EXISTING FORMATIONS

of

Bow

of the few existing watercourses diminishes with the distance from the points at which they rise.

T h e lakes are shallow and become great marshes or white salt deserts during the summer (e.g. the Salt Lake).

Those to be seen welling out on the edges of the old formations have a very low rate of flow, scarcely ever exceeding

1

or

2

1. a second. T h e water is generally of good quality.

On

the other hand, the waters of the Karst type rising from the resurgent Neogene limestones at the bottom of the deep valleys close to the Sakarya sometimes have a rate of flow of some hundreds of litres a second or more.

W e m a y mention particularly the springs in the villages of Katirli, Kurt, Taciri, Ozun bey, Salc Ucagi,

and

Naci Faki.

There are a fair number of wells, and the names of villages are derived from the special features of their wells, a5 Bas Kuyu (great well), D a r Kuyu (narrow of these wells shows that the underground waters also have a n outlet into the Sakarya river.

There are few springs.

T h e stratigraphic series comprises an impermeable P R O B A B L E W A T E R - T A B L E S substratum consisting of grano-diorites, gneiss, mica

T h e probable water-tables, working downwards, are:

1: In the alluvial deposits, where they are sometimes from

10

to

20

m. deep.

2. In the Neogene limestones, where there are two levels,

the

upper one at approximately

850

m. and the lower one at

800

m. above sea level

(Fig. lb).

3. In

the old limestones and marbles, which have escaped erosion.

schists, clay schists, greywacke, marbles, compact limestones or quartzites. T h e Tertiary envelope consists of sparse Nummulitic limestones mainly of lacustrine Neogene formation, with volcanic rocks such as ande- sites and basalts covering large areas. This envelope is from 250 to

300

m. thick and becomes t h e r from north to south. Alluvial deposits and scree are found

almost everywhere, but cover only small areas.

4.

A t the junction of the

old

impermeable bed-rock and the later Tertiary formations (see

Fig. lc).

TECTONIC C H A N G E S

T h e Neogene formations are generally very slightly folded (30-50). N o surface faults have been observed but, as certain regions such as

the

t o w n of

Ilgin

are b o w n for their earthquakes, it

is

pite possale that there are deep-seated dislocations affecting the bed- rock itself.

R E S U L T S O F B O R I N G

T h e 110 m. shaft

sunk

near the Polatli farm showed

U S that there was no p o u n d water in the 41m. depth

of alluvial deposits but that, on the other hand, a certain amount of water was present

in

the limestones at a depth of

63

m. (see

Fig. lb).

T h e e shafts sunk to depths of

35

m.,

76

m., and

HYDROGEOLOGICAL FINDINGS 96

m. respectively

in

the neighbourhood of the Alti- nova farm, where the alluvial deposits

and

scree are T h e low precipitation is insufficient to counter-

18

m. deep, also failed to yield water. Water was balance the

high

rate of evaporation and the losses due struck on meeting the green rocks and calcareous marl to infiltration into the porous strata

and

particularly Neogene formations, or at a depth of about

65

m.

into the fissured limestones. Owing to this, the rate T h e rate of flow is over

1 1.

a second (see

Fig. IC).

Prospection for underground water, and adaptation of drilling methods C H E M I C A L A N A L Y S I S O F T H E W A T E R

Hardness for carbonate:

12.530.

Total hardness:

11.290.

Residue of evaporation at

1050:

240 mg/l.

Residue of calcination at red heat:

175.6 mg. /i.

H,CO,: 152.5 mg.

/i.

C1: 20.6 mg./l.

SO,: 12.8 mg./l.

SiO,: 20.8 mg./l.

Fe,O,

+ &,O,: 1.1

mg./1.

Ca:

46.2 mg./1.

Mg: 14.2 mg./1.

Alkalis: trace.

W e shall have to carry out further boring at the Gozlu farm. T h e shafts proposed are spaced out along a line measuring

100 km.,

at distances of

40

to

60 km.

from one another. This arrangement

will help

us

in

checking the results secured

by

geological study and will give us information about the quality and flow of the ground water.

In

the K o n y a region w e have

sunk

vertical shafts, intercalations of

red

clay and various salts, m a y contain using either rotary or percussion

drills.

_{fresh, salt or} brackish water.

If

people are to be settled cussion type uses far less water, it is the m

in

these regions, the first necessity is to

find

adequate suitable for use, provided that core-samples are not supplies of

drinking

water.

It

is therefore necessary

needed. to locate the fresh water levels and to cut out the waters

There are, however, other Neogene basins

in

Turkey which are not drinkable. For this purpose it m a y

in

which the shafts must be sloping or horizontal. This perhaps again

be

necessary to sink sloping, horizontal is the case on the northen and southern boundaries of or vertical shafts in M e r e n t instances.

the Neogene basins

in

central Anatolia, where the strata There are,

in

addition, great tracts

in

Turkey where are sharply sloped

by

flexure or as a result of faulting. water shortage is due to the presence of huge flows of

In

this connexion, w e m a y mention

the

Neogene basin andesite and basalt and enormous limestone outcrops,

of

Beypazari, about

100 km.

west of Ankara.

At

which are found

in

central Anatolia as well as elsewhere.

comparatively small distances from the edges of the

In

these instances, the zone is arid not because of the basin, the water table can be reached more quickly climate but because of its lithological composition.

by

sloping shafts at an angle of 300 to the horizontal There can be little hope of &ding very large quanti- and perpendicular to the strata, which slope south- ties of water

in

the fissures of the andesites and basalts.

wards at angles of from 600 to 700, than

by

vertical Nevertheless,

in

order to obtain as m u c h water as shafts. This is still more necessary as the strata become possible, wells must be

dug,

and radiating shafts sunk, muddier (and therefore impermeable) nearer to the mainly perpendicular to the line of

the

fractures.

centre of the lake basin (see

Fig. 2).

Instead of

sinking

wells,

a

few suitable sites might be Another case which gives rise to serious drilling prob- chosen at lower altitudes, from which horizontal or lems, w h e n water of inferior quality has to be cut out, sloping shafts could be driven into the earth.

is encountered

in

the Cankiri basin north of Ankara. This method is feasible only where the existence of Large areas consisting of great masses of gypsum,

with

pockets of water has been proved

by

geophysical studies.

A s the p

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

It has been noted

in

Turkey that the underground water resources tapped some years ago

in

various parts of the country are showing serious signs of diminishing, especially near the littoral of

the

Aegean Sea between Ayvalik and Dikili,

in

the basins of Thrace and Brusa, around Karaman

(in

the Vilayet of Konya) and

in

the region of Tarsus (Cilicia).

Most of the surface waters, rivers and streams,

dry up

to an almost incredible extent during the summer.

AU

these circumstances have

led

us to investigate,

as a matter of urgency, means of improving the exploita- tion of the country's ground water resources.

Methods

which

m a y be used for this purpose include afforestation and

the building

of a number of large d a m s to hold back

the

surface waters, whose volume is at the m a x i m u m

during

the winter and spring months.

W e feel however that

neither

afforestation

in

the arid regions nor the building of dams is capable of

i French scale.

196

Fig.

2.

The

Beypazari Neogene Basin. Comparison of inclined and vertical borings. _,

197

Prospection for underground water, and adaptation of drilling methods solving the problem quickly enough.

In

a country where steppe conditions predominate, as

in

Turkey, reafforestation takes at least

50

to

100

years, and the lengthy hydrographical studies necessary for the cons- truction of large dams would take from

25

to

30

years.

Moreover, the carrying out of any such programme neces- sitates financial outlay o n a scale at present beyond the country’s means. It is also not yet established that d a m s would b e an economic proposition

in

this arid region, where the forests have been destroyed

and

torrential floods carry

down

enormous quantities of solid material.

It seems to us that the only feasible solution

is

to investigate means of increasing the underground water resources artificially

by

running the torrential rain- water and marsh water into the ground through shafts, whenever the geological structure of the subsoil is suitable.

It m a y be stated that certain areas of Turkey which s d e r particularly from drought, especially the centre and parts of the west and south, have a geological structure which is well suited to the formation of artificial sink-holes or dolinas. These dolinas

would

be m a d e

by

sinking shafts to connect the surface with the porous strata, which

would

thus he replenished

hy surface waters that might otherwise

do

more harm than good.

Nevertheless,

if

this system were to be used, it would be better to begin

by

carrying out experiments on a small scale to see what results are achieved

in

practice

by

a scheme which, in theory, has m u c h ‘to recommend it.

If

this method, which is based mainly on

the

geological characteristics of the subsoil, proves successful, it m a y be of great

help

in solving the problems of draining marshes and controlling torrential flood waters. T h e system would not only reduce the dangers of flood but would replenish the underground water resources, which

in

turn would feed the rivers and streams.

It would

not always be possible to run great quantities of flood water into the low-lying strata, since the latter m a y be permeable, nor to safeguard the flooded areas from the damage caused

by

flood water;

but

the porous underground strata connected

up

with the surface would undoubtedly be replenished

by

the influx of this additional water-a fact which

would

have beneficial results on the country’s water economy.

The carrying out of a programme based on the suc- cessful use of this method would take less time

and

necessitate less capital investment than any of the more classic methods.

D I S C U S S I O N

PROFESSOR LINSLEY.

The

speaker has suggested the desira- bility of using wells to recharge the ground water. Expe- rience in the United States has suggested numerous difficulties with such a procedure.

The

two most significant difficulties are (1) reduction of recharge rates because of sediment in the ñood waters, and (2) reduction of recharge rates because of the formation of a ground water mound around the well.

Use of reservoirs provides a means of removing at least a portion of the sediment and equalizing the necessary recharge rates.

PROFESSOR TOPKAYA.

It

is true that quite a few technical difficulties are still encountered in feeding underground water- tables from surface waters, such as torrents and swampy

rivers which are liable to bring down considerable quantities of solid particles. Here w e have spoken only of the principles, without referring to the purely practical aspect of the problem of the artificial feeding of underground waters by drilling.

I

myself had drawn attention to an article published in the Bulletin ofthe Turkish Geological Society, 1 on the construction of sedimentation basins, dykes and walls to clear the m u d from torrents. These are difficulties which can be overcome.

On the other hand, the development of vast arid zones, formed by alternating clay-marl-limestone horizons, forces US to give serious thought to the problem of artificial feeding and to do all in OUI power to ensure progress in this field.

*

January 1952, vol. 3, no. 2, p. 139.

198

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

( P A R T I C U L A R L Y E L E C T R I C A L ) IN C E N T R A L A N A T O L I A

bY

M E H M E T Y. DIZIOGLU

Maden

Tektik

v e Arama Enstitiisii, Ankara, Turkey

I N T R O D U C T I O N

T h e region under investigation is a plateau,

900-1,100

m. Its annual raiPifall is no more than

250

mm.

high, roughly bound

by

the polygon Cihanbeyli

(1nevi)-

N o continuous water horizons can be observed in Kadinhani-Ilgin-Polatli-Cihanbeyli, its surface area this region; most of

the

water occurrences seem to be

being

about

6,000

sq.

km.

This is shown on

the

associated

with

the soil and the limestones beneath geological m a p of Turkey (Fig.

1).

it: however,

they

have limited lives, running

in

rainy

A s regards rain catchment and distribution, this seasons, and drying

up in

dry seasons.

plateau is self-contained

with

no apparent inlet or outlet.

It is encircled

by

mountains 1,200-2,000 m. high.

It

is traversed

by

gently dipping

dry

stream beds, most of which run towards its deepest part, which is occupied

by

the river Sakarya

with

a datum of

750

m.

height above sea level. Some of the other streams, such as Insuyu and its branches, run into Lake Tuzgölü.

fertile.

p

u R

p

os E

0

F T H E IN v ^E s ^{T I GA^ I} o

This

was Conducted

-th the

prhary Purpose of finding out

the

applicability of

the

electrical and mag- netic methods to underground water investigations in

G E O L O G Y

the region between Polatli and Konya.

This involved:

There is no detailed geological m a p of the region, but 1. Making a study of the true water and rock resistivi- generally speaking, the whole area is covered

by

an ties in m e r e n t parts of the region and correlating almost horizontal Tertiary (Neogene) formation.

On

the resistivity surveys with known data the outskirts and at some places

in

the middle, older facts.

formations have been observed.

The

first formation

2.

Finding out whether each layer or formation had a consists of alternate beds of fresh-water limestone, resistivity characteristic throughout the region.

marl and clay. Near the older rocks, conglomerates

3.

Finding out whether the old formations had a can also

be

observed.

The

average thickness of

the

magnetic susceptibility differing from that of the Neogene formation is in the neighbourhood of

200

m. newer formation.

with

a gradual decrease

in

thickness from north to

4.

Finding out the electrical methocls most suitable south.

The

older rocks consist of diorites, gneisses, for the purpose.

serpentine, marbles, limestones half metamorphozed

It

w a s also desirable to conduct the surveys

in

such a to marble, SChbtS, greywackes and limestones

with

manner as to solve the folIoWing problems near some

nummulites. of the State farms which were short of drinking and

irrigation waters:

1. To investigate the possible water horizons.

RAINFALL ^2.

^{T o}

^find

the shape of the top of the older formations This region between Polatli and Konya is one of

the 3.

T o investigate the possible water accumulations most arid regions of Turkey, though its soil is quite

along some lines.

between the newer and the older formations.

199

Dans le document HYDROLOGY SYMPOSIUM (Page 196-200)