Introduction

The Lahaina District, on the western side of the West Maui Mountains, has several public and private sources of domestic and agricultural water supply for the island of Maui. Domestic water is supplied mainly from wells but includes some surface water. Agricultural water is mainly surface water that is occasionally augmented with ground water from wells.

In cooperation with the County of Maui and in collaboration with the County of Maui Department of Water Supply (MDWS) and the State of Hawaii Commission on Water Resource Management, pumpage, water-level, chloride-concentration, deep monitor well, streamflow, streamflow diversion, and rainfall data for the Lahaina District through the second quarter 2008 are displayed here (click on the tabs above to see each section). Pumpage and chloride-concentration data are current through the end of June 2008. Rainfall data are current through the end of June 2008. Water-level data are current through July 2008. Mahinahina deep monitor well was last profiled in June 2007. Streamflow information is updated through June 2008. Stream diversion data is current through June 2008.

Summary of recent conditions

The 12-month moving mean of reported pumping in the Honolua, Honokowai, Launiupoko, and Olowalu aquifer systems based on the most recent reported values was 2.49, 3.57, 0.63, and 0.05 Mgal/d, respectively. No pumping has been reported for the Ukumehame aquifer system for the year prior to June 2008. Water levels at Alaeloa were at the median during May. Chloride concentration of the pumped water from well fields was generally the same as this time last year. Chloride-concentration data from the Mahinahina deep monitor well indicates no apparent rise in the mid-point of the transition zone since 2001. The midpoint of the transition zone is at -135 ft altitude. The 12-month moving mean of rainfall is below the long-term mean of rainfall at Puu Kukui. Streamflow was below the median during April-June 2008 at the gaging station on Honokohau Stream.

Background information about the Lahaina District

The Lahaina District lies on the western flank of the West Maui Mountain and encompasses about 96 square miles. The boundaries of six aquifer systems have been defined by the Commission on Water Resource Management (1990) and Mink and Lau (1990), as Honokohau, Honolua, Honokowai, Launiupoko, Olowalu, and Ukumehame aquifer systems. The area is characterized by a steep and mountainous region in the island's interior and an area of sloping alluvial and colluvial plains extending west and north from the mountains.

The fresh ground-water system in the Lahaina District contains: (1) dike-impounded water and (2) a freshwater lens floating on saltwater. The dike-impounded water body is found in the mountainous interior part of the aquifer. A freshwater-lens system is found within the dike-free volcanic rocks and also in the minor coastal sedimentary deposits. The general movement of fresh ground water in the Lahaina District is from the dike-impounded water body into the freshwater-lens system and then to the ocean.

Streams in the Lahaina District flow from the wet interior of the West Maui mountains where the water has cut deep valleys into the low-permeability volcanic dike compartments which impound ground-water to high altitudes. Ground water leaking from these breached dike compartments provides flow in the streams (base flow) even during prolonged periods of little or no rainfall. Downstream of the dike compartments, many of the streams are diverted and the water is transported by tunnels and ditches for use in agriculture and domestic needs. The stream diversion structures are designed to capture all of the the low flow, and therefore, the streams are frequently dry in some sections downstream of the diversions.

Additional information about the Lahaina district can be found in:

"Ground-water status report, Lahaina District, Maui, Hawaii": U.S. Geological Survey Open-File Report 81-549 by W.R. Souza, 1981.

"Preliminary report on the water resources of the Lahaina District, Maui: State of Hawaii", Department of Land and Natural Resources, Division of Water and Land Development, Circular C51, 47 p. by George Yamanaga and C.J. Huxel, 1969.

References:

Commission on Water Resource Management, 1990, Water Resources Protection Plan: prepared by George A.L. Yuen and Associates, Inc., for Department of Land and Natural Resources, State of Hawaii, 262 p.

Mink, J.F., and Lau, L.S., 1990, Aquifer identification and classification for Maui: groundwater protection strategy for Hawaii: Honolulu, Hawaii, University of Hawaii Water Resources Research Center, Technical Report no. 185, 47 p.

Rainfall

Data provided by the State of Hawaii Commission on Water Resource Management, the Hawaii State Climate Office at the University of Hawaii at Manoa Meteorology Department, and Maui Land and Pineapple Company, Inc.

Introduction

The Lahaina District has a dramatic range in rainfall between Puu Kukui (altitude 5,788 ft) and the shoreline. The mean annual rainfall at Puu Kukui (greater than 371 in.) is the second highest recorded in the State. Mean annual rainfall declines rapidly toward the ocean and is less than 15 in. at the shoreline. Precipitation in the District is actually a combination of rainfall over all elevations and fog drip at higher elevations where the montane forest canopy intercepts cloud water. Fog drip has been estimated to increase recharge by as much as 20 percent more than just rainfall at elevations above 2,000 ft.

Four rainfall stations are reported here. Station 380, Puu Kukui, at an altitude of 5,790 ft, includes rainfall data for 1928-present. Station 376, Launiupoko Intake, at an altitude of 1,280 ft, includes data for 1917-present. Station 296.1, Olowalu, at an altitude of 30 ft, includes data for 1931-present, and Station 477, Haelaau, and an altitude of 2,980, includes data for 1919-present.

Summary of recent conditions

Rain-gage data are current through June at Puu Kukui rain gage and May at Haelaau, Olowalu, and Launiupoko Intake rain gages. The 12-month moving mean of rainfall is below the long-term mean at Puu Kukui rain gage.

The 12-month moving mean is about 70 percent of the long-term mean (370 in/yr) at Puu Kukui.

The 12-month moving mean is not available at Haelaau (119 in/yr), Launiupoko Intake (45 in/yr), and Olowalu (12 in/yr) due to some missing recent data.

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Twelve-month moving mean of rainfall as a percentage of long-term mean rainfall at Puu Kukui, Haelaau, Launiupoko Intake, and Olowalu rain gages, 1985 to present.

Pumpage in aquifer systems

Pumpage data provided by the County of Maui Department of Water Supply (MDWS) and the State of Hawaii Commission on Water Resource Management.

Introduction

Records of ground-water withdrawal in the Lahaina District are available since 1918, when ground-water was pumped mainly for sugarcane irrigation by Pioneer Mill Company. In 1967, the MDWS began withdrawal for domestic use at Wai Puka. Since 1990 and the demise of sugarcane production, water has been pumped mainly for domestic use, most of which comes from the Honokowai and Honolua aquifer systems. Currently, water is supplied by the DWS and several private water companies. In 1990, the State of Hawaii Commission on Water Resource Management established sustainable yield estimates for each of the aquifer systems (Commission on Water Resource Management, 1990). For the Honolua, Honokowai, and Launiupoko aquifer systems, the sustainable yield value is 8 Mgal/d and for the Olowalu and Ukumehame aquifer systems the sustainable yield value is 3 Mgal/d. These pumpage values were surpassed when agricultural use was high, but since 2000 no aquifer system has been pumped at more than half of the State's sustainable yield value.

Summary of recent conditions

This summary is based on reported pumpage records available from the State of Hawaii Commission on Water Resource Management:

Wells	Reporting agency	Most recent month reported
Honokahua, Napili, Kanaha, Wai Puka	County of Maui Department of Water Supply	June 2008
P-1 to P-6, Hahakea, Honokowai	Hawaii Water Service Company, Inc.	June 2008
Kapalua	Maui Land and Pineapple Company, Inc.	June 2008
Mahanalua Nui	Launiupoko Water Company, LLC	May 2008
Puamana	Puamana Community Association	May 2008
Olowalu Elua	Olowalu Elua Assoc., LLP	May 2008

The 12-month moving mean of reported pumping in the Honolua aquifer system as of June 2008 was 2.49 Mgal/d, a decrease of 0.05 Mgal/d relative to the 12-month moving mean from one year previous.

The 12-month moving mean of reported pumping in the Honokowai aquifer system as of June 2008 was 3.57 Mgal/d, an increase of 0.44 Mgal/d relative to the 12-month moving mean from one year previous.

The 12-month moving mean of reported pumping in the Launiupoko aquifer system as of June 2008 was 0.63 Mgal/d, an increase of 0.02 Mgal/d relative to the 12-month moving mean from one year previous.

The 12-month moving mean of reported pumping in the Olowalu aquifer system as of June 2008 was 0.05 Mgal/d, an increase of 0.02 Mgal/d relative to the 12-month moving mean from one year previous.

No pumping has been reported for the Ukumehame aquifer system for the year prior to June 2008.

References:

Commission on Water Resource Management, 1990, Water Resources Protection Plan: prepared by George A.L. Yuen and Associates, Inc., for Department of Land and Natural Resources, State of Hawaii, 262 p.

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Honolua aquifer system total reported pumpage and 12-month moving mean of total pumpage, 1984 to present.

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Honokowai aquifer system total reported pumpage and 12-month moving mean of total pumpage, 1984 to present.

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Launiupoko aquifer system total reported pumpage and 12-month moving mean of total pumpage, 1984 to present.

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Olowalu aquifer system total reported pumpage and 12-month moving mean of total pumpage, 1984 to present.

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Ukumehame aquifer system total reported pumpage and 12-month moving mean of total pumpage, 1984 to present.

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Table 1. Reported pumpage, in million gallons per day, for aquifer systems in the Lahaina District, Maui, Hawaii, July 2007-June 2008.

Month	Honolua	Honokowai	Launiupoko	Olowalu	Ukumehame	Lahaina District total
July-07	3.04	4.11	0.61	0.09	0.00	7.84
August-07	2.86	4.07	0.73	0.07	0.00	7.73
September-07	2.60	5.13	0.66	0.05	0.00	8.44
October-07	2.41	3.74	0.63	0.05	0.00	6.84
November-07	2.09	3.15	0.49	0.05	0.00	5.78
December-07	2.27	2.72	0.69	0.04	0.00	5.72
January-08	2.34	2.98	0.53	0.04	0.00	5.89
February-08	2.16	3.00	0.47	0.05	0.00	5.69
March-08	2.58	3.55	0.69	0.05	0.00	6.88
April-08	2.38	3.07	0.69	0.05	0.00	6.19
May-08	2.74	3.33	0.72	0.06	0.00	6.86
June-08	2.39	4.03	0.67	0.00	0.00	7.09
12-month moving mean June 2008	2.49	3.57	0.63	0.05	0.00
State sustainable yield value	8	8	8	3	3
Change in 12-month moving mean from 1 year previous	-0.05	0.44	0.02	0.02	0.00

Note: 12-month moving mean is the mean of the monthly pumpage values for a given month and the previous 11 months; Totals in bold are incomplete when pumping data from the State of Hawaii Commission on Water Resource Management does not include all known wells in the aquifer system.

Water levels in wells

Data collected by the U. S. Geological Survey in cooperation with the State of Hawaii Commission on Water Resource Management. Data after September 30, 2006 are provisional and subject to revision.

Introduction

Water levels in the Lahaina District have been monitored for various periods of time since 1935. Currently, the USGS measures water levels in one well in the Lahaina District, at Alaeloa (well 5840-01). The Alaeloa well is located in the Honolua aquifer system. The well was drilled for the State of Hawaii in 1964 and continuous monitoring was done from 1975 to 1993 and from July 2001 to the present. From 1993 to July, 2001, only occasional measurements were made. The well is open to the aquifer between altitudes of -7 and -17 ft.

Fresh ground water in the Lahaina District occurs mainly in freshwater-lens systems and dike-impounded systems (Yamanaga and Huxel, 1969; Souza, 1981). A freshwater-lens system includes a lens-shaped freshwater body, an intermediate transition zone of brackish water, and underlying saltwater. The thickness of the transition zone is dependent on the extent of mixing between freshwater and saltwater. Within the study area, freshwater-lens systems are found in dike-free volcanic rocks of high permeability and sedimentary deposits. West Maui lacks a significant coastal confining unit; therefore, water levels in the freshwater-lens system generally are less than 7 ft above sea level. In the Lahaina District, simultaneous water levels were reported for 11 wells from February 1979 and 1980 and ranged from 2.0 to 6.5 ft above mean sea level (Souza, 1981). Available data indicate that water levels in the Alaeloa well, which penetrates the freshwater lens system, respond mainly to changes in ocean level at the coast.

Additional information about ground water in the Lahaina District can be found in:

"Ground-water status report, Lahaina District, Maui, Hawaii": U.S. Geological Survey Open-File Report 81-549 by W.R. Souza, 1981.

"Preliminary report on the water resources of the Lahaina District, Maui: State of Hawaii", Department of Land and Natural Resources, Division of Water and Land Development, Circular C51, 47 p. by George Yamanaga and C.J. Huxel, 1969.

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click image to show ocean level record, double click image to remove ocean level record

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Recent water-level record compared with historical data

The daily maximum and minimum data show how recent conditions compare to the range of daily water levels measured in the historical record. The entire period of record is used to estimate daily maximum, minimum, and median water levels. The spikes appear because data prior to 1994 were reported at 5-day intervals.

 

Salinity of ground water (including chlorides in pumped water and transition-zone fluid conductivity)

Chloride data provided by the County of Maui Department of Water Supply.

Chloride concentration of pumped water

Changes in chloride concentration of pumped water over time can be a function of the pumping rate of a particular well, pumping at nearby wells, depth of the well, and recharge to the aquifer. Therefore, the evaluation of aquifer conditions based on chloride-concentration trends from the pumped wells has limitations. In the Lahaina District, chloride concentrations in many of the pumped wells appear to increase directly in response to increased pumping at those wells.

For some of the MDWS wells in the Lahaina District, chloride concentration of the pumped water has been above the USEPA secondary maximum contaminant level of 250 mg/L at increased pumping rates. Chloride concentrations have been as high as 875 mg/L in the Kanaha wells. Chloride concentrations have occasionally exceeded 250 mg/L in Honokahua, Napili, and Wai Puka wells.

Summary of recent conditions

Chloride concentrations are currently only available for MDWS and ML&P wells.

Chloride concentrations of pumped water during April 2008 were generally the same at all of the well fields with the exception of Kanaha.

Kapalua chloride concentrations have remained below 30 mg/l.

Honokahua 573 chloride concentration in Apr 2008 was 17 mg/L, whereas in Apr-Jun 2007 chloride concentrations were 16 to 18 mg/l. Honokahua 572 chloride concentrations were not measured during Apr-Jun 2008.

Napili 569 chloride concentration during Apr 2008 was 168 mg/l, whereas in Apr-Jun 2007 chloride concentrations were 153 to 159 mg/L. Napili 570 chloride concentration during Apr 2008 was 89 mg/L, whereas in Apr-Jun 2007 chloride concentration was 39 mg/l. Napili 571 chloride concentration during Apr-Jun 2008 was not measured, whereas in Apr-Jun 2007 chloride concentrations were 78 to 85 mg/L.

Kanaha 575 chloride concentration during Apr 2008 was 328 mg/L, whereas in Apr-Jun 2007 chloride concentrations were 177 to 263 mg/L. Kanaha 576 chloride concentration during Apr 2008 was 235 mg/L, whereas in Apr-Jun 2007 chloride concentrations were 216 to 250 mg/L.

Wai Puka 559 chloride concentration during Apr 2008 was 84 mg/L, whereas in Apr-Jun 2007 chloride concentrations were 58 to 74 mg/L. Wai Puka 560 chloride concentrations during Apr 2008 were 83 mg/L, whereas in Apr-Jun 2007 chloride concentrations were 76 to 108 mg/L.

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Chloride concentrations and combined monthly pumpage for Kapalua well field, 1985 to present.

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Chloride concentrations and combined monthly pumpage for Honokahua pumps 572 and 573, 1985 to present.

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Chloride concentrations and monthly pumpage for Napili pumps 569, 570, and 571, 1985 to present.

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Chloride concentrations and combined monthly pumpage for Kanaha wells 575 and 576, 1985 to present.

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Chloride concentrations and combined monthly pumpage for Wai Puka wells 559 and 560, 1985 to present.

Mahinahina deep monitor well

Mahinahina deep monitor well data collected by the State of Hawaii Commission on Water Resource Management.

Introduction

The Mahinahina deep monitor well, drilled to an altitude of -599 ft, penetrates through the transition zone. Because the amount of water that can be developed from a freshwater lens for potable use is constrained by the salinity of the water, the altitude of the top of the transition zone (where chloride concentration is 2 percent that of seawater) and the thickness of the transition zone are important. Fluid conductivity data have been collected from the Mahinahina deep monitor well since 2001. The movement of the transition zone in a freshwater-lens system is typically in response to water-level changes caused by variations in pumping and recharge. Because the well is uncased below sea level, it is possible that the salinity of the water measured at any depth in the well is affected by borehole flow. Thus, salinity for a given depth may not reflect the actual salinity of water in the aquifer at that depth. Nevertheless, measuring salinity with depth over time provides a general pattern of transition-zone thickness and relative movement.

Summary of recent conditions at Mahinahina deep monitor well

The profile plot indicates no significant rise in the mid-point of the transition zone since 2001. A plot of the position of two salinity values (2-percent and 50-percent seawater salinity) in the transition zone also shows no significant rise of the transition zone through time. The Mahinahina deep monitor well is currently not being monitored by the State of Hawaii Commission on Water Resource Management.

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Fluid conductivity profiles for the Mahinahina deep monitor well, August 2001 and June 2007.

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Altitude of the top (2-percent seawater salinity) and mid-point (50-percent seawater salinity) of the transition zone, Mahinahina deep monitor well, 2001 to present.

Streamflow

Streamflow data collected by the U. S. Geological Survey in cooperation with the State of Hawaii Commission on Water Resource Management. Data after September 30, 2006 are provisional and subject to revision. Diversion data provided by the State of Hawaii Commission on Water Resource Management.

Introduction

Streams in the Lahaina District flow from the wet interior of the West Maui mountains where the water has cut deep valleys into the low-permeability volcanic dike compartments which impound ground-water to high altitudes. Ground water leaking from these breached dike compartments provides flow in the streams (base flow) even during prolonged periods of little or no rainfall. Downstream of the USGS gaging stations, many of the streams are diverted and the water is transported by tunnels and ditches for use in agriculture and domestic needs. The stream diversion structures are designed to capture all of the the low flow, and therefore, the streams are frequently dry in some sections downstream of the diversions.

Currently, four streams in west Maui are gaged by the USGS (Waihee River, Iao, Kahakuloa, and Honokohau Streams) with Honokohau being the most relevant to the hydrology of the Lahaina District. Streamflow has been measured in Honokohau Stream (USGS gaging station 16620000) from 1913 to the present (now a real-time gage) and the median flow during that period was about 15.5 Mgal/d (Flow Statistics for USGS Stream-Gaging Stations Operated in Hawaii from 1909-2005). historical streamflow data is available from several other streams and diversion ditches in the Lahaina District (link to historical data on NWISWeb).

Summary of recent conditions

Streamflow in Honokohau Stream during April-June 2008 was 55 percent of the median for those months, and for the past year streamflow was 108 percent of median annual flow.

The completeness of the reported diversion data varies depending on what data has been reported to the State of Hawaii Commission on Water Resource Management by the various water users (see table 1 below). The most recent diversion data reported is current through March 2008.

 

Further information about streams and diversions in the District can be found in:

"Availability and Distribution of Base Flow in Lower Honokohau Stream, Island of Maui": U.S. Geological Survey Water-Resources Investigations Report 03-4060, 37 p. by Richard Fontaine, 2003

"Preliminary report on the water resources of the Lahaina District, Maui: State of Hawaii": Department of Land and Natural Resources, Division of Water and Land Development, Circular C51, 47 p. by George Yamanaga and C.J. Huxel, 1969.

"Agricultural water use and development plan": State of Hawaii, Department of Agriculture, 256 p. by Water Resource Associates, Revised 2004.

"Sugar water, Hawaii's plantation ditches": University of Hawaii Press, Honolulu, Hawaii, by Carol Wilcox, 1996.

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Streamflow record from previous year

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Recent streamflow record compared with historical data

Monthly mean discharge data show how recent conditions compare to the range of monthly discharge measured in the historical record. The entire period of record is used to estimate the historical maximum and minimum discharge as well as several percentiles.

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Table 1. Streamflow and reported stream diversion data, in million gallons per day

[nr, not reported; ML&P, Maui Land and Pineapple Company, Inc.; LIC, Launiupoko Irrigation Company, LLC; DWS, County of Maui Department of Water Supply; OWC, Olowalu Water Company, LLC; no reported diversions from Honokahua, Kahana, or Honokowai Streams]

	Jul-07	Aug-07	Sep-07	Oct-07	Nov-07	Dec-07	Jan-08	Feb-08	Mar-08	Apr-08	May-08	Jun-08
Mean daily flow at Honokohau Stream gaging station (16614000) [upstream of all diversions]	24.37	15.39	24.20	21.16	15.98	47.54	31.17	37.10	17.40	14.48	12.95	11.52
Mean daily diversion from Honokohau Stream (ML&P)	11.40	10.06	9.11	9.81	12.96	20.53	15.85	13.90	12.69	10.40	9.53	nr
Mean daily diversion from Kahoma Stream
Kahoma Stream (LIC)	7.21	5.28	5.98	4.01	4.37	7.39	7.17	2.43	4.52	6.27	3.94	nr
Kanaha Stream (DWS)	nr	nr	nr	nr	nr	nr	nr	nr	nr	nr	nr	nr
Total	7.21	5.28	5.98	4.01	4.37	7.39	7.17	2.43	4.52	6.27	3.94	nr
Mean daily diversion from Kauaula Stream (LIC)	5.84	5.22	5.46	5.90	5.40	5.06	6.50	5.70	5.73	5.15	4.57	3.70
Mean daily diversion from Launiupoko Stream (LIC)	0.47	0.41	0.47	0.30	0.16	0.41	0.53	0.47	0.58	0.47	0.36	0.34
Mean daily diversion from Olowalu Stream (OWC)	3.85	6.29	7.14	3.69	3.45	4.02	4.68	4.87	4.51	4.45	3.76	1.90
Mean daily diversion from Ukumehame Stream	nr	nr	nr	nr	nr	nr	nr	nr	nr	nr	nr	nr
Total reported diversions from all streams	28.77	27.25	28.16	23.70	26.34	37.41	34.73	27.36	28.03	26.74	22.18	5.94

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