Tianhe Bus Station has direct buses to Zengcheng(Guangming west bus station), which depart every 10-20 minutes. You can get to Zengcheng 1.5 hours later and then take buses to Baishui there anothe 1 hour later. If you are closer to Guangzhou Railway Station, you can take buses to Conghua, about 1 hour, then change to buses to Baishui. Both are ok.