Water System — Full Data Sheet
water 
infrastructure 
This page consolidates the water system’s quantitative argument in one place: the crisis, the proposed response, and how the numbers work.
The crisis
| Metric | Value |
|---|---|
| Reliable supply capacity | 4.26 MGD |
| Current demand | 6.04 MGD |
| Deficit | 41.8% |
| Projected deficit with Kahana Well (2026) | ~15.7% |
| Aquifer management designation | June 2022 (CWRM) |
| Stage 2 Water Shortage declaration | September 2025 |
The Department of Water Supply cannot process new water meters in West Maui. Thousands of displaced residents cannot return — not because lots are uncleared, but because there is no water to serve new construction.
What was lost
West Maui receives over 80 inches of rainfall per year above 1,000 feet. Pioneer Mill Company developed approximately 50 miles of ditches, flumes, and reservoirs to capture this water for sugarcane. When the mill closed in 1999, maintenance ceased.
| Pre-fire asset | Status |
|---|---|
| Honokohau and Honokawai ditches | Degraded, clogged, disconnected |
| 11 water-control structures (1,000–3,000 ft) | Rehabilitable per WSP 2024 survey |
| High-elevation reservoirs | Unmaintained since 1999 |
| Municipal pump stations | Failed during 2023 fire (power loss) |
During the 2023 fire, dry overgrown ditches served as corridors for invasive fire-prone grasses — conducting fire rather than suppressing it.
The proposed system — zone by zone
The distributed capture strategy does not replace the aquifer. It reduces dependence on it, targeting 30% of non-potable demand met through captured rainfall and diverted stream flow.
Zone 1: Hinterland collection (above 1,000 ft)
| Parameter | Value |
|---|---|
| Annual rainfall | > 80 in/year |
| Infrastructure | ~50 miles of rehabilitable ditch network |
| Structures identified (WSP) | 11 at 1,000–3,000 ft elevation |
| Distribution | Gravity-fed (no pump dependence) |
Intake structures restored at stream diversion points; channel clearing and masonry repair on primary ditches; new filtration at reservoir inlets.
Zone 2: Collection ponds (topographic pockets)
| Parameter | Value |
|---|---|
| Sizing rule | 0.5 acres programmable surface per 10 acres drainage area |
| Dual function | Water storage (wet) / public space (dry) |
| Emergency role | Fire-suppression reserve independent of municipal supply |
| Construction | Cut-basalt and concrete-lined (Pioneer Mill engineering standards) |
Zone 3: Interception corridor (Highway 30)
Swales, bioretention cells, and subsurface storage along the boulevard corridor. Intercepts runoff before it crosses impervious road surfaces and is lost to the ocean.
Zone 4: Peri-urban distribution (200–1,000 ft)
| Parameter | Value |
|---|---|
| Retention sizing | 25-year storm events |
| Irrigation | Year-round green vegetation for firebreak function |
| Food production target | 15% of West Maui fresh produce by 2035 |
| Groundwater recharge | Through permeable agricultural surfaces |
Zone 5: Building-scale capture (within the town)
| Parameter | Value |
|---|---|
| Roof catchment (school only) | 57,460 sq ft |
| Collection efficiency | 80% |
| Annual yield (school) | 429,801 gallons |
| Daily average (school) | ~1,178 gallons |
| Demand offset (school) | 12–26% |
| Recommended storage (school) | 160,000–250,000 gallons |
| Filtration | Volcanic gravel before sub-grade tank storage |
Module roofs direct rainfall into gutters between connected units; rooftop cisterns supplement non-potable demand (irrigation and toilet flushing).
Scenario testing
The performance infographic above tests the system against four conditions:
| Scenario | Condition | System response | Performance |
|---|---|---|---|
| Drought | < 10” annual rainfall at coast | Hinterland capture sustains reserves; recycled water prioritized | Adequate |
| Flood | 25-year peak rainfall event | Interception infrastructure captures first-flush; retention basins attenuate flow | Adequate |
| Fire emergency | Active wildfire, grid power loss | Gravity-fed supply from hinterland; collection ponds as reserve | Improved vs. 2023 |
| Combined event | Drought + fire (2023 conditions) | Layered reserves from three zones; distributed storage | Significantly improved |
2023 failure vs. proposed system
| 2023 failure | Proposed response |
|---|---|
| Grid-dependent pumps | Gravity-fed, distributed reserves |
| Single water pressure source | Redundant supply from 3 zones |
| No system backup | Collection ponds as fire reserve |
| System collapse | Layered attenuation across scale |
The proposed system converts a single point of failure into redundant, gravity-fed, distributed reserves.
