Hard Water Map

North Dakota Water Hardness by County

Water in North Dakota has a median hardness of 310 mg/L as CaCO₃ — "very hard" on the USGS scale — based on 50,468 measurements at 10,106 monitoring stations. Nelson County has the state's hardest measured water (589.5 mg/L); Sioux County the softest (119.5). Rank: #3 of the 50 states and D.C.

North Dakota water hardness map — what the numbers mean. Data verified 2026-07-22.

Of North Dakota's 53 measured counties, 52 very hard and 1 moderately hard. The hardest are Nelson County (589.5 mg/L), Steele County (520), and Ramsey County (481). Sioux County is the softest at 119.5 mg/L (moderately hard).

About 100% of North Dakota's roughly 0.8 million residents in counties with gate-passing hardness data live where tap water is hard or worse.

Statewide, North Dakota's median works out to 18.1 grains per gallon and ranks #3 of the 50 states and D.C. Across 50,468 measurements at 10,106 stations — 12,696 of them since 2000 — the middle 80% of readings fall between 136 and 650 mg/L. The public record runs from 1921 to 2024.

See where North Dakota sits nationally on the national map, or what its number means on the hardness scale.

Download the North Dakota water hardness map (PNG) — Water hardness by county in North Dakota: 53 counties mapped from USGS/EPA data, statewide median 310 mg/L (very hard); darker counties have harder water.

By county

Water hardness by county

The table lists all 53 measured North Dakota counties, hardest first. Their medians span 589.5 mg/L in Nelson County to 119.5 in Sioux County — a 4.9× range.

County water hardness, hardest first — median mg/L as CaCO₃.
CountyMedianBandResultsSitesNewest
Nelson County589.5Very hard8111782024
Steele County520Very hard4081592012
Ramsey County481Very hard2,9272762024
Towner County460Very hard6451952023
Traill County427.5Very hard806892024
Divide County391Very hard3471562023
McIntosh County390Very hard2791892016
Adams County388Very hard3231212024
Sargent County380Very hard5172492023
Williams County377.5Very hard8242502023
Hettinger County370Very hard6501552024
Rolette County369Very hard2481492022
Golden Valley County365Very hard3361212023
Walsh County360Very hard1,1701462024
Benson County353Very hard1,3212772023
Richland County351Very hard9271432023
Barnes County342Very hard8871182024
Grant County338Very hard9401482023
Dickey County333Very hard2,9505412023
Logan County330Very hard2782302016
Ward County328Very hard1,3771432024
McHenry County324Very hard2,3792622023
Bottineau County322Very hard1,1851292023
Grand Forks County320Very hard1,6611382024
Griggs County320Very hard6881542016
Renville County319Very hard567362023
Oliver County310Very hard371592023
Sheridan County305Very hard1561022016
Pembina County303Very hard1,7521392023
Emmons County300Very hard5012622024
LaMoure County300Very hard6682532016
Ransom County300Very hard1,2152402024
Foster County296Very hard453672016
Cass County290Very hard2,7142422023
Stark County282.5Very hard1,1032532023
Burleigh County280Very hard1,0401872024
Kidder County280Very hard1611112018
Morton County280Very hard1,2803632023
Stutsman County280Very hard1,2511812024
Mountrail County279.5Very hard7212252023
Pierce County278Very hard172952003
Eddy County260Very hard9011202024
Wells County260Very hard465872023
McLean County252Very hard2,0034162023
Cavalier County250Very hard5991812023
Mercer County240Very hard2,0351902024
Slope County237Very hard5651222024
Billings County230Very hard7022002023
Bowman County230Very hard1,1312572018
Burke County227Very hard3732112020
Dunn County220Very hard9694312023
McKenzie County220Very hard1,4522552023
Sioux County119.5Moderately hard2641052023

ZIP codes

ZIP codes in North Dakota

The ZIP codes below are grouped by the North Dakota county they fall in. Each ZIP takes its 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.

Nelson County · 589.5 mg/L · Very hard

582125822458254†582595827258344†5836158380

Steele County · 520 mg/L · Very hard

580465805658230582405827458277

Ramsey County · 481 mg/L · Very hard

58301583215832558327583305833858345583625837758382

Towner County · 460 mg/L · Very hard

58317583245833158339583635836558372

Traill County · 427.5 mg/L · Very hard

580095801658035580385804558218582195822358257

Divide County · 391 mg/L · Very hard

58730†587655879558833†58844†

McIntosh County · 390 mg/L · Very hard

584135849558581

Adams County · 388 mg/L · Very hard

58639†58649†

Sargent County · 380 mg/L · Very hard

5801358017580325804058043580605806758069

Williams County · 377.5 mg/L · Very hard

587555880158830588435884558849588525885358856

Hettinger County · 370 mg/L · Very hard

58646†58650†

Rolette County · 369 mg/L · Very hard

583105831658329†58353583665836758369†

Golden Valley County · 365 mg/L · Very hard

58621†58632†58654†

Walsh County · 360 mg/L · Very hard

5821058227582295823158233582375824358250582615827058273

Benson County · 353 mg/L · Very hard

58332†5833558343583465834858351†58357583705837958386

Richland County · 351 mg/L · Very hard

580015800858015580185803058041580535805758058580615807458075580765807758081

Barnes County · 342 mg/L · Very hard

5804958062580635806558072584295846158479584805848158492

Grant County · 338 mg/L · Very hard

58529†58533†58562†58564†58569†

Dickey County · 333 mg/L · Very hard

5843658439584415845658474

Logan County · 330 mg/L · Very hard

58440584425846058561

Ward County · 328 mg/L · Very hard

5870158703587045870558707587185872258733587345873558746587565878158785

McHenry County · 324 mg/L · Very hard

587105871258713587315873658741587445876858788587895879058792

Bottineau County · 322 mg/L · Very hard

583185838458711587485875058760587625878358793

Grand Forks County · 320 mg/L · Very hard

5820158202†58203†58204582055821458228582355824458251582565825858266582675827558278

Griggs County · 320 mg/L · Very hard

5841658425584485845258484

Renville County · 319 mg/L · Very hard

5872558740587615878258787

Oliver County · 310 mg/L · Very hard

58530†

Sheridan County · 305 mg/L · Very hard

58430584445846358758

Pembina County · 303 mg/L · Very hard

582165822058222582255823658238582415826258265582715827658282

Emmons County · 300 mg/L · Very hard

57648585245854258544585495855258573

LaMoure County · 300 mg/L · Very hard

58415584315843358454584585846658490

Ransom County · 300 mg/L · Very hard

58027580335805458068

Foster County · 296 mg/L · Very hard

584215844358445

Cass County · 290 mg/L · Very hard

5800258004580055800658007580115801258021580295803158036580425804758048580515805258059580645807158078†5807958102581035810458105†

Stark County · 282.5 mg/L · Very hard

58601†58630†58641†58652†58655†58656†

Burleigh County · 280 mg/L · Very hard

584775849458501585035850458505585215853258558585605857258579

Kidder County · 280 mg/L · Very hard

584285847558478584825848758488

Morton County · 280 mg/L · Very hard

58520†585355855458563585665857058631†58638†

Stutsman County · 280 mg/L · Very hard

58401584025840558420584245842658455584675847258476584835849658497

Mountrail County · 279.5 mg/L · Very hard

58763587695877058771587765878458794

Pierce County · 278 mg/L · Very hard

58313†5836858385

Eddy County · 260 mg/L · Very hard

58356583745838158464

Wells County · 260 mg/L · Very hard

58341584185842258423584385845158486

McLean County · 252 mg/L · Very hard

58531†585405855958565585755857658577587165872358759587755877858779

Cavalier County · 250 mg/L · Very hard

58239582495825558260582695828158311583235835258355

Mercer County · 240 mg/L · Very hard

5852358541†58545†58571†58580†

Slope County · 237 mg/L · Very hard

58620†58647†

Billings County · 230 mg/L · Very hard

58622†58627†58645†

Bowman County · 230 mg/L · Very hard

58623†58643†58651†58653†

Burke County · 227 mg/L · Very hard

587215872758737†5875258772†58773

Dunn County · 220 mg/L · Very hard

58625†58626†58636†58640†58642†58644†58757

McKenzie County · 220 mg/L · Very hard

58634†5883158835588385884758854

Sioux County · 119.5 mg/L · Moderately hard

585285853858568

† 59 ZIP codes are not served by a mapped community water system — most are private-well areas. See well water hardness.

Check any ZIP's utility and hardness →

Source

Groundwater vs surface water

North Dakota's surface water measures harder than its groundwater — 315 mg/L across 36,319 samples versus 300 across 14,109, about 1.1× harder. For well owners that is the better side of a hard bargain: at 300 mg/L, North Dakota groundwater is still very hard, and most of the state's drinking water is pumped from it. Groundwater readings there run 26 to 740 mg/L across the middle 80% of samples. The comparison draws on 8,721 groundwater and 1,381 surface-water monitoring sites; 832 readings above 2,000 mg/L were logged but held out of the medians as outliers.

Groundwater (wells)

300 mg/L as CaCO₃ · 14,109 results at 8,721 stations.

Surface water (rivers, lakes)

315 mg/L as CaCO₃ · 36,319 results at 1,381 stations.

Surface water measures about 1.1× harder than groundwater here.

Chemistry

Water chemistry in North Dakota

Beyond the hardness number, North Dakota's water carries a fuller chemical signature — here is how its measured parameters compare to national benchmarks.

TDS

848 mg/L · n=8,101

848 mg/L — about 3.8× the national county median of 226, consistent with hard, mineral-rich water.

pH

8.3 pH · n=16,898

pH 8.3 — within the EPA secondary range of 6.5–8.5, on the alkaline side.

Alkalinity

280 mg/L as CaCO3 · n=16,792

280 mg/L — substantial buffering capacity, which resists pH swings.

Calcium : Magnesium

70.2 : 50 mg/L ≈ 1.4 : 1 · n=15,461

Calcium is about 46% of North Dakota's hardness (70.2 mg/L Ca to 50 mg/L Mg), a little more magnesium-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 North Dakota

3 aquifer systems supply much of North Dakota's measured groundwater.

  • Sand and gravel aquifers (glaciated regions) — median 340 mg/L across 4,488 samples at 3,087 sites: very hard.
  • Alluvial aquifers — median 330 mg/L across 3,182 samples at 1,164 sites: very hard.
  • Paleozoic aquifers — median 300 mg/L across 13 samples at 8 sites: very hard.

Together these systems account for 7,683 measured samples at 4,259 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

1930s2020s429

North Dakota's decade median moved from 380 mg/L in the 1930s to 426 in the 2020s. Over the series, the decade median peaked at 429 mg/L in the 2010s and bottomed at 260 in the 1950s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.

Scale

Where North Dakota sits on the scale

On the USGS scale, North Dakota's 310 mg/L is very hard — 18.1 grains per gallon, well above the 180 mg/L very-hard cutoff — among the hardest water measured in the US.

SoftModerately hardHardVery hard60 · 3.5 gpg120 · 7.0 gpg180 · 10.5 gpg310 mg/L — Very hard
Harder than 85% of the 2,977 measured county medians.

At 310 mg/L (18.1 gpg), water-softener owners in North Dakota typically set their unit to this hardness — settings calculator.

Questions

Frequently asked questions

Is North Dakota's water hard?
North Dakota's median hardness is 310 mg/L as CaCO₃, "very hard" on the USGS scale and 2.21× the national county median of 140 mg/L. About 100% of residents in measured counties have hard-or-worse water.
Which county in North Dakota has the hardest water?
Nelson County, with a median of 589.5 mg/L as CaCO₃ across 811 measurements. Even the softest, Sioux County at 119.5 mg/L, is still "moderately hard" on the USGS scale.
Is well water harder than city water in North Dakota?
Surface water measures harder here — about 1.1× the groundwater — so wells tend to run softer (groundwater 300 vs surface water 315 mg/L).
How do I find my exact hardness in North Dakota?
Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
Is North Dakota's water harder than the national average?
Yes. North Dakota's median of 310 mg/L is 2.21× the national county median of 140 mg/L, and North Dakota ranks #3 of the 50 states and D.C.

Compare

States with similar hardness

Two states measure closest to North Dakota's 310 mg/L: Iowa at 310 mg/L and Arizona at 300 mg/L. North Dakota measures harder than 96% of states. Browse the full ranking on the statistics page.

More: hardness scale · check your address · national statistics · the national map.

By . Source: USGS/EPA Water Quality Portal — 50,468 North Dakota measurements. Data last verified . Methodology.

Cite this page: “North Dakota Water Hardness by County.” Hard Water Map. Retrieved 2026-07-22, https://hardwatermap.com/water-hardness/north-dakota/