Human-caused modifications to surface and ground water systems throughout Hawaii have drastically altered natural hydrologic regimes (a key fish habitat process), which in turn have profoundly limited the distribution and population sizes of native aquatic fauna. Most water for cities comes from wells, although stream water is used in Upper and East Maui. However, smaller communities and agriculture often rely on surface water obtained through diversions. Irrigation systems have been built to support the cultivation of row crops, such as corn, tomatoes, sugar cane, and nut trees. They transfer large volumes of water from natural watercourses and groundwater and into networks of ditches, tunnels, flumes, reservoirs, and, ultimately, [...]