
  • Local people should be fully educated about environment matters and hygiene.
  • Whatsoever, damage that has been in the past should not be allowed to continue while planning for a balanced development in the future?
  • It is necessary to consider the equilibrium between humans and their environment.
  • It is essential to promote the concept of eco-system, involving education and interpretation of the natural environment.
  • Environment education minimises the negative effects both upon the human and the natural environment and contributes to the management of protected areas.
  • A people's environment movement must be developed in order to collectively harness the people's energies towards confronting the crisis. The time to act is now. The ancient pragmatic wisdom of living in harmony with nature's processes rather than to conquer or subjugate them is essential
  • Polluters must pay principle.

Last but not the least: "Let us all remember that we have not inherited this earth from our forefathers but we have borrowed it from our children".

Conclusion

Booming economy, high population, land locked location, vast area, remotely separated rural areas, which are not easily accessible, large reserves of oil, excellent sunshine, large mining sector and cattle farming on a large scale are factors which are most influential to the total water scene in Sudan. It is expected that the pace of implementation will increase and the quality of work to improve in addition to building the capacity of the private and district staff in contracting procedures. The financial accountability is also easier and more transparent.

It is important to know that efforts to enhance community management are not starting from scratch. The communities manage their own households, agricultural systems, religious or cultural events as well as their relations with state. The communities should be fully utilized in any efforts to promote the local management of water supply and sanitation systems.

There is little notion of "service, invoice and move on". As a result there are major problems looming with sustainability of completed projects. It seems that there has been little shift in paradigm, which does little for the image of the private sector-they are often own worst enemies.

The factors affecting the eco-environmental changes are complex. There are interrelated and interact. The deterioration problems of water and sanitation have attracted some attention in recent years. There is an urgent need to study possible rehabilitation measures to ensure a sustainable and excellent water quality and improved sanitation.

References

Omer, A.M. 1995. Water resources in Sudan. NETWAS 2(7).

Noureddine, R.M. 1997. Conservation planning and management of limited water resources in arid and semi-arid areas. In: Proceedings of the 9th Session of the Regional Commission on Land and Water Use in the Near East. Rahat: Morocco.

James, W. 1994. Managing water as economic resources. Overseas Development Institute (ODI). UK.

Overseas Development Administration (ODA). 1987. Sudan profile of agricultural potential Survey. UK.

Seckler, D. 1992. Private sector irrigation in Africa-Water resources and irrigation policy studies. Win rock International Institute for Agricultural Development.

Salih, A.M.A.; and Ali, A.A.G. 1992, Water scarcity and sustainable development. Nature and Resources 28(1).

Omer, A.M. 2000. Water and environment in Sudan: The challenges of the new millennium. NETWAS 7(2).

Clarke, R. 1991. Water: The international crisis. Earth-Scan Publication Ltd. London: UK.

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