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Preliminary report on the groundwater resources of the Navajo and Hopi Indian Reservations, , , and Halpenny, Leonard, C., 1951, pp. 147-154 in: San Juan Basin (New Mexico and Arizona), Smith, C. T.; Silver, C.; [eds.], New Mexico Geological Society 2nd Annual Fall Field Conference Guidebook, 163 p.

This is one of many related papers that were included in the 1951 NMGS Fall Field Conference Guidebook.

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Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from our website or printed and electronic publications may be reprinted or redistributed without our permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from our website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires permission. This page is intentionally left blank to maintain order of facing pages. I NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN, i PRELIMINARY REPORT ON THE GROUND-WATER the IndianOffice in locatingand developingground- RESOURCES OF THE NAVAJO AND HOPI watersupplies. Since October 20 1950,the Ground INDIAN RESERVATIONS ARIZONA WaterBranch of the UnitedStates Geological Survey I NEW MEXICO~ AND UTAH. hasbeen engaged in a reconnaissanceof the ground- waterresources and geology of theNavajo country. L. C. Halpenny Thework is beingdone at therequest of theOffice I of IndianAffairsand is financedby thatoffice. The Basedon datacollected by J. W. Harshbarger, purposeof the workistwofold; to aidthe IndianOffice H. A. Whitcomb~C. A. Repenning~R. L. Jackson currentlyin locatingand developingground-water sup- J.T.Callahan, S. C. Brown,the author,and others, pliesfor livestock, domestic, and community use; and to i preparea comprehensivereport on theground-water The regiongenerally known as the Navajo resourcesand geology of theregion, which will ¯serve countrylies in northeasternArizona northwestern as a guideto furtherdevelopment and utilization of New Mexicoand southeasternUtah. It includes theavailable water supply. I the areaoccupied by the Navaioand HopiIndian Reservations,and comprises some 16,000,000 acres or Theinvestigation is under the general supervision about25,000 square miles. Most of theregion is in of A. N. Sayre,geologist in chargeof the Ground i Arizona(see pl. I). Roads within the region are WaterBranch of the GeologicalSurvey, and Underthe mostlydirt; a fewhave been gravelled in recent directsupervision of the author of thisreport. The years~but no pavedroads exist except along the workhas been aided by reviewand consultationwith the bordersof thereservations. U. S. Highway89 crosses headsof thedistrict offices in Arizona,New Mexico, I the westernside U. S. Highway66 llesalong the and Utah:Messrs. S. F. TurnerC. V. Theis,and H. southernside, and U. S. Highway666 crossesthe E. Thomas. easternside. The A. T. & S. F. Railroadparallels U.S.Highway 66 alongthe southernborder of the Thewriters aregreatlyindebtedto manyofficials region, of theOffice of IndianAffairs for their cooperation andassistance. Many thanks are especiallydue to Thereare no incorporatedtowns on the Navoio Messrs.J. J. Schwarz,C. Wilson,and L. Kingsley i and HopiReservations. The communitiesare mostly fortheir guidance in thefield and helpful discussion governmentowned and wereconstructed to provide of problems. schools,hospitals, and other services for the Indians. i Tradingposts at mostof theplaces shown on plateI Theclose cooperation and prompt assistance supplythe residents with the necessities of llfe t and renderedby the SouthwesternLaboratory of the Quality thesupplies are brought in by truck.Gallup and of WaterBranch, Albuquerque, N. Max.,is gratefully Farmington~N- Mex.,and Holbrook,Winslow, and acknowledged.Particular thanks are due to J. D. Hem, i FlagstaffAriz., are the trade centers for the region. DistrictChemist for his aid in definingquality-of-water problems. Themost comprehensive report available on the ground-waterresources of theregion is thatof GeneralFeatures of theRegion I Gregory(I 916).From 1934 to 1940the SoilCon- servationService, Department of Agriculturecam- TheNavajo country is a partof thephysiographic piledwell records, furnished geologic information provinceknown as the ColoradoPlateau, an elevated I and generallyaided the Indian Office in developing areaoccupying partsof Utah Arizona,,and ground-watersupplies in theregion. From 1942 to 1948 New Mexico.The New Mexicoportion of the Navaja theTechnical Coordination Branch of theWater Re- countryis a partof theSan Juan Basin r andthe Arizona sourcesDivision Geological Survey, furnished occas- portioncomprises the Black Mesa Basin. i ionalassistance in selecting sites for water wells. H. V. Petersongeologist, was in chargeof thiswork. Theregion lies within the drainage basin of the ColoradoRiver and the principal tributaries, in the The GroundWater Branch had beenworking on a Navajocountry, are the San Juan,Chaco, Puerto, I limitedscale in theregion since January 1948 ass;sting andLittle Colorado Rivers. In thewestern part of the I

| 147 ¯ NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN I

n m region,deep canyons have been cut by the San Juan, topographyand climate.Stream channels have steep LittleColorado, and ColoradoRivers as muchas 3,000 gradients,runoff is rapid,and consequently there is feetbelow the prevailing land surface, littleopportunity forprecipitation to percolate into I theground. Locally, water that may haveentered the m Thealtitude in the Navajocountry ranges from groundemerges deep in inaccessablecanyons from rock stratawhich in otherregions might be satisfactoryaquif~rs. about2,800 feet, at themouth of the LittleColorado m River,to10,.416feet,at thetopof NavajoMountain Waterthat has percolatedinto the groundon somemesa~ ¯ (seepl. I). The mean altitude of theregion is about is returnedto theland surface by seepagealong the m 5~500feet, with only 156 square miles below 4000 base. tfeetand only 42 squaremiles above 9,000 feet (Gregory ¯ 1917,p. II). Theclimate of theregion also has an effectupon [] the ground-watersupplies. Summer rains are of the Mesas,buttes, and canyonsare the primarytopograp- torrentialtype and most of theprecipitation runs off graphicfeatures of the Navajocountry. Erosion re- withoutadequate opportunity to enterthe ground.Re- suitingfrom the strong winds and from occasional chargefrom winter storms and from snow-melt is greater m torrentialrains has produced a landscape that is sharply thanfrom summer rains, but the total annual precipH’atior: angularin appearance, is smalland therefore the total recharge is small-

The climateof the Navajocountry is oneof Theinadequate water supply of theregion is ! extremes,both of temperatureand precipitation. The reflectedin thetype of vegetation.Range lands are summersare hot and the winters are cold; long dry poorowing to theinadequate rainfall, and most of the [] spellsare punctuated by intense storms of shortduration, landis consideredunsuitable for raising cattle. Sheep Meanannual temperature is of theorder of 55° F., with raisingis theprincipal industry of theregion and even extremesranging from 105 ° F. downwardto -20° F. thisa marginalundertaking. Water holes are few and Mean precipitationis about10 inchesa year.The pre- thesheep frequently have to be herded8 to 10 milesto m cipitatlonis greaterthan the mean on theChuska and water.Overgrazing in the vicinityof waterholes II CarrizoMountains, Navajo Mountain and BlackMesa. is common,resulting in a tendencyto increaseerosion. Precipitationon the western part of the NavajoReserva- INna fewremote areas where grass is of betterthan [] tionaverages about 6½ inchesa year. averagequality, water for livestock is unavailable. g

Rainfallvaries widely from one year to another, irrigationby diversion of waterfrom streams is Occasionalwet yearsare succeededby dry years,and beingpracticed in someparts of the region.The n somedrought periods last for several years. The average largestpotential irrigation project is southof Shiprock, [] rainfallat II selectedstations in theArizona portion of withproposed diversion of waterfrom the SanJuan theregion is 9.22inches per year. During the 5 years River-A dam on ChinleWash near ManyFarms, in m 1946-50inclusive, average precipitation wasas follows: thecentral part of theReservation, furnishes water for m a smallirrigation project. Similar small-scale irrigation 1946 8.64inches projectsare at Moenkopi~Ganado~ and Tohatchl. 1947 9.35inches Neai"Tohatchi, flowing wells yield sufficient water ¯ 1948 7.94inches forirrigating a small acreage. Generally there is 1949 9.53inches littlehope for extensive irrigation from ground-water 4.46inches supplies. 1950 [] Thedrought that began in thefall of 1949has not GeologicFormations and their Water-Bearing Properties [] abatedas of JulyI, 1951.Records from the II stations wereavailable through April, 1951, and these records Stratigraphicrelations in theNavajo country are [] indicatethat the cumulative deficiency in precipitation difficultto determine,and in manycases the same g FromJanuary I, 1949to MayI~ 1951was 5.28 inches, formationor equivalentstratigraphic units have diff- erentnames at differentplaces. At thetime this paper The ground-watersupplies of the Navajocountry waswritten the geologic field work was far from corn- [] areprofoundly affected by thedominating factors of plete.The following discussion of thegeology of the I ! 148 I m,, NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN

I1 Navaiocountry is highlygeneralized and is intended In the FortWingate, N Mex.,area wells yield onlyas a backgroundfor the description of the ground- waterfrom both the limestonemember and the Glorieta I waterresources of theregion. Information available sandstonemember of the SanAndres formation. In the on thequantity and qualityof waterobtainable from Navaiocountry, these Permian sandstones generally are thedifferent formations is not complete and has not cleanand well sorted and relatively free of cementation beenfully analyzed at thepresent stage of investigation,thusallowing free movement of waterboth vertically i andlaterally. Rocksof the Misslssipplanthe Pennsylvanlan (?)and the Permian systems crop out in thewalls Thelowermost strata of Triassicage that occur in thecanyons of theColorado River and the Little the NavajoCountry comprise the Moenkopiformation an I ColoradoRiver, at theextreme western edge of the assemblageof siltstone,c aystone, and sandstone beds that Navaiocountry. Rocks of the upperpart of the lle unconformablyon the Permianrocks The thickness Permiancrop out in smallareas throughout the rangesfrom a fewfeet to morethan 400 feet. The I easternhalf of theregion. Onlythe upper200 Moenkopiformationcropsout ina beltparallelingthe to 800feet of the Permianrocks have economic value LittleColorado River downstream to Cameronand thence as sourcesof groundwater in the Navajocountry, northnear U S. Highway89 to Lee’sFerry. Rocks of the Moenkopiformation also are exposedin MonumentValley. I Thelargest source of waterin theregion that is The Moenkopicrops out alongU. S. Highway66 a few availablefrom rocks older than Permian is BlueSprings, mileseast of Sanders,Ariz. It is believedthat the Moen~ whichissues from the Mississippian Redwall limestone koplformation underlies most of theArizona portion of I in thebottom of a 2 200-footcanyonalongthe Little theregion. ColoradoRiver about 13 milesupstream from its con- fluencewith the ColoradoRiver. This spring flows TheMoenkopi formation has no valueas an aquifer about90~000 gallons per minute,but thewater in theNavajo country because the quantities obtainable is inaccessibleforuse by theIndians and is of poor are smalland the high mineral content makes the water quality, unfiteven for livestock use.

Permiansandstone, overlain by Permianlimestone, The Shinarumpconglomerate unconformably overlies I cropsout in thesouthwest part of theregion in the theMoenkopl formation in mostparts of theregion, and vicinityof Cameron~and westof U. S. Highway89 wherethe Moenkopiis notpresent, it I;eson Permian nearCedar Ridge. This sandstone is knownas the rocks.The Shinarumpconglomerate is composedof I Coconlnosandstoneand theoverlyinglimestoneas roundedpebbles and gravels, fragments of petrifiedwood, the Kalbablimestone. In MonumentValley, and in sandstone,siltstone, and claystone. It is believedthat CanyonDeChelly, a sandstoneof approximately theformation is theintroductory phase of thesedimentary equivalentage is referredto as theDeChelly, s~nd- sequencethat includes the Chinleformation. In the i stor~member of the Cutlerformation. Southeast of Nava]ocountry the thickness ranges from about 30 feet Gallup,N- Mex.,in the ZuniMountains the sand- to over150 feet.The Shinarumpconglomeratecropsout stoneand overlying limestone are knowncollectively in a beltalong the Little Colorado River to Cameron, I as theSan Andres formation and individuallyas the thencenorth along U. S. Highway89 to Lee’sFerry. Glorletasandstone member and the San Andres The formationcaps the monumentsin MonumentValley, limestonemember. These Permian rocks underlie a and cropsout in a beltsouthward along the Defiance largepart of theNavajo country, upliftfrom Round Rock to U. S. Highway66. Another I areaof exposureslies along the northern flank of the "[hePermian sandstones of the region are water- ZuniMountains. bearingin mostplaces. However, in manyplaces theylie too deep beneath the land surface to be within The water-bearingpropertiesof the Shlnarump I economicdrilling and pumpinglimits, and in other conglomerateare favorable.Wells tap the Shinarump localitiesthe water they contain is of unsuitable conglomeratein Black Creek Valley, along U. S. qualityfor domestic use. Wells that yield water Highway66 eastof Gallup,northeast of Chinle,and I fromtheCoconinosandstonehave been drilled in alongthe southern and southwestern margins of theNavajo the NavajoReservation at PineSprings, Klagetoh, IndianReservation. Ganado,St. Michaels,and near Cameronand Leupp. ! ! i 149 | NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN " ! TheChinle formation conformably overlies the The Wingatesandston% the Kayentaformation, and Shinarumpconglomerate. In the Navajocountry the the Navajosandstone. The principal area of outcrop i formationis divisibleinto three members: a lower is in thenorthwestern part of theregion and includes i membercomposed mostly of siltstoneand sandstone KaibitoPlateau and the areafrom Kayenta to Mexican beds;a middlemember that is predominatelyclaystane Water.Smaller areas of outcropsare along the east butin theeastern part of theregion contains sandstone sideof BlackCreek Valley and at thebase of thecliffs ¯ beds;and an uppermember that comprises alternating alongU- S. Highway66 eastof Gallup. bedsof siliceouslimestone and siltstane. An irregular

erosionalunconformity a few feetabove the topof TheWingate sandstone does not yieldwater to Jig theuppermost limestone is consideredto be theupper wellsin mostparts of theregion. No wellsare known ¯ boundaryof theformation. This position nearly coincides to yieldwater from the Kayentaformation. The Navojo II withthe topof the"B" memberof the Chinleformation sandstoneconstitutes one of thebest aquifers in the as describedby Gregory(1917, p. 42).The Chinle Navajocountry. On KaibitoPlateau the annualpre- ¯ formationcrops out over a largepart of theNavajo tip¯tat¯onis small but drainage is poorand a largepart country;the thickness ranging from about 900 feet to of themoisture that falls evaporates or is absorbedby over1,400 feet. Along the southernand southwestern therocks. The water that is absorbedpercolates down- sidesof theregion the formation is exposedin a beltmany wardthrough the Navajosandstone ta the topof the i mileswide forming the Painted Desert. Northward from underlyingrelatively impermeable Kayenta formation. [] theLittle Colorado River at Cameronthe belt becomes The Navajosandstone is water-bearingexcept in those narrowerand extends along the west side of EchoCliffs placeswhere local structural deformation has raised the i to Lee’sFerry. The is exposedin the formationabove the water table. The formationis ¯ i southernpart of MonumentValley and in a widebelt relativelyflee of solublemineral matter and therefore southwardfrom Many Farms to Ganadoin ChlnleValley, theground water ;t containsis of goodquality unless in anotherbelt southward from Round Rock along the contaminatedby soluble matter dissolved from other ¯ westside of the ChuskaMountains and down Black formations. CreekValley to a pointabout 7 milessouth of Saint Michaels,and in a beltextending eastward along the TheSan Rafaelunconformably overlies the Glen J northflank of theZuni Mountains. Canyongroup and is of definiteJurassic age. In the ¯ Navajocountry it includes,in ascendingorder the IB TheChinle formation is notsatisfactory as an Carmelformation, the Entrada sandstone, the Todilto aquiferin mostparts of the Navajocountry. Ground limestone,and theSummerville formation. The areal [] waterin theChinle formation generally is toohighly distributionof the San Rafael is lessextensive than mineralizedto be suitablefor domestic use, although thatof the GlenCanyon. San Rafaelstrata form a it is usuallysuitable for livestock. In most places only beltalong the peripheryof BlackMesa, southward limitedsupplies are available because the water-bearing fromthe Four Corners area along the west side of the i sandstonebeds are thin and of limitedareal extent. In ChuskaMountains to LuptanAriz. ¯ and parallelwith BlackCreek Valley the sandstones of theChinle formation U.S.Highway 66 east of Gallup. yieldwater more readily to wells. In thearea north of / theZuniMountains,along U. S. Highway66 a prom- Therocks of theSan Rafael group are not considered inentsandstone in the middlemember contains ground goodaClulfers. The Carmel formation yields limited R waterunder sufficient artesian pressure to causesome suppliesof watertowells in a few places.The permeability wellsto Flow. of theEntTada sandstone is generallylow and it is nota ¯ satisfactoryaquifer in mostplaces. The Todilto limestone, A. recentpaper by Harshbarger,Repenning and a dens%platy, unfractured unit is not water-bearlng. Jackson(1951) describes the occurrence, distribution, In theNavajo country the Summery¯lieformation consists andrelationships of the Jurassic rocks of theNavajo of ’intercalatedmudstone and poorly sorted sandstone. Due i country.In orderto minimizerepetition, the discussion to thesepoor water-bearing properties the formation does i of Jurassicrocks in thisreport will be brief, notyield water readily.

The GlenCanyon group is consideredto be of Accordingto Harshbarger,Repenning and Jackson i Jurassic(?) age. The groupincludes, in ascendingorder (1951)some of theUpper Jurassic units in thearea grade ! !

150 I I NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN I laterallysouthwestward into a distinctsandstone in southwesternColorado. The Mancosshale is not facies.This sandstonefacies is believedto be prim- water-bearingin the Navajocountry. i arilywind deposited,and from its optimumdevelop- ment near Cow Springs,Ariz., has been named the Lying conformablyabove the Mancosshale, the Cow Springssandstone by Harshbarger(see page 103 Mesaverdeformation consists of alternatingbeds of this guidebook).The Cow Springssandstone yields sandstone,slitstone and claystone.Coal commonly I waterto wellsin many partsof the Navajocountry, occursin the shaleunits. The formationhas been It is believedthat, with more knowledge of thisunit, dividedinto manymembers, but a detaileddiscussion groundwater can be developedin many localitiesin of themis beyondthe scope of this report.In the sufficientquantities for livestock and domesticuse. southeasternpart of the Navajocountry the following I memberscomprise the Mesaverdeformation in ascending In the Navajocountry the Morrisonformation order;the Gallupsandstone member, the Dilcocoal is representedby four members.These are, in memberthe Daltonsandstone member, the Bartlett i ascendingorder, the Bluffsandstone member, the barrenmember the Gibson coal member,the Hosta Recaptureshale member,the WestwaterCanyon sand- sandstonemember, and the Allisonbarren member stone member,and the BrushyBasin shale member. (Sears,J. D., Hunt C. B., and Hendricks,T. T., Both the Recaptureand the BrushyBasin members are 1941pp. 101-119).Some of the sandstonemembers are I high in claycontent and generallyare considered 250 feet or more thickand extendover severalhundred poor aquifers.The Bluff sandstonemember contains squaremiles. The aggregatethicknessof these members bedsof well sortedclean sand alternatingwith thin, in the Gallup-Zuniarea is of the orderof 2,000feet. poorlysorted siltstone beds. The memberyields to The Mesaverdeformation cropsout over mostof Black I threeflowing wells in the area betweenToadlena and Mesaand that partof the San JuanBasin which lies Shiprock,N. Mex. Similarlithologic relations are in the Navajocountry. presentin the WestwaterCanyon sandstone member and I it is considereda potential aquifer. The sandstonesof the Mesaverdeformation con- stituteone of the bestaquifers of the region.Throughout The Dakotasandstone is the lowermostof the the San Juan Basindozens of artesianwells produce water Cretaceousrocks in the region.This sandstoneis from thesesandstones. Few wellshave been drilledin I composedprincipally of medium-to coarse-gralned the northernpart of BlackMesa, but in the southernpart sand with a few conglomeraticlenses. In some places the Mesaverdeformation yields water to severalwells. the sandstoneis dividedinto two unitsby an intervening I zoneof siltstoneand claystonewith somecoal lenses. Tertiaryrocks lie unconformablyupon Cretaceous The Dakotasandstone is widelydistributed in the Navajo and olderrocks in someparts of the Navajocountry. country.The formationcrops out alongthe marginsof One zone about 20 to 30 miles wide extendssouth- BlackMesa and alongthe west and southsides of the eastwardfrom near Jeddito to the vicinityof WideRuins. I San Juan Basin.The thicknessranges from a few feet In thisarea the unnameddeposits consist of up to 300 to 100 feetinthe region, feetof poorlyconsolidated poorly sorted sandstone with The Dakotasandstone is considereda good aquifer intercalcatedlayers of siltstone,claystone, and volcanic in the Navajocountry. Many wells in the southern flowsand tufts.The ChuskaMountains are anotherarea I part of BlackMesa and alongthe marginsof the San of Tertiarydeposits. In thisvicinity the Tohatchl shale, Joan Basinobtain water from the formation, about200 to 300feet thick,is overlainby about700 feet of Chuskasandstone. At the easternside of the Navajo I Conformablyoverlying the Dakotasandstone, the country,in the centerof the San Juan Basin,as muchas Mencosshale consists of brownto blacksiltstone and severalthousand feet of Tertiarymaterials have been clays,onewith occasional thin streaks of sandstone deposited. andgypsiferous stringers. It is from500 to moret~han i I, 000 feetthick. The Mancosshale crops out around The water-bearingproperties of the Tertiarydeposits the marginsof Black Mesaand alongsome of the stream are variable,and the rocksare not consideredgood aquifers courseswithin the mesa;along _the southern and south- in the region.In the Jeddito-WideRuins area the rocks i westernsides of theSan JuanBasin;andin a largearea in same placeshave satisfactoryproperties as an aquifer, extendingnorthward from Toadlenato the type locality but commonlythey lle in mesas,so that waterwhich may ! ! I 151 | NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN I

havepercolated into them seeps out againaround Gallup,N. Mex.,the steepwesterly dipping Nutria ! thebase. Precipitation on the is monocllneforms the northwest flank of theZuni Uplift higherthan average; no wellshave been drilled be- whichdelimits the southwestern part of theSan Juan i causesprings and small water holes yield sufficient Basin.Two prominent laccolithic mountains occur in [] waterfor livestockand domestic use. The Tertiary the northernpart of the Navajocountry. These are rocksin thecentral part of theSan Juan Basin lie the CarrizoMountains which lie northof the Defiance i mostlyoutside the boundaryof theNava[o Indian Uplift~and NavajoMountain which lles in the north- [] Reservation.Within the Reservation these rocks westernpart of theregion (see pl. I). The regional i supplywater for several shallow dug wells, attitudeof the bedsis modifiedby manylocal mono- clines,anticlines, and synclines. Each of thesehas [] Alluvialdeposits, consisting mostly of fine- its effecton the occurrenceof groundwater. Generally I grainedunconsolidated sand with some gravel silt groundwater is morereadily available in thesyncline andclay, underlie most of thestreams and drainage thanon an anticline.Due to structuralhighs, aquifers channelsin theregion. The thickness of thesedeposits are exposedto rechargefrom rainfall, snowmelt and i rangesfrom a few inchesto a maximumof about200 runoff. i feet,but in mostplaces the thickness is lessthan 50 feet. Faultingis notvery extensive in theNava[o i country.There are several notable strike faults along II TheQuaternary alluvium is water-bearingin those themonoclinal limbs of theDefiance Uplift and small placeswhere recharge is availablefrom springs or flood tensionfaults occur at severallocalities along the runoff.Where there is 10 feetor moreof alluviumbe- elongateddome. In the southwesternpart of the region [] lowthe water table there is usuallysufficient water faultsof smalldisplacement have been found in the [] availableto supplya dugwell or an infiltrationgallery. Kaibablimestone. In thisarea the faults and joints However,the storage capacity of thealluvium is small arebelieved to facilitaterecharge to theunderlying andthe water table fluctuates rapidly in responseto Coconinosandstone. Some faulting has occurredin i changesin therelation between recharge and discharge, the Mesaverdeand older rocks in the extremeeastern i Furthermore,down-cutting of the streamshas lowered partof theregion south of Crow¯point. thewater table in manyplaces and reduced the storage [] capacityof thealluvium. Thestructural features of theregion are of major II importancein the occurrenceof groundwater. The Igneousrocks in theNavajo country occur as BlackMesa basin and theSan JuanBasin are large dikes,necks, and lava flows. The regionis dottedwith saucer-shapeddepressions. Water enters the permeable i theseigneous rocks particularly in the Hop¯ Buttes formationswhere they are exposed at the landsurface Ill volcanicfield south of the HopiIndian Villages. The andmoves down dip toward the center of theBasin. igneousrocks of theregion are not known to be water- Thewater moves slowly and dissolvessome of thesol- gg bearingexcept in BuellPark, where springs issue from ublemineral matter contained in therocks through agglomeraticbreccia. Three springs in thisarea yield whichit passes,becoming progressively more highly | 150to 250gallons per minute, mineralized.The ground water is dischargedfrom the formationby springsin canyonsor alongmesa escarp- Themajor structural features of theNava[o ments,by pumpedand flawingwells, or by upward i countryare the BlackMesa Basin the southwestern seel:-ageinto overlying beds. partof theSan JuanBasin and the interveningDefiance Uplift(see pl, I). The Black Mesa Basin is in theAriz- In selectinga site for a waterwell the structural i ona partof the Nava[ocountry. The eastward-dipplng relationsshould be considered.Wells drilled near [] b~dsof theKaibab and Echo Cliffs monoclines form the theoutcrop will penetrate the formation above the westernside of thebasin. The Black Mesa Basin is zoneof saturation.Farther down dip, a greaterwell boundedon the northby the CombRidge monocline, B depthwill be requiredI butthe formation will be [] Thewest flank of theDefiance Uplift is theeastern saturatedand the well will be successful.Toward the marginof thebasin. T he easternmonoclinal limb of centerof thebasin1 many miles from the outcrop zone, thisbroad anti cllnal structure forms the western edge waterwould be encounteredat greatdepths and may of the San JuanBasin. Two and one-halfmiles east of be toohighly mineralized for domestic or livestockuse. i ! !

152 i I NEW MEXICO GEOLOGICAL SOCIETY ¯*¯¯SECOND FIELD CONFERENCE * SAN JUAN BASIN ! Localstructural conditions alter these generalized witha drawdownof 36 feet.it is believedthat many ¯ relations.Faults impede or divertthe movement of morewells for livestock and domestic use could be groundwater and thus affect the likelihood of successfullydeveloped along thenorth end of the I obtainingwater from wells in somelocalities. DefianceUplift, in BlackCreekValley, along the northflanks of theZuni Mountains, possibly in parts PrincipalAquifers of theRegion of ChinleValley, and possiblyin thesouthern and i southwesternpart of the Navajocountry. In general,the aquifers of theNavajo country areless permeabl e thanthe principal aquifers in . . TheNavajo sandstone, inthe western andnorth- otherparts of Arizonaand New Mexico.The reader westernpart of theNaVajo country, is consideredone: .I shoulclbear in mindthat the terms "good aquifer" of thebest aquifers. A well recently drilled to a and "pooraquifer" are relative. For example,in. depthof 1,240feet at KaibitoDay Schoolyielded 10 theNaval o countrya wellthat yields as muchas 100 gallonsper minute with a drawdownof I footduring I gallonsperminuteis rare,butin partsof southern a bailingtest. A well¯drilled 840 feet deep at ¯ Arizonaand New Mexicoa wellthat yields less than Kayentain 1948yielded 100 gallons per minute with 500gallons per minute is considereda failure. The a drawdownof 184 feetduring a pumpingtest. Three permeabilityof the aquifers in theNavajo country~ springsat TubaCity yield¯ a totalof morethan 125 I basedon pumpingtests, ranges from I to 40 gallons gallonsper minute.In a canyona fewmiles east of per dayper foot. The¯permeability of the gravels TubaCity a groupof springsyield about 200 gallons of the GilaRiver, near Safford, Ariz., commonly per minute.Other springs, west of TubaCity~ yield is 500to 2,000gallons perdayperfoot. over200 gallonsper minute.Many more wells could I be drilledinto the Navaio sandstone for livestock and ThePermian sandstones of theregion constitute domesticuse without overdeveloping theformation. one of the principalaquifers. Recharge occurs Therequired depth ranges from 300 to ITS00feet. i directlyon theoutcrops and through the overlying limestonewhere it is faultedor deeplyfractured. In TheJurassic Cow Springs sandstone described by thesouthwest part of theNavajo country several Harshbarger,Repennlng, and Jackson (1951, p. 103) wlndmill-poweredwells pump water from the Coconino potentiallya good aquifer. The formationis widespread I sandstoneat a rateof 3 to 5 gallonsper minute. These andapparently has uniformlygood water-bearing wellsarebelieved capable of producinggreater discharges properties.The formation is believedcapable of withlarger pumping equipment. Two wellsrecently additionaldeyelopment in some areas. I drilledto a depthof about2,450feet¯nearKI.agetoh eachyield 35 gallonsper minute from the Coconino TheDakota sandstone is water-bearingin most sandstone.A well at Ganadois reportedto be capable placesand is considereda good aquifer in theregion. gg Of yielding100 gallonsper minute from the Coconino Theground water is of suitablequality for domestic II sandstone.Nutria Springs which issue from the usein mostplaces, although in thoselocalities where Glorietasandstone member of the SanAndres formation shaleand coal predominate the water is morehighly on thesouthwest flank of theZuni Mountains, discharge mineralized.Further development for livestock use morethan 200 gallons per minute.Other notable springs is justifiedin mostof theareas where the formation I are in the FortDefiance area and nearToadlena. Areas is withineconomic reach of thedrill. of potentialfuture development of the Permian sand- stonesfor livestockand domestic water supplies include Consideringthe areal distribution andthe quantity I ChlnleValley south of Chinle,Black Creek Valley from of wateravailabletowells,theMesaverdeformation Red Lakesouth to Oak Spring,and furtherdevelopment of theSan Juan Basin contains the best aquifers in the in tlloseareas where wells have already been drilled, region.Many of the wellsin thebasinflow; a well Therequired depth of wellswill range from 800 to 2 000 ,873feet deep, drilled a fewmiles east of TwinLakes I feet. " flows90 gallonsper minute and has a staticshut-in pressurethat would lift water over 250 feet above The Shinarumpconglomerate is water-bearing in a rthe landsurface. The Gallupsandstone member I largepartof theregion.Thegreatestyieldis obtained the Daltonsandstone member, and the Hostasand- fromwells in BlackCreek Valley; at St. Michael’s stonemember are theprincipal water-bearlng Schoola yieldof 50 gallonsper minute was obtained, membersof the Mesaverdeformation and all are ! ! I 153 I NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN I believedcapable of furtherdevelopment. Water springswhose source is underlyingbeds. At the mouth fromthe Mesaverdeformation is of satisfactory of CanyonDeChelly the alluviumis over 200 feet qualityfor domesticuse in someplaces, but in other thickand is rechargedfrom surface runoff and effluent I placesthe watercontains excessive amounts of waterfrom the Permiansandstones along the Defiance sodium,sulfate,and bicarbonate. In some places uplift.A welldrilled into the alluviumto supply fluorideconcentrations are excessive.In the Black the communityof Chinleyielded 500 gallonsper minute Mesa Basinfew wellshave been drilledinto the with a drawdownof 65 feet. I Mesaverdeformation but threewells drilled during Summary thefirst half of 1951indicate that small supplies are availablein thoseareas where structural and recharge Althoughground water is widelydistributed in conditionsare favorable.Here also, the water is I the Navajocountry, the quantityavailable at any softbut is highlymineralized in somelocalities, localityis small.The aridclimate and the rough terrainof canyons,mesas, cliffs, and buttescombine The Quaternaryalluvium is not considereda to reducethe amountof rechargeavailable to the dependableaquifer throughout the Navajocountry I aquifers.The aquifershove low permeabilityand do becausethe amountof waterit containsfluctuates not transmitwater readily, kithologic changes in quicklyin responseto changesin recharge.Many someof theformations affect the availability of shallowwells fail in droughtyears. Water from the groundwater to wellsin somelocalities. Locally, I alluviumhas a widerange of dissolvedsolids Con- structuraluplifts have raised some formations above centrationand may be of good,fair, or poorquality, the watertable and havediverted the slowlymoving dependlngupon local conditions.Nevertheless, the groundwater in other localities.However, in most alluviumconstitutes an aquiferthat can be tapped I parts9 f the Navajocountry sufficient ground water for relativelycheaply and, if it is realizedthat ,wells livestockand domesticuse can be developed,although arelikely to failat times,can be usedto furnish in somea~eas wells as deepas 1,500to 2,000feet are livestockand domesticwater supplies. The alluvium requiredto obtainsufficient water. There is little I is notadequate to supplywater for irrigation, school, hope of developingground water in sufficientquantity communities,or hospitals,except in thoseplaces for irrigationexcept from alluviumin placeswhere whererecharge occurs from perennialstreams or from rechargeis abundant. I I

SelectedReferences I

Gregory,H. E. (1917)Geology of the Navajocountry: U. S. Geol. SurveyProf. Paper 93.

Harshbarger,J. W., Repenning,C. A., and Jackson,R. L. (1951)Jurassic stratigraphy of the Navajocountry; I New Mexico GeologicalSociety Guidebook of the San Juan Basin, New Mexico and Arizona, pp. 93-103. I Sears,J. D., Hunt,C. B., and Hendricks,T. A., (1941)Transgressive and regressiveCretaceous deposits southernSan Juan Basin,New Mexico:U. S. Geol. Survey Prof. Paper 193-F. I I I I

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