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Calcium carbonate production in most freshwater tufa systems is controlled by a combination of physico-chemical precipitation, and biomediation associated with procaryote-microphyte biofilms. Inorganic precipitation is dominant under turbulent flow regimes, whereas biomediation necessitates sluggish flow or static water. We show here that temperature is also likely to affect tufa formation rates and architecture, leading to the development of a clearly definable range of fabrics. Two contrasting models are proposed: Warm semi-arid tufas: well seen in the Ruidera Pools National Park, Albacete Province, Central Spain, where tufa barrages consist of vertical, narrow rimmed arcuate structures. Frequently these are bounded both upstream and downstream by deep lakes. Laterally accreting mammilate stromatolites dominate the upper two thirds of lake margin subaqueous overhangs, whereas conical growth-forms …