ABSTRACT
Climate change is expected to significantly deteriorate water quality in heavily managed agricultural landscapes, however, the exact mechanisms of these impacts are unknown. In this study we adopted a modelling approach to predict the multiple effects of climate change on hydrological and biogeochemical responses for dominant solutes and particulates in two agriculture-dominated temperate headwater catchments. We used climatic projections from three climatic models to simulate future flows, mobilisation and delivery of solutes and particulates. This allowed an examination of potential drivers by identifying changes in flow pathway distribution and key environmental variables. We found that future climate conditions will lead to a general increase in stream discharge as well as higher concentrations and loads of solutes and particulates. However, unlike previous studies, we observed a higher magnitude of change during the warmer part of the year. These changes will reduce the relative importance of winter flows on solute and particulate transport, leading to both higher and more evenly distributed concentrations and loads between seasons. We linked these changes to the higher importance of superficial flow pathways of tile and surface runoff driven by more rapid transition from extremely wet to dry conditions. Overall, the observed increase in solute and particulate mobilisation and delivery will lead to widespread water quality deterioration. Mitigation of this deterioration would require adequate management efforts to address the direct and indirect negative effects on stream biota and water scarcity.
ABSTRACT
The social-ecological system of the Lake Manyara basin (Northern Tanzania), a UNESCO Biosphere reserve (BR) suffers from social-economic and environmental problems due to decreasing water levels, erosion and land and water use conflicts. We propose an integrated assessment of the social-ecological interactions of the area to support future sustainable management. Within the Drivers-Pressures-State-Impact-Response (DPSIR) framework an integrated literature review and several methods of knowledge collection were combined to identify future management priorities and challenges. During focus groups with farmers and pastoralists, stakeholders confirmed the role played by land use changes as driver and pressure in the landscape, e.g. through increased erosion rates and siltation of the lake. Moreover, economic and social issues were identified as prominent factors being influenced by, or influencing these processes. These statements match the scientific literature. During participatory mapping exercises different spatial and resource allocation perceptions appeared amongst pastoralists and farmers. The multidisciplinary approach proved to be useful to acquire an integrated and comprehensive understanding of the state, challenges and opportunities of Lake Manyara BR, to feed into a decision support system in service of an integrated management plan. Our assessment suggests that improved water governance in a multi-actor approach (with a focus on distribution of benefits, rights, and a specific role of the water authorities) should be a priority for future integrated management strategies. Also, awareness raising amongst decision makers, scientists and local communities is needed to demonstrate the advantages of an integrated approach. And finally, visible and fair mechanisms to share conservation revenues should be designed in a way that local benefits can be obtained together with incentive mechanisms for co-management and conservation.