Assessment of water quality in Mohale dam and associated rivers in Lesotho

The study assessed Mohale dam and the associated rivers’ water quality over 5 years and comparing it to the water quality standards. It was believed that since this dam and the rivers occurred at elevations of between 2000m and 2900m above sea level, there was minimal anthropogenic pollution. Monthly data of the dam and the rivers water quality for the period 2003-2008 on pH, electrical conductivity (EC), potassium (K), sodium (Na), calcium (Ca), magnesium(Mg) and turbidity were collected from the Lesotho Highlands Authority (LHDA) database. In 2009 data for base cations (K, Na, Ca and Mg) and heavy metals (Fe, Cu, Zn, As and Pb) content were collected. The results showed that during the period 2003-2008, across sites and years, the pH and mean concentration of base cations were below the minimum permissible levels (mpl). However in 2009 Ca concentration had risen to values >200mg/ l while the levels of heavy metals, i.e., Fe, Cu and Zn were still lower than mpl, those of As and Pb were higher than mpl. The most important water quality variables differed across sites and, as such, their close monitoring is required in order to prevent their likely built up that may pose danger to health of the nation and associated countries.
L’étude a évalué le barrage de Mohale et la qualité de l’eau des rivières associées pendant plus de 5 ans et la comparant aux standards de la qualité de l’eau. On croyait que, comme ce barrage et les rivières ss situent à une altitude comprise entre 2000m et 2900m au dessus du niveau de la mer, il y avait un minimum de pollution anthropique. Les données mensuelles du barrage et de la qualité de l’eau des rivières pour la période 2003-2008 sur le pH, la conductivité électrique (CE), le potassium (K), sodium (Na), calcium (Ca), magnésium (Mg) et la turbidité ont été recueillies à partir de la base des données de l’administration des régions montagneuses de Lesotho (LHDA). En 2009, les données pour les cations basiques (K, Na, Ca et Mg) et le contenu des métaux lourds (Fe, Cu, Zn, As et Pb) ont été collectés. Les résultats ont montré que, durant la période 2003-2008, à travers les sites et les années, le pH et la concentration moyenne de cations basiques ont été inférieurs aux niveaux minimaux admissibles (MPL). Cependant en 2009 la concentration en Ca avait augmenté à des valeurs> 200 mg / l tandis que les niveaux de métaux lourds, à savoir, Fe, Cu et Zn étaient encore inférieurs aux niveaux minimum admissibles (MPL), ceux de As et Pb ont été plus élevés que MPL. Les variables les plus importantes de la qualité de l’eau varient selon les sites et, en tant que tels, leur surveillance étroite est nécessaire afin d’empêcher leur susceptible accumulation qui peut présenter un danger pour la santé de la nation et des pays associés.
Date of publication: 
Region Focus: 
Southern Africa
RUFORUM Conferences and Workshops
Licence conditions: 
Open Access
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Printed resource

About the RUFORUM 2010 Biennal Conference
"The 2010 RUFORUM Biennial Conference was the second in the series. The main objective of the Biennial conferences is to provide a platform for agricultural research for development stakeholders in Africa and beyond to actively exchange findings and experiences, while at the same time learning lessons towards improving performance of the agricultural sector and ultimately people’s livelihoods. The biennial conference is RUFORUM’s most comprehensive meeting for the diversity of stakeholders in agriculture. It is especially dedicated to graduate students and their supervisors, grantees in RUFORUM member universities and alumni. It is a platform for peer review, quality control, mentorship, networking and shared learning. This record contains an extended abstract accepted under the theme of Natural Resource Management"