PRELIMINARY REPORT ON PHYSICO-CHEMICAL PROPERTIES OF MAIN CHANNEL AND TRIBUTARIES IN UPPER AND MIDDLE REACHES OF THE CHANGJIANG RIVER, BEFORE AND AFTER DAMMING OF THE THREE GORGES PROJECT

This paper dews with the physico-chemical properties of lake water and their seasonal changes during 1997—1998 in upper and middle reaches of the Changjiang River. The result are summarized as follows: 1. The normal conditions of water quality were: Water temperature was 16.93℃, S ecchi transparency (cm)—damming before was 11, damming after was 19.57. pH damm ing before was 8.4, damming after was 8.14. conductivity was 322.5μs/cm. Alkali nity, as CaCO3 was 118.69mg/l. Hardenss was 9.26 Germany Degree. Chemical oxyg en demand was 1.84mg/l.; 2. The contents (mg/l) of nutrient elements were: NH4-N 0.226, NO2-N 0.023, NO3-N 0.748, Total nitrogen 1.299, Total phosphorus 0.194, PO4-P0.049, silic ate 3.898.