HAWAII RESERVOIR REPORT

Last Updated: December 20, 2025

Across the nation, the storage levels of various dams and reservoirs present a mixed picture, reflecting the diverse hydrological conditions that characterize the country's vast geography. In some regions, reservoirs are experiencing surpluses, while others are facing significant droughts, painting a complex tableau of water management challenges and priorities.

A notable surplus can be observed at Colorado's Granby Reservoir, where storage levels have surpassed averages by a considerable margin, touching 400,755 acre-ft against a typical 384,875.32 acre-ft. This can be indicative of higher-than-average snowpack melting or increased river flows, benefitting local water supply and possibly hydroelectric power generation. However, the situation is starkly different for Elephant Butte Reservoir in New Mexico, where current storage is dramatically lower than average, currently at 138,842 acre-ft compared to an average of 829,569.15 acre-ft. This points to a potential crisis in water supply for irrigation and urban consumption, likely necessitating stringent conservation measures and possibly reflecting changes in precipitation patterns or allocations upstream.

Such disparities underscore the importance of adaptive water resource management to handle the hydrologic variability that affects reservoir and dam operations nationwide. For water management researchers and hydrologists, understanding these dynamics is crucial for planning, as it impacts everything from agriculture and municipal water supply to flood control and ecological preservation. Maintaining balance in reservoir levels is a dance with nature's unpredictability, emphasizing the need for robust data monitoring and responsive management strategies to safeguard against the extremes of droughts and surpluses.

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.