Abstract:

Lake Nakivali is one of the four small lakes that form what is known as the Koki lakes system. It is 14 km long, 6 km wide, 26 km2 in area and has maximum depth of 3.5 m at high water level. The lake is located in a lake-swamp complex with River Rwizi as the principle inflow, and a number of peripheral lakes among which are four major ones, i.e. Lakes Nakivali, Mburo, Kachira, and Kijanebalola. Lake Nakivali is a controlled lake with four official landing sites, namely: Kikusi, Kahirimbi, Kashojwa and Rukinga. The latter three are located within a Refugee settlement whereas Kikusi is outside. The Nakivali Refugee settlement initially established for Rwandese of Tutsi origin in 1963, now has at least seven nationalities which include people from Rwanda, Democratic Republic of Congo, Somalia, Sudan, Ethiopia, Kenya and Eritrea. By the end of 2006, the lake’s hinterland of about 378 km2 contained 43,448 people of whom 22,448 were refugees. This large population has had stressful impacts on both land and lake resources to the extent that now there is an apparent overfishing on the lake. Measurements of water quality parameters reveal a change in some of them from the situation that prevailed about 80yrears ago. Water clarity (Secchi reading) has dropped from 0.5 to 0.25m and the pH has risen to 9.7 from 7.7. Water temperatures at 250C have however not changed much. The lake is eutrophic with concentrations of total phosphorus 171,µgL-1, a chlorophyll-a 57.9 and nitrate 25.8 µgL-1.Phytoplankton is dominated by blue green algae, greens and diatoms while benthic organisms consist mainly of molluscs, lake flies and earthworms (oligochaetes).