Being the primary source of recharge for shallow groundwater systems, precipitation is of utmost importance for groundwater sustainability, particularly in semi arid to arid regions of the world. Although it is very difficult to set a concrete relationship between groundwater levels and precipitation totals due to many reasons including but not limited to overexploitation and unaccounted extraction patterns, it is still very important to find ways to understand the major mechanisms and details of the decreasing groundwater levels. One such way is to examine the long term trends of precipitation and groundwater levels in shallow aquifer systems.

The Torbali-Bayindir aquifer is mostly of alluvial in origin and is under the influence of declining precipitation totals and anthropogenic stress. Long term analysis of the data demonstrated a general declining pattern in groundwater levels at an average rate of about 0.75 m/year, which is partly associated with decreasing precipitation patterns and partly with overexploitation of the aquifer. The results further indicated a very fast response of the groundwater levels to precipitation events. This finding strengthens the fact that alluvial systems in this region are short-circulated with an extremely dynamic structure. The slopes of rising and falling limbs of well level curves indicate the high conductance of the system, which also is a clue for the fact that systems similar to the one in Torbali-Bayindir plain are among the ones that will be severely impacted from the consequences of climate change.

Acknowledgements The authors would like to express their gratitude to Mr. Ertan Kazanasmaz of second Regional Directorate of State Hydraulic Works for providing support throughout this work.

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