Title: Water quality and pressures assessment of Mabamba Bay Wetland, Uganda

Author: Judith Namumbya

Supervising Institution: IHE Delft  - Institute for Water Education

Year: 2019



Wetlands are ecotones between terrestrial and aquatic ecosystems. Mabamba Bay is a Ramsar site, a source of livelihood and a habitat to waterbirds including vulnerable species on the IUCN red list. Protecting and monitoring wetland resources is vital amidst increasing population and demand for ecosystem services and goods. An analysis of 12 water samples for physicochemical variables was used to ascertain the status of its water across four channels of Gombe, Kadozi, main and Lake Channel. The water quality status of this wetland indicated its interaction with the surrounding catchment. Analysis showed its ionic concentration ranged from 15±2.2 to 67±15.4μscm-1. The low oxygen profile obtained in all the three channels showed the nutrient status of the wetland was influenced by its redox potential that determined its biological and chemical processes. The C: N: P molar ratio obtained was compared to the Redfield ratio which showed that nitrogen was limiting and the wetland is a carbon dominated system. Concentrations for example along Gombe channel were 1333:0.4:1.1 of C: N: P. The bioavailable phosphorus was also high in the lake with 27 μgL-1. Total phosphorus was highest in the lake with 69±9.2μgL-1 and was least in the channels inside the wetland. Total nitrogen was low in Gombe channel with 5±2.30 mgL-1 and highest in Kadozi with 12±4.00mgL-1. Local communities influence and shape the wetland. An assessment of individual perception in the community showed ecotourism and transport services were the main activities in the area. A further comprehensive assessment of the data obtained from interviews with the DPSIR tool showed that current conservation measures need to be maintained for ecological integrity and resilience of the wetland against impacts of human activities and natural factors. A quick analysis of recent changes in vegetation biomass in the wetland done using remotely sensed images using the Normalised Difference Vegetation Index for a span of four years, showed, a slight reduction in the NDVI score from 0.3 to 0.29 in 2015 and 2018 respectively, in densely vegetated areas. An analysis of 10 year waterbird monitoring data obtained from NatureUganda, showed a stable trend in most of the common waterbird species such as the African jacana (Actophilornis africanus), the long-tailed cormorant (Microcarbo africanus) and the yellow-billed duck (Anas undulata) and shoebill (Balaeniceps rex), which was likely an indicator of maintenance of habitat quality. This wetland was under monitoring by the local community who indirectly used waterbirds as an indicator for conservation since it was a source of livelihood to the local community.