Hard Water Map

Colorado Water Hardness by County

Water in Colorado has a median hardness of 157 mg/L as CaCO₃ — "hard" on the USGS scale — based on 218,893 measurements at 18,406 monitoring stations. Prowers County has the state's hardest measured water (1300 mg/L); Larimer County the softest (18). Rank: #18 of the 50 states and D.C.

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

Of Colorado's 63 measured counties, 30 very hard, 13 hard, 13 moderately hard, and 7 soft. The hardest are Prowers County (1300 mg/L), Bent County (980), and Kiowa County (710). Larimer County is the softest at 18 mg/L (soft).

About 75% of Colorado's roughly 5.8 million residents in counties with gate-passing hardness data live where tap water is hard or worse.

Statewide, Colorado's median works out to 9.2 grains per gallon and ranks #18 of the 50 states and D.C. Across 218,893 measurements at 18,406 stations — 108,828 of them since 2000 — the middle 80% of readings fall between 20.1 and 628 mg/L. The public record runs from 1900 to 2026.

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

Download the Colorado water hardness map (PNG) — Water hardness by county in Colorado: 63 counties mapped from USGS/EPA data, statewide median 157 mg/L (hard); darker counties have harder water.

By county

Water hardness by county

The table lists all 63 measured Colorado counties, hardest first. Their medians span 1300 mg/L in Prowers County to 18 in Larimer County — a 72.2× range. 1 more Colorado county lacks gate-passing data.

County water hardness, hardest first — median mg/L as CaCO₃.
CountyMedianBandResultsSitesNewest
Prowers County1300Very hard8811792026
Bent County980Very hard2,0201452025
Kiowa County710Very hard155802025
Sedgwick County683Very hard644322023
Otero County660Very hard2,3101882023
Logan County656Very hard855672026
Cheyenne County642Very hard111372015
Morgan County570Very hard1,791702024
Weld County550Very hard8,2756822026
Crowley County480.5Very hard177762023
Delta County382Very hard5,5614062026
Washington County370Very hard68322023
Montezuma County332Very hard4,7895142025
Mesa County310Very hard8,9486392026
Pueblo County299Very hard4,6544242026
Montrose County290Very hard5,7183972025
Rio Blanco County288Very hard7,5146392026
Baca County279Very hard2661922023
Denver County256Very hard2,4971732026
Lincoln County256Very hard40212018
Arapahoe County238Very hard4,6973932025
Ouray County236.5Very hard3,9452042026
Adams County228Very hard7,2353332026
Las Animas County225Very hard1,8362152026
Huerfano County220Very hard863812023
Garfield County210Very hard9,7316272026
San Miguel County190Very hard3,1641672025
Kit Carson County185Very hard122292021
Moffat County180Very hard4,8063732026
Yuma County180Very hard836902024
Pitkin County170Hard3,2542002025
La Plata County160Hard8,8336242026
El Paso County156Hard6,6208302025
Broomfield County150Hard951999
Custer County140Hard435902025
Fremont County140Hard1,9462082025
Routt County140Hard5,4085762026
Eagle County138Hard8,2344652026
Elbert County134Hard479872024
Teller County134Hard766982026
San Juan County128.5Hard3,9943072026
Dolores County120Hard3651132024
Douglas County120Hard1,7853372025
Jefferson County110Moderately hard4,3326132025
Park County100Moderately hard2,4876542025
Lake County90.1Moderately hard5,4174912026
Gilpin County90Moderately hard9721152022
Conejos County88Moderately hard3,0052162025
Jackson County88Moderately hard2,0652242026
Costilla County86Moderately hard599782025
Summit County80Moderately hard3,0713932026
Gunnison County77.2Moderately hard7,9517062026
Alamosa County72Moderately hard9031722026
Archuleta County68.5Moderately hard2,0142162026
Clear Creek County68.3Moderately hard5,3575212025
Saguache County62Moderately hard1,3272872025
Chaffee County58Soft2,8102662025
Hinsdale County57.9Soft7522092025
Boulder County46Soft6,9134842026
Rio Grande County44Soft1,8731662025
Grand County41.7Soft8,3603502026
Mineral County31Soft1,1961752026
Larimer County18Soft20,8396162026

ZIP codes

ZIP codes in Colorado

The ZIP codes below are grouped by the Colorado 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.

Prowers County · 1300 mg/L · Very hard

81041†8104381047†81052†

Bent County · 980 mg/L · Very hard

81044†81054†81057†81092†

Kiowa County · 710 mg/L · Very hard

81021†81036†81045†81071†

Sedgwick County · 683 mg/L · Very hard

80737†80744†80749†

Otero County · 660 mg/L · Very hard

81030†81050†81058†81067†81077†

Logan County · 656 mg/L · Very hard

80722†80726†80728†80736†80741†80745†80747†80751†

Cheyenne County · 642 mg/L · Very hard

80802†80810†80825†80862†

Morgan County · 570 mg/L · Very hard

80653†80654†80701†8070580723†80733†80750†

Weld County · 550 mg/L · Very hard

80504805148051680520†805308053480542†80543805468055080610†80611†80612†806158062080621†80622†80623†80624†806318063480642†80643†8064480645†8064680648†80649†806508065180652†80729†80732†80742†80754†

Crowley County · 480.5 mg/L · Very hard

81033†81062†81063†81076†

Delta County · 382 mg/L · Very hard

8141081413†8141681418†81419†81428†

Washington County · 370 mg/L · Very hard

80720†80740†80743†80757†80801†80812†

Montezuma County · 332 mg/L · Very hard

81321†81327†81328†81330†81331†81334†81335†

Mesa County · 310 mg/L · Very hard

815018150381504†81505†81506†81507†8152081521†81522†81523†81524†81525†81526†81527†81624†81643†81646†

Pueblo County · 299 mg/L · Very hard

81001†8100381004†81005†8100681007†81008†8101981022†81023†81025†81039†

Montrose County · 290 mg/L · Very hard

81401†8140381411†81415†81422†81424†8142581429†

Rio Blanco County · 288 mg/L · Very hard

81641†81648†81650†

Baca County · 279 mg/L · Very hard

81029†81064†81073†81084†81087†81090†

Denver County · 256 mg/L · Very hard

80202802038020480205802068020780209802108021180212802168021880219802208022280223802248023080231802368023780238802398024680247802498026480266802908029380294

Lincoln County · 256 mg/L · Very hard

80804†80818†80821†80823†80826†80828†80833†

Arapahoe County · 238 mg/L · Very hard

8001080012800138001480015800168001780018†80105†80110†8011180112†8011380120801218012280137†

Ouray County · 236.5 mg/L · Very hard

8142781432

Adams County · 228 mg/L · Very hard

80011†80019†800228002480030800318004580102†80103†80136†80221802298023380234802418026080601806028060380640

Las Animas County · 225 mg/L · Very hard

81020†81024†81027†81046†81049†81059†81081†81082†81091†

Huerfano County · 220 mg/L · Very hard

81040†81055†81069†81089†

Garfield County · 210 mg/L · Very hard

81601†81630†81635†81637†8164781652†

San Miguel County · 190 mg/L · Very hard

81423†81426†81430†81431†81435†

Kit Carson County · 185 mg/L · Very hard

80805†80807†80815†80834†80836†80861†

Moffat County · 180 mg/L · Very hard

81610†81625†81633†81638†81640†

Yuma County · 180 mg/L · Very hard

80727†80735†80755†80758†80759†80822†80824†

Pitkin County · 170 mg/L · Hard

81611†81612†8161581623†81642†81654†81656†

La Plata County · 160 mg/L · Hard

81122†81137†81301†81303†81326†

El Paso County · 156 mg/L · Hard

801328013380808†80809†8081780819†80829†80831†80840†80864†80902†80903809048090580906†8090780908†80909809108091180913†8091480915809168091780918809198092080921†8092280923809248092580926†8092780928†80929†80930†809388093980951

Broomfield County · 150 mg/L · Hard

8002080023†

Custer County · 140 mg/L · Hard

81252†81253†

Fremont County · 140 mg/L · Hard

81212†8122181222†81223†81226†81232†81233†81240†81244

Routt County · 140 mg/L · Hard

80428†80463†80467†80469†80479†80483†80487†81639†81653†

Eagle County · 138 mg/L · Hard

80423†80426†81620†81621†81631†81632†81645†81649†81655†81657†

Elbert County · 134 mg/L · Hard

80101†80106†80107†80117†80830†80832†80835†

Teller County · 134 mg/L · Hard

80813†80814†80816†80860†80863†

San Juan County · 128.5 mg/L · Hard

81433†

Dolores County · 120 mg/L · Hard

81320†81323†81324†81325†81332†

Douglas County · 120 mg/L · Hard

80104†80108†80109†80116†80118†8012480125801268012980130801318013480135†80138†

Jefferson County · 110 mg/L · Moderately hard

80002800038000480005800078002180033†8012380127†80128†8021480215802268022780228802328023580401†80403†8041980425†80433†80453†8045480457†80465†80470†

Park County · 100 mg/L · Moderately hard

80420†80421†80432†80440†80448†80449†80456†80475†80820†80827†

Lake County · 90.1 mg/L · Moderately hard

80461†81251†

Gilpin County · 90 mg/L · Moderately hard

80422†80427†80474†

Conejos County · 88 mg/L · Moderately hard

81120†8112481129†81140†81141†81148

Jackson County · 88 mg/L · Moderately hard

80430†80434†80473†80480†

Costilla County · 86 mg/L · Moderately hard

81123†81126†81133†81138†81151†81152†

Summit County · 80 mg/L · Moderately hard

80424†80435†80443†80498†

Gunnison County · 77.2 mg/L · Moderately hard

81210†81220†81224†81225†81230†81237†81239†81241†81243†81434†

Alamosa County · 72 mg/L · Moderately hard

8110181136†81146†

Archuleta County · 68.5 mg/L · Moderately hard

8112181128†81147

Clear Creek County · 68.3 mg/L · Moderately hard

80436†80438†80439†80444†80452†80476†

Saguache County · 62 mg/L · Moderately hard

81125†81131†81143†81149†81155†81248†

Chaffee County · 58 mg/L · Soft

81201†81211†81227†81228†81236†81242†

Hinsdale County · 57.9 mg/L · Soft

81235†

Boulder County · 46 mg/L · Soft

80025†800268002780301†80302†80303†80304803058031080455†80466†80471†80481†805018050380510†80540†80544

Rio Grande County · 44 mg/L · Soft

81132†81144†81154†

Grand County · 41.7 mg/L · Soft

80442†80446†80447†80451†80459†80468†80478†80482

Mineral County · 31 mg/L · Soft

81130†

Larimer County · 18 mg/L · Soft

80512†8051380515†80517†80521805248052580526†8052880532†80535†80536†8053780538†80545†8054780549†82063†

† 362 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

Colorado's groundwater measures harder than its surface water — 280 mg/L across 12,763 samples versus 152 across 200,519, about 1.8× harder. Wells draw from groundwater, so well owners in Colorado tend to see the harder number — 280 mg/L, very hard. Groundwater readings there run 27 to 1100 mg/L across the middle 80% of samples. The comparison draws on 6,156 groundwater and 11,719 surface-water monitoring sites; 2,761 readings above 2,000 mg/L were logged but held out of the medians as outliers.

Groundwater (wells)

280 mg/L as CaCO₃ · 12,763 results at 6,156 stations.

Surface water (rivers, lakes)

152 mg/L as CaCO₃ · 200,519 results at 11,719 stations.

Groundwater measures about 1.8× harder than surface water here.

Chemistry

Water chemistry in Colorado

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

TDS

228 mg/L · n=19,790

228 mg/L — about 1× the national county median of 226, consistent with hard, mineral-rich water.

pH

7.9 pH · n=62,710

pH 7.9 — within the EPA secondary range of 6.5–8.5, on the alkaline side.

Alkalinity

92 mg/L as CaCO3 · n=100,693

92 mg/L — modest buffering capacity.

Calcium : Magnesium

38.6 : 7.4 mg/L ≈ 5.22 : 1 · n=137,561

Calcium is about 76% of Colorado's hardness (38.6 mg/L Ca to 7.4 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 Colorado

3 aquifer systems supply much of Colorado's measured groundwater.

  • Alluvial aquifers — median 328 mg/L across 752 samples at 326 sites: very hard.
  • Colorado Plateaus aquifers — median 240 mg/L across 989 samples at 624 sites: very hard.
  • High Plains (Ogallala) aquifer — median 160 mg/L across 197 samples at 156 sites: hard.

Together these systems account for 1,938 measured samples at 1,106 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

1930s2020s560

Colorado's decade median moved from 560 mg/L in the 1930s to 156 in the 2020s. Over the series, the decade median peaked at 560 mg/L in the 1930s and bottomed at 126 in the 2010s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.

Scale

Where Colorado sits on the scale

On the USGS scale, Colorado's 157 mg/L is hard — 9.2 grains per gallon, above the 120 mg/L hard cutoff, below very hard.

SoftModerately hardHardVery hard60 · 3.5 gpg120 · 7.0 gpg180 · 10.5 gpg157 mg/L — Hard
Harder than 53% of the 2,977 measured county medians.

At 157 mg/L (9.2 gpg), water-softener owners in Colorado typically set their unit to this hardness — settings calculator.

Questions

Frequently asked questions

Is Colorado's water hard?
Colorado's median hardness is 157 mg/L as CaCO₃, "hard" on the USGS scale and 1.12× the national county median of 140 mg/L. About 75% of residents in measured counties have hard-or-worse water.
Which county in Colorado has the hardest water?
Prowers County, with a median of 1300 mg/L as CaCO₃ across 881 measurements.
Is well water harder than city water in Colorado?
Groundwater measures harder here — about 1.8× the surface water — so wells tend to run harder (groundwater 280 vs surface water 152 mg/L).
How do I find my exact hardness in Colorado?
Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
Is Colorado's water harder than the national average?
Yes. Colorado's median of 157 mg/L is 1.12× the national county median of 140 mg/L, and Colorado ranks #18 of the 50 states and D.C.

Compare

States with similar hardness

Two states measure closest to Colorado's 157 mg/L: Florida at 151 mg/L and California at 150 mg/L. Colorado measures harder than 66% 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 — 218,893 Colorado measurements. Data last verified . Methodology.

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