The need for adaptive tools is especially sharp in the context of managing vital water resources. Hawai‘i water experts have recognized that alterations in rainfall, temperature, wind, or other climate phenomena have the potential to devastate natural resources and human communities. This paper briefly describes Hawai‘i’s water resources, and then identifies troubling patterns of climate change that are already evident in Hawai‘i, including (a) declining rainfall, (b) reduced stream flow, (c) increasing temperature, and (d) rising sea level. Each poses serious consequences for the replenishment and sustainability of groundwater and surface water resources. These worrisome trends are then further compounded by the prospect of other looming impacts related to climate change, such as potential changes in the trade wind regime, the intensity and frequency of drought and storm events, the El Niño-Southern Oscillation, and the Pacific Decadal Oscillation. And even without such climate-related trends and risks, the forecast for rising population and increasing water demand presents a compelling need to carefully manage water resources.

The picture is clear. Hawai‘i must adapt to a future that will be different from the present, especially where water resources are involved. Fortunately, aspects of Hawai‘i’s existing laws and policies on water management already include adaptive mandates. This paper describes the general principles of climate change adaptation. In broad terms, “adaptive capacity” is defined by laws and policies that require water management to be: (1) forward-looking—focused on crisis avoidance as well as crisis mitigation; (2) flexible—able to adjust to changing needs and conditions; (3) integrated—able to address climate-related impacts that cut across political and geographical boundaries; and (4) iterative—utilizing a continuous loop of monitoring, feedback, and reevaluation.

This paper analyzes the structure of Hawai‘i’s water management scheme, with a special focus on adaptation. Water is the only natural resource addressed in a stand-alone section in the state constitution. That section, along with other constitutional provisions, mandates the long-term protection of natural water resources. These top-level protections are bolstered by (i) the public trust doctrine, which imposes a duty on the state to protect and manage all water resources for the benefit of present and future generations, and (ii) the precautionary principle, which empowers water managers to take precautionary action without first waiting for a crisis to establish absolute certainty of the related risks. The constitution also directs the formation of a single agency—the Commission on Water Resource Management (“Water Commission”)—to establish policies and procedures for water management. This is accomplished primarily through the State Water Code and associated rules.

Numerous aspects of this legal structure exhibit adaptive characteristics. Examples include: forwardlooking mandates for long-term water resource protection; the flexibility of the Water Commission to continuously update and refine estimates of the sustainable yield (the amount of water that can be sustainably drawn from each aquifer); the integrated approach in which the Water Commission oversees a four-part Hawai‘i Water Plan with input from virtually every corner of the state; and the iterative requirement that salinity and other measures of water sustainability must be vigilantly monitored. Springing from this basic framework, Section 4 of this paper identifies twelve potential adaptive tools that are not presently implemented in Hawai‘i, or that are implemented only in part. Each tool is consistent with the existing law and policy framework, and each exhibits adaptive characteristics. Many of these tools are derived from existing models, already tested in in Hawai‘i or elsewhere.