地溫指地面下的溫度，為一具有三維空間分布並隨時間改變的性質。地溫的量測通常經由鑽井的井孔溫度（borehole temperature）所得。井孔溫度為單個地點的地溫量測為沿著井孔，垂直往下（或往上）測量的溫度分布，或稱為溫度井測。井孔溫度反應地底下之岩層（固定）及地下水（可流動）的溫度。地溫分布受到五方面的影響：（1）地表面溫度（ground surface temperature）為日照、植被、氣溫、地形等的影響；（2）過去氣溫變化，例如全球暖化及都市化；（3）岩層的構造、分布及導熱性質；（4）地下水垂直補注及水平流動；（5）較深部的地熱源，例如溫泉、岩漿庫等之影響。 近百年來的全球暖化及都市開發的熱島效應，造成許多地區上部70m的井孔溫度顯著上升。然而學界對於台灣的地下水溫及井溫研究仍少，本研究計畫調查彰雲地區觀測井之井孔溫度，以了解該地區的地溫梯度、水流狀態及是否有變暖的趨勢，以評估台灣中部受到全球暖化及都市化的影響程度。 Subsurface temperatures are the temperatures below the ground surface that distributed in three dimensional and changed with time. Those data are collected by measuring the temperatures vertically along a borehole up or downward and also called the temperature logging. Subsurface temperatures are usually in the balance of rock and groundwater with transferring heat by conduction and convection. Some mechanisms are indentified to contribute those changes of subsurface temperatures: (1) variation of ground surface temperature; (2) past climate change, such as global warming and urbanization; (3) the type and structure of rock strata; (4) groundwater flow; (5) heat source in deeper subsurface. In the nearly century, global warming and urbanization make temperatures increase significantly in the upper 70m of borehole. However, only few studies on the temperature of groundwater and borehole in Taiwan. This research proposes an investigation on boreholes temperatures in Changhua-Yunlin plain, central Taiwan. Our purpose is to understand the geothermal gradient, flow condition and the warming trend and to evaluate the effect by global warming and urbanization in central Taiwan.
