宋神宗時期實施「清汴」即導洛通汴工程，成效卓著。主其事者內侍宋用臣為迎合神宗講求財利的態度，擴大「清汴」的績效，創辦一系列的國營事業，其中以利用汴河水源創設的水磨茶場角色最為重要。水磨茶場是生產末茶的國營事業，其運銷與管理，通稱為「水磨茶法」，初期施行於京城之內，其後推廣至開封府界，影響極為深遠，卻一直不為學界重視。本文認為神宗元豐年間創置的水磨末茶實施期間雖然不長，卻仍展現部分的成效，但是元祐舊臣卻質疑其與民爭利，入不敷出，進而全面廢止；其後執政的新黨則以「紹述」元豐舊法為藉口，企圖擴大水磨茶的產銷規模。尤其是蔡京秉政，主「豐亨豫大」之說，獻媚於徽宗，數次調整水磨茶法，以追求最大利潤，致使歲入由二十萬貫，激增至四百萬貫以上。

＂Qing Sian＂, the project that dredged the Luo River into the Sian Canal during the reign of Emperor Shenzong, was a great success. Catering to Emperor Shenzong's interests in obtaining wealth and profits, the project courtier, Song Yongchen, increased the benefits resulting from ＂Qing Sian＂ and founded a number of government-owned enterprises. Among them the water-powered tea mills utilizing the water of Sian Canal were the most profitable and influential businesses. The system of this government-owned management was commonly known as the ＂Shui Mo Cha Fa＂. In the beginning, it was implemented in the capital and then introduced to Kai Feng; however, it has not been paid much attention by the academia. This study points out that the promotion duration for the tea by water-powered mills during the Yuanfeng period was not long, but the effects were clearly seen. The courtiers of the Yuanyou questioned the government that they should not grab the benefits of people, that the profits were unable to make ends meet and suggested that it should be abolished. The new party who governed the empire took the ＂Yuanyou Political Transition＂ as an excuse and tried to expand the marketing of the tea by water-powered mills. In particular, Cai Jing, who was in charge of governance, strengthened the theory of ＂Feng Heng Yu Da ( a great period of grand prosperity ) ＂. He toyed to Emperor Huizong and pressed for adjustments to the ＂SImi Mo Cha Fa＂ in order to gain the biggest profit. As a result, the annual revenue was increased rapidly from 200,000 guans to more than 4 million guans.