题目解析：
A 用level of the water table去寻找先关描述，定位到这一段倒数第一二句话。Groundwater commonly collects in stream drainages but may remain entirely beneath the surface of dry stream-beds in arid regions. In particularly wet years, short stretches of an otherwise dry stream-bed may have flowing water because the water table rises to intersect the land surface.根据这段最后两句对于wet year的描写可以得出根据降雨量不同, 地下水位是有变化的，在比较多雨的年份，地下水位可能会上涨，和地表交汇。所以 A正确。B不正确，原文明显写到在arid regions降雨量多时干燥的溪床会有水；C也不对，整段都有大篇幅在写和land surface的intersects；D原文没提到。
Because the surface of the water table is not flat but instead rises and falls with topography, groundwater is affected by gravity in the same fashion as surface water. Groundwater flows downhill to topographic lows. If the water table intersect the land surface, groundwater will flow out onto the surface at springs, whether to be collected there or to subsequently flow farther along a drainage. Groundwater commonly collects in stream drainages but may remain entirely beneath the surface of dry stream-beds in arid regions. In particularly wet years, short stretches of an otherwise dry stream-bed may have flowing water because the water table rises to intersect the land surface.
