自由溢洪道与闸控溢洪道相比结构更简单,也更安全,但传统型自由溢洪道由于比流量较小而需要较大的溢流水舌深度,因此造成水库库容大量损失(全世界损失1000亿m3)。一种新型的自由溢洪道———琴键堰(Pianokeysweir)能够使比流量增大到4倍或更多,能大大降低大多数新建大坝的费用,并能以较低的费用提高许多已建大坝的安全性、库容和/或防洪效率。 Free spillways are simpler and safer than gate-controlled spillways, but traditional free spillways require large overflow tongue depths because of their lower specific flows, resulting in a significant loss of reservoirs (a total of 100 billion m3 lost in the world) . A new type of free spillway, the Pianokeysweir, can increase the specific flow rate by a factor of 4 or more, greatly reduce the cost of most new dams, and increase the cost of many large Dam safety, storage capacity and / or flood control efficiency.