QUESTIONS STILL UNDER I DISCUSSION

Choice of a uniform method of presenting the results of analyses, to permit diíîerent types o€ water to be properly compa.red.

Development of rapid colorimetric and polarographic methods.

study

of the reasons for the presence of salt

in

shale and calcareous marl.

Study

of the influence of temperature on evaporation, and hence on the concentration o€ salts in the water.

Possible reduction of the salinity of water

in

arid countries,

by

prolonged

pumping

by

the distribution of flood waters.

Direct connexion between the restoration of soil, the feeding of water-tables and the reduction of the salt content of water.

Methodical study of harmful salts,

with

a n indication of quantities, e.g. magnesium and sodium salts, and salts resulting from base-exchanges, etc.-and their effect on different crops.

Decision on the limits and practical conditions for using “liming” and ‘rmarling” methods-provided they are not

unduly

costly-capable of causing base- exchanges and permitting the cultivation of certain types of land, despite the presence of salts

in

the water.

Research in arid countries into the principal cases

in

which the earth has been made saline

by

the use of saline irrigation water. Discussion of such cases.

Warning against this danger

in

areas newly brought under cultivation.

Improvement of our knowlege about the €allowing prob- lem: “saline irrigation water, and pedology”.

Other points might also

be

suggested for discussion.

The subject of

the

physics and chemistry of undergroimd water is too vast to be studied

in

a few pages.

Certain facts have, however, been definitely estab- lished and are applicable to arid countries: the mineral content of limestone is always low, whatever the climate,

and therefore countries which have

big

limestone hori- zons offer prospects for the future. T h e results obtained

in

Southern Algeria and Tunisia, both of them limestone countries, have recently given proof of this fact. Syria, Egypt, Argentina, etc., might also be mentioned.

T h e mineral content of sand and sandstone is more subject to climatic influences, but is still acceptable.

On

the other hand, shale and primary formations

in

general,. marl, calcareous marl, fine sandstone and alluvial soil crossed

by

clay or silt always give only very poor quality water, with a variable flow and few possibilities of use.

Water-tables which lie only a short distance beneath, the surface are influenced

by

climate and their mineral content increases rapidly, especially in stony alluvial deposits. T h e m a x i m u m amount of water should

be

drawn off from the head of the water-table, and‘where possible the flow of water underground should be avoided where it is too close to the surface.

Lastly, running water €rom rivers seems to be of great importance

in

countries with impermeable subsoils, and m a y directly influence the mineralization of ground water.

In the light of our knowledge of these questions,

I

would suggest that Unesco should try to collect more substantial documentation, firs t on the most important and typical observations m a d e in arid countries (average mineralization of water, variation of such mineralization

in

time, influence of climate, etc.), and secondly , o n the effects of h u m a n activities and the successes and failures encountered

in

utilizing water (reduction of salinity through irrigation or alternatively, its increase through exhaustion of water-tables, accidental concentration, effect on adapted crops, etc.).

Thus, the problems of the mineralization of ground water

in

arid countries, and of that of other types of water

in

excessively variable climates, are both exceed-

ingly

important, not only because of the complexity of the problems themselves, bat because of their practical consequences on life and cultivation.

Unesco deserves our gratitude for having undertaken the difficult task of studying the problems of arid countries, and it seems to m e that w e should request it to centralize the pestions

and

observations arising out of the present report, and also extract therefrom, for a future meeting, documentation which

would

contain all the necessary de tailedinformation on concrete instances of the utilization of water

in

arid countries.

will

then be possible to reach even more precise conclusions, and above all to secure more accurate indications of what might be done elsewhere.

The physical and chemical properties of underground water

B I B L I O G R A P H Y

ARCELANUAULT, J. “Hydrogéologie tunisienne”, Annales des

MIEGE.

“La question des eaux salées au Maroc”, Revue de mines et de la géologie, no. 1, 1947. géographie marocaine, no. 3, 1932.

BUIST, C. “On volcanoes in India”, Transactions of Bombay

NEWBOLD.

“Temperature of the springs, hills and rivers of Geograpcphical Society, vol. 10, 1852. India and Egypt”, Philosophical Journal, vol. 10, 1846, COLE, Ralph

C.

The quality ofwalesfor irrigation in connection p. 102.

with the water analysis program of Region

II.

OLDHAM. “Thermal springs of India”, Memoirs of the Geolo-

DONEEN,

L. D. “The quality of irrigation water and soil gical Survey O J India, vol. 19, pt. 2, 1882, pp. 1-63.

permeability”, Soil Science Society of America Proceedings,

RENICK.

Base-exchange in, ground water by silicate as illustrated vol. 13, 1948. in Montana, “U.S. geological survey water supply paper”, FROMMURZE, H. F. “Bromine in South African underground no. 52013, 1924.

water”, South African Science, vol. 11, no, 8,194.9, pp. 170-74. SCLAGINWEIT, R. Journal ofthe Royal Asiatic Society ofBengal.

GAUCHER.

“Essai d’une représentation cartographque des

SCIIOELLER. “La

température des eaux souterraines”, Travaux facteurs de salure de la plaine de Relizaine”, Bulletin du du laboratoire de géologie de la faculté des sciences de l’Uni- Service de la carte géologique de Z’AZgérie, fascicule 10, 1950. versité de Bordeaux, t. 1, no. 1, 1949.

HERON,

A.

M. “The physiography of Rajputana”, Proceedings

- .

“L’influence du climat sur la composition chimique des of the Indian Science Congress, 1948, pp. 119’32. eaux souterraines vadoses”, Bulletin Société géol. de France,

HOLLAND Th.

and CHRISTIE,

W. A.

K. “Origin,of salt deposits Nov. 1941.

of Rajputana”, Records of the Geological Survey of India,

- ^.

^“Essai^sur^laqualité chimique de l’eau destinée à l’ali- vol. 38, Pt. 2, 1909-10, pp. 154-86. mentation de l’homme dans les pays arides”, Chronique des HUME,

A.

C. Report on the administration of the Inland Customs mines Coloniales.

Department for the year 1867-1868. WARTH, H.

“The

salts of Sambhar Lake in Rajputana and of

LA

TOUCHE, T o m D. “Geology of Western Rajputana”, the saline efflorescence called

Reh

from Aligarh in the Memoirs of the Geological Survey of India, vol. 35, pt.

I,

North Western Province”, Records of the Geological Survey pp. 1-115. of India, vol. 24,, pt.

I,

1891, pp. 68-69.

MEPKERSON.

Indian annals of medical sciences, Calcutta, no. 3, WILCOX,

L.

V. The quality of water for irrigation use, “Techni-

1854. cal Bulletin”, no. 962, Sept. 1948.

m s c u s s r o N

PEOFESSOR

PlCARD. There is one interesting observation that in artesian basins on a regional scale salinity decreases in the deeper aquifers. This might be because the borders of these basins, which are usually high mountains like the Eastern Australian Alps, receive pure rain water percolating into the deeper aquifers.

However, the upper aquifers which originally might have contained fresh water owe their present salinity to water which has been leached out of saline soils (Sebha, sbotts) and has percolated down to the upper strata.

MR.

ROBAUX.

It

is true that water which is filtered through water-bearing strata in mountains generally remains fresh during its flow in depth and that it is €ound in a pure state

on boring.

The cause m a y be, on the one hand the abundance of rain in mountainous arcas, permitting an extensive flow to the water-bearing horizons, and ou the other, the absence of evaporation in these areas, which, together with the rapid flow, might enable the water to remain pure.

As to the role played by the saline areas of the Sebha and the shotts in producing saline waters, this has not yet been properly studied since two very different phenomena have been noted. W h e n the soil of the Sebha forms an impermeable stratum and the underlying horizon is a good aquifer, the waters in depth are pcrfectly sweet; for example the waters of the Shott Chergui in Algeria, o€ the Gharb in Morocco, etc.

If, on the other hand, there is a communication between the upper and lower zones, the water is salt, as

with

the waters of the Shott of Zarzis in Tunisia, of the Medja in Tangiers, etc.

The whole question of salinity appears here to be a function OF the permeability of the horizons sep

MR. CAGNIARD.

Although

I

a m not a

ject dealt

with

by the speaker,

I

should like to ask

if

any systematic study has been made of the practical possibilities OP desalting land by controlled cropping with special species of plants. The most valuable would be those most rapidly able to concentrate in their tissues the maximum salt content, so long, of course, as they were harvested and removed each year.

It

would not be necessary for these plants, grown solely for their desalting effects, to have any economic uses.

After several years, they could give place to usable species.

If

this has never been tried, it might be‘advisable to under- take the systematic establishment of the anniial desalting capacity of each species.

MR.

ROBAUX. It

is not impossible, but

I

a m not really able to deal

with

the question, which is an agricultural one. A

priori, if such an underlaking were possible, one would expect to find that the salt lands had been desalted by spontaneous vegetation, but this is not the ease.

It

might be very diifficult to find plants capable of the required effect.

R E S E A R C H O N T H E C H E M I C A L P R O P E R T I E S O F T U R K E Y ’ S U N D E R G R O U N D W A T E R

R E S Q U R C E S

bY

K E R I M O M E R C A G L A R

Professor of the Faculty of Agriculture, Ankara, Turkey

Water is an extremely important factor in the life of nations. F r o m the earliest times, m e n have therefore been constantly compelled to view the question of water resources as a social problem and to engage

in

Gerce struggles for possession of a spring, a river, a lake or a sea.

Turkey is one of the countries for which the question of water is of crucial importance.

In

view of the low annual rainfall

in

various parts of the country, and especially

in

central Anatolia, the land cannot be m a d e productive without irrigation. For centuries the Turks have therefore striven to make use of surface and ground water and have employed m a n y devices for this purpose. Although the first achievements

in

this field date back to the time of the Ottoman Empire, it is only fair to state that really systematic efforts were begun mainly after the establishment of the Republic.

A s it is not always possible to draw the water required for agricultural and other purposes from lakes and water courses, w e are sometimes compelled to have recourse to ground water. It must unfortunately be admitted that

in

m a n y parts of Turkey, large-scale research has not yet been carried out to determine the true features of our underground water system.

Nevertheless, such research as has been done to date, though of purely local interest, entitles us LO place the greatest hopes

in

our ground-water resources.

In

this paper, w e shall confine ourselves to a study of the chemical composition of these waters and a description of the results of

23

years of research.

T h e underground waters with which w e are concerned

u1

this study, though largely concentrated

in

central Anatolia, nevertheless occupy a fairly extensive area of the country.

A N A L Y S I S A N D C H E M I C A L C O M P O S I T I O N O F U N D E R G R O U N D W A T E R S I N T U R K E Y

A

study of the chemical composition of Turkey’s underground waters reveals that, as the water perco- lates through the various layers of earth, its character is more affected

by

the nature of the strata in question than

in

regions where the rainfall is heavy.

In

fact -and this comment applies particularly to the parts of Anatolia where underground water resources are of special value-during the formation of soil

by

the disintegration of rocks, the various water-soluble salts produced

by

the decomposition of minerals have, as a result of the lack of rain, accumulated underground.

T h e properties of these salts can be ascertained

by

analysis of water-saturated soils

in

the dry regions of Turkey,

of

surface water flowing over the

&y

soils

in

question, or of the water which has accumulated under-

ground after percolating through the various layers of earth. These salts include the chlorides, sulphates, nitrates, alkaline bicarbonates and carbonates, and alkaline earths. T h e presence of alkaline bicarbonates and carbonates in ground water has caused us to consider s o m e of the special features of these salts

in

the course of our analyses.

Careful examination of the tables annexed to this paper, giving the results of analyses of Turkey’s underground waters,

w i l l

reveal that most of these waters are not characterized

by

permanent hardness and contain a certain quantity of sodium carbonate (esti- mated

by

calculation). Without entering into long explanations, w e m a y mention that, in Turkey, waters of this type are infinitely more c o m m o n than

in

any 29

other country. A s water containing alkaline carbonates (Na,CO,,

K,CO,)

or alkaline bicarbonates (NaNCO,,

IC13C03)

is neutralized

by

titration with a n acid, the temporary hardness due to alkaline earth carbonates and bicarbonates is always greater than the total hardness.

In

order to avoid such discrepancies, it is essential to correct the results of the analyses

by

the recognized methods.

In

order to clarify this point, it m a y be useful to take as a n example the sample of water

No.

^4,^from

the region of Ankara, shown

in

the lists annexed to this paper. A s indicated

in

those lists, the total hardness of this water is 19.19 (German scale).

TO

establish the temporary hardness resulting from the presence of alkaline earth metals (a hardness which is, incidentally, due to bicarbonates), it is necessary to multiply

by

the index 2.8 the number of cubic centi- metres of n/10

HC1

used to neutralize the alkalinity of 100 CU. cm. of water, methyl-orange being the indicat0r.l W e thus arrive at the figure of 20.86 on the German scale for the temporary hardness

of

this water, i.e. the hardness due to the presence of hicar- bonates. As, however, this latter figure is higher than the figure of 19.19, representing the real total hardness, it requires correction.

In

these conditions, the temporary hardness of the water is the same as its total hardness. T h e difference of hardness (20.86

-

^19.19

=

1.67) is due to the alkaline carbonates and bicarbonates which have been neutralized. This figure must be reduced to CU. c m . of n/10

HCl

(1.67

x

2.8), each to the presence of alkaline earth salts such as the chlorides, sulphates, nitrates and other salts associated with acid radicals.

One of the Characteristics of the waters found in the

dry

regions of Turkey is that s o m e of them, are very rich

in

chloride, sulphate, nitrate and hydrocarbonate ions. There can be no doubt of the importance of ground water containing these salts, from the point of view of irrigation and the watering of the ground.

W h e n the concentration of salts

is

above a given figure, the water cannot be used for irrigation.

In

point of fact, w e have found

by

certain experiments

in

Turkey that, w h e n plants- were watered with ground water rich

in

salts, the resdts were negative and the plants dried

up

and withered. Samples Nos. 1 and 2, whose composition is shown

in

the list, were taken from the wells of the National Assembly

in

Ankara. Flowers watered with these waters (and particularly flowers introduced from Europe) withered a w a y

in

a very short tirne.2

A

study of Turlrish underground waters, from the point of view of their salt content, shows that certain of them, for example, contain simultaneously chlorides,

sulphates, nitrates, bicarbonates, and carbonates, which brings them into the category of waters rich

in

salts.

Certain others contain only chlorides, sulphates or nitrates, for example, or one or more of the various other salts. Samples of differen1 typcs are shown

in

the lists annexed.

On

the basis of these characteristics, Turkey's underground waters m a y

he

classified in the agriculture. The category, incidentally, includes most of our underground waters. There is nothing harmful in the composition of these waters, which contain only minute quantities of alkaline bicarbonates.

UNDERGROUND W A T E R S W H I C H A R E S A L T

T h e waters

in

this category m a y be divided into two groups: slightly salt water; and very salt water. They m a y also be differentiated as containing only one salt or more than one salt.

S L I G H T L Y S A L T W A T E R S

These waters contain from

0.5

to 1 gm. of matter

in

solu- tion per litre (cf.

Nos.

15,

30,

etc.

in

the list).

S A L T G R O U N D W A T E R S

These are generally waters containing at least 1 gm.

of salt per litre. They

may he

subdivided into five categories, according to the nature of the salts entering into their composition.

I.

Waters Containing Chlorides

If

a water is to

be

placed

in

this group, it must contain at least 250 mg. of chloride ions per litre, plus 1 gm.

1 I£ 100 CU. c m . of water are used, each CU. c m . of n/10 IICl absorbed, using methyl-orange as the indicator, corresponds to 28 mg. of Ca0 per litre of water. As 1 mg./l. of C a 0 corresponds, in turn, to lo of hardness on t h e G e r m a n scale, iî the n u m b e r of CU.

c m . of n/10 HCI employed is multiplied b y the index 28: 10

=

2.8, we arrive at the quantity of carbonate or the degree of hardness, on t h e G e r m a n scale.

Plants acclimatized to Anatolian soil exhibit great resistance b o t h to the salts accumulated in the soil a n d to t h e salts present in t h e waters. Experiments carried ont b y myself and b y other writers h a v e s h o w n that t h e planta in question are capable of absorbing nutriment in soils presenting a m u c h greater concen- tration of salts than is found elsewhere.

Dans le document HYDROLOGY SYMPOSIUM (Page 25-28)