Water System - Zone by Zone

The proposed water system addresses the fundamental paradox: West Maui receives enormous rainfall at elevation, but virtually none reaches the town. The strategy operates across five zones, each with distinct capture and distribution functions.

Zone 1: Hinterland Collection (above 1,000 feet)

Above the highway, where rainfall exceeds 80 inches annually. The historic Pioneer Mill ditch system, approximately 50 miles of ditches, flumes, and reservoirs, captured this water for sugarcane. When the mill closed in 1999, maintenance ceased and the infrastructure deteriorated. The proposed strategy rehabilitates key segments:

• Intake structures restored at stream diversion points
• Channel clearing and masonry repair on primary ditches
• New filtration integration at reservoir inlets
• Gravity-fed distribution eliminates pump dependence, critical because the 2023 fire demonstrated that pump-dependent systems fail when power is cut
• WSP’s 2024 survey documented 11 water-control structures at 1,000-3,000 feet elevation that could be rehabilitated

Zone 2: Collection Ponds (topographic pockets)

Strategic placement of retention basins in natural depressions between hillside contours:

• Each pond captures stormwater during rain events
• Sized at 0.5 acres programmable surface per 10 acres drainage area
• Dual function: water storage during wet periods, usable public space during dry conditions
• Emergency reserve capacity for firefighting independent of municipal supply
• Construction uses cut-basalt and concrete-lined techniques consistent with Pioneer Mill engineering standards documented by WSP

Zone 3: Interception Collection (Highway 30 corridor)

Linear capture systems at the convergence point where mountain water meets the urban edge:

• Swales, bioretention cells, and subsurface storage along the boulevard corridor
• Intercepts runoff before it crosses impervious road surfaces and is lost to the ocean
• Feeds water into the peri-urban agricultural park for irrigation
• Highway 30 itself becomes a water management infrastructure, not just a road

Zone 4: Peri-Urban Park Distribution (200-1,000 feet)

The agricultural buffer between boulevard and highway serves as the primary distribution zone:

• Irrigation maintains green, fire-resistant vegetation year-round, the firebreak function depends on consistent water delivery
• Retention basins sized for 25-year storm events
• Groundwater recharge through permeable agricultural surfaces
• Community garden and small-scale farming use captured water productively
• Low-activity landscape with pedestrian and cycling trails

Zone 5: Building-Scale Capture (within the town)

At the smallest scale, every building captures rain:

• Module roof slopes direct rainfall into gutters between connected units
• Volcanic gravel filtration cleans water before sub-grade tank storage
• Permeable paving at street level allows infiltration
• Rooftop cisterns supplement non-potable demand, irrigation and toilet flushing
• Collectively reduces demand on the municipal aquifer supply

The System as a Whole

No single zone solves the water crisis. Reliable capacity is 4.26 MGD against 6.04 MGD demand, a 41.8% deficit. The distributed capture strategy does not replace the aquifer but reduces dependence on it. Each zone attenuates demand incrementally: hinterland capture provides non-potable agricultural water; building-scale capture reduces domestic demand; the combined effect gives the aquifer room to recover.

This is the same principle as the buffer framework: resilience comes from cumulative attenuation across multiple layers, not from any single infrastructure solution.