Assessment of impacts of socio-economic activities on water quality within Mulunguzi Catchment, Malawi

Abstract

The main objective of this research was to assess the impact of socio-economic activities on water quality within Mulunguzi hydrological catchment. The rate of timber harvesting has not matched the rate of planting within the catchment which renders a large percentage of the catchment bare. The socio-economic activities within the catchment do not incorporate measures to safeguard the quality of water resources. Despite the fact that the mentioned activities are a threat to water quality, there is insufficient information on the impact of socio-economic activities on water quality within the catchment. The study was conducted from January to March, 2008 and aimed at determining surface water quality in relation to socio-economic activities and to quantify the resultant pollutant loads. Socio-economic activities in the catchment were timber harvesting, animal and fish farming. Methods of study included water quality parameter analysis and documentation review. Water quality parameters studied included turbidity, pH, temperature, DO, faecal coliforms, nitrates, phosphates, sulphates, iron and manganese. Nitrates, phosphates and sulphates were analyzed using ion chromatography; iron and manganese through atomic absorption spectrophotometer. Turbidity, pH, temperature, dissolved oxygen and faecal coliforms were analyzed according to standard methods. The results showed that nitrates concentrations ranged from 0.01 to 0.27 mg/L, phosphates 0.0 to 0.4 mg/L and sulphates 0.16 to 0.59 mg/L. Turbidity values ranged from 0.18 to 13.5 NTU, faecal coliforms ranged from 1 to 173 CFU/100. Iron and manganese concentration ranges were 0.0 to 10.6 mg/L and 0.0 to 0.68 mg/L respectively. Significant differences (p<0.05) were observed between upstream and downstream of timber harvesting activities in terms of turbidity and faecal coliforms; the Trout farm in terms of turbidity, faecal coliform, nitrates and phosphates; and for settlements in terms of turbidity, faecal coliform and sulphates; and finally for animal farming in terms of faecal coliform. Socio-economic activities were contributing more pollutant loads in terms of nitrates. The pollutant loads are accumulating at the bottom of the dam The results suggest that water quality within the catchment is being affected by socio- economic activities under consideration. The activity affecting water quality most was trout fish farming and least was animal farming. There is need for awareness campaigns to promote behavior change among various stakeholders as well as good management and practices within the catchment on the importance of protecting water sources.