Alaska Water Hardness by County
Water in Alaska has a median hardness of 69 mg/L as CaCO₃ — "moderately hard" on the USGS scale — based on 16,032 measurements at 3,534 monitoring stations. Fairbanks North Star County has the state's hardest measured water (140 mg/L); Petersburg County the softest (6). Rank: #31 of the 50 states and D.C.
Alaska water hardness map — what the numbers mean. Data verified 2026-07-22.
Of Alaska's 24 measured counties, 2 hard, 13 moderately hard, and 9 soft. The hardest are Fairbanks North Star County (140 mg/L), Denali County (130), and Yakutat County (119). Petersburg County is the softest at 6 mg/L (soft).
About 14% of Alaska's roughly 0.7 million residents in counties with gate-passing hardness data live where tap water is hard or worse.
Statewide, Alaska's median works out to 4 grains per gallon and ranks #31 of the 50 states and D.C. Across 16,032 measurements at 3,534 stations — 1,862 of them since 2000 — the middle 80% of readings fall between 19 and 170 mg/L. The public record runs from 1911 to 2023.
See where Alaska sits nationally on the national map, or what its number means on the hardness scale.
Download the Alaska water hardness map (PNG) — Water hardness by county in Alaska: 24 counties mapped from USGS/EPA data, statewide median 69 mg/L (moderately hard); darker counties have harder water.
By county
Water hardness by county
The table lists all 24 measured Alaska counties, hardest first. Their medians span 140 mg/L in Fairbanks North Star County to 6 in Petersburg County — a 23.3× range. 5 more Alaska counties lack gate-passing data.
| County | Median | Band | Results | Sites | Newest |
|---|---|---|---|---|---|
| Fairbanks North Star County | 140 | Hard | 1,195 | 534 | 2003 |
| Denali County | 130 | Hard | 544 | 78 | 2011 |
| Yakutat County | 119 | Moderately hard | 107 | 28 | 2023 |
| Southeast Fairbanks County | 110 | Moderately hard | 919 | 93 | 2005 |
| Yukon-Koyukuk County | 110 | Moderately hard | 918 | 117 | 2007 |
| Kusilvak Census Area | 102 | Moderately hard | 298 | 15 | 2023 |
| Nome County | 96.5 | Moderately hard | 73 | 33 | 2004 |
| Bethel County | 93 | Moderately hard | 451 | 69 | 2011 |
| Northwest Arctic County | 90.5 | Moderately hard | 150 | 66 | 2002 |
| Anchorage County | 78 | Moderately hard | 2,514 | 533 | 2015 |
| North Slope County | 77 | Moderately hard | 409 | 162 | 2023 |
| Haines County | 73 | Moderately hard | 55 | 22 | 2023 |
| Matanuska-Susitna County | 68 | Moderately hard | 1,907 | 365 | 2023 |
| Chugach & Copper River census areas (combined — measurements predate the 2019 split) | 62 | Moderately hard | 1,548 | 318 | 2023 |
| Hoonah-Angoon County | 61.4 | Moderately hard | 70 | 30 | 2010 |
| Wrangell County | 51 | Soft | 156 | 13 | 2023 |
| Juneau County | 36 | Soft | 943 | 182 | 2023 |
| Kenai Peninsula County | 34 | Soft | 1,827 | 477 | 2014 |
| Lake and Peninsula County | 32.6 | Soft | 212 | 63 | 2017 |
| Skagway County | 23.8 | Soft | 58 | 4 | 2004 |
| Prince of Wales-Hyder County | 18 | Soft | 269 | 30 | 2023 |
| Sitka County | 18 | Soft | 228 | 38 | 2005 |
| Ketchikan Gateway County | 9 | Soft | 302 | 54 | 2023 |
| Petersburg County | 6 | Soft | 50 | 14 | 2006 |
| 291 additional results from sites without county attribution (not shown). | |||||
ZIP codes
ZIP codes in Alaska
The ZIP codes below are grouped by the Alaska county each mostly falls within (by land area). Each ZIP takes that county's measured median — shown in the group header — so this is a ZIP-to-county guide, not a separate reading for every ZIP. To check the water system serving a specific address, use the lookup.
Key: a † after a ZIP means it has no mapped community water system — usually a private-well area. Plain ZIPs are served by a mapped community water system.
Fairbanks North Star County · 140 mg/L · Hard
997029970399705†99707†99709†99712†99714†99725†99775
Denali County · 130 mg/L · Hard
99704†99743†99744†99755†
Yakutat County · 119 mg/L · Moderately hard
99689†
Southeast Fairbanks County · 110 mg/L · Moderately hard
99706†99732†99737†99738†99764†99776†99780†
Yukon-Koyukuk County · 110 mg/L · Moderately hard
9955899590†99602†99627†99665†99675†99691†99701†99720†99722†99724†99726†99730†99733†99740†9974199745†99746†99748†99754†99756†99757†99758†99760†99765†99767†99768†9977499777†99781†99788†99790†
Nome County · 96.5 mg/L · Moderately hard
99659†99671†99684†99739†99742†99753†99762†99769†9977199772†9977899783†9978499785†
Bethel County · 93 mg/L · Moderately hard
99503†9955199552†99557†995599956199575†9957899589†9960799609†99614†99621†99622†99626†99630†99634†99637†99641†99651†9965599656†99668†99679†99680†99681†99690†
Northwest Arctic County · 90.5 mg/L · Moderately hard
99727997369974999750†99751†99752†99761†9976399770†9977399786
Anchorage County · 78 mg/L · Moderately hard
9950199502995049950599506†99507†99508995139951599516†99517995189953099540†99567†99577†99587†
North Slope County · 77 mg/L · Moderately hard
99519†99721†99723†99734†99747†99759†99766†99782†9978999791†
Haines County · 73 mg/L · Moderately hard
99827†99850†
Matanuska-Susitna County · 68 mg/L · Moderately hard
99623†99645†99652†9965499667†99674†99676†99683†99688†99694†99729†
Hoonah-Angoon County · 61.4 mg/L · Moderately hard
99820†99825†99826†99829†99832†99841†
Wrangell County · 51 mg/L · Soft
99903†99929†
Juneau County · 36 mg/L · Soft
99801†99824
Kenai Peninsula County · 34 mg/L · Soft
99556†99568†99572†99603†99605†99610†99611†99631†99635†99639†99663†99664†99669†99672†99682†
Lake and Peninsula County · 32.6 mg/L · Soft
9954899549†9956499565†9957999606†99613†99625†99640†99647†99648†99649†99653†99695†
Skagway County · 23.8 mg/L · Soft
99840
Prince of Wales-Hyder County · 18 mg/L · Soft
99830†99836†99918†99919†99921†99922†99923†99925†99926†99927†
Sitka County · 18 mg/L · Soft
99835†
Ketchikan Gateway County · 9 mg/L · Soft
99901†
Petersburg County · 6 mg/L · Soft
99833†
† 160 ZIP codes are not served by a mapped community water system — most are private-well areas. See well water hardness.
Source
Groundwater vs surface water
Alaska's groundwater measures harder than its surface water — 120 mg/L across 3,343 samples versus 59 across 12,678, about 2× harder. Wells draw from groundwater, so well owners in Alaska tend to see the harder number — 120 mg/L, hard. Groundwater readings there run 45 to 356 mg/L across the middle 80% of samples. The comparison draws on 1,713 groundwater and 1,813 surface-water monitoring sites; 42 readings above 2,000 mg/L were logged but held out of the medians as outliers.
Groundwater (wells)
120 mg/L as CaCO₃ · 3,343 results at 1,713 stations.
Surface water (rivers, lakes)
59 mg/L as CaCO₃ · 12,678 results at 1,813 stations.
Groundwater measures about 2× harder than surface water here.
Chemistry
Water chemistry in Alaska
Beyond the hardness number, Alaska's water carries a fuller chemical signature — here is how its measured parameters compare to national benchmarks.
TDS
100 mg/L · n=1,513
100 mg/L — below the national county median of 226.
pH
7.8 pH · n=1,553
pH 7.8 — within the EPA secondary range of 6.5–8.5, on the alkaline side.
Alkalinity
49 mg/L as CaCO3 · n=3,628
49 mg/L — modest buffering capacity.
Calcium : Magnesium
21.7 : 3.3 mg/L ≈ 6.58 : 1 · n=2,704
Calcium is about 80% of Alaska's hardness (21.7 mg/L Ca to 3.3 mg/L Mg), a little more calcium-rich than the national ~68% calcium share.
Parameter medians may include a small share of quality-control samples; the hardness lane is fully QC-filtered.
Aquifers
Major aquifers under Alaska
One aquifer system supply much of Alaska's measured groundwater.
- Alaska unconsolidated-deposit aquifers — median 110.5 mg/L across 88 samples at 60 sites: moderately hard.
Together these systems account for 88 measured samples at 60 sites. Aquifer medians pool samples across a whole system and can mask local variation — see the national aquifer map for how these compare across states.
Trend
Hardness over time
Alaska's decade median moved from 115 mg/L in the 1910s to 71.7 in the 2020s. Over the series, the decade median peaked at 115 mg/L in the 1910s and bottomed at 58 in the 1970s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.
Scale
Where Alaska sits on the scale
On the USGS scale, Alaska's 69 mg/L is moderately hard — 4 grains per gallon, between the 60 and 120 mg/L soft and hard cutoffs.
Questions
Frequently asked questions
- Is Alaska's water hard?
- Alaska's median hardness is 69 mg/L as CaCO₃, "moderately hard" on the USGS scale and below the national county median of 140 mg/L.
- Which county in Alaska has the hardest water?
- Fairbanks North Star County, with a median of 140 mg/L as CaCO₃ across 1,195 measurements.
- Is well water harder than city water in Alaska?
- Groundwater measures harder here — about 2× the surface water — so wells tend to run harder (groundwater 120 vs surface water 59 mg/L).
- How do I find my exact hardness in Alaska?
- Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
- Is Alaska's water harder than the national average?
- No. Alaska's median of 69 mg/L is below the national county median of 140 mg/L; it ranks #31 of the 50 states and D.C.
Compare
States with similar hardness
Two states measure closest to Alaska's 69 mg/L: Delaware at 63.9 mg/L and Arkansas at 62 mg/L. Alaska measures harder than 40% of states. Browse the full ranking on the statistics page.
More: hardness scale · check your address · national statistics · the national map.
By Marko Visic, MPharm, BSc Physics. Source: USGS/EPA Water Quality Portal — 16,032 Alaska measurements. Data last verified . Methodology.
Cite this page: “Alaska Water Hardness by County.” Hard Water Map. Retrieved 2026-07-22, https://hardwatermap.com/water-hardness/alaska/