Shares in water groups advance ahead of tomorrow's preliminary ruling from the water regulator on their five-year business plans. According to Nomura, investors have been overly pessimistic about Ofwat's plans. The broker thinks the sector may rally tomorrow when Ofwat's report turns out to be more benign than expected.Severn Trent, on which Nomura keeps its 'buy' recommendation, leads water groups higher, with Northumbrian Water Group, United Utilities and Pennon also in positive territory. Mining stocks fall back after some good gains lately. They were given a reminder of the uncertainty that has plagued the sector lately by BHP Billiton, which sees a mixed year for commodities.Top performing sectors so far todayForestry & Paper 2,469.33 +6.63%Automobiles & Parts 2,104.26 +1.69%Gas, Water & Multiutilities 3,637.68 +1.47%Electricity 6,210.82 +1.41%Mobile Telecommunications 2,636.17 +0.53%Bottom performing sectors so far todayMining 14,823.77 -2.51%Aerospace and Defence 2,561.88 -1.65%Life Insurance 3,020.84 -1.30%Electronic & Electrical Equipment 1,197.16 -1.19%General Industrials 1,742.53 -1.05%