康熙三十三年（1694年）因地震地陷所造成的「康熙臺北湖」是一個歷史的事件，也是一個自然的事件，要重建「康熙臺北湖」的古地理環境並探討該湖的消長，需要用自然史的角度來解讀史籍文獻的記錄，過去的學者雖曾提出許多看法，但是並沒有正確的描繪出該湖應有的景象，本文對旣有史料的解讀提出一些全新的看法，配合自然史的觀點來重建郁永河所見的「康熙臺北湖」的景象，並探討其消長。研究結果顯示漲潮時該湖的水深可能可達四到五公尺，但其因地震所造成的眞實地陷量可能僅在三公尺以內。該湖滿潮時的水域可能包含現今基隆河下游及其北側、社子島、淡水河社子島段的河道和關渡平原的一部分，估計其面積約為30平方公里左右，但因該湖受潮汐影響，其水域面積變化相當大。盆地面的上升、沉積物的加積、降雨量減少和人為的拓墾是該湖消失的重要因素。

The formation of the ancient K'anghsi Taipei Lake after the earthquakes of 1694 is an important natural and historical event in the life of the Taipei Basin. In order to reconstruct the evolution of the lake, it is necessary to interpret the historical literature from a natural history perspective. Although previous researchers have generated much information a about the lake, they did not provide an accurate description of it. In this paper the author reconstructs ancient K'anghsi Taipei Lake and discusses its evolution based on new interpretations of the historical literature. In general, the maximum flood tide depth of the lake was four to five meters. However, considering the difference is sea level at high and low tides at the Tanshui River mouth, the actual deepening of the lake caused by ground subsidence after the earthquakes may be less than three meters. The area of the lake was thus strongly affected by the tidal current. It covered only the northwest corner of the Taipei Basin, including the Shetzu Sandbank, a portion of the Kuantu Plain, and a part of the Keelung and Tamsui River channels during flood tide, and its estimated maximum flood area was approximately 30 km². Uplift of the Taipei Basin, accumulation of sediment, a decrease in precipitation, and human a activities are the key factors causing the disappearance of ancient K'anghsi Taipei Lake.