In the fall of 2020, commission staff proposed a new IIFS of 1.77 million gallons a day for He`eia Stream. Stream users, including non-profit groups involved in restoring and maintaining an ancient Hawaiian fishpond and nearby agricultural fields, had complained about inadequate flow. Commission hydrologist Ayron Strauch, who had studied the relationship between groundwater withdrawals and stream flow in the area, said last year that flows into He`eia dropped to a trickle \u2014 300,000 gallons a day \u2014 in the dry season.<\/p>\n\n\n\n
Last June, the Water Commission ordered the BWS to reduce its withdrawals from a tunnel in Ha\u02bbik\u016b to 0.3 million gallons a day, in the hope that that would increase stream flow.<\/p>\n\n\n\n
Under the same commission order, the BWS must complete by June 2023 a feasibility study and preliminary engineering design of a 10-foot-thick bulkhead 1,200 feet inside its Ha\u02bbik\u016b Valley tunnel. The bulkhead, which would keep more of the water inside the mountain, is intended to result in more base flow in He`eia Stream.<\/p>\n\n\n\n
In recommending the new bulkhead, commission staff noted that the \u201csubstantial ecological and cultural values supported by He\u2018eia Stream, including habitat for native amphidromous species, restored native riparian environment, a healthy estuarine and near-shore ecosystem, recreational and aesthetic values, as well as the productivity of the He\u2018eia fishpond and wetland to support a biocultural food production system, merits restoration of He\u2018eia Stream to pre-tunnel baseflow. \u2026<\/p>\n\n\n\n
\u201cSuch action would increase spring flow in Ha\u2018ik\u016b while providing a more reliable source of water supply for HBWS. This solution is expected to increase the natural capacity of the high-elevation groundwater system to store and discharge water to streams and springs in the moku of Ko\u2018olaupoko.\u201d<\/p>\n\n\n\n
If the BWS determines that constructing the bulkhead is feasible, it has three years to complete construction. Commission staff will then \u201cevaluate the resultant effects on stream baseflow and may amend the interim IFS or amend the HBWS water use permit as needed.\u201d<\/p>\n\n\n\n
If the BWS finds a new bulkhead infeasible, commission staff will recommend a new IIFS or amend the BWS\u2019s water use permit as needed.<\/p>\n\n\n\n
Modeling Results<\/em><\/strong><\/p>\n\n\n\n At the commission\u2019s April 19 meeting, USGS hydrologist Scot Izuka presented preliminary results from a model of the He`eia and adjacent Waihe\u02bbe-Kahalu\u02bbu watersheds. Izuka stressed upfront that the results were preliminary and subject to revision, and that they were also based on a model created for a different island-wide study. As a result, the model was \u201crather coarse\u201d \u2014 its resolution, at 500 square feet, is much wider than a stream. It also did not factor in all of the stream reaches.<\/p>\n\n\n\n The He\u02bbeia watershed study was done in cooperation with the BWS, while the Waihe\u02bbe-Kahalu\u02bbu study was done in cooperation with the Water Commission.<\/p>\n\n\n\n\n\n Izuka presented maps showing the effects of BWS groundwater wells and tunnels in Ha\u02bbik\u016b, Kahalu\u02bbu and Waihe\u02bbe, six sources in total.<\/p>\n\n\n\n The map for Ha\u02bbik\u016b tunnel, which was assumed to have withdrawals of 0.53 mgd, showed that the tunnel lowers groundwater levels by at least two feet beyond the immediate watershed.<\/p>\n\n\n\n The tunnel also reduced stream flow not just in He`eia, but in Kahalu\u02bbu and \u201call the way to Waihe\u02bbe, probably even farther,\u201d he said. <\/p>\n\n\n\n The stories for the other five sources were the same: the effects of BWS withdrawals on groundwater and stream flow extended well beyond the immediate watersheds, even as far as the leeward side of the island.<\/p>\n\n\n\n Water does not care about topography, but follows the path of least resistance, Izuka explained.<\/p>\n\n\n\n When looking at the effect of all six sources, the area impacted was much larger. A total of about 5 mgd was estimated to be withdrawn from the three tunnels, and 1.67 mgd came from the three wells. Those withdrawals resulted in a reduction in stream flow of 3.19 mgd in the Waihe\u02bbe – Kahalu\u02bbu watershed.<\/p>\n\n\n\n He said the results were not \u201cearth-breaking news,\u201d since it was always known the withdrawals would affect stream flow. However, the USGS studies have gone a long way toward quantifying those effects.<\/p>\n\n\n\n Water Quality<\/em><\/strong><\/p>\n\n\n\n After Izuka\u2019s presentation, commissioner Mike Buck asked how the USGS results might inform the commission\u2019s decisions on IIFS.<\/p>\n\n\n\n While Izuka sidestepped the question, Dean Uyeno, head of the commission\u2019s stream protection and management branch, said that the USGS work supports a lot of the work Strauch had already done.<\/p>\n\n\n\n Strauch added, \u201cWe will be developing IFS, understanding that it\u2019s pretty much a one-to-one relationship.\u201d He said that the commission would be using the information from the USGS studies “as we move forward across Windward O\u2019ahu. We\u2019re still digesting the data for now. But yes, we are definitely moving forward on using this.\u201d<\/p>\n\n\n\n Usagawa of the BWS seemed concerned that the study results would be used to justify further reduction in withdrawals from the tunnels and wells. <\/p>\n\n\n\n He questioned the confidence with which management decisions could be made based on information from a coarse model that did not account for individual dikes. <\/p>\n\n\n\n To conserve water, he also asked whether there was a way to pipe some of the water in He`eia Stream to the lo`i kalo being farmed near the fishpond, rather than letting it flow into the wetland. \u201cThe conveyance system should be looked at for losses in addition to cutting us back more,\u201d he said.<\/p>\n\n\n\n \u201cLastly, I was wondering if the study \u2026 would look at water quality, not only quantity,\u201d he said.<\/p>\n\n\n\n He noted that the Kahalu\u02bbu estuary is \u201cone of the most cesspool-polluted estuaries on the island,\u201d with 740 cesspools in the area, he said. <\/p>\n\n\n\n \u201cIf you\u2019re restoring [land] for farming, the Food Safety Modernization Act lays a lot of food safety conditions on farmers. \u2026 Would you eat leafy vegetables if it was irrigated with cesspool-contaminated water is my question. I was wondering if at least that would be mentioned in the study or not,\u201d he said.<\/p>\n\n\n\n He added that in the course of conducting an environmental impact statement for a proposed learning center in Waihe\u02bbe, the BWS discovered that part of the Waihe\u02bbe Valley and the neighboring Ka`alaea Valley had unexploded ordnance from the time the area was used for target practice during World War II. He said testing by the federal government found 19,000 mg\/L of lead, as well as arsenic and the explosive contaminant RDX. <\/p>\n\n\n\n \u201cThat contamination affects farming, to me. If you\u2019re only taking two samples and the two are positive and are that high, there are some public health issues there,\u201d he said. He added that the BWS has talked to the Army Corps of Engineers and U.S. Rep. Kai Kahele about the possibility of remediating the ordnance sites. <\/p>\n\n\n\n \u201cUnfortunately, there’s a ton of these sites around the world they need to remediate, but I think that needs to happen before we can think about how much water we can return to the stream to promote agriculture when the water and the soils are contaminated,\u201d he said.<\/p>\n\n\n\n In any event, the BWS would continue to work with the community and government agencies toward a balanced solution, he said. One possible solution may be pumping a well on land near the state hospital in K\u0101ne\u02bbohe.<\/p>\n\n\n\n Commission chair Suzanne Case asked Izuka whether closing a tunnel would increase storage capability in the dikes it taps and increase stream flows on a broader basis.<\/p>\n\n\n\n \u201cTheoretically, yes,\u201d Izuka said, adding that it would depend on how the tunnel was closed. <\/p>\n\n\n\n \u201cBulkheads are usually built at a dike. So if you were to restore it completely to its natural condition, plug up the dikes, it would depend on climate. Climate is a little different from what it was in the 1940s. It may take a little bit longer to restore, but, theoretically, it would restore,\u201d he said.<\/p>\n\n\n\n He noted that given the evidence indicating that the tunnels and wells are affecting streams outside the valleys in which they occur, plugging tunnels would restore water to all of the streams from whence it came.<\/p>\n\n\n\n “Just using Ha\u02bbik\u016b tunnel as a mental experiment, if you were to plug that up and the head would build up, it would restore some of the flow in He`eia Stream,\u201d he said, noting that some would go to Ioleka`a Stream and as far away as Kahalu\u02bbu Stream. <\/p>\n\n\n\n (For more background on issue, see, \u201cCommission Pressures BWS to Meet Proposed He\u02bbeia Stream Flow Standards,\u201d from our March 2021 issue, and \u201cWater Commission Orders Honolulu BWS To Take Steps to Restore He\u2018eia Stream,\u201d from our July 2021 issue. Both are available on our website, www.environment-hawaii.org.)<\/p>\n\n\n\n \u2014 Teresa D<\/em>awson<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":" Preliminary groundwater modeling results from the U.S. Geological Survey seem to support what staff with the Commission on Water Resource Management believed when they proposed new interim instream flow standards (IIFS) for He`eia Stream in Windward Oʻahu more than a … Continued<\/a><\/p>\n","protected":false},"author":1,"featured_media":14381,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[496,28],"tags":[3],"class_list":["post-14380","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-may-2022","category-water","tag-teresa-dawson"],"_links":{"self":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/14380","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=14380"}],"version-history":[{"count":0,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/14380\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/media\/14381"}],"wp:attachment":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14380"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14380"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/environment-hawaii.org\/wp-content\/uploads\/2022\/05\/Image-5-5-22-at-3.06-PM.jpg\")
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