Storm Water Drainage Systems’ Effectiveness and Adequacy in Managing Storm Water Discharge in Kisii Municipality, Kenya

Urbanization and increased developments have put pressure on important infrastructure like storm water drainage networks, often resulting to flash floods and blockage of drainage structures. This study assessed the effectiveness and adequacy of storm water drainage systems (channels) in Kisii municipality, in collecting and discharging storm water. The study areas for drainage networks were selected purposively based on the drainages type (concrete, earth and grass lined). Discharge was calculated based on the amount of rainfall, duration of rain, land use and slope of the study area. Land use maps and drainage network were generated in Personal Computer Storm Water Management Model (PCSWMM) using satellite maps and digital elevation models respectively. The effectiveness was established by routing runoff water in the PCSWMM. Surcharged culverts and joints indicated inefficient storm water drainage systems, resulting to ponding and flooding. Results from this study indicated that there were instabilities in conduits and surcharge in nodes. Surcharging of nodes was experienced for up to 22 hours at Daraja Mbili while ponding in Mwembe lasted for up to 22 hours. The level of surcharge and flooding on Rivers was experienced within 15 minutes of a rainfall in Nyanchwa sub catchment

Occurrence and distribution of Organochlorine Pesticide Residues in Water and Sediments of Earthen Fish Ponds in South Western Kenya

Persistent organochlorine residues in the environment are a threat to ecological health of aquatic organisms and pose a health risk to both animals and human consumers. Organochlorine pesticides were determined in water and sediments collected during wet and dry season from selected riverine and earthen fish pond sites in high altitude catchment areas within Kuja River (Kenya) between August 2016–May, 2017. Analysis of DDT and metabolites, Hexachlorocyclohexanes (HCHs) isomers and cyclodienes using a gas chromatograph (GC), and electron capture detector (ECD), confirmed using GC - Mass Spectrometry (MS). Mean (± Standard error) results of DDTs, cyclodienes and HCHs in pond waters were:- below detection level (BDL) to 0.27±0.03µg/L, BDL to 0.11±0.00µg/L, and 4.39±1.01µg/L respectively; and BDL to 0.23±0.01µg/L, 1.20±0.005µg/L, and 1.71±0.02µg/L in river water respectively. Sediment mean OCPs contents were significantly (p<0.05) higher for Dieldrin (3.043±0.43µg/kg), Endrin (2.56±0.460µg/kg), Heptachlor (3.61±0.02µg/kg) DDT (2.97±1.32µg/kg), Endosulfan (6.31.27±1.051µg/kg), Methoxychlor (2.15±1.641µg/kg) and Lindane (2.96±1.32µg/kg), respectively. A longitudinal spatial distribution pattern was noted for both water and sediment OCPs contents, demonstrating that cyclodienes are predominant contaminants in point and non-point sources in water courses. The study recommends continuous monitoring of OCPs in upstream catchment areas for informed management and policy decisions on pesticide use. Keywords: Kuja-Migori River; Organic contaminants; Organochlorine Pesticide