The impact of the 1997/98 El-Nino rains on the water quality of lake Naivasha, Kenya

  • K. S. Makhanu
  • E. C. Mwachiro
  • C. K. Kamau
  • A. Gachanja

Abstract

Lake Naivasha and its environs is host to a fast expanding flower and horticultural industry of great economic value to Kenya. These activities however pose significant environmental impact on the lake ecosystem due to the nature of chemicals used in the production and processing of such products. The fact that Lake Naivasha is a Ramsar site of immense ecological and bio- diversity values to the entire world community makes continuous monitoring of the Lake's environmental quality a necessary exercise. In conjunction with the Lake Naivasha Riparian Association (LNRA), researchers from the Jomo Kenyatta University of Agriculture and Technology carried out an intensive study of the Lake water quality between June to September 1998. This time frame has major significance as the Lake level had risen substantially from the recent El- Nino rains. The lake level at the turn of the 20th Century had in fact been restored. We discuss the variation of the Lake water quality through an environmental quality index (EQI) from published data over the years before the El- Nino rains and immediately after the El- Nino rains. From the two sets of data, the effect of the El- Nino rains on the EQI is clearly evident as the general long term general variation of the Lake's EQI. Through our study we have isolated pertinent physico-chemical parameters which can easily be incorporated in a simple water quality-monitoring model for long-term evaluation of the environmental status for the entire Lake ecosystem. With such tools in place, the current status of the entire Lake ecosystem can be known within a time frame as short as one week.

(Journal of Civil Engineering, JKUAT: 2002 7: 105-116)
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