Surface water has been extracted from Arusha National Park (ANP) to meet human demand for over 30 years; however, there has been no evaluation of the impact of extraction on surface water quality, budget or ecological integrity. A reduction in water availability and flow is likely to also have impacts on the distribution and space use of large mammals. To assess the surface water quality and budget, 30 water sources were measured for three months over the dry and wet seasons. Nearly 70% of water is extracted, with the complete extraction of surface water common during the dry and early wet seasons. However, extraction did not lead to a decrease in downstream water quality, but wetland plant diversity was highest in areas with no surface water extraction. Extraction also influences large mammal space use: abundance along seven transects was typically higher upstream of extraction sites, especially in the case of large herbivores. Impacts of extraction therefore include the disconnection of streams, changes in space use of large mammals, decreases in plant diversity and changes in species composition of the riparian wetlands. We therefore recommend that monitoring and evaluation of extraction as well as sustainable water use practices be introduced as a matter of urgency.