The filling phase of Mazvikadei Reservoir,Zimbabwe

Limnological measurements during the first year of filling of the newly formed Mazvikadei Reservoir in Zimbabwe showed variations in dissolved oxygen as well as soluble forms of phosphorus and nitrogen. The ratios of calcium to other major cations were: Ca:Mg = 0.38, Ca:Na = 0.50 and Ca:K = 2.0. The low Ca:Mg ratio may suppress development of mollusc populations, thus keeping the reservoir snail free. Conductivity was 160 µScm^-1. Daytime pH was 6.95–7.8. The water was dark-brown in colour, 90% of incident light was attenuated in the top 0.75 m in May, and in the top 3.5 m in August. Positive net photosynthesis was only recorded above a depth of 0.1 m, at 0.5 m and 1.0 m depths, it was negative. Zooplankton consisted of nine rotifer, four cladoceran, two cyclopoid and one calanoid species.