ala wai monitoring station

The Ala Wai Canal, an important recreational resource on the Island of O'ahu, is a tidally influenced, artificial canal completed in 1927 to drain the Waikiki area. The canal is 3,100 m long, varies in width from about 51 to 83 m and today varies in depth from 5 m to only a few centimeters. According to Sunn et al. (1977), the peak runoff to the canal is 161 m3/sec from Makiki Watershed (683 ha), 382 m3/sec from the Manoa-Palolo Watershed (2,528 ha, 58% of the total Ala Wai Watershed), and 118 m3/sec from Waikiki, Kapahulu, and Ala Moana area (combined area of 1,659 ha) for a total peak runoff of 661 m3/sec. The Ala Wai " . . . [C]anal has become a polluted, highly eutrophic water body" (Glenn and McMurtry, 1995), in all likelihood, primarily as a result of the runoff from the encircling watershed.

In order to understand and quantify pollutant loadings to the Ala Wai Canal and nearshore Mamala Bay, we are collecting data from a network of stations located in the largest of the Ala Wai watersheds--the Manoa-Palolo Watershed, the Ala Wai Canal, and Mamala Bay. Our uppermost station is WK which is located on Wai-a-ke-akua Stream (Water of the Gods) at an elevation of 85 m and about 2.5 km from the watershed divide and about 9 km from the mouth of the Ala Wai Canal. This relatively pristine stream combines with Wai Iki and several other small streams to form Manoa Stream, which runs through the residential community of Manoa. As Manoa Stream flows through the Manoa Valley it accumulates pollutants from runoff. Anthropogenic activity in the valley center leads to pollution which is carried into the stream. Increased vehicular traffic and urbanization near the University of Hawai'i, in Kaimuki and in Moiliili, as well as channelization, lead to degradation of the waters of Manoa and Palolo streams, which join slightly upstream of our Station KHS located about 8.5 km downstream of the watershed divide at an elevation of only 3 m above sea level.

In addition to Stations WK and KHS, we routinely sample a number of other stations in the watershed, Ala Wai Canal, and Mamala Bay. These stations are shown in the 3-D map below.