Afromontane-savanna rivers present unique features such as savanna grasses and large mammalian herbivores (LMH, both wildlife and livestock), which interact with the river and are likely to affect the river's functions. LMH transfers significant amounts of nutrients and organic matter during feeding, watering, and their movements, and this may be likely to shape how Afromontane-savanna rivers function. To establish this, sites were classified based on land use and stream orders. A total of 82 sites were selected for sampling for nutrients, dissolved organic matter (DOM), and modelling of whole-stream/ ecosystem metabolism. Land uses were grouped into five broad categories forested (19), agricultural (26), low-density livestock (15), high-density livestock (12), and hippos (10) sites. There were significant (PERMANOVA, p<0.05) spatial variations in water physico-chemical parameters, nutrients, DOM quantity, and measures of ecosystem metabolism among land uses and not among stream orders. Sites influenced by LMH had high electrical conductivity, temperature, and dissolved oxygen levels (p<0.05). LMH inputs had varied effects on nutrients, with ammonium and DOC associated with hippos and high-density livestock streams (p<0.05). Total dissolved nitrogen (TDN) and nitrates were higher in agricultural sites and low livestock density streams than in the high livestock and hippo-influenced sites. Hippos and high-density livestock streams had high aromaticity and high molecular weight DOM (p<0.05). In contrast, low-density livestock and agricultural streams had photodegraded and low molecular weight DOM. The ratio of gross primary production (GPP) and ecosystem respiration (ER) was greater than one (GPP/ER >1) in low-density livestock and agriculture sites. At forested sites, the ratio was less than one, which is an indication of heterotrophic conditions. The findings of this study show that irrespective of their location on the fluvial continuum, LMH strongly influence the biogeochemistry of Afromontane-savanna rivers.