Deborah Abong'o

Occurrence, abundance and distribution of benthic macroinvertebrates in the Nyando River catchment, Kenya

A baseline study was conducted of the occurrence of macroinvertebrates at 26 sites in the Nyando River catchment in 2005–2006. A total of 13 orders and 16 families of Arthropoda, Mollusca, Platyhelminthes and Annelida were collected, with the order Ephemeroptera being most abundant in the up- and mid-stream reaches, followed by Hemiptera and Plecoptera respectively. The downstream sections of the river were dominated by Hirudinea and tubificids, as the water quality deteriorated mainly due to local land use, raw sewage effluent discharge and annual floods. Insects and annelids were the main invertebrates found and the extent of pollution increased from mid-section (Site 15) downwards as the river flowed into the Winam Gulf. Stringent management measures are required to safeguard the environment and ecosystems of Lake Victoria.

Assessment of Dissolved Ions and Microbial Coliform in Water from Selected Sites of the Upper Athi River Sub-Catchment Area, Kenya

Twenty one water samples were collected and analysed for dissoved ions and microbial coliforms from selected sites of the Upper Athi River sub-catchment basin. The metal ions analysed included Ca, Cd, Cr, Cu, Fe, Mg, Mn, Na, Pb and Zn while anions included Cl , CO3 2/HCO3 , F , NO2 /NO3 and SO4 2as well as faecal coliforms. Physical parameters analysed included pH, electrical conductivity (EC) turbidity, total dissolved solids and colour. The analysis was carried out using atomic absorption spectrophotometry, titrimetric, ion selective electrode, gravimetric and lactose broth methods. The results showed that levels of dissolved ions in ground water were higher than in surface water while surface water had higher number of faecal coliforms. The high levels of dissolved ions in ground water was attributed to the geology of area while high levels of iron and faecal coliforms in river water samples was attributed to anthropogenic activities