WAILUKU - Uncertainty about the allocation of surface water from the streams of East and West Maui has caused the Department of Water Supply to suspend for the time being its interest in a joint venture with Alexander & Baldwin to build a treatment plant at Waiale.
Water Director Jeff Eng said he hopes for a favorable decision from the state Commission on Water Resource Management on permanent instream flow standards in Na Wai Eha and also in a separate petition on East Maui streams.
"We believe we are a protected public trust user," he said.
But the commission is obligated by the State Water Code to provide sufficient water in the streams to allow stream fauna to thrive and to provide for downstream users, such as taro growers.
The Waihee, Waiehu, Iao and Waikapu streams, the four steams of Na Wai Eha, are diverted by the Wailuku Water Co. to irrigate the former Wailuku Sugar Co. lands as well as Hawaiian Commercial & Sugar Co. fields.
The county department draws a small amount of Na Wai Eha water now, around 1.5 million gallons a day to support the Central Maui demand of 24 mgd. But the average Na Wai Eha flow of 50 mgd is a potential source to meet the county's growing needs in South and Central Maui.
It is facing potentially an even more serious disruption in source in the Upcountry system. The county gets almost all its Upcountry water, 7 mgd to 8 mgd, from surface sources - including up to 5 mgd from the Wailoa Ditch operated by HC&S's water manager, the East Maui Irrigation.
As in Na Wai Eha, East Maui taro farmers have petitioned the water commission to establish permanent instream flow standards that will mandate release of water now diverted by EMI. Preliminary flow standards already have been approved for eight of 27 streams diverted by EMI.
Eventually, stream flow standards will be set streams tapped for the West Maui water system, which draws roughly 60 percent of current demand from surface sources.
For streams that have been diverted for sugar plantations since the late 1800s, and which are also tapped for household use, that will mean more water in the stream beds and less water diverted for farming and households.
Under the Water Code, HRS 174C. instream flow standards must consider adequacy for wildlife habitat, recreational use, maintenance of ecosystems, aesthetic values, navigation, hydropower, water quality, irrigation, domestic water supplies and "traditional and customary Hawaiian rights."
On the Na Wai Eha system, A&B had proposed a treatment plant to handle 9 mgd, split half and half with the county. Eng said when he took the county job, "that was apparently a viable project."
It may yet be, since domestic use is a factor in allocation of stream flows. But the commission must first determine how much diverted water must be restored to the streams.
That decision will certainly be appealed and the final resolution could be many years off.
In East Maui, preliminary flow standards for eight streams are intended to provide data on the validity of the commission's analysis. Eventual permanent stream flow standards are subject to further adjustments.
For the Upcountry system, the county will need to consider more reliable sources as well since any more demand on the EMI sources is a threat to the sugar industry.
With the county drawing up to 5 mgd from EMI's Wailoa Ditch, the summer flows to Hawaiian Commercial & Sugar Co. fields can be too low to allow replanting of upepr elevation fields.
There is more. The ditch flow also provides fire flow protection for the Puunene Mill, and HC&S figures it needs 13 mgd for that purpose. During the summer, when the county's demand is always at its peak, the minimum amount needed coming into Kamole is nearly 20 mgd.
Last week, flows in the ditch fell to 22.7 mgd.
Harry Eagar can be reached at email@example.com.