Pia Mill Reservoir dam
Pia Mill Reservoir
Pia Mill Reservoir, located in Koloa, Hawaii, is a privately-owned earth dam constructed in 1910 for irrigation purposes along the WaihoHonu Stream offstream. With a height of 16.5 feet and a storage capacity of 38.6 acre-feet, this reservoir covers a surface area of 6.1 acres and serves as a vital water resource for agriculture in the region. Despite its historical significance, the dam is classified as having a high hazard potential with a poor condition assessment, emphasizing the need for ongoing maintenance and risk management.
Managed by the Department of Land and Natural Resources (DLNR), Pia Mill Reservoir undergoes regular inspections with a frequency of 5 years to ensure its structural integrity and compliance with state regulations. Despite its moderate risk assessment, the reservoir's emergency action plan (EAP) is currently under revision as of March 2021. With a spillway width of 22 feet and a maximum discharge of 440 cubic feet per second, the reservoir plays a crucial role in water storage and distribution for local agricultural activities, highlighting the intersection of water resource management and climate resilience in Hawaii's diverse ecosystem.
As climate change continues to impact water availability and extreme weather events, the sustainability of Pia Mill Reservoir remains a key priority for stakeholders. With Tulsi Gabbard representing the area in Congress, ongoing efforts to address the dam's maintenance needs and emergency preparedness are crucial to safeguarding this essential water infrastructure for future generations. By integrating risk management measures and updating the EAP to meet guidelines, Pia Mill Reservoir can continue to support irrigation needs while adapting to the evolving challenges of a changing climate in Hawaii's water resource management landscape.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Pia Mill Reservoir -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Sf Wailua River Nr Lihue | 150 cfs | → |
| Eb Of Nf Wailua River Nr Lihue | 51 cfs | → |
| Left Branch Opaekaa Str Nr Kapaa | 4 cfs | → |
| Waimea River Nr Waimea | 295 cfs | → |
| Waialae Str At Alt 3 | 15 cfs | → |
| Wainiha River Nr Hanalei | 145 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Pia Mill Reservoir.
Track Pia Mill Reservoir in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Pia Mill Reservoir
Where does the data for Pia Mill Reservoir come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Pia Mill Reservoir.