A test of the Lake Habitat Survey method in Cleveland Reservoir and Lake Chivero (Manyame River Basin, Zimbabwe)

Résumé 0

The Lake Habitat Survey (LHS) method has only been applied once in a tropical African reservoir and could potentially be a useful tool for hydromorphological impact assessments. This study (October 2012) tested the application of the LHS method to two Zimbabwean reservoirs, Cleveland and Chivero, which are impacted differently by human activities within their catchments with varying levels of physical impacts and lakeshore use. The Lake Habitat Quality Assessment (LHQA) and Lake Habitat Modification Score (LHMS) were used to assess the habitat quality and the magnitude of human impact on the reservoirs. Cleveland Reservoir LHQA (78 out of 112) and LHMS (16 out of 42) scores are indicative of relatively low human pressure (e.g. angling and canoeing). Results show that although Cleveland Reservoir is coming under increasing anthropogenic pressure, it does not appear to suffer from major alien plant invasion as compared to Lake Chivero, which scored 62/112 and 32/42 for the LHQA and LHMS, respectively. There were no significant differences between the numbers of vegetation layers in the riparian vegetation of the two reservoirs. However, there were significant differences in the number of macrophyte species and shoreline/riparian pressures between the two reservoirs. In conclusion, the use of the LHS can better enhance quality and reliability of lake hydromorphological assessments in tropical systems, where such an investigation is required to support decision making, after adaptations of the method have been made, i.e., inclusion of catchment impacts on lakes and reservoirs in LHS scoring metrics.