词汇是基础，首先带着大家熟悉本篇 托福阅读 文章中的疑难词，方便全文阅读(学霸略过此部分)。
capsule n. 胶囊;太空舱adj. 压缩的vt. 压缩
replenish vt. 补充，再装满;把…装满
persistent adj. 固执的;持久的
scarce adj. 缺乏的adv. 仅仅
Deplet vt. 耗尽
Lucrative adj. 有利可图的
underscore vt. 强调
Lack of Snow Leaves California's 'Water Tower' Running Low
Snowpack—which essentially serves as a water tower for the western United States—produces vital meltwater that flows off the mountains each spring. Like a time-release capsule, snowpack refills streams and reservoirs and waters crops and cities through the dry summer in this largely semiarid region.
But the snowpack is becoming more like a snow gap, as temperatures in the Cascades and Sierra Nevada become too warm for the snow that replenishes the ecosystem each winter. Temperatures in the West are rising, and winter storms—which have been in infrequent for years—are bringing more rain and less snow.
As a result, the water tower of stored mountain snow—which typically provides one-third of California's water—is no longer refilling each winter, leaving a gap in summer water supplies. California now faces a fourth year of severe surface water shortages, and there isn't a broad plan to deal with the scarcity of water that's being created by persistent shortfalls of snow. Groundwater has served as a Band-Aid by compensating for the lost water, but aquifers are being pumped faster than they can replenish, and like snowmelt,