Here are the interim instream flow standards approved by the Water Commission for six East Maui streams:
Honopou: A minimum flow of 2 cubic feet per second (1.29 mgd) at the 383 ft. elevation of lower Honopou Stream is intended to ensure that an adequate amount of water reaches the more than 20 downstream users, although staff did not explain why that amount would be adequate. A second minimum flow of 0.72 cfs (0.47 mgd) at the 40-ft. elevation would keep the stream from drying out as a result of domestic and taro uses. The amount is the absolute low flow under undiverted conditions. Currently, as little as 0.51 cfs flows below the Haiku ditch, which is the lowest of the four ditches that cut across the stream. If the stream were not diverted, staff believes that 3.6 cfs of ground water would (2.3 mgd) be flowing out of the stream.
Hanehoi: For Hanehoi and Huelo (Puolua) streams, the commission came up with a total of three flow standards. Because neither stream had any gauging data, staff used a model to estimate natural flow. Interim IFS A (0.89 cfs) for Huelo Stream and IIFS B (0.63 cfs) for Hanehoi, would provide an estimated 80 to 90 percent of natural habitat in the streams’ lower reaches for certain native species.
Interim IFS C (1.15 cfs or 0.74 mgd) for the middle reach of Hanehoi Stream is an estimate of the lowest natural base flow and is intended to meet the needs of biota, downstream users and the Huelo community.
For Paluhulu Stream, the commission recommended an interim IFS in its lower reaches of 5.5 cfs (3.56 mgd), which represents 50 percent of the natural median base flow. The staff estimated this amount would provide 80 to 90 percent of the natural habitat for the five species studied by the USGS and enough water for downstream users. Currently, 4.8 cfs is available for stream organisms and downstream users.
Waiokamilo: Staff recommended an interim IFS for the lower reach of Waiokamilo Stream of 4.9 cfs (3.17 mgd), which is the estimated median total flow. Its report notes that EMI stopped diverting water from this stream in July 2007 and mentions the Land Board decision that year to release 6 mgd into the stream.
Wailuanui: For this stream, staff recommended a minimum flow of 3.05 cfs (1.97 mgd) at the 620-ft. elevation of the stream’s lower reach, below the confluence of east and west Wailuanui streams. Like some of the other streams, this flow was chosen because it represents 50 percent of the natural base flow, which generously provides for habitat restoration. Staff notes that this amount will also make more water available to downstream users. Currently, only 1.0 cfs is available for biota and downstream uses.
— Teresa Dawson
Volume 19, Number 5 November 2008
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