Ni‘ihau is approximately 70-square miles or 44,800-acres, and sea cliffs are a prominent feature of the eastern coast. Approximately 78-percent of the island is below 500-feet in elevation. Ni‘ihau has no perennial streams. Among Ni‘ihau’s most unique natural features are several intermittent lakes.
Halulu Lake is a natural freshwater lake covering approximately 182 acres and Halāli‘i Lake is an intermittent lake covering approximately 841 acres (considered the largest lake in Hawai‘i.) The water comes from rainfall, which only averages between 20 to 40 inches per year on Ni‘ihau. During dry years, the lakes are typically dry.