Mantua Reservoir N
Box Elder County, UtahView mapDirections
Utah DWQ publishes the water-quality measurements for Mantua Reservoir N. Here is what has been measured.
- Oligotrophic
- Impaired · Algal growth
- Limited data
Mantua Reservoir N in Box Elder County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 1.8 µg/L.
Mantua Reservoir N is a cold, clear oligotrophic lake in Box Elder County, Utah. Overall water quality is declining over recent sampling years. Compared to the 14 other monitored lakes in Box Elder County, Mantua Reservoir N ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2021-06-01. Methodology: how these readings are compared.
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Mantua Reservoir N is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), temperature. Check local advisories before you swim.
Whether Mantua Reservoir N is safe to swim in today is a call for the Utah Division of Water Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Mantua Reservoir N
These are the measurements Utah DWQ publishes for Mantua Reservoir N, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 3 ft of visibility. Phosphorus 11 µg/L. Chlorophyll-a 1.8 µg/L. TSI 46.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 11µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.8µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 46 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Mantua Reservoir N
Answers come straight from the public measurements and survey records on this page.
Stays via Stay22
Stays near Mantua Reservoir N
Compare lakeside cabins, hotels, and vacation rentals near Mantua Reservoir N in Box Elder County, Utah — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Mantua Reservoir N
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Utah’s top lakes →
Follow Mantua Reservoir N’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Mantua Reservoir N
Water Quality Trend: Worsening
Based on 6 years of monitoring (2015–2023).
Water clarity
Improving6 years
Phosphorus
Worsening+20.64 µg/L/yr3 years
Chlorophyll-a
Worsening+19.23 µg/L/yr3 years
EPA Impairment Status
Mantua Reservoir N is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit UT-L-16010204-033_00 · Official waterbody report
Nearby Lakes in Box Elder County
Frequently asked questions about Mantua Reservoir N
Where is Mantua Reservoir N?
- Mantua Reservoir N is a lake in Box Elder County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Mantua Reservoir N?
- Mantua Reservoir N in Box Elder County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 1.8 µg/L.
Is Mantua Reservoir N safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Mantua Reservoir N is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), temperature. Check local advisories before you swim.
Explore Mantua Reservoir N across LakeQuality
More lakes in Utah
Other Lakes in Utah
Oligotrophic Lakes in Utah
Where this data comes from
53 measurements from 1 monitoring station, 2015–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX53 samples · 2015–2021
Analytical methods
- Field Measurements
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database