既然教材上没有用定冠词，记住就可以了，今后自己使用时也不用冠词就是了。

据个人理解，含有 Valley 的专有名词有些加定冠词the，有些不加定冠词 the，可能与表达习惯有关。下面我查到的一些词典例句，列如下，供参考：

▲不用定冠词的例句

Oak Valley

I had thought we might travel as far as Oak  Valley, but we only managed the first lap of the journey. 我原以为我们最远能到达橡树谷，结果只走完了第一段路程。

Simi Valley

He chose Simi Valley in Ventura County mainly because it was conveniently close to Los Angeles. 他选择住在文图拉县的西米山谷，主要是因为这里离洛杉矶很近，很方便。

Yakima Valley

In the spring, the rolling hills around Yakima Valley turn white with blossom. 春天，亚基马山谷四周起伏的山丘上开满了白花。

▲用定冠词的例句

the Happy Valley

I had no wish to go to the Happy  Valley. 我不想去快活谷。

the Harlem  Valley

I ran straight up to Columbia County, then turned East, came down the Harlem  Valley and thence home. 我一直跑到哥伦比亚县，然后向东转，沿着哈勒姆山谷，从那里回到家。

the Loire  Valley

There’s something about the Loire  Valley that makes you want to savour every moment.  卢瓦尔山谷有某种特殊气息，让人想要充分享受在这里的每时每刻。

the Nile  Valley

The Nile Valley keeps a temperate climate throughout the year. 尼罗河流域一年四季气候温和。

the San Fernando Valley

magnificent views over the San Fernando Valley 圣费尔南多河谷的壮丽美景