WATER INFORMATlON BULLETIN NO. I6

A RECONNAISSANCE OF THE WATER RESOURCES

IN THE PORTNEUF RIVER BASTN, IDAHO

by

R.F. Norvitch and A.L. Lawn

United States GeologicaI Survey

Prepared by the United States Geological Survey

in Cooperation with

Idaho Department of Reclamation

Published by

Idaho Department of Reclamation

R. Keith Higinson

State Reclamation Engineer CONTENTS

Page Abstract ...... 1 Introduction ...... 2 Purpose and scope ...... 2 Previous studies ...... 7 Acknowledg~nenlts ...... -4 Numbering systcrn ...... 4 Use ot' metric units ...... 4 Physiography ...... h Topography and landforms ...... h Drainage ...... 7 Uppervalley ...... 7 Lower valley ...... 8 Climate ...... 8 Gcologic units and their water- bearing characteristics ...... 11 Wa tcr resources ...... 1 6 Sources ...... 16 Groundwater ...... IS Water-level fluctuations ...... 19 Well and aquifer charactcrjstics ...... 23 Springs ...... 24 Surface water ...... 31 Floods ...... 39 Quality or water ...... 40 Useofwafer ...... 45 Ground-water irrigation ...... 45 AboveTopaz ...... 45 BelowTopaz ...... 47 Surface- water irrigation ...... 47 Municipal and industrial scrpplies ...... 48 CONTENTS.. continued

Page Interrelation of surface and ground water and the effects of pumping wells ...... 50 Recommendations for future studies ...... -51 Waterbudget ...... 51 Water- table [napping ...... 52 Hydrology of aquifers ...... -53 Irrigation system ...... 53 Geologic mapping and deep test drilling ...... 54 Special problems ...... 54 Summary ...... 54 References cited ...... 56

ILLUSTRATIONS

Figure 1 . Indcx and topographic nap of Portneuf River basin ...... In pocket 2 . Diagram showing the well- numbering system ...... 5 3 . Distribution of precipitation on the Portneuf Kiver basin ...... 9 4 . Graph sl~owingaverage monthly ten~perat~ircand precipitation at McCammon . Grace. and Pocatcllo ...... 13 5 . Map showing the gc:cncralizcd gcology of the Portneuf River basin ...... -14 6 . Geohydrologic sections of Marsh C'r eek valley and Portneuf Valley ...... 15 7 . Map showing con tours on t l~cwatcr fahlc in fall I '468 and locations of wclls and springs ...... I7

8 . Hydrographs of observation wells ...... ; ...... -22 9 . Map of the stream drainage systtln~. location of measuring sites, and selected stream ..discharge data ...... 32 Figure I'agr 10. Graphs showing annual monthly mtan discliarges at selected gaging stations ...... -53 I 1. Graph showing flow duratiotl cutves for selected gaging stations ...... -34 17. Graph showing flow-duration curve of daily flow, Portneuf River at Topaz, during irrigation season (May 1-Sept. 30) ...... -36 13. Graph showing Eow-flow frequency curves. Portneuf River at Topaz, during irrigation season (May l -Sept. 30) ...... 37 14. Graph showing high -flow frequency curves, Portneuf River at Topaz, during irrigation season (May I-Sept. 30) ...... -38 15. Graph showing the magnitude and frequency of floods on the Partneuf River at Topaz ...... 41 I. Map showing khemica1 characteristics of water from selected wells, springs, and streams, and the location of sample collection sites ...... 42 17. Diagram for the classification of irrigation waters ...... 44 18. Map of Portneuf River basin showing generalized extent of irrigated lands ...... 46

TABLES

Table

1. Description and wa ter-bearing cllaracteristics of geologic units ...... 12 2. Characteristics of flowing wells in the vicinity of Arimo ...... 20 3. Chemical analyses of water ...... 21 4. Records of weILs ...... 25 5. Selected data on n~unicipalwater supplies ...... : ...49 A RECONNAISSANCE OF THE WATER RESOURCES 1N THE PORTNEUF RIVER BASIW. IDAHO

ABSTRACT

The part ol' ttlc Portneuf River basin dcscsibed includes an area sf al~ntlt1 .I60 stluitrc il~ilesin soutlicastern Idaho. It lies on the CoIumh~aRiver sidu of t11c divide betwrtn the Columbia River hasin and the Great Basif1 drainages.

Thc ;lveraso nnuual water supply of tlne basin is estitniited to he sligIltly more than 1.2 million acre fcrt, Precipitation otl the basin contributes about 1.2 million acre-feet, importation [sf wattr from tfae ~rijacentBear River basin contributes about 0.0 14 nlillion ;rcre- feet and 311 unknown amount is contributed by underflow from the Bear River hasin.

Tllc major ;~i]uifersin tIlc basin are the Salt Lake Formation of Tertiary age and the ;~ll~wizhi~~and basalt of Quaternary age. Recent geophysical work suggests that the cenlral part of Gem and Portneuf Vallcys, on the eastern side of ttie basin, is a structrlral trough (graben) that Iliay cor~tairras much as 8.000 feet of sediments. These srdiinentary deposits tnay contain a trcn~cndousvolurnc. ot'ground water in storage.

Tlie nulor use of' watcr is Ibr irrigation. About 13.500 acres are irrigated with grut~nd . water. Gross pumpage is about 30,000 acre-feqt per irrigation season and the average consumptive irrigation retluircrnunt is about 1.1 acre-feet per acre. Thus, annual net putnpage for irrigation a ahout 14.800 acre- feet. There is no evidence to date that the atllrifers are hcing over- developed hy 13u1nping.

Ko~~ghly91,300 acre'- Feet of xurhuc water is distributed snnl~allyto irrigate about 20.000 acres of land.

An apparcnr loss in streamflow t'rom Portneuf River and Marsh Creek ol' about 87 cubic fcet per second (63.000 acre. feet per year) occurs somewhere betwctn the gaging at;llions ;it Topaz and McCarnnion and the gaging station at Pvcatello which is otll nf Illc urca 01' study. ProbahIy the I'ortncuf River is perched above thrt water table, 31 least in Zhc reach from Inkom to the Portncul- Gap and sollie distanct: bcyvnil. thus faciIitt~tingth~s Iuss.

Major ]terns {jn whIc3.1 t~~tul-cwork should focus r'nr a more cniiipreliznsivc wrltcr -resources cvdli~ation01' thc basil1 arc. (1) wi~terhi~dp~t, (2) hydrologic rnappillg, (3) hydrology of ;~cluifcrs,(41 irrig;!tion sysicrn, (5)geologic mapping. ailtl ((3) special prohlenis. INTRODUCTION

This report presents the res~~ltsof a reconnaissance of the water resources in tlae part of the Portneuf River basin that lies upstream from the Portneuf Gap. The area of study includes about 1 ,160 square miles. and. cxccpt for a srrralt area in Gem Valley, is bounded by surface-drainage divides in the surro~rnding highlands, figure 1. Because both the surface- and ground-water divides across Gem Valley are somewhat nebulous, the boundary in the valley was drawn on the hydrologic-areas boundary adopted by the Idaho Department of Reclamation. T11c southeastern boundary of the area lies along the dividz between the Columbia River basin and Ihe Great Basin. The area. as described above. will subsequently be referred to in this report as "tile Portneuf River basin" or "the basin".

Purpose and Scope

This hydrologic reconnaissance of the Portneuf River basin was made by the U.S. Geological Survey in cooperation with the Idatla Department of Reclamation. It is part of an overall program to evaluate the water resources in the State so that an orderly optimum development of those resources can be attained.

The primary purpose of this report is to present and discuss the hydroIogic data collected during this reconnaissance. In addition. hydrologic: problems that have resulted from use of the water resources are pointed out, and the scope required of some future project aimed at describing more fully the water resources of the basin is presented.

The work accomplished during this reconnaissance, made in the period July 1968 to June 1969, consisted of (1) a partiaT it~vcntoryof water wells in the basin; (2) establishment of new stream-gaging sites and ground-water observation wells: (3) geoIogic and hydroIogic mapping; (4) mapping of areas irrigated with ground water; (5) an evaluation of the irse of ground and surface water for irrigation; (6) an evaluation of the interrelation between surface and ground water; (73 a generalizecl appraisal of the chemical quality of the water resources; and (8) an evaluation of the need for and the possible methods that co~ild be used to make a comprchensive quantitative study of the water resources of the basin.

19rt.viousStudies

No overall geologic or l~ydrologicstudy of the Portneuf' River basin has been made although parts of the geology and some Facets of the hydrology have been included in reports of other areas. The earliest geologic mapping was done in the northern and northeastern part of' the basin by Mansfield (Mansfield and Heroy. 1920: Mansfield. 1929, 1952) who reported on the geography, geology. and mineral resources of the Fort Wall Indian Reservation. Later geologic works cansisted of local stzd ies that described the geologic formations and structure of highland areas in the basin. The limits of, and referertces to, those stud~esare shown on the generalized geologic map (fig. 5). The generalized geology of the entire basin is shown O~Ithe State geologic map (Ross and Forrester, 1947).

Early hydrolopic work in the ;irca consisted of srreamflow measurements made at different times in the Portrleuf River and in Topance and Pebble Creeks during the period I91 0- 15. The records of those memurernents and later streamflow measurements made through September 1950 are contained in Water-Supply Paper 13 17 (U.S. Geologcal Survey, 1956). Subsequent strcarnflow records are contained in Water-Supply Paper 2737 (U.S. Geoloeici~lSurvey. 1963) :~nd in an annual series of reports titled Water- Resources Data--- for Idaho.

Heroy (MansficId and Heroy. 1920) briefly describer1 the surface-drainage systen-t of tho basin in all early study of the water resaurces of tlre Fort Hall Indian Reservation. Fragmentary information on the irrigation system in the basin is contained in Water- Supply Paper 657 (Hoyt. 1Y353 which is an early report on water use in the Snake River basin.

Portneuf Rivcr basin in a report on the Snake River in southeastern Idaho. Plate 19 of that report slrows contours on the water table (for 1928-29) in the upper Portneuf Valley and along Marsh Creek frotn Virginia northward. Mundorff and others (1 964, p. 44, 941, in describing the hydrology of subareas of the Snake River basin, include estimates of water yield for the parts of the Portncuf River basin above Topaz and above Pocatello. An early reconnaissance sti~dyby Twiss ( 1939) of the Marsh Creek valley from Red Rock Pass to about a mile north of McCammon briefly described the geology and ground-water resources in that parl of t Ile basin. Tw iss inclisded a generalized geologic map. a wa ter-table eontotrr map, and 3 map briefly categorizing water conditions in the valley.

Other reports that discitss topics related to the geology and water resources of the basin inclt~dea geographic study of Marsh Creek valley by Strawn ( 19641, a soil survey of a large part of the basin by Lewis and Peterson (1921), a preliminary report on the Portneuf--Marsh Valley Canal Project by Woodward (1956). and a reconnaissance report of erosion and sedimentation in the basin by %lcmlland Qnstott (1965).

111 addition to the above reports. the U.S. Army Corps of Engineers has made flood--control project stirdies ncar Inkom and Lava Hot Sprrngs. Some prclin~inary unpublished data on the results of that work were available for use in study. Acknowledgments

Many farmers in the area &operated fully in offering information about their irrigation practices and in allowing water-level measurements to be made in their wells. Operators of small businesses also cooperated in providing well data. Municipal officials and employees were helpful in providing infomatien on town water-supply systems. OfficiaIs of the Utah Power and Light Company, Preston, Idaho, and the Idaho Portland Cement Company, Inkam, Idaho, were very helpful in offering data for use in this study. To all of the above. the authors are grateful.

Numbering System

The numbering system used in Idaho by the U.S. Geological Survey indicates the location of a well or spring in the official rectangular subdivisions of the public lands (fig. 2). The first two segments of the number designate the township and range. The third segment gives the section number and is followed by three letters and a numeral, which indicate, respectively, the quarter section, the 40-acre tract, the 10-acre tract, and the serial number of the well or spring within the tract. Quarter sections are lettered a, b, c, and d in a counterclockwise order from the northeast quarter of each section. Within the quarter sections, 40-acre: and 10-acre tracts are lettered in the same manner. Thus well 7s-38E-13ddbl is in the NW%SE%SE%sec. 13, T. 7 S., R 38 E., and is the first well visited in that 10-acre tract.

Use of Metric Units

In this repoat, the units that indicate concentrations of dissolved solids and individual ions determined by chemical analysis and the temperatures of air and water are metric units. This change from reporting in "English units" has been made as a part of a gradual change to the metric system that is undernay within the scientific community and is intended to promote greater uniformity in reporting of data. Chemical data for concentrations are reported in milIigrams per liter (rng/l) rather than in parts per million, the units used in earlier reports of the U.S. Geological Survey. For concentrations less than 7,000 mgll, the number reported is about the same as for concentrations in parts per million. Air and water temperatures are reported as degrees Celsius (QC).

The following table will help to clarify the reIation between degrees Fahrenheit and degrees Celsius. w- BOISE $++qBASE LINE

7s-38E- 13ddbF

FIGURE 2.-- Diagram showing the well-numbering System. (Using well 7s-38E-13ddbl). TEMPERATURE-CONVERSION TABLE

For cornversion of temperature ira degrees Celsius IaC) to degrees Fahrenheit ( OF). Conrersjons are based on the equation, 'F = 1.8O C + 32. Temperatures in "E are rounded to nearest degree. Underscored equivalent temperatures are exact equivalents. For temperature conversions beyond the limits of the table, use the equation given, and for converting from O F to C, use C = 0.5556 I' F - 321. The eauatians say. in effect. that from the freezing point (oOC, 320 F) the temperature hses (or falls) 5 OC for every rise (or fdI) of 9QF.

PHYSIOGRAPHY

Topography and Landforms

Physiographically, the area is in the northeastemmost extension of the Basin and Range Province of the Intermontane Plateaus (Fennernan, 1931, pl. I). It is in the Great Basin Section which is characterized by isolated ranges separated by aggraded desert plains. Three north-south trending mountain masses occur in the basin. They are the Pocatello and Bannock Ranges on the west, the Portneuf Range through the center, and the Chesterfield Range and Soda Spring Hills on the east. The three mountain lineaments delimit two roughly parallel, internan tane valley areas-Marsh Creek valley on the west and Portneuf and Gem Valleys on the east. The two valley areas are connected by a gorge about 18 miles long. cut through the Portneuf Range. The general land-surface altitudes in the upper valley (Portneuf and Gem Valleys) range from about 5.400 to 5,800 feet above mean sea level. whereas the general land-surface altitudes in the lower valley (Marsh Creek valley) range from about 4,500 to 5,000 feet. Extreme altitudes in the basin range from about 4,485 feet on the valley floor in the gap at Portneuf to 9,260. feet atop Bonneville Peak, about 6 miles southeast of Inkom, in the Poltneuf Range.

The most prominent landform in the upper valley is an extensive basalt (lava) plain that makes up the surface of the southern half of the valley (see Fig. 5 for locations). From its leading edge, which extends roughly from the mouth of the Portneuf Gorge to a point midway between Chesterfield and Hatch, the basalt surface slopes generally upward toward probable eruptive sources in the Blackfoot Lava Field, east of Tenmile Pass, and in the vicinity of Alexander Crater. In the area between the edge of the basalt plain and the dam of the Portneuf Reservoir, the Portneuf Valley floor is chfefly flat and low in relation to the surrounding plain. North of the reservoir, the vaILey narrows considerably and ex tends into a topographically rugged upland In the extreme northern part of the basin.

Apparently, basalt from the upper valley flowed through the Portneuf Gorge into the lower vdley where it forms a low-lying plateau on the east side of Marsh Creek. This plateau extends from about 2 miles nasth of Arims northward to the canfluence of Marsh Creek and Postneuf River. Beyond the confluence, the basalt forms terraces abng the river downstream to Portneuf Cap. Other notable landforms in the lower valley are deeply dissected pediments on both sides extending the full length of the valley, and alluvial terraces lying between the pediments and the flood plain of Marsh Creek, largely upstream from McCammon.

Drainage

Drainage from the basin joins the Snake River at American Falls Reservoir and thence joins the Columbia River drainage to the sea. The Portneuf River and its largest tributary, Marsh Creek, are the major streams in the study area. The total length of the Portneuf River within the basin boundaries of this study is about 70 miles. The pattern of drainage is shown in fgure 9.

Upper Valley

Only that part of the upper valley north of the basalt plain is drained surficially. Intermittent streams flowing uut of the mountains along the east and west sides of the basalt plain lose their entire discharge to the ground before they reach the basalt surface. Part of the lost discharge finally joins the Partneuf River as ground-water dischage from springs that occur in and about the river flood plain in the west part of the upper valley where the rives flows into the Portneuf Gorge. Similarly, with the possible exception of Topance Creek, streams that flow on to the alluvial flat in the central part of the upper valley, such as Twentyfourmile, Eighteenmile, and King Creeks, Iose most, if not all, of their discharge before they reach the river. Some water from Topancc Creek is diverted into Partneuf Reservoir and thus into Partneuf River. However, water in the other creeks mentioned is either diverted for irrigation or seeps into the subsurface. The river-channel gradient between Portneuf Reservoir and a point about 6 miles downstream is only about 5 feet per mile. The water table is at or near land surface causing marshy tracts of land in that general area. Thus the central part of the upper valley is poody drained in places. The channel gradient steepens appreciably as the river flows through Portneuf Gorge, dropping about 575 feet in the 25-mile reach (23 feet per mile) between the outlet from the upper valley area and Mdammoa. Under natural conditions, the river gains water as it flows through the gorge. It receives ground water from seeps and springs (including discharge from hot springs) and the discharge from Pebble, Fish, Qempsey, and Bob Smith Creeks, and a number of smaller tributaries.

Lower Valley

Marsh Creek flows generally northward from its headquarters area near Red Rock Pass to its confluence with the Portneuf River near Inkom. It flows sluggishly in a valley whose major features were formed during the massive flood of Lake Bonneville waters to the Snake River (Malde, 1968). Its channel meanden over a flood plain that is much larger than could have been formed by the present-day stream. Because the stream gradient is low, about 4.5 feet per mile, and the water table is at or near land surface, marshy areas occur along much of the flood plain. A large part of the discharge of Marsh Creek comes from springs. Prob~bIythe only perennial tributaries are North Fork, Birch, and Hawkins Creeks. Because much of the discharge from these creeks is diverted for irrigation during the growing season, most of the late-summer discharge of Marsh Creek is due to springs and irrigation return flow. Flow in the tributaries that rise in many small canyons in the mountains to the east and west is intermittent and most, if not all, of the flow is lost by seepage into the valley-fill sediments before reaching Marsh Creek. Much of the lost flow, however, reappears as springs and seeps along the Marsh Creek channel and flood plain. The total length of Marsh Creek. exclusive of its north fork, is 52 miles.

Near McCarnrnon, the Portneuf Rives bends sharply northward and flows in a channel on the east side of the low-lying basalt plateau in the lower valley. At its confluence with Marsh Creek near Inkom, the river again beds sharply and flows westward through Portneuf Gap, then northwestward to American Falls Reservoir.

Climate

Climatic conditions in the basin are variable, largely because of the appreciable topographic relief. Figure 3 shows the areal distributioil of precipitation based on the period 1920-67. Annual average precipitation ranges from less than I5 inches an the valley-floor areas near Downey and Bancroft tB as much as 35 inches on some of the higher mountains. FIGURE 3.-- Distribution of precipitation on the Portneuf River basin, Idaho. Conditions are generally semiarid over much of the valley lowlands and subhumid in the upper benchlands and in the mountains. Humid conditions may exist in some high-altitude forested areas. Because summer precipitation is generally low and afternoon temperatures are high, arid conditions may exist seasonally in the Eower valley areas.

Earlier precipitation maps covering the P~rtneufRiver basin are in gross disagreement with each other. For this reason, additional new data now available from stations h and near the basin wen used to construct a new precipitation map. Precipitation data from shost-term stations were carefully adjusted by correlation with longer records to obtain estimates for precipitation during the 1920-67 base period. Precipitation in intermountain basins IS mghly dependent upon altrtuae and general topography. POT thrs reason, precipitation at a given point in the Portneuf River basin is dependent upon the surrounding altitudes as well as the altitude at that point. Therefore, the concept of effective altitude, sakthan actual altitude, was used in plotting the effects of altitude on precipitation. This concept was developed by Peck and Grown (Peck, 1962) for use along the Wasatch Front in Utah, and is defined as the average of the altitude obtained at eight points of the compass a mile and a half from the point.

Weather records are sparse in the basin. Early stations now abandoned were maintained at Downey and Chesterfield. Records at these stations were obtained during relatively dry years and do not represent average conditions in these valleys. Monthly and annual averages of precipitation data obtained from Weather Bureau records for these stations are as foflows:

Averqe precipitation (inches) Month Chesredeld Downey (1894-1920)~ (1895-1902)~

Jmmr~ 1.28 0.84 February 1.06 .45 March 1.33 1.24 April 1.03 1.10 May 1.86 1.27 June 1.28 .4 2 WY .86 .28 Aupt 1.03 .40 September .83 -36 ' October 1.07 .98 N~vember 1-00 .68 December 1.14 .78

- -- Annual (period ofrecard) 13.77 8.80 hnud (adjusted te 1920-67 base period) 16.55 12.03

'chesterfield records are pastid for yean 1894, 1918-22. Averages are computed from a~dablcrecords only.

2~owneyrecords are partid for years 1895-97. Averages are computed from available records only. More recent records of temperature and precipitation were collected for the period 1949-67 at McCarnrnon. These records are compared on figure 4 with the records at Pocatello and Grace, two stations outside of, but near, the periphery of the basin. Average monthly temperatures at McCammon are in close agreement with those at Pocatello but are somewhat warmer than those at Grace.' However, the distribution of average monthly precipitation at McCamrnon is more like that at Grace than at Pocatello. Climatic conditions at Grace are probably similar to those in much of the upper Gem and Portneuf Valleys.

Several snow courses are measured within the basin. Their locations are shown ~II figure 3. Only the Pebble Creek ( 1945 -6 1) and Dempsey Creek ( 195 6-69) courses have sufficiently long records to warrant averages at this time. The average of the annuaI maximum wafer content of the snow accumulations at those stations for the periods indicated above is 14.6 and 1 1.4 inches, respectively.

GEOLOGIC UNITS AND THEIR WATER- BEARING CHARACTERISTICS

For the purposes of this study, the geologic formations in the basin are grouped into units of pre-Tertiary, Tertiary, and Quaternary ages. Table I gives a generalized description of the geologic units and their water-bearing characteristics. Figure 5 is a compilation of the generalized geology in the basin and is based on previous mapping done by those authors whose works are referenced jn the figure. Where the work of different investigators in adjacent areas did not coincide, arbitrary geologic- boundary connections have been made. Because field geologic mapping was not a part of this reconnaissance study, aerial photographs were used to extend contacts into areas not covered by available maps. Because no detailed field mapping has been done in Marsh Valley, that part of figure 5 should be considered as highly generalized. However, the occurrence af the geologic units in Mash Valley was &iscussed by Strawn (1964) and Twiss (1939) and their works were used as guides to complete the map.

The geohydroIogic sections in figure 6 which illustrate geohydrologic conditions in aquifers underlying major areas of ground-water pumping, were drawn using drillers' logs of wells. The sections indicate the subsurface conditions that may be expected in wells drilled in the general areas traversed by the sections. The thickness of the Quaternary basalt as drawn in section 3-B' was partly based on preliminary geophysical work that was done about 5 miles to the south in Gem Valley. The sections are necessarily generalized because of the complete lack of geohydrologic test drilling anywhere in the basin. Table 1. Description and water-hearing characterisrics of geologic units in the Portnerif River basin

System Geologlc wit Description War er-bearing characterj st ics

Soil, clay, silt, sand, gravel, and boulders. Sand, qravel, and boulder untts nre rhe major Includes well-sorted Holocene al1uvim de- source of suyrpl:, to irrigation and dorncstic , posited in stream channels and stream wells ill Marsh Creek vsLley and in nurther? floadplains; IaZLe clays Interbeddad with par? of Pbrrnauf Valley. Specific capacit lcs* older alluvim in subsurface; alluvial fans [from reported data) of vells range from le5s hlluv~rnand at the base of mountaln slopes; hill wash than 3 to as much as 1,200; at some places colluvlum and landslide debris generally composed of part of yield may Ire from the undprlying T41 Quntcmary poorly sorted rock fragments derived from (Salt Lake Formation). nearby s;ources; and older alluvium. In some places underlies baralt and overlies Tertiary sediments from which it is diffi- cult to differentiate. Includes windblom (loess) sediments as overburden.

Calcium carbonate deposit. Generally light- Unknokm as suurcc of supply. Where ~aturated buff or cream colored; ranges ft.m fine- and of wfficlent thickness, may be a good textured !lard varieties, ro coarse-textured local saurce. Travertine ugen or cavernous varieties. Probubfe source is mineralr zed springs. Occurs 95 high, dam-li ke terrace deposits in Portneuf Rlver gorge, especially nrar Lava Hot Springs.

Igneous extrusive f1mq rock [lava) mtd cindcrs. Malor source of supply to irrigation wells In Basalt 1s gellerally medium-dark g-my C~ndcrs sourhcrn half of Porrneuf and northern psrt I are generally reddish brown, Textural uf Gem Valleys. Mngnltude of yleld dep-nds Fasa lt varletles range from mass~~~e,very fine grain- on IOCFI~permeability of the forination at ed to vesicular. FracTur~d,flssureJ, nnd ind~vldua: well sitcs. Specific cxpacitj rs jointed; shows collapsed structure in places. of a,-115 ranse f~omahout 2 to 3,000.

Conglomerdte, sandstone, grit, whitr cslcarcous Little knnnn as tc water-hearing capah] ljtles. clay, and volcanic tuff. So115 fomed on swr- Lsrp.cly hscausc it is d~fficult to distinguish Salt Lake face we coinmonly whitc or light colorcd and frnnh older alluvium 1n driller<' !og~. Also j Tertiary ForroaYion irrt~rspersed with grawls of largely local whrrc unir 15 penet~atetl,the uell $cner%llp orrgin. Contams boulders as much as 4 to 5 IS producing rlsti from older ailuvrum. h good feer In diameter; matrix of conglomerate is source of rupply at some vlnc?s. white, felativcly soft, loose textured, and calcareous.

Consolidated sedinentsry format~ons;composed re!+ a~llsore known to penetrate hedrock in of limestone, dolom~te,sandstone, qu;lrtzite, basin; heace, little data is nvailahle. Bedrock, shale, and chert. Solurlon cavlties in l~mestone,if present Pre-Tert law undifferent~ated and when penetrated, will transmit Large qumt~tierof water to wells. S~condarg op~niiigs~such as fractures, in othcr bed- rock forrnatlans generally do not yield water st high rates.

* Well yield measured in gpm per foot of vater-level drawdown tnual B.2OC

McCommon Average onnual 14.94 inches

\,Grace \ Average annual 14.21 ~nChss

I Dota from U.S. Weather Bureau, Averogc ~nnual9.82 inches Deportmenf of Commerce 0 1 I I 1 1 I I I I I 1 JAN. FEB MAR APR. MAY JUNE JULY AUG. SEPT OCT. NOW. DEC.

FIGURE 4. -- Average monthly temperature and precipitation at McCammoa, Grace, and Pocatello, for the period 1944-67. uNITCG 5TlrES OEPhRTMEYT OP '1L IMTEQlCR PREP4RED IN COBPERlT1QN WlTW THE GCOL~GIC-L SURVLl 104H0 OEPARTYENT Or AECCIMfiTlOM - ,e r 8.J-m

Lluvlum and col hrvlum

Con ta tt --.- Drainage basin Lnundary

~1.m ,PO- u 5 ~.n~;qi~.n 5~,..,, e. vs, ""4 P7<~jnn,ldnhm -W,rm,ng,8q93, '3MG t08lk rnd Plr2'r::o. Idlno, ,414

FIGURE 5.- Map of the generalized geology in the Portneuf River basin, Idaho.

14 0

IL. WATER RESOURCES

Sources

It is estimated from the precipitation map (fig. 3) that about 1.2 million acre-feet of precipitation falls on the basin in an average yeas. By comparison, Mundorff and others (1964, p. 96) estimated 1.09 million acre-feet for that part of the Portneuf River basin above PocateIla, a Iarger area than is covered in this study. However, they used an average rainfall of 15.6 inches (based on a regional precipitation map); whereas the average precipitation computed for the basin from figure 3 is about 1 9.6 inches. thus accounting for the difference in estimates. Part of the precipitation flowsout of the basin in streams, part is evaporated, part is transpired by native vegetation and crops, and the remainder seeps into the subsurface to recharge the ground-water aq uifess. In addition to precipitation, an unknown amount of recharge is postulated to enter the basin as ground-water underflow through Tenmile Pass and through the gap in the mountains near Soda Point. The postulated flow through Tenmile Pass is questionable and is based on the existence of a possible ground-water continuity and sauthwestward flow from a water table whose altitude is about 5.950 feet in the Blackfoot Lava Field, to a water tabIe whose altitude is about 5,450 feet west of the pass. If the altitude of the water table within the pass or underlying the basin boundary east of the pass rises above 5,950 feet, ground-water flow would not cross the divide.

Subsurface recharge to the basin through the gap near Soda Point is probable because the approximate location of the ground- water divide in Gem Valley as shown in figure 7 is such that it is possible for part of the underflow moving westward through the gap to move northward and another part to move southward. Furthermore, Bright (1963, p. 961, in a study of ancestral drainage patterns of the Bear River system, suggested that the ancestral Bear River most likeIy flowed nsrtlzward from Soda Point and, thence, through Portneuf Gorge. If that is SO, this ancestral drainage channel may contain permeable deposits that would allow ground-water to move readily northward under favorable hydraulic-gradient conditions.

It is not possible at this time to assign meaningful quantitative values to the amount of underflow that may move into the Portneuf River basin from the Bear River basin. N. P. Dion (oral commun,, 19691, in a study of the water resources of the Bear River ba~in, estimated the average annual ground -water underflow through the gap near Soda Point to be about 56,000 acre-feet. Only some unknown part of that would recharge the ground-water reservoir in the Portneuf River basin. Because the geohydrologic conditions at Tenmile Pass are unknown at this time, no estimate can be made of inflow at that place; if, indeed, inflow actually occurs.

In addition to the natural recharge to the Portneuf River basin, some water for irrigation is imported from the Bear River basin through the Soda and West Branch Canals. FIGURE 7.- Contours on the water table in fall 1948 and locations of wells and springs. Bahc,c.rl on rouyh cstiiii3tcs obtaincd I'rum canal company personnel. tlic lotiil ijl~purtatio~lof' watcr amou~ztsto abr~ilt 13.W00 acre Feet pcr ywr On thc ~niliiisside. ~hout4.0OU acre l'cct nf the cli~cli;~rgt*01' Birch ('rctmk in thc PortnL>tit'River ~~SIIIis d~vcrtcll n111>(1~1tly into IJcvil C'rccnk in thr Hwr Klvcr h;~sin.

C'clnsidcring thC i~nktiowais;~t~si tt~i- lack ol'good clilr~l~italivcdat;~. a rough c8stiinatc of tllc i029F i~iputof watrr to Zhc I\ortlit'~it' River bns~nia S~~IPIL'W~I;~~ill L~XCCSS nl' 1.3 ii~illlon ;Icrc lclct E~CFYC;IT.

C;ro;lititl water occ.i~rhit1 vil-l~ii~llycvcry pzulr.rgtc ilirit willlit\ tl~cb;isin. As show11 ill tahlC I. tJ~cv~~:?jt~raqilikr~ (w;~tcr bc'ai-ills rocks) Jrc tl~cSalt Lakc I:ur~liatjun of Tcrtirrry a+- ;IIIA ~IICi~lltlvit~rii and l>;~sait ol't)~lnr~rnaryagv. l'lic. illtiliiatc wiircc ot'gruilnd walcr in tllc 3rl~1if:rs1s prcLipitaf ion t hilt t'ilJls 1ipon tl~cland surt'act.. Kcchrlrge to the aqi1irc.l-s nccurs ;IS (1) pr~~il~ilrltiol~Ihal ]?C'TL'~>~;I[L!~ to 111~'regi~nal water tahlc: (2)Icakilgc from irrig;ttioii c-;ln;ll< ;in11 tlitctrcs: (3)sccpagc frunl irrigated ti~rrl~I'iclils: (4) 1111tlc~rl2owfrom thi3 :llli;~~-t*nl Bcar Kivkkr t~;~sin(LL~S~~III~CI): ;lllrl 1.5) Ic;ikag~b l'~.r~iiltli~ !~O~I~IICCII ~~ibrt ~IICPUTIIIP'L~~* Kcscnoir (sits]~ectecl).C;rt~~~nil water Jihc-f~arge!,fmni the nqriil'crs hy ( 1 ) c*v;lputmtls~Jir;1ti11t1 at 111lrccs wl~cr~tl~c ~\';LIL'T t:~I,lt is r~<;ir I;liid s~1rt'lrc1' or witl~iliTLYICII OF ~~IITC~;I~C~~~I~V~CS (\vatci- Irwirlg plai~ts);( 2 ) s1)1-i1igil~~w c!r- sccl"i at tlrc t~ascol' s~ct-l>sli,pcs or ;rl(311g xt rc.:itlr c31;inncls and Hood ~~laili~:(3 ~?i~~lip;~gc t'rc~~ii irrigat ior-t. liirlnic*il~al.cln~ncst ic. i111~l~IIL! il\lr);11 u~c~11.;.;11111 I!~SC~I;II.~C* (I-ot~il10~ ing ~rlls:;111rl 1-11 unllcrl'low €'rot111t1c. hrtsin thruu~11taortncut. Gii]~, artcs~allaquicer. Well 7s 3QE - 14dbc 1. at Hatch, reportcrlty llows at times and a ~iu~i~bt~rof ut1it.r wells near Hatch have shallow water levels that arc higher tll~~nthe rcgion;tl w,!tcr tahle. Thosc condition\ indicalc that a11 artpsian uqitil'cr. probably c~fal~precinblc cxtcl~t. occurs in tlic vicinity of Hatch. 'Tshlt. 2, takcn fmn~'T'wiss F 1939). lists data pertaining to flowing wells in the vicinity of Arin~o.Tllc approximate locations oi' thosc wells arc ~nclladedin figure 7. It wiisTwiss' opinwn that the artcsian conditions near Anmo wcrc iluc tu takcbeds at dift'erent deptlas in the valItly fill and that thc wells werc not ail complutcrl in the satne artcsian ayuikr. None of tllc wells listed in t;rhlt. 2 wcre visited during this study: however. a ct~ernicalanalysis was rirarlr of watrr from wcll 10s 37E- 7cbcl (table 31 wllicl~ is in the saine vicinity. Altl~ough the che~~liculmakcup of the water I'min wclt 10s- 37E- 7cbcl is nut great!y rltfltrcnt, exccpt it1 its sodium uontt~lt,I'rom that ol'water rrom wclls tapping watcr table aquifers, the fcnipctaturc of alie artes~an watcr is consistcntty about 30 to XQ C' warmer and suggcsts rclittively cl~lcrpcirculation for the lirtc- siclii water.

C;t-neriilly, wells am drilled only duep cnougl~to c~hlainwater t'or the need!, at hand. Tl~us,ciccp gscllogic a11d hydrologic data arc lacking in [lie h3\111. Kc'ct't~tgeoptlysicol work done 1t1 Portiiol~fand Geni Valleys (Mahcy and Oriel. l Oh1)) tntiicaled that thc central part ot' thcso va1lt.y~is structur~lly;I trougli (grilhon) that is dcepcst in tllc area north of Bancroft and that tnay contain as tnuch ils 8,000 feet of- Tcrtiary (Salt Lake Fornlation) strata overlain by yoilngcr habalt and alluv~alcleposith. If tl~cscstrsta arc porous and pcrnlcdhlc. there is ;! brctticndot~svolii~iit- of ground water i!~stor~ge in tlicsc vul1t.y~.

Watcr -Level Fluctuations

Aa a lurt oi' this study. six wcIls were sslectcd to tllonitor for fl~~ctliationsin ground water levels. Three of the wclls were erluippct! wit11 c~ntinrlouswatcr level rtcorders and three were meitsu~dpcriudicull y. Tlic tocat ions uf tbc obsclwat iun wclls arc sliowtr in iigt~re7; tl-ic hyJrt~gr;~plirccurd tor each ic ~liownin fig~rrc8. Exccllt fr)i wcll 95 30E 2chcl. tl~e wctrrds are rlot 101ig t'noligh to completc unc an~urllcycle of fluct~tatio~~:therefore, little interpretation of the records can hc ~iiudc.Interpretation is confaunclcd further bccausc ;ID i~rlusu;lllylarge amount of rccl~argcin the spring lVhC)lnudc I hat periori 11onr~'prt~sctltativeof nornul conditions.

Lo~ig t~rtiiv,~ri:~tions in w;~turlcvel in the I'orti~~~rt'Kivcs hi~sinarc unktlown, hut in sttiail,~r or licarhy twsi 11s w lirrt. records are availiihlc. Iiy dmpr;~~~lisart. used to correlate water Icvol cliangcs with o~l1t.rknown hydrologic cvcnts. Undcr 1131ii~aI~ondition?,, w:~tcr lcvcls drc gc~icrallyhighest ill thc spririg during tlic pc*siod of rnaxi~iiumrecharge: dccli~~t. t hrougli Il~c su mtncr when cvi~pntranspira ti011 rates art. tr igll and d ischi~rgi:excccds recllarpc: tvttd to Icvcl (rut. but c~~i~t~nut:downward. in the l'all: arc lowrst in wintcr whcrl innst

Tabla 3. ChaaicaI knalyacs of water in the Porcneui Riwr basln. (ChtmicaI constituents expressed In mllliprems per litar.1

--Ground Water bS;39F,-SSdaai 1 12- 4-68 In 63 - 65 20 10 4.1 287 0 36 - 17 0.2 0.4 359 365 2dd 14 539 8.1 - - - - 0.4 a FlmingweII 75-3SE-21dadl 2 12- 3-h8 7 25 - 77 31 43 8.6 370 0 47 - 48 .2 2.7 458 464 420 16 777 8.2 - - - - 1.0 u

--Surface Watar I

Porrneuf Rnver near .3 a cIIc~~PT~~c~~[17 7-22-66 i~ 10 - 97 18 9.4 3.0 180 a ZZ - li .3 .1 204 200 I66 EB 142 7.9 - - 0.04 11

Forrneuf hues ncnr PmcneuF ?O H-29-59 18 34 0.02 - 70 31 50 10 559 S 47 - 48 .d 1.2 473 474 SO2 0 473 8.3 5 - - 26 1.9 a

00 21 4-24-bfi B 24 - 68 2 28 6.2 302 0 34 - 31 .2 2.5 360 365 260 13 605 8.2 10 - - 19 .8 a

[ 91.7 Hot Sprinjis ?>. 1 14 3-20-52 40 29 .d? - 100 34 127 SO 443 0 78 - 147 4 1.2 7 - 3gO D 1,28U - S - 0.54 39 2.8 s

-1/ 3 - 11.5 1,.5.; h - State of Idaho :/ 'Total Imr.

-j/ Co,

-d! Tm~l5~lids -Continuous record ---"-* Bimonthly rneosurement W

,i 65 - 1I I ', *# 66 -~onnock county , , 8: IOS-36E-Bdddl **d 57 111111t411kI'11'~'1i~~'I

Bannock County II w ~S-~~E--Z~C~OI+

FIGURE 8.-- Hydrographs of observation wells. evapotranspiration h,ix stopped; nntl use again in thc spring to colliplcte the annual cycle. In irrigated areas, this cycle nlliy hc alterd considerably. Whorc ground -watcr irrigation ts prevalunt, the anni~allowest watcr Icbcts i1sua1Fy occ~isin late summer owing to regiorlal pumpage. as indicated ln well 9S -Job. 2cbcI In surfacc - water irrigated areas, where canal losses and seepage frorn fields tnay constitute the pri~lcipal rechargc. high water levels usiaalCy occur in late summer. In are:lr, of mixed irrigation. any combination of the above events may occur.

The cornlnun 11se of ob~tlrvation-. we11 hydrcrgraphs is to determiiw long.- lerm water -level treiids. 1 K watcr levels anriiially return to aboi~tthe sane position. cllrnatic cycles being considered. then recharge to and discllargc from the gro1111d- water aquifcr are in near balancc. However. if water levels follow a cvnt~nuinglong-term declining trend. then discharge exceeds ~ecl~argeand ground wster is being nitr red t'rom the aquifer.

Thcrc is no widcnce to date that any of the aquifers in the Portneuf basin are being overJcvclopc.d hy 17u1iipingfor irriyatior~;in fact. comparison of the water-table map in figure 7 with the water- table map of Steams and othors E 1438. pl. 19) indicates little. it' any. change sinct. the lC128-29 period. Howcver. because long-term continuous water-level data art. lacking in the basin, some of the observrition wells seIeuted for use in this strrdy should hc ~neasilretl on into the future. These measurements would provide a record of such water level cliangcs as may occur as a result of use ot' the basin's water reSOLIrUt'S.

Water Icvclb in 53 wells wcre measured in late Marc11 19(~9.These levels were uatnpared with watcr lcvels ~i~casurcdin the same wells in Ihc fa11 of 1968. Water level changes ranged fro111 ;t h---foot decline to an 18 -foot rise. Thc maximum rise was in well TS-381.:- 1 ladh l , situated closc to thc mountain fnothilis. indicating that spring rcc-Ilarge probably had already started a1 that place. The nraxiinum decline was in well 11s-37E-28abdl. siluated quite f~rfro111 rcchdrgc arcas. indicating that therc tht early spring rechargc was nat yet fuily rr'fecti~e.('hanges in 77 percent of the wells were within thc range of only 3 fret in either directio~i.

Tran.;miss~vity is ;In wquitkr charac tcristiu that is detiilurl as tltt nurnbcr of gal Ions ot' wilfcr, ~t tlic prevailing temperature. that will pass ill I day thrt~ugliit 1 -foot wide vertical strtp of an aquifer. extending the solurnted thickness of the aquifer. under a hydraulic gri~dicnlof 1 foot per ii~ot.It may be rlrtertninctl by ir~tctprctotiollof data Vrnin properly co~~ductcdp~nnlping tests.

In St.ptcml~crli1hX. rr pt1111pingtest wa'; tlldrlc 111 well 85 39b. 10;ld31 hy the Idaho 1)clwrtmt'tat of Kcclarnatinn. *I-l~cwell was purupctl vontinu~dlyfor ahuut 25 liours at ii rutc of about 1,575 gprn (gallons per minute). Ditring the test. the niaximuni drawdawn of water level in the pumping well was only 0.6 foot. There was no measurable drawdown of water levels in three observation wells at distances of from 0-7 to 2.7 miles fror-l~the pumping wt.11. The test data show that the basalt aquifer at the well has an apparent transniissivity of about 3 million gallons per day per foot.

Meager data are available Or? the hydraulics of the wells in the basin. Some drillers' reposts contain pumping--rate and water-.level drawdown dala obta1nc.d dunng perfor~nance tests made upon can~plcticln of the wells. Thsse tests are run for various lengths of time and setdam, iT ever. is any notice given to rates of drawdown. Howtver. these data do offer some suggestion of well capabilitres. The drawdown and yivld data from 44 of the wells listed in table 4 were used to compute specific-capacity values. Specific capacity is a well function and expresses yield in relation to unit drawdown. The values obtained ranged from 2 to 3.000 gpm per foot of drawdown. and the median vatue was 26 gprn per foot of drawdown. Both the high and the low values wcrv for wells that penetrated basalt, thus illiistrating the high variability uf yields from wells in the basalt aquifer. This high variability in we11 yields is indicative of' the fact that the abitity of the basalt to transmit water is also highly variable.

Springs

There are hundrcds ol' springs and sceps in the basin. T11ey generally occur ncur thc base of small canyons cut into the high mountain slopes and near tlie base of terraces. at and slightly above strean] levels. Both hot (above mean annual air temperature) and coId (mean annual air temperilfure or bcIow) springs occur; the c;oid, of course, art. much more numerous. The springs supply domestic and irrigation watcr to many fr~rms,and municipal water to tnany towns in the basin. They also account for much of the base flaw in Marsh Creek and in Portneuf River.

The approxiniate locatiot~sof some of tlic springs in the basin are d~owrrin figure 7. Many were not visited during this rt'conii~iswiice and all tl~clocations of those shown in Marsh Creek valley were obtained From Twiss ( 1939).

Y ietds frorn tht different springs vary greatly. Many sprir~gs111 t hc nlo~zt~tainousarcas are intermittent- Ilowing only clur111gthC wettest parts of' the year and dcriving their discharge Frol~slocal wurccs, whcrcas riiany in thc tower valley areas arc perennial. deriving their discharge from tnort. extensive and distant sources. Crystdl Springs (I-&.7) are high in the ~nountainsbut are porenniat. Thry provide the entlru lnu~iicipalsupply for M~Ca~nmotl anti. reportedly. their discharge is greatest in June and lcast in Fchruary or March. Nutnurous springs occur in the upper valley along the flood plaill ot' Portnerlf River from where the river enters Portneuf Gorge to roughly 4 miles upstreani, The accumulated yicld Table 4. Records of wells.

Altitude: Feet nbovc maen sea lwcl: tu narrmst ccnth whew Water leuel: Feet belw land-surface datm. spirit levered; nhvlr nuraber and Swroxlmatc where taken from topogrnphic mp or altlmnter reading. USE of uatcr; I - irrigation; H - dmastic; I - industrial; P - public supply; 5 - stock; U - unused Depth ta well? To nearest fout belw land surface; largely Srcm raportad data, some depth soundings. Remarks: Log - driller's 101: available; CA - chemcal analysis of water svallable: yield - reported we11 yield In gpm (gal- Cssing dapth: Feet belas land surface to first perforations. lan? per mnute), usually obtained during initla1 well per- formance test shortly after drilling. Drawdawn in feet below Wall finish: 0 - open and; P - perforated casing; static water level In %ell. X - open hole.

Aquifer: meired (P) where doubtful Qai, quatarnary and/or older alluvim, includes lake deposits Qt, QuaternaTy traverrinr Qb, Quntcrnary or older basalt 751. Tertiary 5alt Lake Formation ' Prt-Tettiary sedimentary rocks. undlPEerentlared

Land- surfacc Depth Casing 9011 Water lave1 Pump Date of Well No. airitudr of well Diameter Depth fknish 4qulfer Depth Dace H.P. well [feet) (feet! (~nches) [feet) [feet) measured completion

OriginaL depth - 80 Ft: hog

Qal .Tsl? 7.92 9-16-18

gal ,Tsl? 13.83 9-16-68 Original de'ptll - 212 R; log; yield - :SO g~m with 155-ft drawdown

pal 1.~8 9-26-68

Log: flnulng; CA

Pol

Q*l .51 9-27-68

QSl,Tsl? 13.41 5-19-68 top; yield - 40 EI" gal? 43.63 11-16-68

City of Inkom; yield - 1,ooa tpm with 14-ft drawdorn; CA

fidctl 4,540 h0 12 42 P Qal 51.80 12- 3-68 7.5 N 1937 Lot; C4; ariglnal depth - 485 ft; gmps continually

7.5 N 1953 tag: yield - 155 gpm with 3.8-ft draw dm

7s-38E-llaccl 5,579.8 200 12 90 P qaL,T$17 10.62 9-23-60 U 1967 Log

lladbl 5.370 250 16 18 P 39.66 12- 4-68 ~oa I 1957

19adbl 5,340 163 20 60 P - 14.87 10-30-68 125 I 1962

l3ddbl 5,935 175 45 X '3 20.18 10-18-68 I25 t - Log; yield 1,200 gpm with- 68-ft dtawdown

23cdal 5,307.0 45 16 39 X gal? 1.57 10-29-68 50 1 1966

24abal 5,330 135 12 0 - 75 I 1960 Yield - 1,800 gpp

24hddl 5,320 132 16 21 P pb 4.79 10-16-68 100 1 1966 kg; yield - 1,400 gpm with SO-ft drawdown

P5 21 -32 9-24-68 25 I 1951 Log; yield - 1,800 Tahle 4. Records nE wells. [Continued) Lnnd- surface Caclng We1 1 Water level Date of Well No. altltude Dlam~ter Depth ilnish Irquifer Dep:h Uat f well Remarks (feet) Ilnchc$] [feet] !feet) measured completion

7s-30E-25baal 5,315 I4 4 X Oh 6.61 1tl-29-68 1950 Log; yield - 1,580 ppm with 16-ft drawdown

5,320.7 1965 Lag 5,350 - Log 5,335 1951 Log; yield - 3,000 gpm vrith I-ft drawdck~l

5,318.7 1951 Yield - 2,403 gp with 12-f drawdown

5,310

5,335

5.335 l9S2 Log; yield - 2,530 pm with 43- ft drawdown

5.340 1451 Log; yield - 1,sao gpm with 46-ft drnwdm~!

5,355 - Original depth - 06 ft 5,322.3

5,330

5,356.6 - Yield - 2,003 gpm with 2-:t drawdourn

5,350

5,547.4

5.353.7 1961 Original lepTk - 77 ft; yield - 60 gpm virh 50-9t drandwm

5,530.R 1969 tug; yielZ - 1,200 gpm with 90-ft drawdown

5,496.Q 96 1,og; well used to flow: c~ased in 1967; yirld 200 gpm

5,497.4

5,506.1 1954 kg; yield - 500 gprn with 50-ft dr;lMaKn

5,490

5.490

5,490

2,488.7

s,43f.

5,371.4

5,970 1961 Log 5,529.0 1967 Log

5,330 t455 Yield - 3.000 gpm Table 4. Records oF w?Lls.

Lond- Surface Dcpth R'zrc~ lcvel Usr Date sf U'cll No. dlrlwdr of hell Depth DBT e of we1 l Remarks :fCCtJ (feet) [rcet) n~a5ured water camplet loa iS-39E-17cbcl 5.925 110 13 .Pl 9-23-68 I 1.556

l Sdbc 1 5.330 I50 6.68 9-25-68 I 1964 Log: yield - 1.800 gpm with 65-fr drawdown

5,335 6b I 1956

5,375 90 I 1958

5,d73.4 540 I Yield - do0 gpm with 240-ft drawdew

5.47s 2 11b U

5,452.4 155 u 1961 Log; yfeld 100 wrn

5,535.6 160 I 1956 Log; yfeld - 1,160 ppm with negligible draw. dm: CR

5,SPIO 274 u 6,260

18 H

149 I 1961 Log; yitld - 1.800 Wrn with 60- ft drawdown lOccel U

Zlddbl 1'6 I lPb3

33hhal 64 I 1960

BS-39E- ldadl 5,522.7 107 I 1951 Leg; yield - 1,600 gpwith 9-ft drsrdnm; C A

5.517 225 H Old Earn welt

5,402 87 U R*povi~dto m11- tain 1'50da retm" 5,391 235 S 1955 Log; yield - 160 flm with exces- sive drawdown

5,415 I13 (dry) 9-11-68 U 5,3i6 160 48.20 9-10-68 I 1963 Log; yield - 495 with 183-it drawdom

5,JBll 202 I 1954 Log; yield - ED0 RPm

5.388 115 H 1966

5,385 29 5 I L954 Log; yield - 1,000 gpm with SO- ft drawdown

9bacl 5,434 600 U 1968 WW well; not yet used

Qbcbl 5,425 249 U

lOadal 5,524.8 34 5 1 2967 Log: yield - 1,575 gpa with 0.6-ft drawdm

5.430.4 108 U Old well

5.450 17 3 I log: yield - 1,350 gpm with 5-fr dfwdown Table 4. Records of wells. hnd- Surface Depth Cnsing Well Water 1 eve1 hmrp Use Date of Well No. altitude of well Diameter Depth finisk Aquifer DepPh Date H.P. of well (feet] [feet) [inches] (feet] [feet) measured water cornplation

5,440 290 100 t 1967

5.435 575 U 1968 New well; not y~tused

5,430 2 75 1954 Well was nmr usbd: plugged at I0 ft

5,420 111+ 25 P 1909 l?]hrgency use fm city of flancro#t; CA

5,425 185 30 P 1935 Clty of Bancroft supply; yield - SO0 gpm with 0.2- ft drawdom; CA 5.460 355 U 1954 hp; yleld - 300 gpm with 45-ft drawddm

5,4413 I70 110 I 1467 Log: yiald - I,e50 gpm with t -Ex draprdowr

8s-POE- Scccl 5,596.2 240 - u

Sdbdl 5,438.5 2 65 S 1969 New well, nut yet ussd

5,545 147 U 1957 Log; yield - 610 gpm wlth 150-ft drawdwm

5,508 115 16 97 0 gb,Qal? 250 I 1967 he; yield - or Tsl? 2,288 gpm with 73-ft drawdm

9s-36E- Zddcl 4,725 75 N 1961 Lop; yield - 20 gpm with negll- gible drawdown; CA 106 u Old well

4 s N 1963 Log; yield - 20 gpm with 2-ft drawdm

56 30 I

5u H t 962 Lng; yield - 20 gpm with 5-ft drawdown; cafe well: CA

:Ddbbl 3* - H Motel well

Zlbbbl 250 100 I 1963

Zlcdbl U 1968 New well; not yet used

BS-39E- Zcbcl .5,4B0.3 96 6 Qb? U

2ddbl 5,49S 132 12 I1 o Ob 30 1 1953 Log; yield - 1,350 grim with ncgligihie rlrawdokn

9aadl 5,463.5 84 6 \ H Old well; CA

lodddl 5.475.1 9 t 6 Qb? H

llcbcl 5,480 6 Qb: U

lJdhbl 5 ,dB5 175 16 W 1 v' 20.0 I 1967

1dcdcl 5.485 6 Qb? J? H

15adal 5,495.4 150 6 I2 X Qb? r, H ].and- surface Dsprt. Cas ir.6 Well Water level Punn Use Date of Uell No. nlritudc of well Uiameter Ucpth flnish -4qulfrr Oe?t:~ Date H.P. of well Remarks (feet1 [fect) irnches) (t'eft) {fscc] measured water completion

95-39E-16adal S ,486.4 5 1 i, 29.22 12- 6-63 3/4 H

9s-+$DL- 4cddl 5,576.0 2 (W 4 337 P rlh 146.4% 12- 6-h4 - !I

~C~CLs p7.9 150 4 qb ? A?.OO 8-25-h7 - U - Old *ell

IRdchl 5.515 190 18 24 P Qb 92.00 10-31-68 100 1 1954 Log; yield - 1,310 gpm with 9-ft drzudom I T 1963 Iq; yield - 700 mm

I 1966 kg; ?--ell - 150 pmwith 200-:t drawdwn

I I 1961 Log; yicld - 6-ft1,350 dravdm gpm with

I 1865 Log; yield - 2,600 gpm with 178-ft drawdown

3 2 4 Q=l (dry) 10-28-68 - U

232 4 215 0 Qal? .Tsl? 5

400(?) '4 0 (flw] 12- 3-68 - S - Old well water temp. 19%: TR

P 1958 L&&: Flowed rhen drilled; village of Arimo supply

1 1961 Log; yield - 450 gpwlrh 155-ft drawdm

44 5 1h 40 P I

1U9 1 b 49 P Pal I

42 16 21 1' I

6 5 16 - U

4 2 4 2 - - Qal? 1 - Dugwell

1

80 I6 31 P PI J 1954 tog: yield - 1,680 gpm with 8- f t drawdown

1 1966 Log: yifld - 750 Grn with 80-ft drawdown

I

I

1

I

I 1961 Log; yieLd - 1,200 gpm with 160-fi drarrdcmn

I 1961 Leg; yield - 325 gpm with 60-ft drawdown

P 1959 Log; yield - 300 amwith 108-ft drnrdm; city of Du*mey sopply: CA Table 4. Records of wells. [Continued]

Land- Surfac< Depth Casing Kell Wntcr lcvcl PTP Use Date of Well No. nltirudt of ~eIl Diameter Ueptb fin~sh 4u:fer GeFth Datr H.. . sf Tiell [feet ) (fpet) Ilnches] (feet) (feet) rnec-utcd water completion 109-178-28abdl 4,855 2 37 16 42 P Qal . Psl* 75 I 1965 Log: yield - 1.200 gpm uith I-ft drawdown

a,as~ 180 50 I l@SS

4,822 218 75 1 1941 Img; yield - 1,350 gpm with 31-fr drawdorm

8,808 162 75 I 1959 Ing: yield - 780 urn with 30-ft drxudawn

4,850 i5n H

4 .Q90 15n U 1955

4,775 15 I

4,802 208 100 I 1967 Log; yield - 1 ,POQ gpm with 180-fr drawdm

4,750 50 I

4,808 225 75 r 1466 Log; yield - 700 gpm virh 144-ft drawdowrr from those springs is included in the river gain between miscelaneous measurement sitcs 7 and 8 and site 9 (fig. 9). On October 23, 1968, the gain in river flow in that reach. due whdly to ground-water discharge, was about 66 cfs (cubic feet per second). It was about 76 cR in December 1968.

The major hot springs in the basin are Downata and Lava Hot Springs. Downata Hot Spring. a recreational site, is located in the SW% set. 12,T. 12 S., R. 37 E. Twiss(1939, p. 20) stated that the spring has a constant flow of about 2 cfs. and postulated that the water obtains its heat from depth. percolating almost 2,500 feet into the Salt Lake Formation before it returns to the surface. Lava Hat Springs includes a number of hot springs in secs. 71 and 37 T 4 C R 2R F rlr &L. 1. , Y.. ... d" CA.. .. Steams and others (1938, p. 171) discussed these springs in same detail and estimated their total flow at about 3 cfs. Chemical: analyses of water from a number of the springs mentioned above are included in tabIe 3.

Surface Water

There are four continuous-record gaging stations measuring stream discharge in the basin three on the Portneuf River and one on Marsh Creek. The locations of these stations and the basin drainage system are shown in figure 9. Also shown is the locatian of the gaging station on the Portneuf River at Pocatello which. although outside the -area studied, produces a record that is irnporfant to understanding the hydroIogy of the basin. Historic data are included in boxes near the location of the long-term record stations shown. Two stations, Portneuf River near Pebble and Portneuf River at Lava Hot Springs, were installed in the fall of 1968; therefore. these short records did not provide an adequate base from which meaningful stream fl ow characteristics could be derived.

Figure 10 shows annual and monthly mean discharges at three long-term gaging S~&Q~IF Thp -1 I955 - 68 wud th~tis the tcltiil period of record for the station at McCammoo. Bccause the records were not adjusted for irrigation diversions or reservoir storage, the discharges as shown are actual. The graphs of annual mean discharges at the comparative stations stay somewhat parallel to one another. Variation in magnitude of the annual mean discharges is largcly caused by climatic changes. However, correlation of monthly mean discharges between stations is quite poor, especially during the summer period of June through September when the discharge at Pocatello falls appreciably below the discharge at Topaz. largcly because of irrigation diversions from the Portneuf River below the Topaz gaging station.

l-tgure 1 I shows flow-duration curves for the three long-term record sE~~IoIIs. I he curves, 3s compiled, show the long-period distribution of discharge without regard to the chronological'sequence of tliseharge. The curves obscure the effects of years of high or low discharge as well as seasonal variations within the year. Because the discharge records used PREPhREZ, 13 C0GPERIT:CN WITH 'HE 1b4r*? OEPhsiUEYT OF QECLAsCCTIQV

a I* !

Porlmeuf Rlver ar Pacotello Oralnope oren 1,250 Iqvore mnlrs Ymfs of rC~or619 1 t - 67 Marlmum rl~schrrrge 2>990Cia 4 1962).I MInlmum dllshorqs 0 4 cfs (19611 . CRveraqe dnchnrgr 251 cts

' A Continsous recori ga~ingst-ation , addltlona? data include* in box wl:%rc l~xgtl-,oE record warrants d liscallanaoua record site and number

Streanflw, rn EEI tccblc tcat pnr second1 : neasured Secember 2 -5, lqhu; e, esrmated -..- oramage basin bounriary

FIGURE 9. -- Map of the stream drainage system, location af measuring sites, and selected stream discharge data, Portneuf River basin, Idaho . 7" OCT WV. DEC. JAN FEE. MAR, APA. MAY JUNE JULY AUG. SEPT.

I I I I I I B I I I T I I Hots: -Discharge not adjusted for ~rrigot~on dlvtrs!ens or reservorr storcga .' ; Portneuf River at Pacotello .. .

" 1-hrtneuf River ot Topaz

A - // '\ - - //\ / \ 0 \ - / \--*A- / '------4 \ ,'Worth Creek near HeCornmon - '-/

FIGURE lo.-- Annual and monthly mean discharges at selected gaging stations for the period 1955-68. Portneuf River at Pocofel lo (bese period 1920-601

Reference point used in text-

Morsh Creek near McCammon (base pertod 1955-681

Note : Discharge not adjusted for irrigation F diversions or. reservoir storage.

I0 I 1 I1 1 I I I I 1 5 2 5 I0 20 40 60 80 90 95 98 99 PERCENT OF TIME MEAN MONTHLY DISCHARGE WAS EQUALED OR EXCEEDED

FIGURE 11,-- Flow duration curves for selected gaging stations in the Portneuf ~iverbasin, Idaho. (Based on mean monthly discharges) . to compiIe the curves have not been adjusted for diversions or reservoir storage, the curves reflect discharge conditions under past levels of streamflow and irrigation development. The curves indicate that. 50 percent of the time, the mean monthly discharge at Topaz, McCammon, and Pocatello can be expected to equal or.exceed 170, 69, and 228 cfs, respectively. The decline in the curve for Pocatello below 220 cfs is due primarily to irrigation diversions upstream.

The curves shown in figures 12, 13, 14 represent characteristics of flow of the Portneuf River at Topaz during the irrigation season, May 1 to September 30, only. The, curves are based on the streaqflow record for the period 19 13- 15, 1920-68, and are applicable so long as hydrologic conditions upstream from the Topaz station are not altered appreciably.

Figure 12 is a flow--duration curve of the mean daily discharge for the irrigation season. It may be used to determine the chance that a specified mean daily flow would be exceeded during that period. For example, the curve shows that for the peiod of record a mean daily flow of 200 cfs (cubjc feet per second) has been exceeded 54 percent of the time during the irrigation season.

The low-flow frequency curves shown in figure 13 and the high-flow frequency curves in figure 14 were computed using the log-Pearson type III procedure whereby logarithms of the flow data are used to determine the Pearson type IT1 cumulative density curve that best fits the data. Figure 13 is useful ta determine the chance that the low-flow during a period of time will be less than a given mean discharge. For example. a mean discharge of 100 cfs for any 30-day period of low flow may be expected to occur once in about 7.2 years, and that the same mean discharge during a I-day period may be expected to occur once in about 3.3 years.

Figure 14 indicates the chance that the high flow for a period of time will be greater than a given mean discharge. Thus, a high-flow mean discharge of 500 cfs for a 60-day period can be expected to occur once in about 45 years, and a l -day mean discharge of 500 cfs may be expected to occur once in about 4.5 years.

During this study 19 miscellaneous stream-gaging sites were measured at different times to establish a basis for a better understanding of the stream system in the basin. Figure 9 shows the locations of these sites. Instantaneous discharge measurements taken at the miscellaneous sites in December 1968 and recorder station measurements for the same period are shown in small boxes near each site in the figure. The discharges measured during that period are believed to represent base-flow conditions in the basin. Relative gains in flow in different reaches of the streams are shown by these measurements. For example, the gain in discharge of the Portneuf River between sites 7 and 8 and gaging station Portneuf River near Pebble was 38.4'cfs minus 4.3 cfs and 5.6 cfs or 28.5 cfs. Similarly, the gain in h id' 4 z2 0 0 0 0 In 0 In N cu - 0 MOW MOT 60 NOTLWfla URLV3TCINI 806 'CINO~RS236 A336 318fl3 NI 'R~XWI~SICIW3M 1.01 1 .I 1.2 1.3 1.4 1.5 2 3 4 5 6 78910 20 30 40 50 t 00 RECURRENCE INTERVAL, IN YEARS

FIGURE 14.-- High-flow frequency curves for Portneuf River at Topaz, during irrigation season (May 3 to September 30). that c.ct~~sudsrvcrc il;u-i~i~gc.particularly in tlic towns ui' H;mcrulf and Lava Hor Spri11~5.A description 04. that tloud in thc I'ort ncuf River basil] :I lid in ~01~1~11'~ll1(1:1110 and ~~ortl~~*;~~lc.rn Ncv;l{l;i is g~vciiin a rc-lwtt by ~'EI~IIII~., anif Lamke ( IOh2).

I:ipurc 15 ta rr tlocxi t rcili~cr~cycklnrC fur flit POT[IICII~' Kivcr ;it -1 oj~zco~~~pi~tr~rl I>y itic It,g 1'c.arl;oii ty 13~. 11 I ~ncrliod li~t~.~-pscr;~~IOII ot' t11c L*irrvc is iti~l~~.;~te~l114 tli~ IIO~C r~*l'crril~gt to Ilic point w'l~crcthc 10 YC;IF li~iccrossc\ i IIC C~IIVC'on tllc grrlph. 'rtlc tc~l;ttivtI~

tlat, lclf lisnd scgn~ct-rtejl tilt cuwc rt.pr~.>crrtcannt~at IIL>;I~ ~llwIi;~rgrst11;ll I~I;IYhc L~XI~CL~CL~ to I~UL+II~ ,L\ d I.C~IIII 01 110rnl~lSHOW 11ltFt rlinc>lI ctl11rl1t lo115 ~170~~'1'1)ptlz. TIIC ~ICCII. ri~hr ha11iI scpiiic~iloi tlic celnlc ih clct~licil 1100~1~tl~al t>c.c~~rr~d rltlri~lg II~ILISLI~I wtnicr contlitio~iswIic.11 l.ro/r.n ground. r;lint>ll. ;inri w;iriii tc~nl~urafuscsrcsulled in C'XCL~~S~YC' afnc>uiits crl c,vcrl:tn~l s~tilot'f hl;iny marc- years ol' rcconl :trc 11ccdrt1 tcl detinc hctlcr tlic' riglit IIJIIC~~.~rt01' thc r-elwt.

.4 knowtcdpc oi tlac ~n;~gnilutlcand I'rcilue~ic*~ot' I lootl\ tiial irIay bc. c.)cpck~.tccltcl occur is cslic~iiiallor tllc tlesign of t3riilgc3. u~itvtrt,. dn~ns.or ott~cr\trt~ciiircs that 111;1y 11~' al't'cctctl by Ilooils. itnil I'oi- tlr>c~d pi:tin t!~+vcl~~p~iieii~.

Analyscs (11' II) gror~~ltl watcmr >,111lj?l~ls co11~'tc'd LIS 3 p;Irt tliis st utly ,IFI~ni~t~~c'rijr~s ofhcr i11ii11ys~sof I>otl\ s~~rt;lctitlid ~I.C)LIII~wi~tcrs madc prii~r11) tlils stud' ;lrc lilrlcd ill l;iblC 3, .4 3clcc.tctl i~oinl~i-r01' tl~chc- ;~~iitlys~\ ;lrr tI~'pictt'~I ;I\ p;~ttt'r~is(Stil'l'. 105 1 ) 111111 ;I~C plot tcil

111 I'igr~rc I h ~)L';%I.tlwir pcri~itsof- collr*c.l loll. 1)isc;t)lv~d t~~i!lcr;~Ico~icc~~tr:~tit~~~> ;I~L* dioti 11 hy tlliL 1mttcr11~it1 I~~~II~c~~~I~v~I.cIII~pCr litihr (111ell). A l~~ill~c~ili~ivaEci~tper 1itt.r i:, unv one tliousa~ltltl~ul' a r~nirc.licr~lic:~S co~i~hining wCiyI?f oi' 3 cclt~hlitt~l'ntin a litcr ol' u;~tcr. and 11 tilay Irc clbt;airir~tl tly tlivi~lingIIIC ccwscritra~ionr)f' tlic co~~stiti~cr~t~n ~~iilliy~.;l~~~s IIL'T litcr hy IIIC ~hc,t~~ic,alco~i~hit~i~ig w~igllt (11' tIlC ~~tlstili1c111.7'11~' j~~ttcrr1hprovide it V~SLI~II rrictliocl For ~.apiJlytl~r~crl~i~~rng \i\llil:lrllics .clr dissirnitariEic-r, in the chc~liicnlcl~irnkctcr I)!' watcr si~rnpltlsc.c)ilc~,tcd at dil'Vul-c~lt ~sluccsor limes.

llxiirnini~t~u~iot tl~cwatcr a~~sty\istl;~f;t ill talllc 3 and I'ip~~rcIh sl~uw:, 1l1i1t tllC prctlorr~inant w:itcs 111 tlic hasill I+ rll' tl~cc*.~lciuni hic,~rllonatc iypc. S(1cliuln l~lcarl~uf~att.itc w:~tc.r occiirr; in tht. L;IV;I I4ot Spriny\ nil in flowirip wt-ll t OS -371- 7cl~l , wllicli ~~roh:jl>ly is rc~~r~s~~if~~li~r01' I11~ i)t licr wt';1r111 iv;ltcr rlt)wi~igivclls 11sic~Iin ki~l~lc2. Tlie jig~~iI'~ca~icc01' tlic I~~CLI~~II~~II~LIIL*~t~f'todfi~1111 ill I IIC \tllarm ;~nd 11ot M iltt'rr, is not bnr~~~n.c~~lcci:r!ly a:, soilii~~ll i> ~iotpruv;rl~-ni in lhcb Iluwr~ataif01 Spriny walcr. 1)r)wndttl w:ltcr iiii't'~>r\F~~rthc~r. l'tw rlc5pifr- it> L~ICV:~ICL~~~*tnp~r:l LI~Ci 4HiS t'k. i~ i>~I~T~L?II~ [litb[~>t illi~~~~ri~Ii/~d \~atcr>in th~* ILIS~II.

W;~lcr in ucll 'IS 401: 4ctltl l 1s 01' IIIC Iri,IgtI~~\lilmhtC;~rl~r~r~:i t L* type. M;iy11~'4lilll hici~rl~onatcwiitcr ;II\o \c.c-~~~hltl lv+chvailcilsl OF St?d;~Siliing llills 11) 1ttc. vicinity t,E Stda 36- - I I !I I I I I Ill1

32 - n X 0 wU 28 - p: W F.r H 24- W bt U H m 5 20 - U E 0

d

x 12 - d is 1,020 cfs 5. uW E a- 3 2 U V1 H -

0 I 1 1 1111111 I I i Ill I 1 I I f 1.01 I.f 1.2 1.4 2 3 4 5 6 78910 20 30 40 50 100 RECURRENCE INTERVAL, IN YEARS

FIGURE IS.-- Magnitude and frequency of floods on the Portneuf River at Topaz, Idaho. FIGURE 16.-- Chemical ckaracterisrics of water from selected wells, springs, and streams, and location of sample collection sites. Creek and in central Gem Valley, south of the ground-water divide IN. P. Dian, Oral commun., 1969).

The value of pattern comparisons in deciphering ground-water flow is shown by the patterns for wells 7s-39E-30aah 1, 8s-39E-ldadl , and 9s-40E-4cdd1. Water in these wells is from the basalt aquifer and, except for Lava Hot Springs, is more: mineralized than any of the other waters shown in figure 16. In accordance with the statements an direction of ground-water flow on page 18. the analyses indicate that the water apparently moves downvalley ta the discharge point at the Hansen spring (NWXNW%NE% sec. 25, T. 7 S., R 38 E.). The water at the spring is less mineralized. probably having been mixed with water from the alluvial aquifer in the northern part of the valley. The mixture at the spring results in a magnesium calciunl bicarbonate type water. Similar water, but of lesser mineralization, was found upan analysis of water from the Portneuf River near Pebble. The lower level of mineralization at this point is caused by dilution of the ground-water discharge with reservoir outflow. The sound-water similarities continue on downgradient in wells 9s-38E-20dca l and 9s-36E-2ddc t and beyond.

The surface-water analyses shown in table 3 and in flEfure 16 represent water samples collected at a particular time; they should not be considered representative of all streamflow past tlre sampling sites shown. Time and volume of discharge must be taken into account when sampling a stream. For example, the analysis of Rapid Creek near Inkom is very low in dissolved solids largely because the sample was taken in April when snowmelt accounted for most of the discharge. Had the sample been taken during a period of base flow, the concentration of dissolved soljds would have been greater.

The analyses listed in table 3 indicate that for human consumption no chemically "bad" water has been detected in any of the wells, springs, or streams sampled, The dissolved solids in some of the waters exceed the 500 mgll limit recommended for use by the U.S. Public Health Service (1962) but the excess is not critical. Some of the waters have pH values of more than 8.0 and may be considered as slightly alkaline, hut they are. nevertheless, potable. Most of the waters listed are hard. Trace-element studies have not been made, but there is presently no reason to suspect that deleterious concentrations of trace constituents occur.

Figure 17 (U.S. Salinity Laboratory Staff, 1954) shows the suitability of the different waters for isrigatio~l use. The samples are numbered as shown in the "'salinity diagram number" column in table 3. The classifications on the diagram are bascd on specific conductance and on SAR (sodium -adsorption ratio). SAR = Na+ Ca*' + Mg*, in which 2 the concentrations are expressed in milliequivalents per liter. Values for 24 samples of water are plotted on the diagram as shown. All samples plotted fa11 within the S1, bw sodium water, classification. S1 water can be used on most soils with little danger of development of h;r m ful levels of exchangeable sod ium, except perhaps whcn used for sod ium-sensitive crops (Wilcox, 1955, p. 10). SALI NITY HAZARD

FIGURE 17.-- Diagram for the classification of irrigation waters. Most of the samples plotted fall within the C',! and C3 classifjcatiuns, rnediuln and high salinity waters. respectively. C_'1water can be t~sfdif a moderate amount of leaching occurs. Plants with inoderate salt tolerance can be grown ilr niost places without special practjcrs of salinity control. C'3 watcr shoulcl 1101 bc i~stclon soil5 wit11 rt'strictt'cl drainage. Even wit11 adequatc drainage. spccial management for salir~itycontrol ]nay he scquired. and only plants with good salt tolerance shaulcl he grown.

The nrajor use of water in the hi1si11is ror irrigation. l'ollawed by muniuiprlt. industrial. domestic, and stock usv: but not necesurily in ttiat ort1c.r. Tlicrt. are roughly 33,500 xrcs of irrigatcd Fasn~land, six rnunici~~alitichthat liavc. prrhlic water supplies, and onu industrial plant that uses an appreciable an~ountof watcr. No est irnate was rnade during this study of the use of water by the farm poptrlatian or hy livestock.

An attempt was madr to crlitviss all the ~rfigiltionwells if1 the basin. Table 4 contains data on tile 148 wells visited for this study. Fighty six of thcse wdis are used for irrigation purposes; the remainder are used either fur do~nestic,stock. industrial. or public supply purposes, or are unused. Thc wclls in the upper valley above Topaz range in dcpth frotn 32 to 040 feet and II;IVC 3 ~nedi;~tidepll~ of 150 fcet below land sur1;ice. The wells in the lowcr -.v" 2 7 tt, 'iQ

Most of thc well owners visited wcrc askod Zir cstin~attrtllc aniount of ground wutcr IJLII~PC~for jrrigat~~nand the acreage on which ground water was used. The geographlu location of the acreage irrigatcd hy ground water is shown in figurt. 18. and estimi1tt.s of total pumpage are given below. For convrnience, the estimates of pumpage art. totallcrl separately for thosc lands upstrca~ni'rclfin Topaz and thost. lands downstream from Topaz.

uiay intt'rcl~unge tlae use ol' curface and gro~uldwater on tlrose lands that are shown as "irrrgated Ily ground wat~'r"ill 'igurc I#. Tltat is. durlng a year of abundant strcarnflow. thc v Itlay puln ,> less ground watcr than they w ~ul~'during a year vf' Clt'ticicnf streanltlow.

Abovc '~'nl:a>

rt w~thwound d

w. tcr. Tftc lo CI .I imllnt c i' \v;~tcrpumped du~ingthe irrigation season is ahout 20.800 PREPQRED IU COOPE4PITIOY WITH ?HE IXd3 QEPhRTMCKT OF 4ECLAWRflOhl , ,B i

Em Lar4 1r:~rated by surface v*tsr

Land lrrlqated by ground water -..- Drarnaqe basan boundary

- 7 3 6 1 13 V8l.r 8- 8-

FIGURE la.-- Map of Partneuf River basin showing generalized extent of irrigated lands. ac~e--feet. This amounts to about 2.2 acre--feet pumped per acre. It is estimated. using the metirod of Jerrsen and Criddte ( 1952) and the 1964 Census of Agri~.ultutt.Prclirninary Reports for Banilock and Caribou Counties (IJ.3. Burcau ol' the Census. 1966). that the average consumptive crop use in the basin is 1.4 acre-feet per acre per irrigation season, and that the average consumptive irrigation rcquireinent (consumptive crop use minus seasonal precipitation) is 1.1 acre-feet per acre. Thescfore, about 50 percent of the total pumpage is consumed hy crops; a large part of the remainder seeps into the subsurface to retilsn to the aqnifers. It is not known how much. if any, of tlle excess putnpage runs directly overland to the streams. Net punlpage for irrigation above Topaz is estimated to be 111,400 acre- -feet per season.

BeIow Topaz

An estimated 4.000 acres below Topaz is irrigated in whole or in part with ground water. The total amount of water pumped per irrigation scrtsr>n is about 9.200 acre- feet, or about 2.3 acre -feet per acre. Because purnpwc data were lacking in this part of the basin. the avcrage amount of water pumped per acrc ~rrigatedwas derived from estimates obtained from 10 farms in Marsh Creek valley. The avcragc consurnptjve use and the consumptive irrigation requirtmtnt are similar to those ahovc Topaz. thus at1 estimated 48 percent of the pumpage below Topaz is coi~sumedby crops. Tllerufore, net pumpage below Topaz is aboiit 4,400 actt: --.feet per season.

The total wusonril net pumpage fox the entire basin is r~yghly14.800 acre--feet and the total gross pumpage is roughly 30.000 am--feet. The above purnpagc t'igures are general seasonal estimates and will vary l'ronl year tu year depending on elinlate and. if present trends ot'grounr! water dewlap~neatcontinue, the punlpage will probilhly increase.

Surtice -- W3tt.r Irrig ;I t'ion

Of the approxin~atctotal of 33.500 acres of irrigated land in the basin, about 20,000 acres are irrigated solely with surfdie water. En addition, an unknown but probably small part of the 13.500 acres irrigated wilh ground water is also supplied partly with stirface water. ?'he scope of this reconni~issancc dirl i~otEnulr~de detailcd snapping of thc surface watcr isrigr~lcd acreage, but tlic pt.t*cralir.cd louatioil of surface -water irrigated lands as compiled largely by the U.S. Soil C'onsb-rvation Service ii shown in ligi~~s18.

Ttle rn ljor sources of the surface water arc Portncut' ll,ver and Marsh Creek. their tributaries, :lcl imported watcr fntn Bear River. Total rc-s~:r\~oirstorage aipacity in the h;~n is ah I tt 25.7 10 acre frc.1 Tli~Iou;i t on aiitI cipacititb\ nl' Port-trrc,~'. kI:~wkins.rlnd CI- sterficll tcscrvr rs. the ~mlysigni (cant storage facilities ill the basin, a ILI r,f some of the la. 2r canal trr shimKI? in tii UIL. s. Quantitative evaluation of tlie amount of uater distributed by the surface-water irrigation system as it is presently established is difficult. There is a serious lack of (I) suitable daily distribution recortis. (2) gage-height readings in Portneuf Reservoir. (3) records of inflow to and outflow from the reservoir, and (4) measuring devices for obtaining inflow and outflow records. Further, the gaging stations at the heads of the canals below Topaz are poorly placed and their records are affected by adverse conditions in the canals. Waodward ( 1956, p. 18) noted these deficiencies, and since that repart a Parshall flume was constructed in the outlet channel below the Portneuf Reservoir to obtain better outflow records.

Despite the lack of data an attempt was made to approximate the amount uf surface water used for irrigation in the basin. The Watcrmaster"~Report for Water District 17, governing the distribution of Portneuf River water. shows that for the period June 1 to September 15. 1907. about 77.300 acre-feet of water was distributed from the Portneuf River and other streams in the district (Marsh Creek and its tributaries are not part of District 1 7 1-30.400 acre- fect was distributed above Topaz ancl 46,900 acre-feet was distributed below Topaz. Any diversions prior to June 1 or later than September 15 were not recorded. The avtrrage discharge of the Portneuf River at Topaz for the period B 920-68 between June 1 and September 15 was about 41.500 acre-feet. The average discharge for the same perloci in 1967 was about 1,000 acre--feet more than the long-term average; therefore, the quantity ot water available for distribution In 1Y6'1 was Somewhat above normal

In addition. estimates were obtained for distribution from the Bear River system to the West Brand1 and Soda Canals. Flow in those canals totalled about 14,000 acre--Feet. Thus. the amount of surfarc water distributed from all major sources of water is probably at lcast 9 1.300 acre-feet per irrigation season. Assuming that the total irrigated land is 20.000 acres. then ahaut 4.6 acre feet of water per acre is distributed, but that figure is deceptive for there is probably at lvrtst 30 percent loss in the distribution canals. Perhaps. on the average, ahoi~t3 acre fret per aurt is available at thc Farm headgates.

The above cslculations arc vcry rough approximations. Because distribution data arc lacking, bet!ur dctcrn~inationscannot he made at illis time: hewever. the approxitnations do give an idcir ;IS to thc rnagnitu 1c of' the surfiicc-water irrigation system and the amount of water used.

Municipal and lnd lstrial Suppl e:,

Tahlc 5 lists selectecl I;I';I ~11 six inunici ~nlsupply sl st,:ms. The arin~~zll-usedata in

t1.r tahlc wt.1, o!>t:~inedti ,)I 11~Ijniversity of 1d;iho Watt r Kesources Itcsrrarch Institute

( ' '68. p. 10 4'1 I). Thv 01 l1rr Ida wtrc aoluired from ptrsons dircctly or indirectly

n p011~il)i~'1'11- tl~cwater s 1p1'1~ I I 1:,1ch mum .ipiUty. Apprnai matn

c,+;, *A,- Vbk,LLu L _. W.kt,,r, r& because sand

- - uqnr-~~+ IIOC , Ir" P...,. .P -- -- (L weii on srand'~yj nation when needed ------e- I sprln~5. wells P~SBTVQI~S- Z -- 11 17C -n1 - - - -- 1 on~ eat~meters -- 3 -- 27 L U dl ------Tnknm 5?R 7: well4 7n1 .7 1 rernr~rnir- 147 system - - YL,~- - --" - PI->> PI->> 1

-- 1 ,..n 1 1 1 ETV7 [lclfiEl we71 - L WLLL - [Sqplementa2.1 159 .UUU aelons narlon wntn neeaea nor: ye-. . - -

~nstalled The Idaho Portland Cement Co~r~panyplant at Inkon] is thc o11Fy large industrial user of water in the basin. The plant Elas two main wells, at least one of which is pumped at a11 tirnc..s throughout the year. Total annual pumpage is about 470 acre-feet (153 nill lion gallons). Of that. abr~~~t40 acre-feet (13 miIlion gallons) is used consumptively in kilns. Most of the remainder circulates through thc plant and is discharged Ento the river.

INTERRELATION OF SURFACE AND GROUND WATER

AND THE EFFECTS OF PUMPING WELLS

Since about 195 1. the quantity of ground water pwnlped for irrigation has grown from an almost negligible amount to ahout 30,000 acre fcet per irrigation season. Tliis 1s about one third as much as the total quantity of surLicc water uscd for irrigation In tlic hasit~.The use of ground water co~iiinu~sto grow as mure and inore farm owners arc tlzl-nine to irrigation from ground . water and giving up dry farming practices. Also. they arc using increasing amounts of ground water to replace or supplement unpredictable surt'acc water supplies. As a result 01 this increased use of ground water, cluestians lii~vt.arisen conccriring the rffects of grou11d water withdrawals on the flow of streams and how thest. effects call be appraised. I

During this study, attempts were made through usc of historical records to deterin ine if any changes had occurrecl in stseamflow as a result of gsot~nd water withdrawals in tlic upper valley. Several rneans of identifying possible changes wcrc tried. but in nearly all c~scs tlie data and records available were too meager or too ~hortto irllow ~iieaningfulanaly~is.

Cornparisu~i of the averagu a111iuaIdischarge of the Furt~etlt'River at TopL!/ ~ith precipitation records at PocateIlo and (;race revealed no dt. finite indication of a red~~ctir,~~in Ilow that might bc caused by ground water pumping in the upper valley. CP1angc.s in tlie storage capacity and operational procedures for Portz~~z~fReservoir, coupled wit11 iln attendant changc in the irrigation distribution pattcrrl olsu precluded use ol' most average flow data as an indication of change in the outllow from thc upper valley.

An attempt W;IS made to Incasurc possihlc effects (11' purnl~ingon strcamt'low t~y monitoritig thc cllsnge in grountl- water dischi~rgt. to t lie Portneuf Rivcr hc~wt~c~i ~nisccllaneousiiicasirrc~nent sites 7 and 8, and site 0 (fi. 9 1. Huwevcr, repeated monitoring of these sites s1luwc.d tlo conclusive itldication of' redticlion of ground-water rI~st.hrrrgc attributable to pumping. As tnight be cxpcctcd, there are Inany facturs other than pu~nping that influence tllc interchange bctwctln ground water and s~~rl'rtuewater in the tlpp~rt13sin. Sa~ncof the marc iml~ortantarc it~creascdcvnpotranspirotio~~ by growing crops, changing locations ~ndt inling of' recharge from surface-water irriguticjn ~pplications.and 1hc wry slow adji~strnentLY~ graut~d -water levcls to withdrawals fr'rarn ,$n acluifer with large stor;ige c:~~.lacity.Thc dat;i ccrllccted from tllc ~nclnitoringsuggest that if pumping has any c1'l'cc.t upan thc streai~~tlow.tllc Bog in gsolind water lcvcl changcs l~robsblycauses the etTect to occur after the irrigation season when sirearnnow monitoring at the ~nisccllaneous measurement sites is discontinued. D~"tailed records and rne8surenrcnt of these and other factors must be madc over a period of at least one full year before any judgment may bc made as to the potential effect of ground-water pumping upon streamflow.

RECOMMENDATIONS FOR FUTURE STUDIES

Although some quantitative data are contained in this report, they are based on a rninlnurn time Tor analysis; and, as in all rcc~nnaissancestudies, the results can benefit by the collection of additional data. Thus, future work needed to make a comprehensive study would i~~cludeelaboration on some of the topics described herein and the acquisition and interpretation of new data. Major items on which future work should focus are (1) a water budget, (2) hydrologic: mapping, (3) hydrology of aquifers, (4) the irrigation system. (5) geologic mapping. and I GI special problclrls.

Watcr Budget

A fim water budget would be helpful in making a quantitative evaluation at' thc water resources in the- basin. Tht. clemcnts in a water budget are total inflow to and total outflow from the basin. Those elernents must be balanced, taking into account changes in storage. inflow includes precipitation on and underflow and importation into the basin. Outflow includes evapotratlspiratian wift-iin the basin. and exportation, stream flow and underflow out of the basin.

As part of the inflow dctesrninat~nn.a pwcipitation map (fig. 3) was made ditring this study. It is based on the only precipitation data available to date. Refinement of the rnap can be accon~plishedonly by establishing new precipitation stations. Rain gages placed at strdtegic sites in the mountains would hclp refine the present map, but long-.-term record sites --one in the upper and one in the tower valley - woikld hclp most in making any future map. These slloutd be established as soon as possible.

Anotlicr part of the inflow determination is the underflow from the adjacent Biackfout and Bcar Rivcr basins. particularly at Tenmile Pass and at Soda Paint. Underflow at Tcn~nilePass is pnstulatcci for reasons, mentioned previously. At least two hydrogeologic tcst wells would have to be cunstn~utedto evaluate the potential for and the amount of underflow. Gcuphysical profiles in conjunction with tile test wells would be sdvisabtc to obtain tliaxi~irumvalue from the drillitlg, One test wcIl is needed at the basin boundary east of the pass and anotl~erat the crest of the pass. If water levels measused in the test wolts showed that a contini~ousgradient did exist between the ilrljaccnt basins at that place. then a ttailsrnissjvity value would he needed for the in terve~iingaqi~i t'er. The transmissivity val11e could be detcrnlined by making pelinping tests using the tcst wells. Knowing the width of' the aquifer through the pass. thc hy drnulic gradient. lend the transmissivity. a val~lct'or itndcrflow ttirough the pass could be calculated (Ferris and others, 19h2, p. 73).

Determination vf volumes of unilcrflow into thC basin near Soda Point would reyuiro a clnsely controlled water- tahlo contour map to be r~tadeof Ule area extending from the pass at Soda Point and spreading out over the ground--water divide in Gem Valley. Additional water levels in wells and precise topograpllic leveling would he needed tu tlraw the map and accurately locate tile gro~~nd-water divide. A flow net of the arca of interest could then be dmwn to obtain a eraclient and deternrine u width of flow. Transmissivity valucs could be deteriiiincd using wells in the area. Givcn the three needed valites. the above citcd rnethod could again be appl~udto calculate the uinount ot watcr bung cuntnht~tcllto the Pnrtneuf River Basin.

As stated ahovc. the outflow clcments includc cvapotr;inspiratiorl. strcamflaw. and irnderflow out of t1w basin. Methods to estimate thc evapotranspiratio~iare available (Roseberg and othen, 1938) and need not be elaborattld on here. To cletenr~ine the streamflow out of the basin, it would be necessary to establish a continuously recording surface--water gage in the Portncuf Gap. To determine the z~ndertlowthrough the gap and out of the basin, at least one aurl prcfcrably two geollydrologc test wells sl~ouldbe dnllcd in the gap. CeopI~ysical stitdiles probably should be made to axtend the test --tmle information. The wells shoulrl he drilled to bedrock. The rate of underflow could then he determined as explained for Tenmile Pass. Also. the tinnness of the builgct wotilct bc enhanced by determining the hyslrologjc cross section at Pebble so that outflow t'rtln~only the upper valley could be evaluated. The methods used previously also would apply here.

Watcr- ,Table Mapping

The water tabl~.,.rup (fir. 7) dr~wnfur this stlldv is not coll~t-r[ttt. .: hilt ~ov~n. 3.onlv areas of major ground water pumping. Alsn, topopraph ic. control is lacking for bcttcr definitiqn of ltllt. contours now dmwn. 'The well canvass shoirld Ise extended, and observation wells cstahlished in nuudcd ascas to uon~j-rlctucontnuritig uf the watcr table throughout thc en tiru basin. 'Tile canvass sliuuld nuke a pastici~tarcfL)rt to search out ihosc wells measured by Steams and others 11C138) in 1928-29 so il~cycan be inclucltxl on thc new map. Watur Icvcl mo;lsuremcnts S~IQUICI then hu madc it1 the autilann st, rc.asonublc* comparisons cilr~hc ~iiadcof water .!eve1 changes occurring bctweci? 111~- 1928 pcriod arrd the timc thc later measurenicnts wvre made. Also. watcr--tt.vol meusurerncnts ~l~arEcin the six observation weIls established as a part of this study should be continued into thc Future so that long term water -1evcl trends can be establislied. As u part of rlie canvas a rcprcscntative nu~nhvsof springs also should he schedmfcd al~iltheir ~Icvatiundctcrn.tinc~l. 113ta an the h!rdr;rulic c.I~;~~actcristicsoi' thu iturnpingtests. AItl1ui1~11tllc rcsr~l(sol~tar~ic'cl fr0i21 pumping tests arc apprcrxirnations. thcy ;Ire uscful in evaluating lllc pcrforlnancv 01" an aquifer. Transmissivity atld storage coel'fioicn ts may hc uortrputcrI. I~ydrologic[loutid:~rlc~ locatcd. and future eftccts of puiiiping predicted frotu data clcrivcd from sucE1 tot\. I llv stomgc c.ovflicient is dihlined us tbc volih~licuf watcr an aquiLer rcll*asc.s from or takcs 11110 stontp per ini it surfr~ccarea of tl~eat1urft.r per unit chnngc in the compoiie~~tof \]cad nonnill to tliut surfac~' Thc tehth iilvnlvc cantrollccl 11i1111pinp;111d il~caslrrt.niclltoi ur:ltcr

It 1.VI E\ rn thc ~>unlplnc~wcll and ~n twarhv observa2ion wi'llh. hr>llt hcl'orc- and dul-inr! ~?i~~il~~itltl :11111 AI tcr ~?umpingis stopped.

In so~ilc pli~ucs. pumpinp tc\t\ to clcicrt~lirlc ttlt Iiyc~ri~ul~cchasacteristics t>l' thc arl~~ii'~+l.sIriay lief be practical. t-sti~llatcs of trausn~i\siv~tyv;~luu\ may be ohtainal.ilc* by dctcr~niningspccilic capacities of rcprcsetztative wclls iit ttic ilif'erc-n t acluifcr.;. HONLm\t.r. snor,tpc cucfficic~llscannot hc nl~t;111l~C1it1 this nlaflnt'r.

In rclirt~olito I~yilrnloyy.it 1s s~ippcstcdthat f ht* riiiscc~l;~n~ousstroitrn mc~iisuri~~~~c~~tb Ile ctjnttnued ;I[ least t11~ougIi onc rriini~al cyclc. It' a co~~ll?rchen~ivcsttitly is startcti. odditlono1 ~ncasurt.nieiits of Haler lcvcls in wells ;lnll of struan~llowSIICFUICI bv III;ILI~ ;is nccdid.

A hettcr meam sl~oultlhr: devised tu obtain qna~ititiitivcdata from tllc prchclil s~~rt'rlccwafer irrigation systc~n.Woodwanl (105b) ~sointcdoirt sonw sliortcorn~iigsin tl~e rccordiilg 01' flow irllo ,ind o~~tot thc Pnrtneul' Keservo~s.IJopct'ully, tlicsc d~ortcorningscan t9u climi~iated.A full iluarif i tative htucly rvould incl~iilctlw acrl~iisitioriand compilation ol' !Itc following !ncas~~rcnicnts.

I~iHow ti, ['ortneuf Kcsc~voir; oi~lflow r'rc,n~ I'ortncuf Hc.scrvoir: wutcr- lcvcl tluuturitioz~sill I'ortnc~af Rewrvoir; tlow into main cani~ls;dtvcrsions 0111 of 'l'opancc. King. I'cbblc. Twcntyt'our~~~ilr,Eighrvunmilc. Ilempsey. Fisl~.Bob Smith. Marsh, Birch. H;~wkit~b. JIKI I;;IT~~CII('FCC~S. C'rystal Springs. ancl any other sources froin which significant amo~lnts of iv;ltcr arc hcit~gdivcrtcil I'rt'li.ral)ly ttic rccords on then I'ortnc~~i'Kcservo~r sl~ould Pc cll~t;~~nt'clwrth co1iZini1(~1~3yrccori1111g L~C'VIL'L'S. Also, tnorc" ~'oiill~l~tt'rccortls sl~c)~~lrl ohtilil~ctli~i tllc flow in Srda and WCS~Bran~tl Callilia wlii~lljn~port wafer fro111 the' 13~'iit. liivcr systc111.

licfinctl tlctcrnii~~o~ic~n01' tlic itniuunt of gr~1~1id\v;tfcr IIK'I~ S'DF i~rigiafionis nVc~1c~J. An rrtlc~iil~tsl~o~~ltl I>c 111311~ 111 I~()LI;IZC'rt'c~r(3s on tlit- ini.rr;lxcJ usc of ground w;itcr l'or 1r1.1g3tio11i11 tlw I~;I~IIF. Geologic Mapping and Deep Tcst Drilling

'Tilt! geologic map for this stirdy was compiled from the work of previous studies made in the basin. Mapping in the Marsh Creek valley is almost completely lacking. At least reconnaissance geoiogiu mapping should be completed if future hydrologic work is to be done in the basin. Also, geophysical work (p. 19) has shown the apparent occurrence of a structural trough that may contain sediments as much as 8.000 feet thick in central Portneuf and Gem Valleys. A nurnber oF deep geohydralogic test holcs should be drilled to either prove or disprove the occurrence of such a structurz.. for this deep trough could constitute a valuable source of ground water.

Special Problems

Special problclns that inay arise will probably be related to infringement on water rights among the different irrigators in the basin. Thc interrelation between ground artd surface water is a problem of that nature. One method of approach Is suggested in this study on page SO. Some other method may be workabIe, such as an analog model which can be used to help describe the overall functioning of the natural system and the stresses imposed or; it.

Interferences among pumping wclls also may crcatu special problems- Such problcnls can be evaluated through use of field pumping tests.

SUMMARY

The average annual total supply of water to the basin is slightly greater than 1.2 million acre-feet. Sources of supply are precipitation on the basin and postulated underflow from adjacent basins, Some water also is imported from the Bear River for irrigation.

An apparent 87 ci's (63.000 acre- Fret per year) passes as underflow suii1ew11t.t-c -. I>etweell the strealn gagrng statiotls Yortneut Krver at lopaz and Marsh CrecB near MuCamtnon, and the station Partneuf Rivcr at PocatcHo. The actual averagc an1111a1 n~c.asusedloss between those stations is 12 cfs. The lower rcac1.r sf' the Portneuf Rivcr, at least bctween lnkorll and beyond I'ortneuf Gap, apparently is perched abovc tl~crcgistlal water table, tIltfs filcilitating the loss. But, it is not know11 haw 111uch of the 87 ut's occurs above the Portncuf Iiap.

The major ground - water aquifkrs are llle basalt and alluvium of Quaternary age atrd thc Salt Lake Formation of Tertiary age. Ground --water wulls ill the basin range from 32 to 640 feet in depth. The median well depth is 150 feet below land surface in the upper vatley and 168 feet in the lower valley.

General ground-water rnwernent is from the uplands to the center of the valleys, and thence, downgradient in the direction of streamflow. Some movement may occur vertically upward through leaky confining strata where water-table aquifers are underlain by artesian aquifers.

Chemically the predominant water in the basin is of the calcium bicarbonate type. Sodium bicarbonate water occurs in the Lava Hot Springs and in some warm-water flowing wells near Arirno in Marsh Creek valley. The mast highly mineralized water, excepting Lava Hot Springs, occurs in the basalt aquifer in the upper valley. The water seems to become less mineralized as it moves downgradien t, presumably by dilution. Some of the waters used for inigation are in the medium and high salinity classifications.

Approximately 91,300 acre-feet of surface water is diverted during an annual irrigation season to irsigate about 20,000 acres of land. This includes about 14,000 acre-feet imported from the Bear River. A total of about 30,000 acre-feet of ground water is pumped per season for irrigation, of which, about 20,800 acre-feet is pumped in the area upstream from Topaz to irrigate about 9,500 acres, and about 9,200 acre-feet is pumped downstream from Topaz to irrigate about 4,000 acres, The estimated average annual consumptive use of crops is about 1'4 acre-feet per acre per season, and the consumptive irrigation requirement is about 1.1 acre-feet per acre. Thus total net ground-water purnpage in the basin is roughly 14,8100 acre-feet.

Since about 195 1, ground-water purnpage: for irrigation has grown from an almost negligible amount to an amount equal to about one third of the total quantity of surface water diverted and applied for higation. The trend is toward greater use of ground water. Ultimately, this trend might reduce strearnflow, but data needed to estimate the time and the quantity of this reduction are not available. Direct measurement of seepage losses dong selected stream segments during the pumping season may be useful if an attempt is made to evaluate possible Iasses in stream discharge resulting from ground-water withdrawals. REFERENCES CITED

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