Dams and Reservoirs in Evaporites

By Petar Milanović, Nikolay Maksimovich and Olga Meshcheriakova

This book shares essential insights on evaporites and their effects on dams and reservoirs. The intensity of the solution and suffusion process in evaporites (gypsum and salt) is much greater than the solution of carbonates, and evaporites are particularly vulnerable at dam and reservoir sites.

Moreover, the presence of evaporites in the vicinity of dams or reservoirs often leads to serious problems: numerous dams in countries around the world (e.g. China, Germany, Iran, Iraq, Peru, Russia, Spain, the Unites States, and Venezuela) have been affected by evaporite dissolution problems. Several of these dams were seriously endangered or ultimately abandoned, even though the best available engineering prevention and remediation practices were applied. Conventional geotechnical methods based on treating the underground (e.g. grout curtains) or surface (e.g. protective blankets) were not successful.

This book presents and analyzes revealing case studies in this regard. Toimprove geotechnical remediation in connection with preventing seepage from reservoirs situated in evaporites, particularly in gypsum, it puts forward a new chemical solution that, after painstaking laboratory testing, was successfully applied in the field.

• Language: English
• Publisher: Springer
• Release date: May 25, 2019
• ISBN: 9783030185213

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© Springer Nature Switzerland AG 2019

Petar Milanović, Nikolay Maksimovich and Olga MeshcheriakovaDams and Reservoirs in EvaporitesAdvances in Karst Sciencehttps://doi.org/10.1007/978-3-030-18521-3_1

1. Distribution of Evaporite Karst in the World

Petar Milanović¹  , Nikolay Maksimovich²   and Olga Meshcheriakova³  

(1)

Belgrade, Serbia

(2)

Institute for Natural Sciences, Perm State University, Perm, Russia

(3)

Institute for Natural Sciences, Perm State University, Perm, Russia

Petar Milanović (Corresponding author)

Email: [e-mail]

Nikolay Maksimovich

Email: [e-mail]

Olga Meshcheriakova

Email: [e-mail]

1.1 General

Evaporite karst is developed widely throughout the world, though it is more common in the northern hemisphere, reflecting the current distribution of evaporite formations. It develops in all climatic settings, from cold Arctic to hot arid or humid tropical, from the lowest land to high mountains. The global distribution of gypsum, anhydrite, and salt known to have accumulated over geological time is presented at Fig. 1.1 (Kozary et al. 1968).

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Fig. 1.1

Global distribution of evaporite karst, Kozary et al. (1968)

According to Ford and Williams (2007), most of the evaporites accumulated over geological time are now buried beneath later carbonate or clastic rocks. At many cases, evaporites are removed by dissolution or reduced by folding and thrusting as it is in the Andes. More than 90% of anhydrite/gypsum and more than 99% of the salt displayed here do not crop out. Hydrogeologically active karst within these evaporite rocks probably covers an area comparable to active carbonate karsts.

The common belief that arid environments are preferred for gypsum karst development is not strictly correct. Although gypsiferous formations do suffer intense karstification when exposed at the surface in very humid regions, and thus may be quickly destroyed there, the development of inter- and intra-stratal gypsum karst can be widespread and vigorous in such conditions. Gypsum karstification is common in deep-seated geological settings also, i.e., those with little or no visible expression at the surface. When not only the geomorphological, but also the geological and hydrogeological evidences of karstification in gypsum are taken into account, appreciation of the extent of gypsum karst terrains throughout the world is considerably increased (Klimchouk et al. 1996).

Evaporite rocks are widespread all over the world and underlay about 25% of the global continental surface. Klimchouk et al. (1996) listed more than 35 countries and regions with recorded outcrops of gypsum. Halide rocks are widespread also. In areas of the former USSR, salt deposits cover more than 2.3 million km² (Korotkevich 1970). The substantial number of dams and reservoirs that are located in evaporites has given rise to many problems. Due to the high solubility of these rocks, increasing seepage losses are a common consequence of reservoir filling. In the worst cases, due to the load-bearing capacity of the foundation rocks being weakened by solution, there can be catastrophic collapse of parts of the dam, etc. structure. Another important problem is water pollution where the addition of dissolved solids from evaporites renders the water unusable for human, agricultural or even, in some cases, industrial use, particularly where reservoir water is in direct contact with the salt rocks.

1.2 Distribution of Gypsum Karst

On the global scale, surface outcrops of gypsiferous strata appear quite limited. This apparent scarcity can be explained by the relatively low resistance of gypsum (a soft rock) to all types of denudation processes, rather than being a limited occurrence of sulfate rock deposits. The extent of sulfate rocks either at the surface or at depth beneath it is great: Ford and Williams (1989) estimated that gypsum/anhydrite and/or salt deposits underlie 25% of the continental surface (approximately 60 million km²), while Maximovich (1962) calculated that the area of the continents underlain by gypsum/anhydrite alone is about 7 million km². Karst processes operate extensively in intra-stratal settings beneath various types of cover beds, particularly where the gypsum/anhydrite beds occur within at least the upper few hundred meters of a stratigraphic sequence. Taking this into account, gypsum karst appears to be a much more widely developed phenomenon than commonly believed.

The largest areas of sulfate rocks are found in the northern hemisphere, particularly in the USA and Canada, Russia, China, Iran, Spain and the UK.

In USA, gypsum deposits are present in 32 states, and they underlay about 35–40% of the regions where Precambrian through Quaternary strata are in outcrop (Dean and Johnson 1989, Fig. 1.2).

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Fig. 1.2

Gypsum/anhydrite deposits in the coterminous USA (Dean and Johnson 1989)

In Russia and the surrounding former USSR states, Gorbunova (1977) estimated the extent of sulfate rocks to be about 5 million km².

According to Lu and Cooper (1996), China has the largest gypsum resources in the world. They range in age from Precambrian to Quaternary, and their genesis includes marine, lacustrine, thermal (volcanic and metasomatic), metamorphic, and secondary origin (Fig. 1.3).

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Fig. 1.3

Map showing the age and distribution of the main genetic types of gypsum in China. (1) Cambrian marine gypsum; (2) Ordovician marine gypsum; (3) Triassic marine gypsum; (4) Carboniferous marine gypsum; (5) Cretaceous lacustrine gypsum; (6) Tertiary lacustrine gypsum; (7) Late Tertiary–Quaternary lacustrine gypsum; (8) thermal and metamorphic gypsum (typical localities); (9) secondary deposits of gypsum produced by karstification. Abbreviations are for names of provinces (Lu and Cooper 1996)

In Iran, there are large areas of rock formations containing evaporites, mostly gypsum and salt. Figure 1.4 shows the distribution of the Gachsaran, Upper Red, and Sachun formations, the chief gypsum/anhydrite hosts. The total outcrop of the gypsum formations is about 80,000 km², 5% of Iran’s land area (Raeisi et al. 2013).

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Fig. 1.4

Areas containing outcrops (black) of the principal gypsum formations in Iran. The Hith Anhydrite area is too small to show at this scale Raeisi et al. (2013)

According to Mancebo Piqueras et al. (2011), Spain has the highest proportion of gypsiferous rock outcrops in the world. Broadly, gypsiferous geological formations occupy 21% of the total surface area of the nation, with some 9% being massive evaporite formations.

Many other countries within the American continents, Europe, and Asia host important, and commonly quite extensive, gypsum karst. For instance, karstified evaporites cover large area at cold regions of Wood Buffalo National Park in northern Alberta, Canada (Fig. 1.5). It is very like the Pinega karst near Arkhangelsk, Russia, in many respects.

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Fig. 1.5

Wood Buffalo National Park, Alberta, Canada. The bedrock geology is 5–30 m of horizontally bedded dolomite underlain by 100 m+ of gypsum with silt, shale, dolostone interbeds, etc.

Courtesy of D. Ford

Detailed characteristics of many of these are provided within the national reviews comprising later chapters of this volume. The aim of this chapter is to present a brief overview of the geographical distribution of gypsum karst in the world, with particular reference to those areas that are not described separately, either due to a real scarcity of data or because the authors were unable to involve local experts. The general order of the reviews begins in the Americas and proceeds toward the east.

The first brief global reviews specifically dealing with gypsum karst were provided by Maximovich (1962). Since then knowledge of gypsum karst, in terms of its morphological and hydrogeological peculiarities, development mechanisms and geographical distribution, has increased dramatically. Recently, the global distribution of gypsum karst has been considered by Nicod (1976, 1993), Cooper and Calow (1998), Klimchouk et al. (1996), and many other authors.

1.3 Distribution of Saline and Gypsiferous Soils

The processes of evaporite dissolution that must be taken into account in hydrotechnical construction can also occur in soils containing salts and/or sulfates dispersed within them.

Soils containing salts are widespread in many countries. The origin of salts in soils (unconsolidated rocks) is associated with the dissolution and chemical weathering of consolidated rocks, which cause the conversion of some of their constituent minerals to saline solutions. Saline accumulation in soils is typical in semiarid and arid regions with negative soil water balances, where the annual amount of precipitation often does not exceed 25 mm/year, Petrukhin (1993), Ashoor (2003).

According to their degree of solubility in water, the salts present in soils may be subdivided into readily, medium, and weakly soluble categories. The light- and medium-soluble salts are generally referred to as water-soluble salts.

Saline and gypsiferous soils occupy large areas in Asia (Mongolia, China, Iran, Afghanistan, Iraq, Syria, Pakistan, India), in North Africa (Libya, Egypt, Algeria, especially in the Nile Delta), the Americas (USA, Canada, Mexico, Argentina, Chile, Peru), in Europe (France, Spain, Italy, Romania, Greece), and in Australia. Soils containing salts are widely distributed in the CIS countries—in the southern part of Russia and Ukraine, in Kazakhstan, Central Asia, and Caucasus (CIS—Commonwealth of Independent States members of former USSR). About 10% of the CIS is occupied by deserts and semideserts, in which soils with significant salt content are predominant (Petrukhin 1993). According to Chokhonelidze (1957), the total area of saline and gypsiferous soils is about 750,000 km².

Nafie (1989) estimated that gypsiferous soils occupy 724,000 km² of the continental surface. These soils are also widespread in Iraq where, according to various estimates, they cover 20% (Barzanji 1986) to 50% (Al-Mukhtar 1982) of the nation.

1.4 Distribution of Karstified Salt

About one half of the major sedimentary basins of the world (>110) contain salt (halide) strata. Saline deposits are widespread on the planet. They are found within all continents and seas, and the fringes of the oceans, being absent only in the modern abyssal depths, Korotkievich (1970) and Belenitskaya (2013, 2016, 2017).

Only those salt bodies (or parts of them) that, after their formation, lie at considerable depths and are insulated by overlying impermeable and insoluble strata may not be affected by solution by circulating groundwater. However, the probability that even such bodies will remain completely intact, especially in their peripheral parts, is small. In this regard, we may presume that the area displaying some salt karst features will, in general, be almost as large as the area of the original ancient salt deposit.

An important feature of many saline basins is the complication introduced by salt-dome tectonics, producing saline domes. Locally intensive structural deformation is characteristic in more than half of the major saline basins of the world, including the vast majority of the largest of them (Fig. 1.6).

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Fig. 1.6

Salt and salt-dome basins around the world Belenitskaya (2013). (1) Folded cover strata areas with discrete residual and injected tectonic saline features; (2) basement terraces on ancient platforms; (3) continental rifts: a—Neogeodynamic, б—Pre-Cenozoic buried; (4) oceanic rifts; (5) limits of salt basins of different material–geochemical types; mixed types are shown by a combination of signs: a—chloride–sodium, б—chloride–potassium, в—sulfate–potassium, г—sulfate–sodium, д—carbonate–sodium; (6) areas of salt tectonic manifestations; (7) age of salts (field fill color corresponds to the stratigraphic age of salts; in the presence of thick salts of two or three ages in the sequence, striped shading is used); (8) known salt and sulfate occurrences in rocks of Precambrian age

In the territory of the former USSR, the total area of salt deposits exceeds 2.3 million km², of which the Angara-Lena marginal trough (more than 0.6 million km²) contains the largest area of rock salt deposits, plus the Pre-Caspian syncline and the Pre-Ural marginal trough (0.3 million km²), etc (Fig. 1.7), Korotkevich (1970).

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Fig. 1.7

Map of the distribution of salt deposits in the former USSR. (1) Areas with modern salt lakes; (2) areas with fossil salts Dzens-Litovsky (1962), Korotkevich (1970)

It is worth noting that the influence of climatic factors on karst formation in rock salt that lies above the local base level of erosion is very large, and below it—very little or none. When a rock salt massif is located above the local base level, the rate of karstic processes is determined chiefly by the amount and nature of the precipitation available, i.e., by zonal geographical factors. This explains the almost complete absence of salt outcrops on the surface in the humid climatic zones today because they are so rapidly destroyed there and the presence of considerable amounts of surface salt in the arid zones.

In a different manner, leaching of salt bodies can occur to varying extents below the surface of the earth and even beneath geologic horizons containing saltwater. Such karst development can also occur with very different intensities, regardless of the zonal geographic features of the region. The geological, tectonic, and hydrogeological features in the particular salt deposit area are the chief determinants of the possibility and intensity of any flow of aggressive groundwater coming into contact with the salt. Geological and tectonic factors determine these geographically azonal features. Groundwater is zonal (stratified). This zonality is reduced to nothing if a layer of saturated brines develops and remains practically motionless on the lowermost salt formation. In this situation, karst formation ceases regardless of the climatic zone (Korotkevich 1970).

References

Al-Mukhtar, A.N. 1982. Distribution of gypsiferous soils and their effects on the safety of structures. J.Al.Muhangiss. Baghdad (in Arabic).

Ashoor, H.M. 2003. Accounting for the process of dissolution of gypsum contained in soils, when calculating the deformation of the foundations of building. PhD thesis. Saint-Petersburg, (In Russian). 125.

Barzanji, A.F. 1986. Distribution of gypsiferous soils of Iraq. In Symposium on Gypsiferous Soils and Their Effects on the Structures and Agriculture. The institute of water and Soils researches, Ministry of Irrigation. Iraq (in