The National Weather Service has issued a flood warning for the Hood River.  The river had reached flood stage at 13 feet at about 4 p.m., and is expected to crest at 13.5 feet at 6 p.m.  The river is expected to go over its banks in a few locations, and minor flooding of low-lying property and roads adjacent to the river is likely.   Officials advise people to stay away from river banks that may be eroded away by the high and fast-flowing water.  Heavy rains are expected to continue for the next three days.   Local health officials advise at least two sewage treatment plants in the area have released wastewater into local rivers and streams. Sewage overflow happens when the treatment plant is overwhelmed with greater than normal flows. Excessive runoff has also carried contamination from livestock and other domestic animals into the local waterways.