Ground Water and Sustainable Yield

History

This section is a timeline of groundwater related activities in the Haiku-Upcountry area. This section starts where the section on 2003 Consent Decree ends (the CD is still operative but our history of it ends in 2017). You can read that narrative here.

2017

Maui County DWS issues an FEA to drill a second well, Po’okela B, in the Makawao Aquifer.

2018

An EIS is issued for the Kealaloa exploratory well in the Makawao aquifer.

2019

The County of Maui Department of Water Supply issued a Maui Draft Water Use and Development Plan (WUDP) that mentioned future Haiku wells over 20 times, as future source of water for South Maui.

2024

Kealaloa exploratory well in the Makawao aquifer is completed.

Free Market Ventures, a private equity fund from the mainland, proposes to drill several wells in Kula and to enter into an agreement with DWS to provide water at a guaranteed rate. The public reaction was strongly against the project, primarily because it looked like a bad deal for Maui. The County Council declined to authorize the mayor to enter into negotiations with Free Market and the deal collapsed.

Aquifers and Sustainable Yield

There are four different types of groundwater on Maui: 1) basal water floating on salt water; 2) dike confined water; 3) water perched on relatively impervious soil or rock formation; and 4) shallow groundwater. The greatest groundwater reservoir is the basal water table near sea level, which is a fresh water lens that “floats” on seawater. Of these four, current research shows that basal water is the operative type for the Haiku-Makawao-Paia aquifer system.

Aquifer recharge is an important part of the aquifer as it determines how quickly water can be extracted from it. An aquifer might have lots of stored water but if the recharge rate is low, its stores will be quickly depleted if the extraction rate exceeds the recharge rate.

The following map shows rainfall isophets, which are lines along which the average rainfall is the same. Rainfall amounts increase perpendicular to the lines. The map also shows aquifers. The numerical value for each aquifer is the sustainable yield (SY) for that aquifer. Not surprising, the aquifers with the highest yields are where the rainfall is the highest, which is the northeast flanks of mountains. This map and the sustainable yields shown are from data taken in 2016. As we will see, projections for SY have decreased since then.

Recharge depends upon rainfall as well as the terrain and coverage. Deforestation has changed the coverage but that largely happened in the 19^th century. Harvesting timber and clearing land for cattle and agriculture were the big drivers of deforestation. Climate change is happening now and is the biggest threat to recharge. The USGS, and other organizations, are modeling the effects of a change in rainfall patterns.

The map below shows the effect of diminished rainfall on Maui aquifers. Red shaded aquifer indicate diminished recharge, with 70% loss at the worst.

Water Quality

Quality of groundwater in Haiku, and all of Maui, is affected by agricultural operations, cesspools, livestock, wildlife, and natural contaminants. But the biggest problem for human consumption is from agricultural herbicides and pesticides. In particular, several pesticides used in the era of pineapple plantations have had a lasting effect. The following map shows the location of pineapple fields in the area of Haiku.

There are three operative public wells in the “Upcountry” area of Haiku, Makawao, Pukalani and Kula. Their potential for contamination by agricultural chemicals requires constant monitoring. As discussed above in the History section, two public wells (H’Poko 1 and 2) were found to have contaminants at a level high enough to trigger concern. Those two wells are only used as a backup to other sources.

Well	Elevation	Aquifer	Proximity to Agriculture
Haiku Well	830’	Haiku	Downslope of, and under former pineapple fields.
Kaupakalua Well	1000’	Haiku	Upslope of pineapple. Under cattle fields.
Po’okela A & B	1800’	Makawao	Close to former pineapple fields, close to cattle.

Water quality reports are issued annually by the DWS for each water system they administer. Different tests are run depending on the water sources used by the system. The Makawao system water report is available here [link to Makawao DWS Water Quality Report 2023]. Here is the table of all the tests run:

This table covers three wells in the Makawao water district and it is only reporting the highest value among all three.

Well reports from individual wells are sometimes available, particularly the initial water analysis done when the well was drilled.  Sometimes those will show a different amount. For instance, the Haiku well had 8.4 PPM of Nitrate when drilled but now shows a maximum of 0.61 PPM.

Well reports:

1. Haiku well
2. Po’okela well

County Plans for Groundwater Resources in Haiku-Upcountry

Current municipal wells in the area of Haiku, Makawao, Pukalani and Kula are listed in the table below. Only three of these are actively used in the municipal water supply (Po’okela A is being phased out and replaced with Po’okela B).

Well	Well Number	Aquifer	Year Drilled	Pumpage / Capacity
Haiku	5419-01	Haiku	1971	0.3 MGD / 0.5 MGD
Kaupakalua	6-5317-01	Haiku	1998	0.6 MGD
Hogback test (2)	5418-01	Haiku	2002	0 / 1.0 MGD
Kealaloa test (2)	6-4918-01	Makawao	2021	0  / 1.0
Po’okela A (3)	5118-02	Makawao	2003	1.0 / 1.3 MGD
Po’okela B	5118-03	Makawao	2017	0.0 / 1.3 MGD
H’Poko 1 (1)	5420-02	Paia	1992	0 / 1.0 MGD
H’Poko 2 (1)	5320-01	Paia	1993	0 / 1.0 MGD

Notes:

1. H’Poko wells were not intended for the Haiku-Upcountry water system, according to the EMPlan, these wells were to feed water directly to the Central water system, but have not been connected to the Central Maui water main. They are currently only used for production in times when other sources cannot keep up with demand.
2. Several of these wells are either test wells or on a standby status due to the 2003 Consent Decree, but test wells are often converted to production wells. So obviously there is a big increase in the number of wells from the single well that existed in Ha’iku pre-1990.
3. The East Maui Plan as enunciated in the 1993 FEIS lays out the plan by the County of Maui to make up the shortfall in water resources the island will experience over the next few years. The following maps illustrate this.

The next two maps illustrate the problem the County has with water supply. The first map shows the DWS water systems. The blue lines are water distribution pipes. There are four systems in the map:

• Makawao
• Upper Kula
• Lower Kula
• Central

Population growth and resort hotels are in the Central District and water demand will increase substantially there, according to the WUDP. The Haiku aquifer, which feeds into the Makawao water district, will be least affected by climate change, according to modeling. The map below shows that there is no interconnect from the Makawao district to the Central district to transport water from the former to the latter, yet the Central District is running out of water supply. So the goal of the MDWS is to connect the two systems (this was made clear in the EM Plan) and the other goal is to increase production of groundwater throughout the Haiku-Makawao aquifers to then ship to Central and South Maui (South Maui is in the Central district). Pa’ia would possibly be a contributor also since it has two wells but those wells are affected by organic chemicals and are also under court restraint.

The second map illustrates the exporting of water from Mau’s wet side (the northeast) to the drier parts of Maui. The danger here is the problem dry communities all across America (e.g., Las Vegas, Pheonix and Salt Lake City) are experiencing – oversubscribing to water sources that change with time. Maui needs to be extremely careful that it does not fall into that trap.

Summary

Demand for water on Maui is growing. According to the 2019 WUDP, the Central water district is where most of the demand will come from but it does not have the ground water capacity to meet that use. East Maui historically has lots of rain but how that will play out with climate change puts reliance on East Maui in doubt. Furthermore, the County DWS is not able to meet the demand in Ha’iku as it is, so exporting water before that is resolved is not reasonable. Other factors, such as the presence of contaminates in the aquifer, and unknowns in the geohydrology and recharge rate add to the uncertainties. The county is forced to drill wells higher in elevation to get above contaminates, but those wells are expensive to drill and operate. The effect significant water extraction will have on streams, other private wells, and the near-shore ecosystem are additional unknowns that need to be resolved. In short, there is a lot more research that needs to be done on the Ha’iku aquifer, and even then, at some point its limit to provide will be reached.