Climate change is impacting Hawaiʻi in many different ways, and the Ala Wai Watershed is no exception. Sea level rise is a threat to the coastal and low-lying areas, changes in rainfall patterns will result in more heavy rain events, while at the same time reducing the average rainfall that recharges our groundwater. Changing weather patterns make hurricanes more intense and their likelihood more difficult to predict. In addition to climate change considerations increasingly featuring in the decision making on infrastructure, long-term planning, and disaster preparedness, there are several initiatives and institutions who specifically address climate change on Oʻahu and in the Ala Wai Watershed.
The State’s Climate Change Mitigation and Adaptation Commission (previously the Interagency Climate Adaptation Committee) was created in 2017 and is tasked with providing direction, facilitation, coordination and planning among state and county agencies, federal agencies, and other partners about climate change mitigation (reduction of greenhouse gases) and climate change resilience and adaptation strategies.
Planning for the Ala Wai watershed’s water demand and supply, future water demands, and supply options to meet those demands is addressed in the Board of Water Supply’s Primary Urban Center Watershed Management Plan (PUC WMP), prepared by Townscape Inc. The PUC WMP is a holistic watershed management plan that addresses the health and inter-relationships of land and water resources within the 105 square miles of urban Honolulu. This plan is in the drafting and public input phase and considers the climate impacts of changing rainfall, temperatures, and sea level rise as far out as the year 2100.
Some adaptation measures, in particular to sea level rise, may require adjustments to the City & County’s Land Use Ordinance (LUO).
The US Army Corps of Engineers (USACE) was asked to develop the Ala Wai Canal Project to reduce the impacts of a 100-year flood caused by heavy rains overflowing the streams and canal, which will become more likely due to climate change. Although the project was not conceived to address sea level rise, the preliminary designs take into account an intermediate sea level rise scenario of 2.5 feet by 2075 and 4 feet by 2125.