Against the recommendation of an advisory board, Pitkin County commissioners on Wednesday gave preliminary approval to buy more water to boost flows in the often-depleted Roaring Fork River. Commissioners approved on first reading a resolution and ordinance to spend $442,500 to buy 4.68 shares from the Twin Lakes Reservoir & Canal Co., which is about 3.5 acre-feet of water, according to a staff memo. The deal is in addition to the $6.5 million P…