THE USE OF SOILS INFORMATION ON THE CENTRAL VALLEY PROJECT, CALIFORNIA1

WALTER W. WEIR AND R. EARL SroRiE2

ONE of the main purposes of the Central ValleyProject of California is the redistribution of ir-

rigation waters in the Sacramento and San JoaquinValleys. The runoff in the Sacramento Valley con-stitutes about two-thirds of the water supply of thecombined valleys while the San Joaquin Valley con-tains about two-thirds of the irrigable land. Briefly,the water distribution plans for the project are ( i)storage of flood waters by the Shasta Dam on theSacramento River below the mouth of the Pit River;(2) a regulated, all season, flow in the lower Sacra-mento; (3) storage on the San Joaquin River bymeans of the Friant Dam; (4) diversion up the SanJoaquin Valley from the Friant reservoir, a distanceof about 165 miles, so as to provide supplementalsupply for lands in the upper valley; and (5) pump-ing Sacramento River water up the San Joaquin Val-ley, about no miles to Mendota, where it will be usedto irrigate lands previously irrigated from the SanJoaquin River below the dam. (See Fig. i.)

NEED FOR SOIL DATAAlthough the Central Valley Project is one of the

nation's outstanding engineering undertakings in-volving the ultimate expenditure of hundreds of mil-lions of dollars, an important, although somewhat less

FIG. i.—Panoramic Perspective of Central Valley Project,California.

spectacular, feature has been the attention given tosoils. The major portion of the state's 5 million acresof irrigated land is located in the Central Valley, butportions of this, especially in the upper or southernend of the San Joaquin Valley, has not had adequatewater and there are large areas, also mainly in theSan Joaquin Valley, which do not now have irriga-tion at all. With conservation, and storage on thestreams in both valleys, there will still be insufficientwater to irrigate all the lands in both valleys. It isthis fact in particular, that has made information ofthe soils of these valleys necessary in order wisely todetermine which lands should be provided with waterand which should be denied water.

Potentially, at least, there are some lands, not nowirrigated which are more productive than other areaswhich are quite adequately supplied with water. Thesupplying of supplemental water to lands now irri-gated, the irrigation of new lands and the redistribu-tion of water between lands of varying quality in-volved a problem of great economic importance, thesolution of which determined the economic feasibilityof the project. The main question was of course, willthe increase in yields on lands now inadequately ir-rigated plus the yields on lands not now irrigated,pay for the irrigation works? Obviously the answerdepends upon the cost of the works, the price of agri-cultural products and the productive capacity of thesoil. The engineer can estimate the probable costs,the economist can make some sort of prediction offuture prices and the soil scientist has the job of es-timating the productive capacity of the soils.

We knew of this project and its probable needs asfar back as 1933 when the University of Californiastarted a detailed soil survey of those portions ofthe valley where information was either meagre orlacking. Most of the new lands to be irrigated as wellas those to be supplied with additional water were inTulare, Kern, and Kings Counties, and soil surveysof these areas were pushed to completion during thenext four years (1934-37).3 None of these reports

Contribution from the Division of Soils, University of California, Berkeley, Calif.2Drainage Engineer and Associate Soil Technologist, respectively.3STORIE, R. E., and CARPENTER, E. J., Soil survey of the Visalia Area California. U.S.D.A. Bur. of Chem. and Soils, Series

1934. (In Press.)STORIE, R. E., el al. Soil survey of the Pixley Area, California. U.S.D.A. Bur. of Chem. and Soils, Series 1935. (In Press.)ANDERSON, A. C., et al. Soil survey of the Wasco Area, California. U.S.D.A. Bur. of Chem. and Soils, Series 1935. (In Press.)COLE, R. C., et al. Soil survey of the Bakersfield Area, California. U.S.D.A. Bur. of Chem. and Soils, Series 1936. (In Press.)RETZER, JOHN L., et al. Soil survey of the Kings County Area, California. U.S.D.A. Bur. of Cherri. and Soils, Series 1937.

(In MS.)

366

WEIR AND STORIE: USE OF SOILS INFORMATION 367

have as yet been published, but the data have beenmade available to the Central Valley Water Authori-ty arid the Bureau of Reclamation, U. S. Dept, of theInterior under whose jurisdiction the project is be-ing constructed.

To the soils man a detailed soil survey and a de-scription of the soils so delineated unfolds a wealthof information but the material is often a little tootechnical and some times too detailed for the engi-neer or the economist to use to its fullest extent. Sinceit was engineers and economists who were to makethe ultimate use of this information we used the soilsas basic data from which to prepare maps and tabu-lar material on alkali, soil ratings, land use, naturalland types, and land use-capability. (See Fig. 2.)

METHODSThe soil surveys were of the standard type long

since developed by the Bureau of Soils and its succes-sors, with whom the University of California hasbeen cooperating for nearly 30 years. The methodsare so familiar as need no further discussion here.Fig. 2, A is an example of a detailed soil map.

ALKALIAlkali is an important feature of the soils of the

desert and semi-desert regions such as the San Joa-quin Valley and must be thoroughly considered insuch an undertaking as this, consequently, the ex-tent and distribution of alkali in these soils receivedspecial attention. The alkali data were superimposedon the soil map and three degrees of concentrationwere indicated. Alkali affected areas were enclosed inred lines, each body being designated by a symbolsuch as "A" for strongly affected areas in which thegrowth of crops is prohibited by the high concentra-tions ; "M" moderately affected areas in which con-centrations were sufficient to prohibit the growth ofmany cultivated crops but not to prohibit the growthof some grasses; "S" slightly affected or spotted areasin which the effect on cultivated crops was onlyslight or inextensive and visible concentration wasnot readily apparent. Areas that were free from al-kali were left without a symbol or were marked "F".

Alkali determinations were made on carefully se-lected soil samples by means of a Wheatstone alkali-resistance-bridge together with close field observa-tions on the appearance of the land and its vegetation.At each point where an alkali sample was taken theamount of alkali present was shown on the map inred in the form of a fraction, the numerator being

the percentage of alkali in the surface foot and thedenominator the average percentage of alkali for a6-foot column, i.e., . The Central Valley Water0.05Authority was furnished with an alkali map of thearea on the same scale as the soil map showing thedifferent grades of alkali in color. (See Fig. 2, B.)

From the soils and alkali data, a soil rating mapwas prepared showing the Storie Index4 rating foreach soil type and each soil-alkali complex.

RATING

The Storie Index is prepared by first grouping thesoils into profile groups as follows : Group I — soil onrecent or young alluvial fans or other secondary de-posits having relatively uniform profiles which areunderlain by unconsolidated material; Group II —soils on older alluvial fans, alluvial plains or terraceshaving moderately dense subsoils underlain by un-consolidated material; Group III — soils on olderplains or terraces having dense clay subsoils under-lain by unconsolidated material ; Group IV — soils onolder plains or terraces having hardpan subsoil layersgenerally underlain by unconsolidated material ;Group V — soils on older terraces and upland areashaving dense clay subsoils resting on moderately con-solidated substratum ; and Group VI — soils on up-land areas underlain by bedrock. '

Each profile group is given a percentage rating,called the "A" factor rating, which ranges from 95-100% for group I, 80-95% f°r grouP H> 40-80%for group III, 5-60% (depending on the depth tohardpan) for group IV, 20-40% for group V, and20-70%, depending on the depth to bedrock, forgroup VI.

Each soil type is given "B" factor rating based onthe texture of the surface soil ranging from 100%for very fine sandy loam, fine sandy loam, loam, andsilt loam down to 50% for clay and as low as 10%for very stony sands.

Other factors, such as drainage, alkali, acidity, ero-sion, etc., are grouped as "C" factor and given per-centage rating covering a rather wide range in values.An example of the "C" factor rating for alkali wouldbe as follows : Alkali-free, 100% ; slightly affected, 60to 95% ; moderately affected, 15 to 60% ; and, strong-ly affected, 5 to 15%.

The Index rating of any soil is determined by mul-tiplying the three factors together A X B X C = In-dex. The Storie Index is a single figure expressing

4SxoRiE, R. E., An index for rating the agricultural value of soils. Univ. of Calif. Agr. Exp. Sta. Bul. 556. 1933. (Revised 1937.)

368 SOIL SCIENCE SOCIETY PROCEEDINGS 1940

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-NATURAL LAND DIVISIONS

RATING

RATING

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} STRONG CONCENTRATIONS

.NATURAL LAND DIVISIONS~| . LEVEL TO GENTLY SLOPING, DEEP. MEOHJM TO LIGHT TEXTURE IRRIGABLEJ ) PA

l^d SAME AS A). SLIGHT ALKALI.

"J jj(3 LEVEL TO GENTLY SLOPING, COARSE TEXTUHED

l L OVERFLOWED, COARSE TEXTURCO, LOW IN NUTRIENTS1 FLAT AREAS, MEDIUM TO HEAVY TEXTURE, FREE TO SLIGHT Al

•J I~l _ FLAT AREAS, HEAVY TEXTURES, DRAINAGE FAIR TO POOR, SLIGHT ALKALIJg junw1 3 FLAT AREAS, HEAVY TEXTURES, DRAINAGE DEFICIENT, MODERATE ALKALIJ j RATING

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(I' I 7| DIVISIONS Ai,Ai«A» SUITABLE FOR WOE RANGE OF FIELD CROPS, ft L FA L FA, ORCHARDS, AND Vl

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FIG. 2.—Presentation of soils information in map form for use in Central Valley Project, California. A, soils; B, alkali; C, soilrating; D, natural land divisions; B, use capability.

WEIR AND STORIE I USE OF SOILS INFORMATION 369

the relative agricultural rating of the soil based solelyon soil characteristics. It is entirely independent ofsuch factors as location, availability of irrigationwater, frost hazards, etc. The values assigned to eachof the rating factors have been carefully worked outby Storie and associates from long experience withthe soils of California and when used with a reason-able degree of judgment and understanding give a fig-ure which has proven to be remarkably consistentwith actual production. One should remember howev-er, that the soil rating can be no better than the soilsurvey from which a knowledge of the soil is obtainedand the more accurate and detailed the soil surveythe more accurately can the soils be rated.

Soils rating between 80 and 100 are considered asexcellent, or grade i soils; those rating between 60and 79 are considered good, or grade 2 soils; .thosehaving a rating of 40 to 59 are fair, or grade 3 soils;20 to 39 poor, or grade 4 soils; 10 to 19 very poor, orgrade 5 soils; o to 9 nonagricultural areas, or grade6 soils. A soil rating map was prepared which showednot only the index rating on each body of soil but wasalso colored to show the grades in which the soil wasplaced. The index rating figures on the map aid ininterpreting the relative value of any two particularsoils even though they rnay be in the same grade; asfor instance, a soil rating 79 would be in the samegrade as one rating 60, a difference of 19% in theextreme, whereas a soil rating 80, would be one gradehigher than a soil rating 79, although the differenceis only i%. (See Fig. 2, C.)

NATURAL LAND DIVISIONSAlthough the Storie Index rating has proven to be

a very useful tool in determining the relative valueof any two or more soils it gives, as has already beenmentioned, a figure which relates only to the charac-teristics of soil itself and is independent of environ-mental factors and as such does not necessarily indi-cate the feasibility of irrigation or the best crop usesfor any particular soil. As for example, soil rating60% would be classed as a good soil but it may befound on a rolling hilly area where irrigation wouldbe entirely infeasible or in an inexcessible area wheretransportation would be costly ; or it may be on gentlesloping alluvial lands where it could be readily irri-gated and easily farmed. Obviously the cropping andland-use features of these three tracts would be verydifferent.

In order to make the soils information and the

rating tables more usable, to those who are develop-ing the Central Valley project, a fourth map combin-ing these features with the natural physiographic fea-tures of the area was made. This combination hasbeen termed the "natural land division".5 In this thesoils have been grouped as follows: Division A con-sists of recent and young secondary soils havingsmooth gently sloping relief; division B consists ofsoils in basins or semi-basins that have slow surfacedrainage and smooth very gently sloping relief; divis-ion C consists of low terrace soils, having well-drainedmoderately to strongly developed secondary profileswith a gently sloping hummocky relief; division Dconsists of strongly developed secondary soils occu-pying high terrace positions with rolling or hum-mocky relief; division E consists of primary soils oc-cupying rolling or hilly relief. Each of these majordivisions is further divided into groups of soils hav-ing similar or closely related textures, profiles, simi-lar drainage, and alkali conditions, etc. Of great im-portance is the fact that each division has similarcultural requirements, and, a narrow range in indexrating. These subdivisions are indicated by subscriptsto the division letter as AI, Az, A3, etc., BJ, B2, etc.with the better agricultural soils in each major divis-ion having the lower subscript number. This group-ing of soils into natural land type divisions has notyet been fully standardized for the entire state andso far each areas surveyed has been grouped in thismanner somewhat independent of other areas. It isnot however, difficult to include areas as large as acounty on a single set of the natural land type divis-ions and still keep the groups to a reasonable number.Generally, a county "natural land division" map willshow 15 to 25 types, where there are 50 to 100 soiltypes on the soil map. (See Fig. 2, D.)

The natural land divisions are shown on a map incolor with various shades of yellow for division Asoils, shades of green for division B soils, blues fordivision C soils, purples for division D soils and pinksto reds for division E.

USE CAPABILITYWe have found the natural land division classifi-

cation to be most useful in determining the use-capa-bility of our soils since all soils having similar profiledevelopment, a narrow range in texture, location, ortopography would be grouped together. Each divisionalso has a narrow range in index rating. It is obvi-ous therefore that soils in any natural land type group

'STORIE, R. E., The natural land divisions of Santa Cruz County, California their utilization and adaptation. Univ. of Calif.Agr. Exp. Sta. Bul. 638. 1940.

370 SOIL SCIENCE SOCIETY PROCEEDINGS 1940

would be so nearly alike and have so much in com-mon that there would be practically no difference intheir general crop response. (See Fig. 2, E.)

USE OF DATA

DISTRIBUTION OF WATER

• The practical application of this material was theuse made of it by the Bureau of Reclamation in esti-mating the amount of water charges that might beborn by the various units which might be servedwith water. For example it was found that certainareas were composed of soils which, although topo-graphically suited for irrigation, contained so muchalkali or had subsoils so heavy textured that theycould not be expected to produce sufficiently tobear the cost of water. There is more land of ex-cellent to good quality in the upper San Joaquin Val-ley than can be irrigated with the available water andit is sound economics as well as sound engineering touse the water only on the better lands. In the pastthe Bureau of Reclamation, and other irrigation en-terprises as well, have been guilty of providing waterfor lands that could not pay the costs, but on this proj-ect there appears to be an honest attempt to see thatsimilar errors are not repeated. Such precautions arehowever, not always graciously received by those whoown lands from which there may be a profit throughsubdivision and closer settlement such as usually ac-companies irrigation.

WATER RIGHTS

A detailed soil and alkali survey and the accom-panying compiled soil rating and land use-capabilitymaps has been made of the riparian lands along theSan Joaquin River from the site of the Friant Damto its outlet into the Delta.6 In California lands ripari-an to the streams have certain rights to water whichare superior to appropriated rights but it has notalways proven to be the most economical use of thewater. Frequently those low lying basin areas adja-cent to the streams contain heavy textured soils orsoils with high concentrations of alkali which areunfit for cultivated crops. Water obtained throughriparian rights is frequently used for the irrigation

of salt grass and other native pastures when it mightbe used elsewhere for the production of much highervalued crops. A part of the Central Valley plan isthe transfer of water from the poorer of these ripari-an lands to better lands through the purchase of theselands and their water rights. Land use-capability sur-veys based on a thorough knowledge of the soils of thearea have been extremely valuable in determining notonly what lands should be deprived of their water butthe price that should be paid for such lands and theirwater rights. Reliable information on the quality ofthe soils in these areas has been a material aid in theelimination of serious controversy between the own-ers and the purchasers of these lands and waterrights. Had a full knowledge of soil conditions notbeen furnished to both parties, long and involvedlegal-entanglements might have seriously delayed thework.

As has already been mentioned the construction ofthe Friant Dam on the San Joaquin River and thediversion of the water upstream about 165 miles willfor the most part deprive those lands lower down thevalley of this water. Provision however, is being madeto pump Sacramento River water from the Deltacountry, up the San Joaquin River as far as Mendota,about no miles, and from this point distribute it notonly to lands formerly irrigated with San JoaquinRiver water but furnish water for additional landsnot now irrigated or irrigated by pumping from wells.For those lands on which Sacramento River water isto be substituted, a question has been raised as tothe quality of the two waters and, again, it was in-formation on soils which disclosed such factors asdrainage, porosity, permeability, and use-capabilitythat determined the permissable salt content of theproposed water supply.

The completion of the Shasta Dam on the Sacra-mento River and the resulting stabilization of theflow in that river will make it entirely feasible, froman engineering standpoint, to pump more water upthe San Joaquin River to Mendota than will be re-quired to replace the San Joaquin River water nowused in this area. The question then arose as to loca-tion and quality of the land upon which this addition-al water may be used.

6The Division of Soil Technology, University of California, made soil and land classification surveys and reports for the CentralValley Water Authority on land riparian to the San Joaquin River during 1937-1939 under the following titles:

Soil Survey of the Friant to Gravelly Ford AreaSoil Survey of the Gravelly Ford to Mendota AreaSoil Survey of the Properties of Chowchilla Farms, Inc.Soil Survey of the Stevenson Colony LandsSoil Survey of the Patterson Colony LandsSoil Survey of the Merced to Tuolumne River AreaSoil Survey of the Merced River to the Delta Area

WEIR AND STORIE: USE OF SOILS INFORMATION

LOCATION OF CANALS, ETC.

Surveys have recently been completed covering allof the valley lands in the the west side of the SanJoaquin River from the Fresno-Merced County linenorthward to the mouth of the river and the soils, al-kali, index rating, and use-capability maps of this areahave been made available to the Water Project Au-thority.7 One question remained unanswered, how-ever, namely: of what quality is the land in westernFresno County above the present gravity diversion atMendota? The Bureau of Reclamation wanted thisinformation in order to determine the location andsize of canals and the maximum feasible pumpinglift from the new Mendota diversions. The Divisionof Soils, of the University of California was request-ed to furnish the detailed soils information coveringthat portion of this area lying between the presentirrigated area (approximate elevation 160 feet) andthe 410 foot contour, in other words that area whichmay be reached with a maximum pumping lift of 200to 250 feet.

This survey,8 covering about 240,000 acres dis-•closed some very interesting things about this some-what neglected section of the valley. Considerableacreage of rich, recent alluvial soils of medium toheavy textures, practically free from alkali, lie abovethe 200 foot contour. At the lower elevations coveredby the survey it was found the soils contain some al-kali and if irrigated must be handled with care inorder to prevent waterlogging and a rise in the watertable which would tend to concentrate the alkali onthe surface. Maps and reports on the soils, StorieIndex rating and use-capability classes of the areahas been supplied the Bureau of Reclamation engi-neers who can now intelligently determine the eco-nomical water lift and the location and size of thecanals and pumping plants necessary. These data canalso be used as an aid in land use planning, subdivis-ions for closer settlement and development of thearea.

SUMMARY AND CONCLUSIONSBriefly stated, the Central Valley Project is an

undertaking for the redistribution of irrigation waterand flood control in the Sacramento-San Joaquin Val-ley of California. The Bureau of Reclamation, underwhose jurisdiction the project is being designed andconstructed has made extensive use of soil informa-tion furnished and interpreted, through the use ofalkali, index rating and use capability maps, in deter-mining :1. The location and extent of good soils which can

be profitably supplied with supplemental water.2. Areas of poor soils which should be deprived of

water for economic or other reasons.3. The construction costs which the various units

may be expected to assume.4. The location and size of canals and pumping

plants, and5. The quality and quantity of water which may be

safely used.The soil survey and its interpretation in terms of

soil rating, natural land types and use-capabilityclasses is receiving wider and better appreciationamong engineers, land development agencies andassessors throughout California and the demand forthis work is greater than our present capacity to fur-nish it with available funds and personnel.

Many land development schemes in the West whichhave proven to be failures or partial failures couldhave been prevented had detailed information on thesoils of the area been available, and used. The timehas passed when unfavorable soil information is with-held for fear that it might be detrimental to certaininterests and all concerned now appear to be anxiousfor the truth regarding the soil.

It must be remembered however, that informationon the characteristics of the soil as disclosed by a de-tailed soil survey is fundamental and no interpretationis possible until the basic data is available, and thebetter the work is done, the better and more reliableare the interpretations.

'COLE, R. C., and KOEHLER, L. F. Soil survey of the Tracy Area, California. U.S.D.A. Bur. of Plant Ind. Soil Survey, Series1937. (In MS.)

COLE, R. C., et al. Soil survey of the Newman Area, California. U.S.D.A. Bur. of Plant Ind. Soil Survey, Series 1938. .(In MS.)COLE, R. C., et al. Soil survey of the Los Banos Area, California. U.S.D.A. Bur. of Plant Ind. Soil Survey, Series 1939. (In MS.)"HARRADINE, F. F., Soil survey of the Mendota Area, California. (In MS.)