Longwood Lake Dam dam
Longwood Lake Dam
Longwood Lake Dam in Jefferson Township, Morris County, New Jersey, stands as a historic stone structure completed in 1898 for the primary purpose of recreation along the Rockaway River. With a height of 21.5 feet and a length of 91 feet, this dam stores a maximum of 351 acre-feet of water with a normal storage capacity of 214 acre-feet, covering a surface area of 43 acres. Despite its picturesque setting, Longwood Lake Dam has been classified with a high hazard potential and poor condition assessment, signaling a need for regular inspections and potential maintenance.
Managed by the local government, Longwood Lake Dam falls under the regulatory oversight of the New Jersey Department of Environmental Protection (NJDEP), ensuring compliance with state permitting, inspection, and enforcement requirements. The dam's last inspection in July 2021 revealed its poor condition, highlighting the urgency for necessary repairs or maintenance to mitigate the risks associated with its high hazard potential. It is crucial for water resource and climate enthusiasts to monitor the status of Longwood Lake Dam and advocate for its preservation to ensure the safety of surrounding communities and the sustainability of the Rockaway River ecosystem.
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 Longwood Lake Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Green Pond Brook At Picatinny Arsenal Nj | 2 cfs | → |
| Green Pd Bk Bl Picatinny Lk At Picatinny Ars Nj | 2 cfs | → |
| Musconetcong River At Outlet Of Lake Hopatcong Nj | 14 cfs | → |
| Pequannock R At Macopin Intake Dam Nj | 14 cfs | → |
| Rockaway River Above Reservoir At Boonton Nj | 472 cfs | → |
| Rockaway River Below Reservoir At Boonton Nj | 9 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Longwood Lake Dam.
Boat launches
- Dell Avenue 9, Netcong
- Jefferson Lake Road Sussex County
- North Corporate Drive 2, Riverdale
- Lakeside Avenue Pompton Lakes
- Greenwood Lake Turnpike Ringwood
- West Shore Drive Stillwater Township
Track Longwood Lake Dam 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 Longwood Lake Dam
Where does the data for Longwood Lake Dam 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 Longwood Lake Dam.