Hydrogeological conceptual model of Gazipaþa coastal aquifer (Antalya)

Gazipaþa coastal plain is located in the Eastern Mediterranean basin, within the borders of Antalya province. The mainstay in the coastal plain based on agriculture and the irrigation water need is provided from surface water and groundwater. The sustainable use of coastal aquifer constitutes an important element of risk in view of agricultural production as surface waters are affected adversely by the droughts that occur for consecutive years. In this case information on coastal aquifer reserve is rather old and needs to be updated with contemporary research approaches. In this study, it was aimed to establish a conceptual hydrogeological model of the Gazipaþa coastal aquifer based on geological, hydrological, hydrogeochemical and environmental isotopic data and quantified the water budget components. According to the evaluations, the groundwater head distribution in the plain fluctuates between wet and dry periods during a year, but has not changed at all in the long term. The groundwater chemistry belongs to Ca-HCO3/CO3 facies and the sea water contribution was observed at only two sites near the coast. According to stable isotope data, all of the samples are located on the left side of the Global Meteoroic Water Line deuterium excess value (Dex) of 10, between the Antalya Meteoric Water Line with (Dex=+16) and Local Meteoric Water Line with Dex= +18. These values suggest that the groundwater is recharged by precipitation originating from the moisture over Mediterranean Sea. 3H value of surface and groundwater samples vary between 3.08 TU-0.33 TU and the average value is 1.95 TU. Compared to shallow-circulating groundwater, tritium content of the deep-circulating groundwater is lower and the specific conductivity value is higher. According to alluvial groundwater budget calculations, total annual groundwater recharge of 71.1 Mcm is supplied by precipitation (32.0 Mcm) and by recharge from limestone and marble units (39.1 Mcm) surrounding the alluvium. Groundwater’s discharge components include evapo-transpiration loss (25.3 Mcm), surface flow (10.6 Mcm), irrigation water use (10.9 Mcm), domestic use (2.4 Mcm), evaporation from water table up to 2 m from ground surface (1 Mcm) and, groundwater discharge in to the sea (20.9 Mcm).

Gazipaþa (Antalya) kýyý akiferinin hidrojeolojik kavramsal modeli

Doðu Akdeniz havzasýnda, Antalya ili sýnýrlarý içinde bulunan Gazipaþa kýyý ovasýnda temel geçim tarýma dayalý olup, tarýmsal sulama suyu ihtiyacý yüzey ve yeraltýsuyundan saðlanmaktadýr. Yüzeysularýnýn ardýþýk yýllarda gerçekleþen kuraklýktan olumsuz etkilenmesi nedeniyle kýyý akiferinin sürdürülebilir kullanýmý tarýmsal üretim açýsýndan önemli bir risk unsuru oluþturmaktadýr. Bu durumda kýyý akiferi rezervine iliþkin oldukça eski olan bilgilerin güncel araþtýrma yaklaþýmlarý ile yenilenmesi ihtiyacý ortaya çýkmýþtýr. Bu çalýþmada jeolojik, hidrolojik, hidrojeokimyasal ve çevresel izotopik veriler ile Gazipaþa kýyý akiferinin kavramsal hidrojeolojik modelinin oluþturulmasý ve su bütçesi bileþenlerinin belirlenmesi hedeflenmiþtir. Deðerlendirmelere göre ovadaki yeraltýsuyu yük daðýlýmý yaðýþlý ve kurak dönemler arasýnda salýným göstermekle birlikte uzun dönemde deðiþmemiþtir. Yeraltýsuyu aðýrlýklý olarak Ca-HCO3/CO3 fasiyesinde olup, deniz suyu katkýsý kýyýya yakýn iki noktada gözlenmiþtir. Duraylý izotop verilerine göre örneklerin tamamý Küresel Meteorik Su Doðrusu’nun (Döteryuz fazlasý deðeri (Dex) 10) solunda, Dex deðeri +16 olan Antalya Meteorik Su Doðrusu ile Yerel Meteorik Su Doðrusu (Dex=+18) arasýnda bulunmaktadýr. Bu deðerler yeraltýsuyunun Akdeniz kökenli nemin oluþturduðu yaðýþlardan beslendiðini göstermektedir. Duraylý izotop içeriklerinden kýyý bölgesinde yüzeye yakýn bazý yeraltýsuyu örneklerinin buharlaþmaya uðradýðý anlaþýlmaktadýr. Yüzey ve yeraltýsuyu örneklerinin trityum içerikleri 3.08 TU ile 0.33 TU arasýnda deðiþmekte olup, ortalama deðer 1.95 TU’dur. Dolaþým süresi uzun yeraltýsularýnda, sýð dolaþýmlý sulara göre trityum içeriði düþük, özgül iletkenlik deðeri ise yüksektir. Kýyý akiferine ait yeraltýsuyu bütçesine göre yýllýk beslenim 71.1 Mm3 olup bunun 32.0 Mm3’ü yaðýþtan, 39.1 Mm3 ise alüvyon akiferi çevreleyen kireçtaþý ve mermer birimlerinden saðlanmaktadýr. Yeraltýsuyu boþalým bileþenleri, buharlaþma-terleme kaybý (25.3 Mm3), yüzeysel akýþ (10.6 Mm3), sulama suyu ihtiyacý (10.9 Mm3), evsel su ihtiyacý (2.4 Mm3), yeraltýsuyundan (0-2 m) buharlaþma (1 Mm3), denize boþalým (20.9 Mm3) olarak belirlenmiþtir.