Determination and sustainability of Göksu basin (Seyhan) water potential

Göksu Basin(Adana-Seyhan) is a sub-basin of Seyhan Basin, which is one of the 26 river basins in our country and is very rich in terms of water potential. Göksu Basin is limited to the water section line, mostly in the Mediterranean Region, Adana section, in the eastern part of the Central Taurus Orogenic belt and covers an area of 4392 km². The basin extends in the northeast-southwest direction and is located between 37 ° 33 '- 38 ° 40' north latitudes and 35 ° 35 - 36 ° 41 east longitudes. The basin is located in the Tahtalı mountainous belt topographically, and in the east of it; While Binboğa and Dibek mountainous (2225 m) masses are located from north to south, and in the west of it; It has high peaks in the form of Soğanlı Mountains (2909 m), Beydağ (3058 m) and Bekirdağ Tepe (2706 m) from north to south. The study area offers, geologically and geomorphologically, various lithological features such as limestone, shale, marl; different structural features such as lateral, transitive, thrust, discordant; active tectonic features such as fracture and crack, and different morphological features such as pitches, plateau, basin, polye etc In the basin, there are different formations such as Köroğlu, Evciköy, Yüceyurt, Sümbüldağ, etc. at different ages such as Paleozoic, Mesozoic, and Cenozoic. Under these formations; there are various rocks such as limestone, dolomite, sandstone, marl, conglomerate, etc. In the field; along with the Taurus autochthon, metamorphites, allochthonous units, different stratigraphic structures such as Kireçlikaya and Andırın complexes also surface. These structures offer different structural features such as lateral, transitive, thrust, and unconformity under various formations. In the study area, under various phases from Paleozoic to Quaternary, orogenesis and block tectonisms have occurred, and marine and terrestrial processes have occurred as a result. Under this active tectonic regime control, anticlines and synclines have been developed along with various faults. The northern and southern parts of the site include different morphological-geomorphological development features under the control of the tectonic regime. Especially the basin has increased to a great extent from the Middle Miocene and has entered into a process of becoming a Land with the active tectonic regime. In this way, while the mountainous masses around Tufanbeyli and Sarız were rising, the inner parts were subsidized by dishing, and thus formed as a basin. In the southern parts, again with the effect of the tectonic regime, the faults and subsidence along with slope (drift) occurred in the southeast direction. Thus, anticlinal and synclinal structures and deep fault lines have been formed. With the establishment of the river network, while the alluvialization takes place in the basin ground with the processes of erosion and deposition in the Tufanbeyli and Sarız regions, in the Saimbeyli and Feke regions, steep, deep valleys and slopes have been formed with effective erosion and carriage activities. By all these tectonic and hydrographic processes, peak plains have been formed on the high mountainous masses in the surrounding, and low, medium height and high plateaus have been formed on the low-eroded surfaces under the influence of the faults. As a result of effective river erosion and carriage, deep valleys and slopes and benches and geomorphological units such as polye, uvala, lapya shaped by carstic lithological effects such as limestone, dolomite have been developed. The diverse lithological, structural, morphological-geomorphological features, active tectonic regime, and rich river network played an important role in the physical conditions of Göksu Basin. Under these factors; altitude differences ranging from 300 m to approximately 3000 m, offers a highly hilly topography that is steep and deeply split by streams, high slope values, large altitude differences that vary over short distances. This situation increased the bed slopes of the rivers and increased the hydraulic energy potential of the rivers flowing in the basin. Thus, water structures such as more than 30 dams, hydro-electric power plants (HEPP), regulator, and pond on the Göksu River and its tributaries show a widedistribution. While the Mediterranean climate features are effective in the southern parts of the research area such as Feke and Saimbeyli regions, with precipitation values up to 961 mm and temperature values of 15.3 ˚C; terrestrial climate features are observed in the north of the basin, with precipitation values down to 517.5 mm and temperature values of 7.4 ˚C, in the surroundings of Tufanbeyli and Sarız. According to the Izohyet (co-precipitation) method in the basin, an average of 860.6 mm of precipitation is observed, while it has an average temperature of 12.8 ˚C. In determining the climate type in the basin, Erinç, Improved Erinç, Thourwaite and De Mortanne formulas were applied. While, according to these practices, the results of Erinç and Improved Erinç formulas successfully reflected the climate type of the basin, the results of the Thourwaite and De Mortanne methods also failed to reflect the climate type of the site. Göksu River emerges out of the Şarlak Springs in the Tahtalı Mountains, merging with various springs in the surrounding mountainous areas and forms the Sarız Stream. While the Sarız Stream continues to flow under the name Göksu River at Şarköy, collecting various streams from the surrounding side branches, it shows southward flow in the form of a canyon valley by deepening its bed in an antecedent manner. Meanwhile, by making various deviations in the flow direction due to tectonic effects, combining with Kandil, Hocabey, Kazan, Saimbeyli, Salam, Kocadere, Balık creeks and Asmaca Stream from left and right, by increasing the flow rates, it leaves the study area in Gökdere location. During the formation of the river network of the basin, a variety of drainage systems have been developed, including lithologic, centripetal, hook, and cage due to lithological, morphological and tectonic effects. Göksu River started with a flow of 55 million m³ in Sarız-Şarköy stream gage gauging station (AGI/SGS) by feeding with high flow rate sources during the superficial flow process, it has a strong hydrological-hydrogeological water potential with a total flow of approximately 1,821,170,000 m³ at the Göksu River-Gökdere stream gage gauging station (AGI/SGS) downstream of the river basin downstream. In the formation of soil under different climatic conditions in the basin, climate (precipitation-temperature) has the main effect, and the main material, topography, vegetation, time, and other organic agents play an important role in the pedogenesis processes. Under these processes, zonal and azonal types of basic soil groups were formed in Göksu Basin. According to this, in the southern parts of the area, lime-free brown forest soil has been formed, in the Tufanbeyli basin base, lime-free brown soils have been formed, around Sarız, chestnut-colored soils have been formed, brown forest soils have been formed in high mountainous areas around the environment, Zonal soils such as red Mediterranean soils were formed in the southwestern end of the area. The alluvial and colluvial soil groups are distributed on the river bed and sloping slopes in the limited parts of the basin. In the Göksu Basin, different climatic features have also created diversity in plant species, creating a rich flora area consisting of juniper, fir, larch, cedar, red pine, beech, maquis, steppe and other plant species. In the south-southeastern parts of the basin, depending on the stretch direction of the valleys and the direction of arrival of the air masses and the effects of rainfall and temperature, maquis and red pine species are widely distributed on the bases and slopes of the valley, while generating species such as larch, cedar, fir and juniper. show distribution. In the north-northeast sections, the steppe vegetation covers a large area, whereas in the high mountainous areas throughout the basin, the bare surfaces, where the plant species are weak or absent, occupy a wide area. In determining the water balance and potential of Göksu Basin, the results of the Penman-Monteith method previously applied in the basin were taken as the basis. A new hydrological model has been developed with the digitization formula developed with geographic information system (GIS), analytical hierarchy process (AHP) model program, remote sensing (RS) techniques in order to determine the water potential of the basin and the natural factors on the hydrological cycle. This developed hydrological modeling was applied in the basin and the model results were compared with the current height data at the downstream of the basin (No: 1805-AGI). Accordingly, the surface flow and infiltration levels of the basin turned out to be very successful with a rate of 0.95. The effect levels of natural factors such as lithology, soil, land use / cover, ground cover (Normalized Difference Vegetation Index - NDVI), slope, aspect, which are effective on the infiltration and surface flow of the hydrological water cycle of the basin were determined. According to this; lithology 57.29 %, soil 12.93%, land use / cover 10.27%, ground cover (NDVI) 8.13%, slope 5.66%, aspect 5.66%, were effective on infiltration and surface flow. Within the scope of the sustainability of the basin, the risks and advantages of all natural and human factors affecting the water potential and cycle of the site have been determined, and sustainable integrated basin management has been envisaged. Key Words: Göksu Havzası, Buharlaşma, Hidrolojik döngü, Su potansiyeli(Göksu Basin, Evaporation, Hydrological cycle, Water potential)