In September, Water Commission hydrologist Ayron Strauch presented a draft proposal to amend the interim instream flow standards of 11 streams in East Maui that were not part of a 2018 contested case hearing decision and order amending about two dozen other streams in the region.
By amending the IIFS for those 11 streams, commission staff hopes to satisfy a petition filed by the Sierra Club of Hawaiʻi last year, and establish a water source to meet a small portion of the Department of Hawaiian Home Lands’ request for 11 million gallons per day for its developments at Pūlehunui and Kēōkea-Waiohuli.
Strauch also stated that the bulk of the DHHL reservation would require the IIFS amendments for some of the streams that were part of the 2018 decision and order. He added that those IIFS were ripe for re-evaluation anyway, since new data on stream flow trends and biota have been collected.
At the commission’s October 18 meeting, Strauch noted that the IIFS in the 2018 decision were based on streamflow metrics using a base period of 1942-2001. A more recent base period, 1984-2013, shows that there is less water in the streams than there used to be.
For example, from 1942-2001, West Wailuaiki Stream had a median flow of 10 cubic feet per second. But for 1984-2013, the median flow was only 8.9 cfs, a reduction of 11 percent. For Hanawi Stream, there was a 13 percent drop in median flow.
In comparing shorter, 10-year base periods, Strauch pointed out that one USGS gage on West Wailuaiki Stream showed that flows declined 36 percent between a 1987-1996 period and a 2007-2016 period.
Given the constantly changing data, Strauch said it was worth revisiting the IIFS every three to four years to make adjustments. The 2018 IIFS decision didn’t consider the effects of climate change or shifts in rainfall, he said, noting that Maui has been experiencing an extended drought sine the early 1970s.
He added that East Maui has experienced annual and seasonal droughts since the early 1980s.
In addition to new information on biota provided by the state Division of Aquatic Resources, commission staff analyzed data it collected during 50 biological surveys of every hydrologic unit in East Maui to quantify habitat use by native species.
Based on all of that information, Strauch recommended amendments to the IIFS for Waikamoi, Honomanu, Nuaʻailua, West Wailuaiki, and Waiohue streams.
Commission staff found that even if the streams had been largely or fully restored, that did not necessarily translate into an increase in the number of native species in this stream.
For example, for East Wailuaiki, West Wailuaiki, and Waiohue streams, only Waiohue saw an increase in ʻoʻopu alamoʻo in their mauka reaches after full restoration. None of them saw an increase in ʻōpae there.
At their mouths, no increases were seen in ʻoʻopu nākea, hīhīwai, oehaʻa, or ʻoʻopu akupa after full restoration. In fact, abundances for some species dropped after full restoration.
For those streams that ended in a waterfall, only ʻoʻopu alamoʻo were found in mauka reaches and at the mouth. Native species were most abundant in streams that emptied into estuaries.
Waikamoi Stream, where the stream mouth is an overhanging cliff, was found to support little to no recruitment of native biota.
“These data are certainly surprising to see. Were you surprised?” asked commissioner Paul Meyer.
Strauch said that while he thought there were “a lot of underlying stories to tell with the data,” the take-home message was that full restoration hasn’t had the impact anticipated.
Meyer questioned whether variables such as invasive species might be affecting native species abundance.
Strauch said that was something he’d like to analyze. “I think that we can try and tease apart a little bit. … ʻOʻopu and ʻopae can migrate more effectively than invasives,” he said.
He added that a bigger question that he was unsure if anybody could answer is whether there are other factors, such as fishing in the marine environment or traditional and customary gathering, that are leading to lower abundances. “Maybe they’re being fished out,” he suggested.
Staff’s recommendations for new IIFS were based on specific conditions of each stream. For Honomanu, Strauch said that in the last few years, even when no water is being diverted, the stream is completely drying up for periods of time. It would be impossible and unrealistic to implement an IIFS, he said.
“My recommendation is to make my life easier” and seek the abandonment of three of the four diversions on the stream. “By forcing abandonment of three of four intakes, we’re going to get as much water downstream as possible and to not have to enforce an IIFS that is not enforceable,” he said.
He also proposed reducing the IIFS on Waikamoi, since the stream does not support high quality habitat.
For West Wailuaiki and Waiohue, which had not seen any appreciable change in biota abundance, he recommending amending the IIFS from full restoration to H90 flows, which are the flows in the stream 90 percent of the time. For West Wailuaiki, that would be 2.62 million gallons a day; for Waiohue, it would be 3.33 mgd.
For Nuaʻailua, he recommended that an intake on Spreckels Ditch be abandoned because the stream supports some of the highest quality, low-elevation habitat and estuary.
Strauch said he planned to bring his recommendations for East Maui IIFS and the DHHL reservations to the commission this month.
He said that commission staff met this past summer with Na Moku Aupuni o Koʻolau Hui, which includes native Hawaiian taro farmers and cultural practitioners from East Maui, to discuss the impending IIFS recommendations.
“They understood the reasoning for the modifications to the IIFS,” he said.
Staff also met with Mahi Pono, East Maui Irrigation Company (the diverters), and the Sierra Club, he added.
“The goal is to make sure everybody is on the same page,” he said.
“Hopefully we can put to rest, at least for a couple years, all the East Maui water issues,” commissioner Mike Buck said.
— Teresa Dawson
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