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Conclusions
Water resources especially the groundwater are among the natural resources being subjected to ignorance by human communities around the world. The impacts of the climate change mostly in terms of reduced precipitation and increased temperatures accompanied by misuse and mismanagement of these resources contribute to great losses and in some cases resulted in irreversible impacts on surface and subsurface waters. The problem is especially more common in arid and semi-arid regions where there is a huge pressure on groundwater resources. The environmental impacts of the overuse of groundwater aquifers include the socio-economic losses in the form of increased exploitation costs for water provision as well as the costs for making up for the environmental damages and the challenges of migration etc. On the other hand, the losses imposed on the environment by the groundwater degradation vary from land subsidence, water quality degradation to drying up of the wells nearby.
Turkey is going to be one of the problematic countries in regard of water issues especially in near future. Some of the regions of the country especially the Aegean and Central Anatolian regions have been challenging with the groundwater depletion and its consequences during recent years. Taking into account the limitations of the traditional approaches for monitoring water resources particularly in large scales, the use of remote sensing technology has become popular and common among the scholars and decision makers as well in recent years especially with the emergence of GRACE satellites and the development of data modelling and assimilation systems. Taking the benefits of remotely sensed data, the variations of terrestrial water and groundwater storage over Turkey were analyzed in this study. The results suggested that the total trend of monthly TWSA and GWSA over Turkey is descending with a total decrease of 11 and 6 cm from 2003 to 2016, respectively. The interactions of the GWSA with climatic variables of precipitation and temperature were also studied. The results indicate that there is a good agreement between GWSA and climatic variables with 2-month lag. The best correlation was found between climatology values of precipitation and temperatures and GWSA. The monthly statistics revealed that the impact of increased temperatures on the variations of groundwater storage over Turkey is much more evident compared to precipitation, which indicates that the evapotranspiration resulting from warm weather condition in the country controls the variations of GWS. However, the regression results show that the variations of GWS over Turkey can be modelled with high accuracy using the climatic variables. Findings of this study emphasized the overall feasibility of satellite and modelled datasets to study the large-scale fluctuations of hydro-climatic variables in at country or regional extends.