Little Wood Reservoir
Blaine County, Idaho590 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Impaired · Hydrologic alteration
- Public access
- Limited data
Little Wood Reservoir in Blaine County, Idaho is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 30.2 µg/L. Surface area: 590 acres.
- Area
- 590 acres
- Phosphorus
- 70 µg/L
- Chlorophyll-a
- 30.2 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
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Watch Little Wood Reservoir’s letter
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Why Little Wood Reservoir has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Little Wood Reservoir, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus and algae (chlorophyll-a), but not water clarity.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by IDEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Little Wood Reservoir is a 590-acre lake in Blaine County, Idaho. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, IDEQ, last sampled 2021-07-15. Grade methodology: LakeQuality methodology.
What Little Wood Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Little Wood Reservoir is listed impaired under Clean Water Act §303(d) (IR 4C) for hydrologic alteration. Check local advisories before you swim.
Water quality measurements for Little Wood Reservoir
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Phosphorus 70 µg/L. Chlorophyll-a 30.2 µg/L. TSI 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 70 µg/L | Not graded |
| Chlorophyll-a (Algae) | 30.2 µg/L | Not graded |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 590 acres |
| Public Access | Yes |
No bathymetric survey has been published for Little Wood Reservoir, so its depth is not documented here.
Recreation & Access
- Little Wood ReservoirPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Little Wood Reservoir
Water Quality Trend: ↓ Declining
Based on 13 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.301 m/yr | 11 |
| Phosphorus | ↓ Declining | +1.98 µg/L/yr | 13 |
| Chlorophyll-a | ↓ Declining | +7.79 µg/L/yr | 11 |
Reservoir Info (USACE NID)
Little Wood Reservoir is a man-made reservoir impounded by the Little Wood River Dam (completed 1939), built primarily for irrigation on the Little Wood River Malad River; earth-type dam, 129 ft tall and 3,100 ft long.
- Surface area
- 590 ac
- Normal storage
- 30,000 ac-ft
- Max storage
- 33,300 ac-ft
- Drainage area
- 273.98 sq mi
- Hazard class
- High
- Owner
- LITTLE WOOD RIVER IRRIGATION DISTRICT
Source: USACE National Inventory of Dams, NID ID ID00041 · Operator website · Matched by proximity (0.72 km)
EPA Impairment Status
Little Wood Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4C).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit ID17040221SK012L_0L · Official waterbody report · Matched by proximity (2.46 km)
Graded lakes near Little Wood Reservoir
Little Wood Reservoir has no grade, but these lakes within a short drive do.
Nearby Lakes in Blaine County
Frequently asked questions about Little Wood Reservoir
Where is Little Wood Reservoir?
- Little Wood Reservoir is a lake in Blaine County, Idaho. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Little Wood Reservoir?
- Little Wood Reservoir in Blaine County, Idaho is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 30.2 µg/L. Surface area: 590 acres.
Is Little Wood Reservoir safe to swim in?
- The letter is not a swimming clearance. Little Wood Reservoir is listed impaired under Clean Water Act §303(d) (IR 4C) for hydrologic alteration. Check local advisories before you swim.
Are there boat ramps on Little Wood Reservoir?
- Little Wood Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Little Wood Reservoir. Public access is listed as yes.
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Where this data comes from
3 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Bureau of Reclamation
1119USBR_WQX3 samples · 2021
Analytical methods
- Phosphorus by Single Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory