An investigation into some water quality problems of Lake Kanyaboli in Kenya

Abstract

This study attempted an investigation into some water quality problems of jake Kanyaboli. The geographical location of lake Kanyaboli within the Yala swamp and its size of 10.5km1 make it ideal for this investigation. Further the problem is complicated by the fact that the lake has no outlet and after the diversion of river Yala during the reclamation of the Yala swamp, there is no major inlet into this lake. On the whole it is assumed that the activities around the lake in addition to the hydro-technical measures that has taken place within the swamp have a direct impact on water quality of the lake. This study therefore intended to assess the levels of various parameters in the lake water as well as their pathways. Because the lake lacks an outlet, a unified approach that integrates water quality parameters and that of interstitial water was preferred. Both water samples and bottom sediments were collected and laboratory analysis performed on parameters for both surface water and interstitial water respectively. Results show that the levels of ionic constituents are low, suggesting that this is due to the low solubility of the precambrian rocks within the catchment. On the other hand iron and manganese are reported in levels that are almost equal to or above the recommended levels. Most of the normal water characteristics reflect that lake Kanyaboli is a fresh (TDS), soft (hardness) and an alkaline lake (pH). However colour and turbidity are elevated. Precipitation and runoff contribute significant amount of pollution parameters as shown by the results, implying that catchment activities have an important influence on the quality of the lake water. While phosphorus has not been detected in water, nitrates occurred only in trace amounts. The levels of nitrites, ammonium nitrogen, free ammonia and albuminoid ammonia (0.06mg/l, 0.12mg/l, 0.06mg/l and 0.06mg/l respectively) suggest organic contamination. Permanganate value (4.04mg/l) implies a large IV amount of organic matter. The levels of the above nutrients are elevated in interstitial water and those of nitrates and phosphorus (0.12mg/l and 1.12mg/l respectively) suggest that the lake is eutrophic. Generally the levels of the parameters is higher in interstitial water than in overlying water (except pH and nitrites) suggesting that pollutants are accumulated in the bottom sediments. This therefore is a pointer to the fact that these pollutants have accumulated in the bottom sediments and thus sediments may act as source of these pollutants at certain periods of time and under certain prevailing conditions. Prevention of further pollution appears as the only means of attaining the objective of managing the lake water. From the viewpoint of water quality management, Lake kanyaboli can be used as an experimental lake in the study of water quality arid thus scientific knowledge of great value in controlling pollution may result. Above all, if proper management techniques can be achieved for this small lake, then the lake Kanyaboli example can be applied in other similar situation within the country as the nation faces the need for managing this aspect of its water resource.