High viscosity fracturing fluids for fracturing a subterranean formulation are prepared by: (i) selecting recovered water; (ii) contacting said recovered water with a viscosifying agent, wherein said viscosifying agent is selected from fenugreek gum, tara gum, locust bean gum, guar gum and derivatives of the aforesaid; (iii) contacting said recovered water with one or more other additives for example with a cross-linking agent (A) for cross-linking said viscosifying agent, wherein contact of said recovered water with cross-linking agent (A) takes place when the pH of said recovered water is less than pH 6.5; (iv) adjusting the pH to pH 6.5-8.8.