In Hawaii, there are approximately 376 streams that flow continuously throughout the year. These perennial streams are primarily fed by rainfall (surface runoff) and underground sources of water (subsurface flow). From the mountains to the sea, streams give life to the diversity of ecosystems that form our unique Hawaiian landscape. From the lush rainforests mauka to the coastal areas makai, streams flow through conservation zones, agricultural lands, and urbanized areas near the coast.
Streams are a vital part of our island ecosystem. They provide habitats for native fish and wildlife, support various recreational activities such as swimming and fishing, maintain wetland and estuary ecosystems, and support traditional and customary Hawaiian rights including taro cultivation.
Current Streamflow Conditions
Stream channel alterations include the widening, straightening, hardening, and other general changes to a stream channel that are permanent in nature. While stream channel alterations are often necessary for public access, health, and safety, the protection and maintenance of instream uses must also be considered.
For example, large concrete flood channels are common sights in Honolulu's urban areas. During heavy rainstorms, these structures help to alleviate flooding by carrying water quickly from the upper watersheds to the ocean, limiting damage to surrounding areas. However, these channelizations often reduce habitat for fish and wildlife and eliminate recreational stream activities such as fishing and swimming. Other types of alterations include bridges, culverts, dams, and retaining walls.
Streams are also diverted for many important purposes such as agricultural (vegetables, fruits, flowers, livestock, etc.), domestic (personal use and consumption), and municipal uses (drinking water). Surface water is generally a low-cost source of water when compared to more costly alternatives, such as pumping water from ground water aquifers or paying for water service from a water supply agency such as the Honolulu Board of Water Supply.
Unfortunately, the impacts of diverting water from a stream are similar to those caused by physically altering a stream channel. Reductions in streamflow results in a decreased amount of habitat available for fish and wildlife, increased water temperatures detrimental to stream animals and taro production, limited recreation, and may impact the productivity of corals, fish, and other marine life in nearshore waters.
The Stream Protection and Management (SPAM) Branch regulates the State's surface water resources. One of their primary duties is the permitting of stream channel alterations and diversion of surface waters statewide. Permits allow the Commission to assess the potential impacts of the alteration or diversion on the stream environment. Through these regulations, the Commission strives to ensure the protection and sustainability of Hawaii's precious freshwater ecosystems.
Everyone benefits from healthy streams and the educational opportunities they have to offer. Maintaining a balance between changes to stream environments and the protection of instream uses is a challenging task. Continued cooperation between the government, the public, and the private sector is critical to preserving Hawaii's stream ecosystems for generations to come.
Below are links to other agencies and organizations that provide useful information on the protection and conservation of our surface water resources. Please be aware of the disclaimers and privacy policies of each respective site. Note that by clicking on each link below, a new browser window will be opened.
Trash and other debris in a stream can block stream flow, which obstructs the migration of native stream animals and increases the risk of flooding to surrounding areas. Removing these blockages is an important part of keeping the stream clean and healthy. Who's responsiblity is it to keep the stream clean? Who enforces stream maintenance? What should I do when I witness illegal dumping into the stream? For answers to these questions, explore the links below.
Floods usually occur following prolonged or heavy rainfall associated with tropical storms or hurricanes. The magnitude of the flood depends on slope, soil conditions, and ground cover. In Hawaii, the most common type of flood is flash flooding. Flash floods are powerful and dangerous in that they can develop quickly (within a few hours after a rainfall event) and carry rocks, mud, and all the debris in their path down to the coast. Some floods can even trigger massive landslides, causing property damage and fatality. Since flash floods usually occur along small streams, areas adjacent to streams have higher flood risk. For more information on flood preparedness, explore the links below.
Leptospirosis is a bacterial disease that is passed from animals to humans. Outbreaks of the disease are usually caused by exposure to water contaminated with the urine of infected animals. In Hawaii, rodents, rats, mongooses, pigs, and cattle are among the many domestic and wild animals that can transmit the disease. One of the common ways of contracting leptospirosis is swimming in fresh water ponds or streams. The Hawaii State Department of Health is continually urging people to avoid going in fresh water streams with open wounds. For more information on leptospirosis and prevention measures, explore the links below.