Abstract

Namadzi River catchment with total area of 69,802 hectares is an important river sub-catchment, for both commercial estates and smallholder farming. The Namadzi River feeds into Lake Chilwa, a wetland of international importance under the Ramsar Convention. This thesis report on a study conducted to assess environmental degradation in this river catchment with a focus on forestry cover change impacts on water resources. Aerial photo interpretation and statistical analysis of historical data and rainfall/run-off modelling using RainRu models were used to analyze forest cover change and the relationship between forest cover change and stream flow. Further, the study also looked at the dependency on forest and water resources in Namadzi catchment to examine the socio-economic characteristics of the area. Results show that rainfall has decreased over the years and the decrease is also evident inrun-off and stream flow, two important rainfall dependent variables. Results from Mann Kendall statistic and Sen’s method show that annual decreasing flows are evident, though not significant. At monthly level, decreasing flows were also found in February (significant at 99%), March (significant at 90%), April (significant at 99%), May, July and August (all not significant). In addition, increasing flow trends are found for June, September and November (not significant), October (significant at 95%) and December (significant at 99%). Furthermore, the slopes for all the months are statistically different from zero at 99% confidence interval indicating that stream flow is decreasing over the years. RainRu model results show that the rainfall/run-off relationship has not changed significantly over the years. The results further show a decreasing trend in forest cover from 1965 to 1974 and an increase since 1995. As noted from the rainfall/run-off relationship, the overall picture for rainfall/run-off relationship has not changed over the years. This suggests a direct effect of forest cover (land cover) change on stream flow. Results from the socio-economic study indicate environmental degradation in Namadzi catchment has taken place. The larger percentage of the respondents, 60.3% indicated that indigenous forest has decreased by over 85% compared to 20 years ago. This has been shown by the increased trend in area planted with trees in the catchment.

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School	: School of Natural and Applied Sciences
Issued Date	: 2010

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