Low-Flow Characteristics of Streams Under Natural and Diversion Conditions, Waipio Valley, Island of Hawaii, Hawaii.

摘要

Over the past 100 years, natural streamflow in Waipio Valley has been reduced by the transfer of water out of the valley by Upper and Lower Hamakua Ditches. The physical condition and diversion practices along the two ditch systems have varied widely over the years, and as a result, so have their effects on natural streamflow in Waipio Valley. Recent renovation and improvements to Lower Hamakua Ditch system, along with proposals for its future operation and water-diversion strategies, have unknown implications. The purpose of this report is to quantify the availability of streamflow and to determine the effects of current and proposed diversion strategies on the low-flow hydrology in Waipii Valley. In this report, the low-flow hydrology of Waipipi Valley is described in terms of flow-duration statistics. Flow-duration statistics were computed for three locations in the Waipipi Valley study area where long-term surface-water gaging stations have been operated. Using a variety of streamflow record-extension techniques, flow-duration statistics were estimated at an additional 13 locations where only few historical data are available or where discharge measurements were made as part of this study. Flow-duration statistics were computed to reflect natural conditions, current (2000-2005) diversion conditions, and proposed future diversion conditions at the 16 locations.