Limnology is the study of the physics, chemistry and biology of freshwater environments and the interrelationships of these. A limnological baseline survey of the major dams of the Eastern National Water Carrier ENWC, von Bach, Omatako and Swakoppoort was conducted from January 1984 to December 1986 and reported on in 1987 (Bethune 1987). The report recommended that "quarterly monitoring of the physical, chemical and biological parameters in the three dams be continued". This was done for a further four years from 1987 to 1990. In this report 1984 - 1986 is referred to as the baseline survey period and 1987 - 1990 as the monitoring period. The purpose of this progress report is to present the results of the seasonal monitoring of the three impoundments, Von Bach, Omatako, and Swakoppoort from 1987 to 1990.