US Water Intelligence Insights
National analysis across 2,940 published US county records — drinking-water compliance, watershed health, monitoring records, and streamflow snapshots. Sourced from EPA SDWIS, ATTAINS, WQP, and USGS NWIS.
SDWIS
2,940
compliance records
ATTAINS
1,470
watershed assessments
WQP
2,916
counties monitored
NWIS
2,101
fresh pipeline snapshots
Key Findings
Drinking water compliance varies significantly across the United States. Hawaii leads with an average SDWIS Compliance Index of 78.6, while Alaska sits lowest at 14.0. The national average is 50.2 across 2,940 counties with reporting.
Watershed impairment averages 59.9% nationally across the 1,470 counties with EPA ATTAINS assessments — 619,529 of 1,728,872 assessed water bodies fail Clean Water Act §303(d) quality standards.
Monitoring density isn't uniform: 2,916 counties have water-quality records in the federal Water Quality Portal, with 133,467 monitoring sites contributing 41,744,346 measurements in the past five years.
Fresh USGS pipeline snapshots are available for 2,069 counties. Of those snapshots, 167 are above the full-record annual mean, 1,819 are below it, and 83 are within the comparison range. These are timestamped pipeline observations, not causal or household tap-water conclusions.
State SDWIS Compliance Index Comparisons
Average WaterByCounty relative index by state. This is not an EPA score or a current utility determination.
Highest Average Index
Lowest Average Index
Five-Year SDWIS Compliance Band Distribution
How counties are distributed across five-year SDWIS compliance bands (A–F).
Violation Count vs. SDWIS Compliance Index
Each point is a published county record. The index is a relative WaterByCounty calculation derived from the recorded SDWIS rate.
Violations per 100K Served by State
Average population-normalized health violation rate by state.
Highest Violation Rates
Lowest Violation Rates
Top 10 Counties by SDWIS Compliance Index
The highest relative WaterByCounty index values in the published county cohort.
Autauga County
AL
86.2
Five-Year SDWIS Band A
Bullock County
AL
86.2
Five-Year SDWIS Band A
Chambers County
AL
86.2
Five-Year SDWIS Band A
Cherokee County
AL
86.2
Five-Year SDWIS Band A
Chilton County
AL
86.2
Five-Year SDWIS Band A
Cleburne County
AL
86.2
Five-Year SDWIS Band A
Covington County
AL
86.2
Five-Year SDWIS Band A
Crenshaw County
AL
86.2
Five-Year SDWIS Band A
Cullman County
AL
86.2
Five-Year SDWIS Band A
Dallas County
AL
86.2
Five-Year SDWIS Band A
EPA ATTAINS · Clean Water Act §303(d)
Watershed Impairment Distribution
Counties bucketed by the share of assessed water bodies that fail Clean Water Act quality standards. Only counties with reported §303(d) assessments are included.
0–10% impaired
65
4.4% of assessed counties
10–30%
170
11.6% of assessed counties
30–60%
427
29.0% of assessed counties
60%+
808
55.0% of assessed counties
Most impaired counties
| County | Impaired |
|---|---|
| Imperial County, CA | 100.0% |
| Sutter County, CA | 100.0% |
| Trinity County, CA | 100.0% |
| Prowers County, CO | 100.0% |
| Emanuel County, GA | 100.0% |
| Irwin County, GA | 100.0% |
| Toombs County, GA | 100.0% |
| East Feliciana Parish, LA | 100.0% |
| Dawes County, NE | 100.0% |
| Crockett County, TN | 100.0% |
Lowest recorded impairment shares
| County | Impaired |
|---|---|
| Lowndes County, AL | 0.0% |
| Divide County, ND | 0.0% |
| Rolette County, ND | 0.0% |
| Billings County, ND | 2.5% |
| Florence County, WI | 3.2% |
| Towner County, ND | 3.3% |
| Golden Valley County, ND | 3.6% |
| Iron County, WI | 3.7% |
| Ramsey County, ND | 3.8% |
| Washburn County, WI | 3.8% |
EPA Water Quality Portal · 5-year window
Most-Monitored Counties
Counties with the largest recorded monitoring footprints. Monitoring volume does not by itself indicate better or worse water quality.
| County | Monitoring Sites |
|---|---|
| Lee County, FL | 3,032 |
| Pinellas County, FL | 2,301 |
| Hillsborough County, FL | 2,161 |
| Maricopa County, AZ | 2,147 |
| Charlotte County, FL | 1,633 |
| Barnstable County, MA | 1,168 |
| St. Louis County, MN | 978 |
| Orange County, FL | 909 |
| Lake County, MN | 876 |
| Sarasota County, FL | 870 |
Counts include federal, state, and tribal monitoring locations. Each reading is a single sample analyzed for one characteristic.
USGS NWIS · Fresh pipeline snapshots
Rivers Far From Their Long-Term Mean
Counties whose fresh pipeline snapshot is well above or below the selected gauge's full-record annual mean. A pipeline snapshot is not a continuously updated reading or a tap-water safety measure.
Top 10 above typical
| County | vs typical |
|---|---|
| Callaway County, MO Auxvasse Creek near Reform, MO · Observation 2026 | 4277% |
| Boone County, MO Hinkson Creek at Columbia, MO · Observation 2026 | 4107% |
| Duval County, FL ST. JOHNS RIVER AT JACKSONVILLE, FL · Observation 2026 | 2741% |
| Santa Cruz County, AZ SANTA CRUZ RIVER AT TUBAC, AZ. · Observation 2026 | 1888% |
| Decatur County, IA Thompson River at Davis City, IA · Observation 2026 | 1172% |
| Cochise County, AZ SAN PEDRO RIVER NEAR TOMBSTONE, AZ · Observation 2026 | 1052% |
| Kerr County, TX Guadalupe Rv nr Center Point, TX · Observation 2026 | 1020% |
| Monroe County, FL BROAD RIVER NEAR THE CUTOFF, FL · Observation 2026 | 892% |
| Live Oak County, TX Nueces Rv nr Three Rivers, TX · Observation 2026 | 718% |
| Johnson County, MO Blackwater River at Valley City, MO · Observation 2026 | 702% |
Top 10 below typical
| County | vs typical |
|---|---|
| Apache County, AZ CHINLE CREEK NEAR MEXICAN WATER, AZ · Observation 2026 | 0% |
| La Paz County, AZ BILL WILLIAMS RIVER NEAR PARKER, AZ · Observation 2026 | 0% |
| Maricopa County, AZ GILA RIVER BELOW PAINTED ROCK DAM, AZ · Observation 2026 | 0% |
| Pinal County, AZ GILA RIVER NEAR MARICOPA, AZ. · Observation 2026 | 0% |
| Pike County, AR Antoine River at Antoine, AR · Observation 2026 | 0% |
| Kern County, CA KERN R A ENOS PARK FOOT BR NR BAKERSFIELD CA · Observation 2026 | 0% |
| Orange County, CA SANTA ANA R A SANTA ANA CA · Observation 2026 | 0% |
| San Benito County, CA SAN BENITO R BL HOSPITAL RD BRIDGE NR HOLLISTER CA · Observation 2026 | 0% |
| San Diego County, CA SANTA MARGARITA R A YSIDORA CA · Observation 2026 | 0% |
| Santa Barbara County, CA SANTA MARIA R A SUEY CROSSING NR SANTA MARIA CA · Observation 2026 | 0% |
Fresh USGS pipeline snapshots from selected gauges. Each row includes the observation year; values refresh on the next verified data sync.