This paper is part of a multi-step assessment of the hypothesis that subtropical, semi-arid impoundments may respond differently to increasing nutrient enrichment than similar northern temperate waterbodies (primarily natural lakes) from which the classical lake eutrophication concept has been derived. Common physicochemical indicators of eutrophication are referenced, including nutrient status, phytoplankton biomass (chlorophyll), and hypolimnetic deoxygenation. Data from 89 reservoirs in the southwestern United States and southern Africa were used to examine the eutrophication-related limnology of these lakes. In particular, the effects of a large catchment area:lake surface area ratio (AD:A) on the turbidity, nutrient status, and phytoplankton standing crop were highlighted as distinct features relevant to semi-arid lake classification. The responses of reservoirs in semi-arid regions of the northern and southern hemispheres to nutrient enrichment are contrasted with responses of temperate lakes to highlight their implications for accurately assessing eutrophication of manmade lakes in subtropical, semi-arid areas.