HAWAII RESERVOIR REPORT

Last Updated: March 4, 2026

Amid the complex challenges of water management across the United States, the latest observations of the nation's dams and reservoirs reveal a mixed tableau of water storage levels that reflect the dynamic interplay between natural forces and human intervention. From the vast expanse of Lake Mead in Nevada, grappling with historically low water levels due to prolonged drought and overuse, to the overfilled reservoirs in California such as Lake San Antonio, which is benefiting from recent heavy rains, the state of the nation's water storage is as diverse as its geography.

In New Hampshire, Lake Winnipesaukee at Weirs Beach shows storage levels below average, signaling potential issues for local ecosystems and water supply. Conversely, Pennsylvania's Prompton Reservoir and General Edgar Jadwin Reservoir exhibit slight surpluses, which may provide a cushion against dry spells. In the arid landscapes of the Southwest, reservoirs like Elephant Butte in New Mexico and Arizona's Lake Powell are enduring the consequences of prolonged drought, with storage levels significantly below average, reflecting broader concerns of climate change impacts. Meanwhile, the robust storage levels of Lake Almanor in California demonstrate the benefits of strategic water conservation and management practices in times of surplus. Each reservoir's condition is a story interwoven with the region's climate patterns, such as snowpack and river flows, underscoring the importance of adaptive water management strategies that balance human needs with environmental stewardship.

Hawaii has several reservoirs and dams that provide water for irrigation, hydroelectric power generation, and domestic use. The largest reservoirs in the state are Wahiawa and Kealia, which are located on the islands of Oahu and Kauai, respectively. Both reservoirs are fed by streams that originate in the mountainous regions of the islands, and they can hold up to tens of billions of gallons of water. Snowpack is not a significant factor in Hawaii's hydrology, as the state is located in a tropical region and does not experience significant snowfall. Instead, rainfall is the primary source of water for the reservoirs and rivers in Hawaii. Drought conditions can be a concern in Hawaii, particularly during El Niño years when rainfall is reduced. In 2016, Hawaii experienced a severe drought that affected agricultural production and led to water restrictions. Overall, the hydrology of Hawaii is closely tied to its mountainous topography and tropical climate, with rainfall and streamflow playing a critical role in the availability of water for the state's residents and industries.

Hawaii has several reservoirs and dams that provide water for irrigation, hydroelectric power generation, and domestic use. The largest reservoirs in the state are Wahiawa and Kealia, which are located on the islands of Oahu and Kauai, respectively. Both reservoirs are fed by streams that originate in the mountainous regions of the islands, and they can hold up to tens of billions of gallons of water.

Snowpack is not a significant factor in Hawaii's hydrology, as the state is located in a tropical region and does not experience significant snowfall. Instead, rainfall is the primary source of water for the reservoirs and rivers in Hawaii.

Drought conditions can be a concern in Hawaii, particularly during El Niño years when rainfall is reduced. In 2016, Hawaii experienced a severe drought that affected agricultural production and led to water restrictions.

Overall, the hydrology of Hawaii is closely tied to its mountainous topography and tropical climate, with rainfall and streamflow playing a critical role in the availability of water for the state's residents and industries.