Projecting Aridity from Statistically Downscaled and Bias Corrected Variables for Gediz Basin/Turkey

In recent years, significant temperature increase all across of the world draws attention and climate regimes are shifting in different parts of the world. By the reason of these climatological changes, a study was conducted in Gediz Basin/Turkey, where agricultural production has an important place. In the study prepared, twelve GCMs were utilized under RCP4.5, RCP6.0 and RCP8.5 scenarios of 5th Assesment Report of IPCC for the period 2015-2050. The statistical downscaling methods were employed and the projections were derived right after applying weighted-averaged ensemble mean by Bayesian Model Averaging method and bias correction by equidistant quantile mapping method. The temperature-based potential evapotranspiration formulas were modified in accordance with Penman-Monteith method and the aridity indexes were calculated by UNEP (1992). According to the projections, the mean annual temperature increases between 1.5℃ and 2.2℃ and mean total annual potential evapotranspiration increases between 5% and 8% are foreseen in Gediz Basin for the near future. It is foreseen that semi-arid climate regime may predominate over the region for all of the RCP scenarios under the increasing dryness in basin climate. In addition, it was obtained in the study that sub-humid climate state occurance for all of the regions included by the basin may be unexpected in the future for RCP8.5 scenario. The presence of semi-arid climate conditions may be more potent with the increasing trend of radiative forcing over time.

Gediz Havzası Tütün Tarımı Yapılan Toprakların Bazı Fiziksel-Kimyasal Özellikleri ile Besin Elementi İçerikleri Arasındaki İlişkiler

This study was conducted to examine the soil fertility of the Gediz Basin, where tobacco is widely grown. Soil samples were taken from 60 points at a depth of 0-30cm, and various physico-chemical characteristics and nutritional elements were determined. According to the results of the study, the soils were generally sandy-loamy in texture, slightly alkaline in reaction, calcareous, good in terms of organic matter and in no danger from salinity. The soils of the area are generally found to be inadequate in total nitrogen (94%) and available potassium (62%), and adequate in available P (70%), available Ca (85%), and available Mg (56%). The available Fe (83%) and available Cu (92%) content of the soils was adequate, but available Zn (86%) and available Mn (85%) content was generally inadequate. In a statistical evaluation, positive correlations were found between soil pH-Electrical Conductivity (EC), pH-lime, pH-silt, pH-clay, pH-K, pH-Ca, EC-N, EC-P, EC-K, EC-Ca, EC-Cu, EC-Zn, organic matter (OM)-N, OM-P, OM-Ca, OM-Cu, OM-Zn, % sand-Fe, clay-K, clay-Ca, clay-Mg and Kil-Cu contents, and significant negative correlations between pH-sand, pH-Fe, pH-Zn and pH-Mn, and OM-sand, % sand-clay, sand-silt, sand-K, sand-Ca, sand-Cu and clay-Fe content. With regard to nutrient elements, positive correlations were found between N-P, N-Ca, N-Cu, N-Zn, P-Cu, K-Mg, Mg-Fe, Mg-Cu, Fe-Cu, Fe-Zn, Fe-Mn, Cu-Zn, Cu-Mn, Zn-Cu and Zn-Mn, and strong negative correlations between Ca-Fe. Due to the insufficiency of nitrogen, zinc and manganese elements which directly affect the quality characteristics of tobacco, it is useful to consider them in the fertilization programs in the region.

Questioning of empirically derived and locally calibrated potential evapotranspiration equations for a lumped water balance model

One of the most essential inputs of water balance models is the part in which potential evapotranspiration (PET) is predicted. Especially in the conceptual-based lumped rainfall–runoff models, the steady runoff simulations can be made with acceptable PET predictions. The presented study is about exploring alternative PET equations that can be adapted to a parametric lumped model termed as the dynamic water balance model (dynwbm). Although the use of the Penman–Monteith equation often appears in the literature, a performance assessment was conducted on the dynwbm by using 21 PET equations. The implementation was performed on different river branches in the Gediz Basin, Turkey. The satisfactory PET equations have been selected by means of statistical techniques. As a result of the evaluation, it was observed that one of the radiation-based equations, McGuinness–Bordne, provided the most consistent performance. Alternatively, the presence of parsimonious equations requiring less meteorological variables has been questioned, thus locally calibrated temperature-based PET equations reflecting the PET estimations of McGuinness–Bordne have been proposed so as to be practically utilized in water balance modeling experiments for the basin.