Report on Water for Brewing Tea or Jianchashui Ji is tea monograph written by the late Tang-era author Zhang Youxin (t 張又新, s 张又新, p Zhāng Yòuxīn) in AD 814. This book is the earliest monograph wholly devoted to the quality of water for brewing tea. It was compiled alongside several other texts on tea from the same period into the 13th-century Baichuan Xuehai (百川學海).