18-20 June, 2003, Budapest, Hungary OSSKI Center (Törley Palace)

with Exhibition and Pre-Session on Thermal Energy in Hungarian
"THERMO-BRIDGE"
between East and West for technology transfer and information exchange

           This study is concerned with the geothermal energy and quality of mineral waters at Isparta and surrounding area in Turkey. Turkey is well known for its geothermal resources. The Earth’s crust in Western Anatolia is relatively thin and consequently the geothermal gradient is higher than the world average. This property is important and such places with higher efficiency must be put in use in the near future.

           Turkey, a bridge between Asia and Europe, is located on the Alpine Orogenic belt. Due to the strong tectonic activity and volcanism in this area, many geothermal systems occur, mostly around this recent active volcanism in the western part of Turkey, just as the similar other geothermal areas in the world. Also active volcanoes in recent historical times, frequent earthquakes along active fault zones, high seismic activity created more than 1000 thermal hot springs and enriched geothermal resources of Turkey.

          The study area is located in the SW part of Turkey, which is called the lakes region. Lakes are, Egridir, Burdur, Golcuk and Beysehir. There are many mineral water and hot springs around Isparta and surrounding area, because of volcanic activity and active fault systems in the region. Şifa mineral water is one of the mineral waters in the study area, near Isparta city. Mineral water samples from different localities around Isparta are collected and analyzed chemically. The results of chemical analyses are evaluated in this study by using different diagrams and computer programs for different purposes.

Geothermal energy is one of the alternative sources of energy, which could be utilized for different purposes (Bilgin and others, 2001).  Worldwide, geothermal energy has been mainly utilized for electricity generation, although other uses could be of great potential as well. Turkey has great resources more than 1000 hot springs with this energy source in certain part of the country. Previously, several studies have been conducted with regard to the geothermal wells and their utilization (Bilgin,1999; Kurtman and Samilgil,1976; Shigeno,1996). Mineral Research Exploration Institute has carried out the geothermal energy exploration studies began in 1962. The general prospection, geological, geochemical and geophysical prospections, drilling, test studies and power plant construction have been realized up to date. The first geothermal power plant of 21 MW capacities was installed in the Western Anatolia near Kizildere village.
           The main objective of the study was to determine how the mineral water quality changes from one location to another and also reservoir characteristics of the mineral waters and hot springs.
           The study area lies around Isparta and surrounding area in the SW of Turkey  (Fig. 1). An important feature of present study in Isparta and surrounding area is expressed entirely in the form of thermal springs. Thus there are some physical evidences from surface manifestations of the existence of high temperature resources at shallow depths.
           The location of nearly all mineral water springs and anomalies are extending along fault lines and alteration zones in the study area. The thermal springs are generally distributed along a distance of some 200 km from Isparta and surrounding area.  The temperatures of the springs range from between 22 ^oC and    38 ^oC.
           Prediction of scaling and corrosion in geothermal systems are important in order to be able to take preventive action. The principal concerns with geothermal water source systems are corrosion and scaling. Scaling and corrosion processes are correlated in geothermal system to that factors influencing both process are discussed in that paper and some remedies are also recommended.

Water samples are collected from the field and pH, temperature, and Eh values were measured in situ. Since, in field samples, the pH must be measured immediately, before gas exchange takes place with the atmosphere. The field temperature of the sample at the time of pH measurement should be recorded subsequently.  ICP atomic emission spectroscopic techniques are used for measuring the metallic cations such as Ca, Fe, Mg, Mn. Alkali metals are determined by the atomic absorption

Spectrophotometer such as Na, K, Ca, Mg, Li fluoride, chloride and sulfate values are determined by ion chromatography. On the other hand 5 samples belong to mineral waters and hot spring waters are analyzed in radioactivity as total alpha Bq/l and total beta Bq/l, evaporating under ultraviole lamp and relict of the substance are analyzed WPC 9550 Model instrument by counting method.
         The results of chemical analyses are evaluated by using different diagrams (Piper and Stiff)) and computer programs (WATEQ4F and Datainbas) for different purposes. 

Short information is given about the geology of the study area, since rocks are important from various aspects in order to determine the mobility of various elements in geothermal systems. Metamorphic, sedimentary, ultramafic and volcanic rocks are given outcrop in the study area (Fig.1). The oldest rocks are the metamorphic rocks are called as Sultandag schist and marbles, which are, aged Sillurian. The others are composed of limestone, conglomerates and flysch. Limestone is of Jurassic-Lower Cretaceous age, conglomerates are Eocene in age and  flysch is deposited  during Oligocene. Magmatic products comprise ultramafic rocks, volcanic and pyroclastic rocks. Ultramafic rocks are composed of harzburgite and serpentinite. Volcanic rocks, which are around Golcuk Lake, consist of trachy-andesite, welded tuff, ash-tuff and pumice (Bilgin et al.; 1990). On the other hand these volcanic rocks are of calc-alkaline and alkaline character, the age of volcanism is 4.7 million years.  Geochemical features of calc-alkaline rocks are correlated with those of continental margin type of volcanic arc rocks, and are attributed to plate convergence whereas the alkaline rocks reflecting the characteristics of within plate, such a volcanic rocks are indicative of rift setting and consequently related to an extensional tectonic regime (Bilgin and others,1990). The Quaternary sediments are represented by travertine and alluvium Quaternary travertine and alluvium overlie the volcanic rocks. The regional tectonic movements occurring mainly during Tertiary and Quaternary periods affected the area.

The main aquifer supplying hot and mineralized water to the Kosk hot thermal springs and other mineral waters occur in the Paleozoic marble and Mesozoic limestone. The Paleozoic marble and the Mesozoic limestone is overlain and confined by thick and impervious mud rocks and volcanic rocks of Pliocene and Pleistocene age. The aquifer is recharged by the infiltration of meteoric water; the main annual precipitation 570 mm determined by isotheral method. Recharge is generally provided by infiltration from the meteoric precipitation through the outcropping rocks of high secondary porosity.  The water percolates down into the deep aquifer system where it is heated by the magma tic rocks which have characteristic of higher heat flow.

The quality of spring water reflects the mineralogical composition of the rocks with which the water has been in contact. As water moves slowly through the porous parts of the rocks, its composition gradually changes, some of this material may reach saturation and it will then be precipitated in the form of minerals.

 In Isparta Golcuk area, the largest and most explosive volcanic eruptions ejected tens to hundred of cubic kilometers of magma onto the earth’s surface more or less five million years  ago. When such a large volume of magma removed from beneath of volcano, the ground subsided into the emitted space, to form a huge depression, which is called as Golcuk Caldera  (Bilgin, 1997). Golcuk caldera has thermal activity in the Kokar Dere Valley such as fumeroles that are consist of H₂S, CO₂, S and Cl.

Water samples are taken from mineral springs which reflects underground water directly.  Some determinations are made in the field and most of analyses are performed in the laboratory. Determination usually performed in the field, include temperature, pH, and electrical conductivity (Table-1).

The principal characteristics of mineral water systems have been discussed in that paper for chemical composition of mineral water to gain insight into the possible origin of water analysis.  The silicification around the fumaroles of Golcuk Crater Lake at lower temperature is amorphous silica, grading into quartz at higher temperature. Then two major effects occur as a result of the rock silicification. The porosity and permeability of the rocks are considerably reduced which causes waters to be diverted within the barrier. So here can be seen secondary silicification around Kokardere and

           Dari Dere around Golcuk Volcanism which are good indicator of geothermal resources in the  study area. Major constitutents of Isparta and surrounding area thermal waters are calcium, magnesium, sodium, bicarbonate and sulfate (Fig.2).

The average discharge of the hot spring of Kosk is about 7.1 l/sec, this value does not change significantly throughout the year. The other one Sifa Maden mineral water is bottled and discharge of it is about 10 l/sec. The rest of them are less than one liter.

The waters coming out from Icmeler Spring and Aslandoğmus Spring located near to Karaagac County, flow on the slope and form terrace type of travertine. Both of them are giving CO₂ bubbles to the atmosphere and also occurrence of miniature terraces).  The size of travertine pools is 3-4 cm size. Generally the deposition environment is subarial precipitation of calcium carbonate from mineral springs. As host rock type, carbonate rocks in the surface usually aragonite. Deposit form is a conical mound. As it is deposited by precipitation from mineralized spring waters, it shows successive layers with sometimes-different colors and texture.  Texture is banded, generally, which have fine grained carbonate minerals in both of the locality.

The chemistry of mineral water is rich in variety   bicarbonate dominant water. Low chloride mineral waters containing high HCO₃ and variable SO₄ concentrations may occur near the surface in volcanic geothermal areas where steam containing CO₂ and H₂S condenses into an aquifer. Under stagnant conditions, reaction with rock produces neutral pH bicarbonate or bicarbonate sulfate solutions. Sodium is often the main cation in the waters, since calcium carbonate is not very soluble at high temperature.

The volcanic province, seismic activity and structural geology of the study area are the most important factors for the prospecting of geothermal resources. Also tracy- andesitic and pyroclastic rocks are giving outcrop in a large area in Isparta and surrounding area, which are important as a heat sources.
         Liquids with a pH value from 0 to 7 are acid, whereas over 7 it is alkaline. Mineral water should be as neutral (i.e. as near to 7) as possible. High acidity over a long time may help erode teeth. Adding CO₂ to water increases its acidity.  The mineral waters in Isparta and surrounding area, pH value is changing between 6.8 and 8.1. Therefore, the pH of water as average is near to 7.4 and it is convenient for bottling and drinking water.  Analyses of the mineral waters and hot springs show that the major cations are Ca, Mg and Na the major anions are HCO₃, SO₄, and Cl, the main water type is calcium bicarbonate.

Isparta geothermal fluids are calcium bicarbonate dominated (Fig.2). The reason for this pattern are no doubt, relatively complex, however, water rock interactions are certainly significant factor. Thus, Isparta calcium bicarbonate geothermal geothermal fluids strongly influenced by the presence of regional carbonate aquifer.

Water hardness is caused by the dissolved limestone and dolomite in the water. This is rarely a problem, since the amount is usually very low. Water’s Ca concentration is taking as a measure in the study area and classified according to the following table-2:  Some of the samples Ca and Mg contents are higher than 75 mg/l which are moderately hard and the most of them are lower than 75mg/l which are soft.

Table-2. Classification of spring waters according to Ca concentration

The upwelling mineral waters in Icmeler, Kosk and Aslandogmus gets over saturated with carbon dioxide under decreased hydrostatic pressure, the progressive degassing and expansion during the ascent reduces the density of water in the system cause deposition of calcite on the surface. Another important problem in geothermal systems is encrustation.  This problem can be seen primarily in the return pipes of reinjection wells. It is build up of a slimy reddish-brown colored deposits caused by iron bacteria. This can clog the system as easily as crust. Keeping the water carrying pipes pressurized and free of contact with air prevents scaling in the system. Also use of sulfur oxidizing bacteria with H₂S produced in the bioreactor prevents scaling. These processes will proıvide an economical and environmentally, friendly method also contributes to the reduction of H₂S emission from the geothermal system  (Hirowatari, 1988).

The first step to prevent scaling is to keep all water systems under pressure, the second step is to prevent water temperature rise above boiling point. While scaling is one type of corrosion, another one is galvanic corrosion. This type of corrosion can be seen when dissimilar metals are used together. For that reason, it is recommended not to use iron or galvanized pipe together with the copper pipe in the system.  Recommendable   materials are PVC, polyethylene.

Hot springs and mineral waters occur in many   regions of Turkey.   Both the temperature and chemical composition of the geothermal waters are changing according to locality. The temperature of surface springs in the study area ranges from 23^oC  to 38^oC. Temperature of water discharged from drill hole in many thermal regions is much higher than that of surface springs. It is used in that paper datainbas computer program to find the reservoir temperature and reservoir mineralogy. But the water ascending to surface is mixing with the cold underground water table which alter the chemical characteristics of mineral and hot spring waters, such as combined affects of concentration of aqueous components by water gaining or lost and pH change due to CO₂ lost.  Boiling and dilution cause an irregular dispersion and shift of log (Q/K) curves (Arnorson et all 1982).   For that reason there are some irregularities and shift on log (Q/K) diagrams belong to Isparta and surrounding mineral waters and hot spring water. Calculated reservoir temperatures of study are mineral water is about 80^oC   by using   computer programs (WATEQ4F and Data in Bas). The calculation of reservoir temperature based on chemistry of mixed (diluted) spring waters is highly risky.

Human being has utilized geothermal energy and geothermal resources for the various purposes to improve their life. It is known that our health is affected positively or reverse by the long time exposure of geothermal water. Environmental and health effect arising from the utilization of mineral waters and hot spring waters in Isparta and surrounding area is not containing any negative elements or components to give harm to our life. They are free from water contaminant such as physical, microbiological, chemical and radionuclides.

When temperature of geothermal water is over the 32 ^oC. it can be used directly in spas or to heat buildings, grow crops, warm fish ponds or other uses. So the water of Kosk is 38^oC, then it can be used for the above-mentioned areas. Heat from geothermal resources in Kosk also can be used   to dry ceramics, lumber, vegetables and other products used On the other hand Kosk hot springs  are used for the balneology and bathing.

Kosk hot spring has 38-^oC temperatures, which can be used for bathing, therapeutic purposes and recreation of people. In the context of this paper, mineral rich water like Kosk having beneficial affect on health. Bicarbonated water are stimulating on the hepatic and intestinal function on certain metabolism  (Kreslins and others 2002)  Also the same water as being sulphated can be used stimulating action on the biliary and intestinal function for the problems  with accumulation  of organic waste.

Radioactive substances are those that are unstable in the rocks. Radioactive types of uranium, thorium, and radium emit radiation to reach a more stable condition. This process is known as radioactive decay. Radioactivity is usually measured in curies and the unit typically used the concentration of radioactivity present in geothermal water is the pico curie per liter (one trillionth of a curie). If testing of geothermal water shows that gross alpha activity is greater than 15 picocuries per liter water treatment is recommended.    Study area samples specific activities of total alpha (Bq/L) is changing between 0.082_⁺0.028 - 1.485 +-0.300, total beta  (Bq/L) 0.074+_0.029-1.420+_0.271 (1 Bq = 0.27 x 10² pCi ) by separate locations (Table-1). Since it has radioactivity less than environmental protection agency’s standart of 15 picocuries per liter. So no further action is required.

As a consequence the main aquifer, supplying hot and mineralized water of Kosk, Aslangogmus, Turbe, Orman, Mayas are coming through the Paleozoic karstic marble and Mesozoic limestone. But the water of Tefenni and Sifa Maden Suyu are coming from shales according to Stiff diagrams .

On the other hand, they are not containing any impurities such as that have been commonly found in bottled waters may include compounds containing asbestos fibers, bacteria, fecal contaminants, algae, and nitrates, especially in agricultural areas where large amounts of nitrogen fertilizers are used. They are coming from naturally protected reservoir. The legal description (Turkish Mineral Water Standards) states that the water must come from a protected underground source and must contain at least 250 parts per million in total of dissolved solids, in addition to meeting the bottled water quality standards.

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