Newcastle Reservoir
Iron County, UtahView mapDirections
Utah DWQ publishes the water-quality measurements for Newcastle Reservoir. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- Limited data
Newcastle Reservoir in Iron County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 9.5 ft visibility. Phosphorus: 52 µg/L. Chlorophyll-a (algae): 89 µg/L.
Newcastle Reservoir is a productive, nutrient-rich eutrophic lake in Iron County, Utah. Overall water quality is declining over recent sampling years. Compared to the 1 other monitored lakes in Iron County, Newcastle Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Utah DWQ, last sampled 2020-07-28. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
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. Newcastle Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pH / acidity, temperature. Check local advisories before you swim.
Whether Newcastle Reservoir 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 Newcastle Reservoir
These are the measurements Utah DWQ publishes for Newcastle Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 9.5 ft. Phosphorus 52 µg/L. Chlorophyll-a 89 µg/L. TSI 60.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 9.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 52µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 89µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 60 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Newcastle Reservoir
Answers come straight from the public measurements and survey records on this page.
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Fishing Newcastle Reservoir
Water Quality Trend: Worsening
Based on 6 years of monitoring (2012–2020).
Water clarity
Worsening5 years
Phosphorus
Improving-1.81 µg/L/yr2 years
Chlorophyll-a
Worsening+7.95 µg/L/yr2 years
Reservoir Info (USACE NID)
Newcastle Reservoir is a man-made reservoir impounded by the Newcastle (completed 1956), built primarily for irrigation on the Pinto Creek; earth-type dam, 83 ft tall and 805 ft long.
- Normal storage
- 5,200 ac-ft
- Max storage
- 7,900 ac-ft
- Drainage area
- 134 sq mi
- Hazard class
- High
- Owner
- NEWCASTLE RESERVOIR COMPANY
Source: USACE National Inventory of Dams, NID ID UT00227 · Operator website
EPA Impairment Status
Newcastle Reservoir 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit UT-L-16030006-008_00 · Official waterbody report
Nearby Lakes in Iron County
Frequently asked questions about Newcastle Reservoir
Where is Newcastle Reservoir?
- Newcastle Reservoir is a lake in Iron County, Utah. Its water-quality measurements are published by Utah DWQ and shown on this page as reported.
What is the water quality of Newcastle Reservoir?
- Newcastle Reservoir in Iron County, Utah has water-quality measurements published by Utah DWQ, shown here as reported. Water clarity: 9.5 ft visibility. Phosphorus: 52 µg/L. Chlorophyll-a (algae): 89 µg/L.
Is Newcastle Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Newcastle Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pH / acidity, temperature. Check local advisories before you swim.
Explore Newcastle Reservoir across LakeQuality
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Where this data comes from
97 measurements from 1 monitoring station, 2013–2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Utah Department Of Environmental Quality
UTAHDWQ_WQX97 samples · 2013–2020
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