Konya Ovası ve Çevresinde Yeraltı Sularının Obruk Oluşumlarına Etkisi

Araştırma sahası, İç Anadolu Bölgesi’nin orta ve güney kesiminde yer alır. Konya Ovasıve çevresinin alt yapısınımetamorfik ve kristalen kütleler ile Kretase yaşlıofiolitik seriler ile bunlar üzerinde Miosen ve Pliosen yaşlıformasyonlar oluşturur. Sahada dikkati çeken yeryüzü şekilleri arasında dağlık sahalar, ovalar ve platolar bulunmaktadır. Bu çalışmanın amacı, Konya ovasıve çevresinde oluşan ve son yıllarda oluşum süreleri hızlanan obrukların oluşumu ile obruk oluşumunda etkili olan unsurlarıcoğrafi açıdan inceleyerek bunlara dikkati çekmektir. Çalışmanın hazırlanmasında öncelikle değişik dönemlerde Konya ovasıve çevresinde arazi çalışmaları, gözlemler ve gerekli görüşmeler yapılmıştır. Bu esnada gerek araziden elde edilen arazi verileri fotoğraf, istatistikî bilgi ve görüşme notları , gerekse ilgili literatür çalışmalarıve toplanan istatistikî veriler yorumlanarak obrukların oluşumu ve gelişimi coğrafi açısından değerlendirilmiştir. Konya Ovasıve çevresinde, yarıkurak birinci dereceden mezotermal su eksiği yaz mevsiminde ve çok kuvvetli, nispeten deniz etkisine yaklaşan karasal iklim etkili olmaktadır Bozyiğit, 2000:26 . Araştırma sahasında özellikle son on yıllık periyotta küresel iklim değişikliğine bağlıolarak ortaya çıkan kuraklık ve fazla su kullanımıyeraltısu seviyesinin düşmesine sebep olmuştur. Yeraltısu seviyesi değişimi yıl içersinde de yıllar arasıdönemlerde de görülmektedir. Yeraltısu seviyesindeki bu hızlıseviye düşüşünün somut örneklerine Akgöl Ereğli , Acıgöl Karapınar , Meke Tuzlasıve TimraşObruğu’nda rastlanmıştır. Konya Ovasıve Çevresi’nde günümüze yakın tarihlerde oluşmuşve oluşmakta olan çok sayıda obruk bulunmaktadır. Bunlar arasında: Nebili Obruk 1972 , Akviran Obruğu 1977 , Sekizli Obruk 1983 , Çoban Şamil Obruğu Nisan 1995 , Yavşan Obruğu Aralık 2000 , May Obrukları 2002 , ÇakıllıObruk Ekim 2005 , HacıSeyit YaylasıObrukları 2000, 2006, 2007 ve 2008 , İnoba Obruğu Ekim 2008 , Yarımoğlu Obruğu 7 Şubat 2009 dikkati çekmektedir.

Research area takes place in the middle and South part of Middle Anatolian Region. Area has the length of 80 km in northsouth direction and 50 km in east-west direction. The under structure of Konya plain and around consist of metamorphic and crystalline mass and cretaceous old ophiolite series. Old Tertiary layers as discordant are above them. These layers had not been affected by Alpine movements. The extensive formations at the top are Miocene and Pliocene old formations. Miocene begins with base conglomerate at the bottom and goes on with straight marl and limestone to the top. Pliocene takes place above Miocene formations as concordant and it has been formatted by clay, sand, pebble and gypsum. The aim of this study is to take attention to the rapid formation of the obruk in Konya plain and around last years and research the key elements that play role in the formation of swallow hole from the point of geography. Area researches in Konya plain and around and necessary negotiations are supplied in various times years of 1990, 1996, 1998, 2000, 2001, 2004, 2006, 2008, 2009 during the preparation of the study. The formation and the development of the swallow holes are tried to be evaluated by area data supplied from the area photograph, statistical data and notes of negotiation , necessary literature studies and commenting the statistical data supplied from institutions during this period. The land forms that take attention in Konya plain and around are plain, plateau and mountainous areas. The unions of Aladağ, Bozkır and Bolkar that go along to the south by exceeding the height formed by Geyik Mountain Union in the late Eocene-Oligocene epoch has caused the increase of the height. Thus the sea water had spread to north-northeast and formed an inland sea and lakes in the holes between the heights. Obruk plateau at the north of Konya plain generally shows a feature of a wavy erosion surface that the height of it changes between 1100 and 1150 meters. The plateau has the length of 75-80 km in eastwest direction and the wideness of 65 km in north-south direction. The mountains surrounding the research area are the other morphologic elements that take attention. Bozdağlar, Karacadağ, Karadağ, Erenler-Alacadağ are the heights of the research area that take attention. According to the data of the meteorology stations selected from Konya plain; the annual average of the warmth is between 11. 0 °C and 11.8 °C, annual rainfall intensity changes between 281.4 mm and 329.2 mm. The big distinction in the rainfall intensity occurs because of the effect of the land forms and the air mass. Obvious distinctions between the annual values of the other climate elements are available. Alluvium soils in etude area, hydromorphic alluvium soils in swamp and wetland areas, colluvial soils in inclined areas between the plain and mountainous areas, brown and red brown soils on the surfaces of the plateau and mountainous are more widespread. Erosion, shallowness of soil, drainage, salinity and alkanity are important problems. At the Konya plain Iran-Turan and Europe-Siberia floristic regions vegetation types such as forest, shrub and grassland formations. The affective factors according to the observations for the formations of swallow holes today are the changes of the level of the ground waters, chemical features of ground waters, lithological structure, climate and human. In this occasion CO2 that got into the ground water from volcanic formations around increases the acidic value then effects to the lime stone and dissolves it. Thus underground gaps occur depending to the increased karsting and inner karsting. Argillaceous, grainy and graveled formations above these gaps are getting heavier depending to the conditions of climate and then collapsing from a certain level. If the collapsing reaches to the ground water, water accumulation at the bottom of the swallow hole is available. Especially for the last decade the drought depending to the climate changes and increase of the water usage have caused to decrease the level of the groundwater in research area. The changes of the levels of the ground waters occur within the year and also the periods between the years. According to the measurements of the well in research area in last years ; the decrease at the level of the MeramAlakova well for 12.5 m, the Meram-Hatıp well for 18.5 m, Çumra-Fethiye well for 15.6 m and Çumra-Batum well for 18.9 m have been determined. This speedy decrease of the level has accelerated the formation of the karstic shape named obruk. The concrete samples that the decreasing of the level of the ground water from past to today are seen in Akgöl Ereğli , Acıgöl Karapınar , Meke Saltpan Karapınar and Timraş Obruk Çumra . According to the observations that we have made in various dates on Akgöl; while there has been water in the departed mirror of lake in September of 1998, the mirror of lake has completely lost in July of 2008. In the same way we understand the change of levels at Acıgöl by the formations of travertine. There are travertine terrace sets that are above the actual level of the present for 3 and 6 meters. Although Meke Saltpan has shown the features of a lake till the last decade, it is nearly to loose this feature today. Corridor shaped land links have existed between the cone consists of pyroclastic materials in the middle of the lake and the land around it. There are many obruks that have been formatted lately or being formatted in Konya Plain and around. Obruks are formatted as a result of firstly by the cavitations in topography, then crevices and the collapses. The common obruks formatted lately in research area: Nebili Obruk: It takes place at 1.5 km west of Nebili Village. The diameter of the obruk head formatted in 1972 is determined