Antalya Traverten Platosu yeraltısularının kümeleme ve faktör analizi ile sınıflandırılması

Classification of the groundwaters of the Antalya Travertine Plateau by cluster and factor analysis

Özet

Antalya Traverten Platosu yeraltısularına ait kimyasal ve çevresel izotop verileri "kümeleme" ve "faktör analizi" istatistiksel yöntemleri kullanılarak değerlendirilmiş ve yeraltısularının farklılık ve benzerlikleri belirlenerek gruplandırılmaları yapılmıştır. Antalya Traverten Platosu'nda yer alan kaynak ve kuyulardan yağışlı dönemde belirlenmiş majör iyon $(Ca^{2+}, Mg^{2+}, Na^+, K^+, Cl^-, SO_4^{2-}, HCO_3^-+CO_3^{2-})$, elektriksel iletkenlik (EC), pH, sıcaklık (T), çözünmüş oksijen (DO), CO2, toplam çözünmüş madde miktarı (TDS), kısmi karbondioksit basıncı (PCO2), doygunluk indisi (SI) değerleri ile çevresel izotop içerikleri kümeleme ve faktör analizi yöntemleri ile değerlendirilmiştir. Yapılan değerlendirmeler sonucunda üç farklı grup belirlenmiştir. Bu gruplar, (1) Traverten Platosu'nun üst kesiminden çıkan ve uzun geçiş süresine sahip olan kireçtaşı kaynakları ile alt platoda yer alan Varsak (VAR)-Düdenbaşı (DUD) sistemi, (2) Traverten Platosu'nun alt kesiminden çıkan ve kısa geçiş zamanına sahip olan nispeten genç yeraltısuyu kaynakları ve (3) yüzey sularından oluşmaktadır. Kümeleme ve faktör analizi ile yapılan değerlendirmelerin benzer sonuçlar verdiği ve aynı tür gruplamanın her iki yöntem ile elde edildiği belirlenmiştir. Ayrıca yapılan değerlendirmeler sonucu alt traverten platosundan boşalan Düdenbaşı kaynağının, bölgede daha önce yapılmış hidrojeolojik etüt çalışmasında belirlenenin aksine, üst platodan boşalan Kırkgöz kaynakları ile aynı grupta olduğu saptanmıştır.

Abstract

The aim of this study is to evaluate the isotopic and chemical composition of the water resources located in Antalya Travertine Plateau by using cluster and factor analysis. Major ions $(Ca^{2+}, Mg^{2+}, Na^+, K^+, Cl^-, SO_4^{2-}, HCO_3^-+CO_3^{2-})$,, electrical conductivity (EC), dissolved oxygen (DO), CO2, total dissolved solid (TDS), partial CO2 pressure (PCO2), saturation index (SI) and environmental isotope values of springs and wells have been used to estimate the similarities and disparities between the water sources. The use of multivariate statistical analyses, which allows evaluation of a large amount of parameters, is very helpful in hydrogeologic analysis of complex groundwater systems. Dalton and Upchurch (1978), Williams (1982), Steinhorst and Williams (1985), Usunoffand Guzman (1989), Reeve et.al (1996), Helena et.al. (2000), and the others have emphasized the potential use of the multivariate analysis techniques for the hydrochemical interpretations of the groundwater systems. The study area occupies 630 $km^2$ . The geological structure and the map of the sampling locations are illustrated on Figure 2. The Antalya Travertine Plateau has a stepwise morphology. In the upper step, called as UpperPlateau, there are many springs discharging from the Mesozoic limestone and the travertine. The most important of these springs are the outlets of the Kırkgöz Spring zone discharging from Mesozoic karstic limestone (KGI, KGM, KGO, KGK, KGP). The average discharge rate of these outlets is $15 m^3/s$. The significant springs discharging from the Lower Plateau are Düdenbaşı spring (DUD), Kemerağzı spring (KMA), Mağara spring (MGR), Arapsuyu spring (ARP), and Duraliler-Okul spring (DUO). The average discharge rate of the Düdenbaşı spring is $17 m^3 /s$, whereas the averages of the other springs are between 0.5-2.5 $m^3 /s$. Another important spring is Hurma spring (HRM) dischar ging from Antalya Nappes. The other sampling points in the study area are Bıyıklı (BIT) and Yağca (YGC) swallow-holes at the Upper Plateau, Varsak (VAR) doline, Kapuz river (KPN), Meydan wells (ASO) and the Duraliler pumping station (DUP), at the Lower Plateau. The chemical, physical and isotope data values of these sampling points are given in Table 1. The cluster and factor analysis of the environmental isotopic and hydrochemical data provides the classification of the water sources of the Antalya Travertine Plateau in terms of the ionic composition, the saturation levels and the transit time of the waters. The classification of the standardized isotopic and hydrochemical parameters by cluster analysis is given on Figure 3, while the classification of the water sources with these parameters is given on Figure 4. The parameters are grouped in classes representing i) the major ion composition $(TDS, EC, Ca^{2+} - HCO_3 +CO_3^{2-})$, ii) the degree of the saturation with respect to carbonate minerals (SI, pH, DO), and iii) the source and the age of the water (isotopes, Cl-, Temp). Clustering of the water sources results two distinct classes: Upper Plateau ground-waters and Düdenbaşı springs is located in the same class, while all the other Lower Plateau springs are in the second class. The dolinesfed by Kırkgözler Spring and the Kapuzbaşı surface water are out of these classes. Principal factor analysis provided three principal factors for the processes controlling the ionic and isotopic composition. These are the total dissolved solids, the degree of the saturation with respect to carbonate minerals and the isotopic composition. These three factors explain the 95$%$ of the total variance of the parameters. The correlations of the parameters with the factors are given on Figure 5. The classification with respect to factors indicated that the Kırgözler and Düdenbaşı springs are characterized by high amount of carbonates, and high degree of the carbonate saturation, and higher recharge areas. On the contrary, the Lower Plateau springs are characterized by low amount of carbonates, low saturation levels and lower recharge areas. The principal factor analysis also revealed that the outlets of the Kırkgöz springs have different recharge areas and different transit times.