Opinion ID: 6493113
Heading Depth: 3
Heading Rank: 1

Heading: Surface Water3

Text: Na Wai ‘Ehá are the Waihe'e River and Waiehu, Tao, and Waikapü Streams. The Waihe'e River is the principal water source in Ná Wai ‘Ehá; it is about 26,585 feet long, and its watershed covers 4,500 acres. From 1984-2005, United States Geological Survey (“USGS”) data shows streamflow upstream of all diversions as follows: the Q50 4 flow was 34 million gallons per day (“mgd”), the Q70 5 flow was 29 mgd, the Q90 flow was 24 mgd, and the Q100 flow was 14 mgd. The Waihe'e River’s two main diversions are Wai-he'e Ditch and Spreekels Ditch. See Section H.A.3., infra, for more information about the ditches. The two ditches are capable of diverting all of the dry-weather flow available at the intakes, however, even if all the water is being diverted, streamflow immediately downstream of the intakes may exist because of leakage through or subsurface flow beneath the dams at these sites. The dry-weather flow downstream of the intakes is commonly about 0.1 mgd, but the stream may not have continuous mauka-to-makai surface flow. The Waiehu Stream is formed by the confluence of North and South Waiehu Streams; it is about 23,700 feet long, and its watershed covers about 6,600 acres. Gaging stations on both branches of the Waiehu Stream were discontinued in 1917, but USGS used historical data and record-extension techniques to estimate flows above all diversions for North Waiehu Stream from 1984-2005 as follows: the Q50 flow was between 3.1 to 3.6 mgd, the Q70 flow was between 2.3 to 2.7 mgd, the Q90 flow was between 1.4 to 2.7 mgd, and the Q100 flow was 1.6 mgd (as measured in March 1915). For South Waiehu Stream, USGS utilized the same record extension techniques, and estimated the 1984-2005 flows as follows: the Q50 flow was between 2.4 to 4.2 mgd, the Q70 flow was between 1.9 to 2.8 mgd, the Q90 flow was between 1.3 to 2.0 mgd, and the Q100 flow was 1.5 mgd (recorded in July 1913). The Waihe'e and Spreekels Ditches divert water from both North and South Waiehu Streams; in addition, the North Waiehu Ditch diverts from the North Waiehu Stream and the Cerizos Kuleana Ditch diverts from the South Waie-hu Stream. There is extensive channel erosion below the Spreekels Ditch on South Waiehu Stream, with a 12-foot drop in the elevation of the stream just below the diversion, and there is a vertical concrete apron located in Waiehu Stream. Most of the water is diverted from North and South Waiehu Streams at the North Waiehu Ditch and Spreekels Ditch, respectively; due to these diversions and leakage, Waiehu Stream does not flow continuously from mauka to makai. Tao Stream is the second-largest stream in Ná Wai ‘Ehá; it is about 38,000 feet long, and its watershed covers about 14,500 acres. USGS calculated the 1984-2005 flows above all diversions as follows: the Q50 flow was 25 mgd, the Q70 flow was 18 mgd, the Q90 flow was 13 mgd, and the Q100 flow was 7.1 mgd. The two main diversions off the Tao Stream are the Tao-Waikapü/Tao-Maniania Ditches at an altitude of 780 feet, and the Spreekels Ditch at 260 feet. The United States Army Corps of Engineers channelized significant portions of Tao Stream’s lower reaches and hardened the stream bed and banks with concrete for flood control and drainage. About 2.5 miles above the mouth of the Stream, the concrete channel includes a 20-foot vertical drop. USGS estimates that Tao Stream loses 6.3 mgd in reaches downstream of the Tao-Maniania ditch diversion that are not lined with concrete. In absence of ditch return flows or runoff during and following rainfall, Tao Stream is dry and does not flow continuously from mauka to makai. The Waikapü Stream is the southern-most stream and the longest of the four streams; it is about 63,500 feet in length, with a watershed of about 9,000 acres. USGS, using record extension techniques, estimated the 1984-2005 flows above all diversions as follows: the Q50 flow was between 4.8 to 6.3 mgd, the Q70 flow was between 3.9 to 5.2 mgd, and the Q90 flow was between 3.3 to 4.6 mgd. The lowest recorded flow for Waikapü Stream was 3.3 mgd, in October 1912. There are three diversions off the Waikapü Stream: the South Side Waikapü Ditch (also known as the South Waikapü Ditch) near an altitude of 1,120 feet, the Waihe'e Ditch, and the Reservoir 6 Ditch. The Waikapü Stream is commonly dry downstream of all diversions, both because of the diversions and because of infiltration losses into the streambed; the Stream does not flow continuously from mau-ka to makai.