RESEARCH· ·1970·

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WEEKS B225 149°45' ELMENDORF /" .·~ .. __../'·· / . 61° 15' 0 2 MILES ·. Stream deposits EJ . . Alluvial fan EXPLAN_ATION Gaging station at Fort Richardson diversion dam Gaging station at Elmendorf AFB Measuring site at Post Road ll'IGURE 1.-Sketch of the AlllChorage M-ea, slhowing gaging stations and selooted footures in Ship Oreek basin. -- 'liim cu.. oc( .... "' 0 ... ~ ... cn-o b,QC c Q) 'iiO ..§ ~w I rock NOT TO SCALE 1l'munm 2.-Idea.li:l.ed. geologic cross section along Ship Creek, showing the general direction (arrows) of ground-water movement. channel storage in the reach. If these two seepage runs are disregarded, the average gain in the reach for the remaining nine runs is 21.5 cfs and the standard deviation is 1.9 cfs. Seepage measurements were not made duting the summer months, although the major part of the annual runoff occurs during this period. The mean daily discharge during the high-flow period generally ranges from 200 to 600 cfs, and the discharge measurements are only accurate to about 10 percent. For a discharge of 200 cfs, the possible error in the difference between two measurements is ± 40 cfs, and for 600 cfs, ± 120 cfs. Therefore, ground-water inflow cannot be reliably determined during high flows because the measurement errors will be nearly as large as, if not larger than, the ground-water contribution to streamflow. The seepage data show that Ship Creek gains about 22 cfs in the reach below the Elmendorf gaging sta-
'B226 RELATION BETWEEN GROUND WATER AND SURFACE" WATER 149 TABLE 1.-Ship Creek seepage measurements made at the Elmendorf ,....:"5:..:::5_'-----:--:-r------------.....:. 149 4 .....:.,".;..::5_'----, Air Force Base gage and near Post Road, in cubic feet per second. Date Apr. 27, 1959 1_: _____________ _ Apr. 26, 1960 1 _________ _. ____ _ Oct. 26, 1960 1 _______________ _ Mar. 13, 19611 _______________ _ May 16, 1967 1 ______________ _ Sept. 12, 1968 _______________ _ Nov. 8, 1968----------------- Nov. 15, 1968 _______________ _ Jan. 3, 1969 _________________ _ Jan. 30, 1969---~------------- Mar. 26, 1969 _______________ _ · t Data collected prior to this study. Discharge measurements Elmendorf gage 28. 3 20.4 172 ·19. 2 182 75.0 17. 6 2. 8 2. 3 1.4 1. 3 Post Road 80. 8 44. 6 193 40. 8 191 97. 0 41. 6 24. 0 21..3 23.3 19.9 Seepage gain 52. 5 24.2 21. 0 21. 6 9. 0 22. 0 24. 0 21. 2 19.0 21. 9 18. 6 tion during the low:flow period. Because the groundwater levels are higher in the summer than in the, winter, the ground-water contribution to streamflow is likely to be greater during the high-flow period than during the low-flow period. Thus, it can be concluded that the mean annual gain is at least 22 cfs and possibly more. This discharge is supplied in part by ground-water inflow from the recharge area above the Elmendorf gage ... This can be shown by the following analysis of the unconfined aquifer in the reach of Ship Creek basin below· Elmendorf. The clay bed underlying Anchor~ge is exposed along the coastline and forms a ground-water dam which prevents discharge from the unconfined aquifier to Cook Inlet except through Ship Creek. Field observations have located only minor seeps from the bluffs along the coast. The glacial deposits of the Elmendorf moraine (fig. 1) form a barrier to ground-water movement to the north, and a topographic high forms an unconfined ground-water divide to the south. Thus, except for vertical leakage through the clay, the only sources of recharge to the unconfined aquifer are infiltration of precipitation and ground-water inflow from the recharge area above the Elmendorf gage. The average annual precipitation rut Anchorage is 15.14 inches for the 25 years of record, and the area tributary to Ship Creek in the reach below Elmendorf is about 10 square miles. This average precipitation on the tributary area is equivalent to only about 11 cfs per year. Because direct runoff and evapotranspiration losses reduce the amount of precipitation available for recharge, the recharge to the unconfined aquifer must be less than 11 cfs. Therefore, if changes in storage are neglected, at least 11 cfs must be ground-water inflow to account for the 22-'cfs gain in Ship ·Creek. Potentiometric levels in the reach of Ship Creek basin below Elmendorf have dropped approximately 25 feet in the last 10 years. The seepage data indicate that no significant change in the gain has occurred dur- 61° 15' ..., .~. .·~·· ANCHORAGE i - 1968 I r-:-.---~ 0 2 MILES FIGURE 3.-Sketch showing chauge in area of Ship Creek basin where artesian potentiometric levels were a.bove land surface in 1958 and 1968, as indicated by patterns. · · .. ing this . pe;riod (standard deviation of 1.9. cfs); and field observations have disclosed that most of the gain occurs in the first half mile below the Elmendorf gage. Because the present potentiometric surface is below stream level in this reach (fig. 3), vertical leakage through the clay cannot contribute to streamflow. The 11-cfs gain must come from the recharge area above the Elmendorf gaging station. Consequently, any estimate of recharge to the aquifer system from the area of Ship ·Creek basin between the diversion dam and the gage at Elmendorf must account for this. return flow. The presence of recent stream deposits along Ship Creek (fig. 1) suggests that the 11-cfs return flow may be largely in the form of underflow. That is, about half of the 25 cfs that is lost in the upper reach of Ship Creek actually recharges the aquifer system, and the remaining half moves through the highly permeable gravels under and adjacen.t to the stream downgradient. REFERENCES Cederstrom, D. J., Trainer, F. '\V., and Waller, R. M., 1964, Geology and ground-water resources of the Anchorage area, Alaska: U.S. Geol. Survey Water-Supply Paper 1773, 108 p. Miller, R. D., and Dobrovolny, Ernest, 1959, Surficial geology of Anchorage and vicinity, Alaska: U.S. Geol. Survey Bull. 1093, 128 p. Sommers, D. A., and Marcher, M. V., 1965, Water resources appraisal of the Anchorage area, Alaska: U.S. Geol. Survey open-file report, 34 p. Waller, R. M., 1964, Hydrology and the effects of increased ground-water pumping in the Anchorage area, Alaska: U.S. Geol. Survey ·water-Supply Paper 1779-D, 36 p. t' ·.,
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. ., GEOLOGICAL SURVEY RESEARCH·
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CONTENTS GEOLOGIC STUDIES Petrology
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GEOLOGICAL SURVEY RESEARCH 1970 Geo
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B2 PETROLOGY AND PETROGRAPHY for bi
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B4 PETROLOGY AND PETROGRAPHY has be
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B6 PETROLOGY AND PETROGRAPHY. 32
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B8 PETROLOGY AND PETROGRAPHY TABLE
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BlO · PETROLOGY AND PETROGRAPHY EX
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GE,OLOGICAL SURVEY RESEA·RCH 1970
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B16 PETROLOGY AND PETROGRAPHY Sprin
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B20 PETROLOGY AND PETROGRAPHY Sigva
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B22 PETROLOGY AND PETROGRAPHY EXPLA
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B24 PE~ROLOGY AND PETROGRAPHY schis
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B28 PETROLOGY AND PETROGRAPHY sg•
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B30 PETROLOGY AND PETROGRAPHY Detri
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B32 PETROLOGY AND PETROGRAPHY place
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B34 PETROLOGY AND PETROGRAPHY 66 '
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B36 PETROLOGY AND PETROGRAPHY Post-
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B40 PETROLOGY AND PETROGRAPHY did n
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B42 PETROLOGY AND PETROGRAPHY Creta
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td :t 106'20' r--- 10' 106'00' 38'3
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B46 STRUCTURAL GEOLOGY FIGURE 4.-Vi
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B48 STRUCTURAL GEOLOGY FIGURE 6.-An
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B50 STRUCTURAL GEOLOGY clined slide
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GE,OLOGICAL SURVEY RESEARCH 1970 CA
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B54 GEOPHYSICS (1950), Domzalski (1
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B56 GEOPHYSICS STRATIGRAPHY AND LIT
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B58 GEOPHYSICS STRATIGRAPHY AND LIT
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B60 GEOPHYSICS value. A normal free
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B62 GEOPHYSICS Hammer, Sigmund, 193
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B64 110°45' GEOPHYSICS L I I \ "'\
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B68 GEOPHYSICS A' San 0 p A c I F I
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B70 GEOPHYSICS lies occur over rela
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B72 GEOPHYSICS 36° 00' A' 40___./
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B74 GEOPHYSICS igneous massif is co
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B76 GEOPHYSICS A 50 Bouguer gravity
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B80 GEOPHYSICS FIGURE 1.-Bouguell'
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B82 GEOPHYSICS J I 37·~~------~~--
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B84 GEOPHYSICS B 600 B' 500 400 (/)
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EXPLANATION Pikes Peak • batholit
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DISTRIBUTION OF URANIUM IN URANIUM-
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B92 GEOCHRONOLOGY Fleischer, R. L.,
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B94 ECONOMIC GEOLOGY 103° 35' w 1/
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'B96 ECONOMIC ·GEOLOGY 0 500 FEET
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B98 ECONOMIC GEOLOGY TABLE !.-Summa
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BlOO ECONOMIC GEOLOGY surface seems
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GE 1 0LOGICAL SURVEY RESEA·RCH 197
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B104 EJrucJh of the four samples wa
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B106 ECONOMIC GEOLOGY R. 56 E. R. 5
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B108 ECONOMIC GEOLOGY outcrop under
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BllO Brady, of the Museum of Northe
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Bll2 PALEONTOLOGY FIGURE 1.-ProtobZ
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B114 PALEONTOLOGY c .,;# I I ' ' lO
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B116 PALEONTOLOGY ments, the larges
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B120 L xMH 'xE soo~~B_R~I __ T_I __
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B122 PALEONTOLOGY Tetrataxis sp. Te
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Bl26 PALEONTOLOGY TABLE 2.-Ranges o
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B128 PALEONTOLOGY l
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BI30 PALEONTOLOGY Ocmt/rrence.-P. m
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Bl32 PALEONTOLOGY proximately 5.7 m
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Bl34 PALEONTOLOGY a b c d e f g - D
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Bl36 PALEONTOLOGY --- 1963. The ori
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B138 PALEONTOLOGY core are m1ssmg,
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B140 PALEONTOLOGY death assemblage:
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Bl42 STRATIGRAPHY EXPLANATION l:.\.
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B144 STRATIGRAPHY ver. We do not in
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B146 STRATIGRAPHY age. A stratigrap
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B148 5 10 15 20 X X Plntygonus Pla.
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B152 STRATIGRAPHY at a depth of 58
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••••• 0 .... ••••
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B156 STRATIGRAPHY REFERENCES Brown,
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B158 STRATIGRAPHY In what follows,
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Bi60 STRATIGRAPHY TABLE !.-Stratigr
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B162 SEDIMENTATION with increasing
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llj ...... ~ TABLE 2.-Specific grav
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B166 TABLE 3.-Settling time for a 1
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Bl68 GEOMORPHOLOGY 74° 44° YERMON
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B170 GEOMORPHOLOGY have also been r
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B172 GEOMORPHOLOGY end of Long Isla
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Page 181 and 182: ~ooo ______________ B176 ANALYTICAL
Page 183 and 184: B178 terranes where the search for
Page 185 and 186: B180 Reproducibility Replicate anal
Page 187 and 188: B182 ANALYTICAL METHODS in the aque
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Page 191 and 192: B186 ANALYTICAL METHODS 3.31 percen
Page 193 and 194: Bl88 ANALYTICAL METHODS 3" 2%" Oute
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Page 197 and 198: B192 GROUND-WATER RECHARGE I T I 14
Page 199 and 200: B194 GROUND-WATER RECHARGE Therefor
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Page 203 and 204: B198 GROUND-WATER RECHARGE the basi
Page 205 and 206: B200 GROUND-WATER RECHARGE t \ \)
Page 207 and 208: B202 GROUND-WATER RECHARGE Water is
Page 209 and 210: B204 GROUND-WATER CONTAMINATION rv
Page 211 and 212: B206 GROUND-WATER CONTAMINATION TAB
Page 213 and 214: B208. GROUND-WATER CONTAMINATION fa
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Page 217 and 218: B212 SURFACE WATER plotted, and the
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Page 221 and 222: B216 SURFACE WATER however, if the
Page 223 and 224: B218 SURFACE WATER TABLE 4.-Variati
Page 225 and 226: B220 RELATION· BETWEEN GROUND eral
Page 227 and 228: B222 -0.010 f -0.005 (i) RELATION B
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Page 233 and 234: B228 RELATION, BETWEEN GROUND WATER
Page 235 and 236: B230 RELATION BETWEEN GROUND WATER
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Page 239 and 240: B234 EROSION AND SEDIMENTATION side
Page 241 and 242: B236 EROSION AND SEDIMENTATION s·o
Page 243 and 244: B238 EROSION AND SEDIMENTATION Cont
Page 245 and 246: B240 EROSION AND SEDIMENTATION 2 3
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Page 249 and 250: B244 GEOCHEMISTRY OF WATER REFERENC
Page 251 and 252: B246 HYDROLOGIC TECHNIQUES The upla
Page 253 and 254: B248 HYDROLOGIC TECHNIQUES type in
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Page 257 and 258: B252 formula may also be useful in
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Page 261 and 262: B256 randomly fluctuating component
Page 263 and 264: B258 HYDROLOGIC TECHNIQUES 1.0 ~ Qj
Page 265 and 266: ~ B260 HYDROLOGIC TECHNIQUES 1-3, f
Page 267 and 268: I B262 HYDROLOGIC TECHNIQUES REFERE
Page 269 and 270: ,' B264 Page Gravitational sliding,
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RESEARCH· ·1970·

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