Water Quality by Source: Surface Water vs Groundwater
Your water source matters. Whether your city gets water from rivers and lakes or from underground aquifers affects what contaminants you might find and how the water is treated. Learn about different water sources and browse cities by their source type.
Understanding Water Source Types
Surface Water
Water sourced from rivers, lakes, and reservoirs
Advantages
- Abundant supply in most regions
- Easier to access and treat
- Lower mineral content
- Natural flow helps prevent stagnation
Challenges
- More susceptible to pollution runoff
- Higher turbidity and biological contamination
- Seasonal variations in quality
- Requires more extensive treatment
Groundwater (Aquifers & Wells)
Water sourced from underground aquifers accessed via wells
Advantages
- Naturally filtered through soil and rock
- Protected from surface contamination
- More consistent quality year-round
- Lower treatment requirements
Challenges
- Can contain high mineral content (hard water)
- Slower to replenish if overused
- May have naturally occurring contaminants like arsenic
- Vulnerable to industrial contamination
Mixed Sources
Water from combination of surface and groundwater sources
Advantages
- Supply diversification reduces risk
- Can balance seasonal variations
- Flexibility in water management
- Backup sources available
Challenges
- More complex treatment requirements
- Varying water quality characteristics
- Higher infrastructure costs
- Complex monitoring needs
Common Contaminants by Water Source
Typical in Surface Water
- Microorganisms: Bacteria, viruses, parasites from agricultural runoff
- Nitrates: From fertilizer and agricultural runoff
- Disinfection Byproducts: TTHMs and HAAs from chlorine treatment
- Sediment & Turbidity: Particles affecting water clarity
Typical in Groundwater
- Arsenic: Naturally occurring from rock formations
- Radium & Uranium: Natural radioactive elements
- Minerals: Calcium, magnesium causing hard water
- PFAS: From industrial contamination seeping into aquifers
Browse Cities by Water Quality
Click any city to see their water source type and detailed quality report
Highest Water Quality Cities
New York
New York
95
A+
Detroit
Michigan
95
A+
Los Angeles
California
73
B-
Houston
Texas
89
A-
Chicago
Illinois
82
B+
Las Vegas
Nevada
95
A+
Dallas
Texas
95
A+
San Antonio
Texas
95
A+
Phoenix
Arizona
70
B-
Seattle
Washington
95
A+
Philadelphia
Pennsylvania
78
B
Cleveland
Ohio
95
A+
San Diego
California
96
A+
St Louis
Missouri
95
A+
Charlotte
North Carolina
95
A+
Average Water Quality Cities
Arcadia
California
68
C+
Margate
Florida
69
C+
Des Plaines
Illinois
84
B+
Huntington Park
California
89
A-
Bonita Springs
Florida
81
B+
Lenexa
Kansas
48
F
Casa Grande
Arizona
90
A
Hanford
California
96
A+
Weymouth Town
Massachusetts
96
A+
Lake Havasu City
Arizona
87
A-
Highland
California
88
A-
Palm Beach Gardens
Florida
89
A-
Madison
Alabama
81
B+
National City
California
69
C+
Smyrna
Georgia
76
B
Choosing Filters for Your Water Source
The right water filter depends on both your water source and the specific contaminants detected:
For Surface Water Cities
- Activated carbon for chlorine taste and disinfection byproducts
- Sediment filters for turbidity and particles
- UV filters for additional microorganism protection
- Consider whole-house systems for comprehensive treatment
For Groundwater Cities
- Reverse osmosis for arsenic, radium, and heavy metals
- Water softeners for hard water minerals
- Activated carbon certified for PFAS if present
- Ion exchange for specific metal removal