MAY,1919. MONTHLY WEATHER REVIEW. 309 attended by sufficient duration of warmth to thaw the war, in amplifying the general forecasts for the specific ice, is even more disastrous, unless the flow can be regu- problems in his own region. During the past winter lated to allow all water to pass under the ice. (December, 1918, to March, 1919, inclusive) the State The daily publications and reports of the Weather forecasts were amplified at the Salt Lake City ofice of Bureau, especially the forecasts, are utilized freely in the the Bureau for the Bear River revion, and the coiiditions consideration of this daily problem of water regulation, previiiling over the northwestern states were given to the the superintendent of power hamng made intensive use officinls of the company by telephone each niorning for of the weather map until it was suspended during the theiI consideration in the water regulation problem.

THE COLORADO RIVER. By FREDERICKH. BRANDENBURG,District Forecaster.

[Dated: Weather Bureau, Denver, Colo.. July, 1916.1

SYNOPSIS.-TGSp.'t er concerns the method of river-stage forecast- The mountainous nature of the country and the lack of ing for the Colorado giver and its principal trihutiries, the (;reen, telephone and telegraph Iacilities prevent the establish- Grand, and Elan Juan Rivers. A brief description of the topographic features and courses of these streams is given. Attention is given to meiit of aging stations on any part of the upper Colorado temperature conditions, as these to a large extent control the nielting River. $he usual method of predicting stages from gage of the snows, which in turn make up much of the water su ply. Two readings at upstream stations on the same river is there- rating tables supplement the text, covering the Green antthe Grand Rivers, respectively.--a. L. The Colorado River is formed by the junction, in southeastern Utah, of the Green and Grand Rivers, ant1 is 'oined by the San Juan River, its most im ortant tridutary, a few miles north of the ArizonaXtat State line. (See Fig. 1.) The Green River rises in the mountains of southwestern Wyoming, and thence flows southward. From its source to ita junction with the Grand River the Green is 425 miles in length. Near the Colorado-Utah State line it receives the waters of the E'am,a and White Rivers, which drain northwestern Colorac\ 0. The Grand River, which rises on the western slope of the Continental Divide in central Colorado, is joined by the Gunnison River at Grand Junction, Colo., and also by the Dolores, which drains the western slope of the San Juan Mountains, a short distance above the junction of the Grand and Green Rivers. The San Juan, which rises on the southern slo e of the San Juan Mountains, a part of the Continental 8iyide in southwestern Colorado, is about 200 miles in length. In southeastern Utah and northern Arizona the Colo- rado River flows in a deep, rocky gorge, or canyon, through rac tically uninhabited, and the conditions are verya regionQ sim' ar along the Green and Grand Rivers for about 125 miles above their 'unction. The draina,oe area oi the Colorado River falls naturally into three divisions, the low-lying desert region, the elevated latoau re ion, and the mountain region. Each division Ras its c8' aracteristic climatic features. The lower division extends from the Gulf of California to the most easterly part of southeastern Nevada; the middle division from southeastern Nevada to the rating stations at Elgin, Utah; Fruita, Colo.; and Farmington, N. Mex.; and the u er division includes the area above such stations. Reup er division is bordered on the north and east by the cpontinental Divide and on the west by ran ea of high mountains. &e main flow of the Colorado comes, of course, from the snowfall in its up er reaches. The flow, however, is seldom large except cpuri the periods of melting of the snow in the mountains. Yhe summer rise usually occurs in June. The middle division contributes a considerable FIQ. 1. volume of water during March, April, and often during fore out of the question, and results as unsatisfactory .the first half of May from the melting of snow on the high almost invariably attend an attempt to predicts the stages table-lands. Practically no flow is received from snow- of water on the main river from gage heights on the three fall in tho lower division, although in the northern part rivers uniting to form it because they are so widely of that division there are mountains which rise to an separated and their flow varies so greatly, a different altitude of several thousand feet. method of arriving at results is necessary.

Unauthenticated | Downloaded 09/26/21 10:53 PM UTC 310 MONTHLY WEATHER REVIEW. MAY, 1919 Temperature conditions as &ec ted by different a1 t.i- t,he Green watershed, while henvy rains on the Grand tudes and the wide range in latitude through which the wat,ershed are local in character and unusual. The Colorado River and its trihutaries ilow cont,rol the mountain region draining int,o trhe San Juan, however, is melting of snow and affect the rat.e and datmeof the rise oc.casionally subjected to heavy downpours, causing and the volume of water discharged. One tributary niay destructive fres1iet.s. The bed of t,he main river can be low, while tlie others are high at a corresponding time; accommodate t.he largest freshets that occur in the anotlier year the conditions may be direct,ly the o posite. Green, the Grand. or the San Juan singly, but when two By combining the discharge the volunie in cubic Feet per of these rivers are in flood at t,he same time the lower second is trhe same as though the entire diwharge were river below the point of junction overflows it,s banh and in one stream. Discharge nieasurel1ient.s are made in causes damage. This condition occurs only as the the Grand River at Fruit,it, C'oh., a feu- miles beluw the result) of the nieltiiig of heavy and general snowfall in the of the Grand and Gunnison; and on the Green upper reaches. iver at Elgin, Utah. The clistharge of the 8an Juan is Occasionally t,he measured discharge of the Colorado . est.imrtted from the gage heights nt H station near Farni- River st Yunia is less than t.he aggregat,e discharge of its ington, N. Mes. t,ribut,aries at t.he gaging stations heretofore mentioned. Usually there is an early and moderate crest in the The difference is in part due to the diversion of water for lower trunk stream from t,he melting of snow in t.he a.gricult,uralpurposes under the Tuma reclamation pro'ect. middle division. As this nren is below the rat.ing stations, As tlie masimum amount of these diversions is only ai out an estimate of the amount. of this flow must be made and 6,000 second-feet,, the cause of the smaller flow is most added to the conibined tlisrharge of t.he severd tribu- likely clue to the temporary holding of the flood waters taries at the rating stations above mentioned. Aft,er on the lowlands adjacent to the river, which are slow to the middle of May the disclisrge of the Colorado River re turn. comes almost entireJy from the upper division, simplifying The time iat.ervn.1for crest.s increases with the flooding the forecnsting: for the.lower reaches. of the lowlands. Flood plains cover a large area in the Rating tables showmg the tlischnrge of the Green at lower di~i~ion.For niiles above the station at Topock Elgin and the Grand at, Fruit.s, as det.erminecl by the the valley is 5 or 6 miles wide, and during freshets much Water Resources Branch of the United States Geological of t.his area is covered by wat,er, the overflow beginning Survey, follow: when the gage at, Topock is 11.5 feet; and when at 17 The tables give for each t.enth foot on t!ie gsge t.he feet the river a.tNeedles, Cal., 11 miles upstream, is 3 or 4 number of cubic feet of water per second prrssmg t,he gage. niiles wid e. In practice, in addition to the volunie discharged by the Anot,her factor to be taken into account when fore- Green and Grand, allowance is made for the clischrge casting river age height.s of the lower river is whether from the Srtu. Juan and the smaller tributaries. The the season un der consideration follows a year or two free distance from Elgin on t.lie Green to To~oc~,L4riz., is from freshet,s. During prolonged periods of compara- about 760 miles. The elevation of Elgin is 4,044 feet tively low stages of the water, the immense amount of and of Topock 456 feet-mi average fall of 4.7 feet per silt brought clown from the upper reaches, where the fall mile. The distance from Fruit.8 on tlie Grand t,o Topock is great and the current, swift, is deposited in the bed of is about 735 miles. The elevation of Fruit,u is 4,487 feet, the lower river where the gradient does not exceed 2 feet making the average fall to Topock 5.5 feet per mile. The to the mile and the current is correspondingly sluggish. distance froni Farniin ton, N. Mes., on the San Jum, t,o TTnder this condition the same volume of water causes a Topock is 690 miles. %he elevation of Farmiiigton being higher stage than it would if it had been preceded by 8 5,240 feet, the average fall to Topock is 6.9 feet per mile. freshet during the same or even the preceding year. The distance from Topock to l'uma is about 165 miles; Scouring is rapid when the water is hi h. During the the elevation of Yuma is 137 feet, or an average fall of 1.9 freshet of 1909 it is said the channel at%uma was tem- feet per mile. porarily deepened 40 feet. The average time for a crest to travel from Elgin. to The folbwin.g general principles are fa,irly well estab- Topock is sh htly in excess of six days; from Frulta, lished: six days; anf from Farmington slightly less than six days. In practice sis days is used for the time int.erya1 The relation between the volume disiharged and gage for the combined discharges to reach Topock from Elgn, height.s is close in estreme crests. Fruita, and Farmingt,on. The time interval from the tributaries to the lower The average time for a crest to travel from Topock to river is practically the same in estreme crests. Yuma is six days ; but when there is sua tained very high There is a flattening out of freshet waves before the water upstream the maximum stage at Yunia is likely to lower river is reached. occur as much as eight days later than at Topock. The gp.neml ruks which in practice h.ve controlha -fwe During the greatest flood in 6he San Juan of which casting of the sta es of ,water in th her reaches of the there is record or reasonably authent,ic information, the Gblorado are as-fo Blows: peak traveled from Farmington to Topock in four and 1. Ex ected gage heights at lower stations produced one-half days, and from Topock t,o Yuma in three days. by corn fined discharge at rating stations above, have This flood occurred 0c.tober 6, 1911, nt a time of the year been determined. when the tmik stream is normally ver low, and alt,hough 2. Correction must be made for capacity of channel 8s much of the wat.er was taken up cy flooding of low a.ffected by previous or absence of revious freshets, and ground adjacent to the river, the time inte.rva1 was appre- also for amount of water likely t.0 Ee contributed by the ciably shorter than during the sumnier rises. middle division. 3. The relation bet.ween gage readings and discharge FORECASTING HIGH STAGES IN THE COLORADO RIVER. at the rating stations above on the one hand, and the . Flood wavea as commonly understood are the result nctud gage readings at the stations below on the other, of heavy rains. Heavy, general rains are unknown on as ascertained during the last preceding crest, deter-

! Unauthenticated | Downloaded 09/26/21 10:53 PM UTC MAP, 1919. MONTHLY WEATHER REVIEW. 311 mines the basis for the correction from the normal t.0 be TABLE2.-Rating table for Grand R.im near Fritita, Colo. allowed. - Gate Dis- Di9- Dis- )iller- 4. The differenc.e, if any, during tlie last preceding height. hrge. charge. charge. ence. crest, between actual gage heights at lower stations and - !- the expected heights at such stations must be c.onsirlered FW. SK.-/I. src.-ft. SfC.-fl. Ser.-ft. and an allowance, corresponding to such difference, if any, 3.00 3 oin 12,400 34,joo 720 3.10 3: 130 12. 750 35,220 720 made in the forecast. 3. a0 3,300 13, iin 35,940 720 3.30 3,90 13,470 st;, wo 72u 5. If the combined discharge of the Grand, Green, ancl 3.40 3, b10 13, 530 37,350 2uo 3s inu nu San Juan is in excess of 120,000 second-feet the time 3. XI 3.770 11 741 3.60 3,940 14:WJ 35’ 840 740 interval from these stations is one day longer for the 3. 70 4 110 15 020 39: 5w 7111 3.80 4: 290 l5:460 40.320 3.10 crest at Topock and two days for tlie crest at Tuma. 3. (Io 4 4io 15,9?0 41 OW 16,4110 540 6. There is generally a heavy run-off from the middle 4.00 4: Gfa 41’W 740 division before active nielting sets in in the upper divis- 4.10 4, SKI 16.850 42: 540 540 4.20 5 050 ;!,3s0 43.250 740 ion, and accordingly from 10,000 to 30,000 second-feet 4.30 5’250 ,.&W 44.020 740 4.40 5’ 450 1s 400 44,760 74u are added to the upstream discharge in A ril and the 4.50 5: GGO 1B:W 45,m 540 4. w 5 870 19.44u 46,340 early part of May, the aniount depending on t.K e preceding lY.QG0 46 740 4.70 0: os0 9so 740 4. so G, 300 20 500 47: 73 season’s snowfan. 3i1n4n 740 4.90 b, 520 48,460 740 7. The time interval from the middle division to the 5. nu 6.740 21’5s0 19, m 740 5.10 6,970 22: 140 49,940 stations in the lower division is four or five days. 23 700 740 5.10 7, 3w 50, Gsn 740 8. When one crest follow another, the interveni!lg .7. 30 i.,130 3:2%) r1,4?0 5.40 7,I:iO I.SIN %.im 740 3+, 4Gu 53 (100 740 period being too short for the submerged lands to draul, 5. 5u i.910 740 GO 8. Itill 25, ucjo 53; la0 the tinie interval from the up er division t.o tlic lower S. 740 5. 70 s.41u 2s. tiso 54,350 710 division is reduced one or two %ys. -5. rru s.1:iu 2i,3llO 58.13 5. YO Y 931) ?t;,Y411 55,4130 740 51;. 140 I;. uu u’an 2i 5S0 IXXJ 540 FALLING RIVER. G. lil Y: 40 2< 340 57 340 540 G. 30 9, 710 zs 9im 5s: nsll 740 li. 3u Ill.lJ7U %’a s3 an 59: 5li0 740 G. 40 io. 3sn 30: 360 740 When fallin stages occur in the upper reaches they I;. 50 111, 31l.INll GU. 3110 ;on 540 are due to coo er weather or to the fact that the season’s I;. tin 11 IBI! 31.WJ i;i,~n B 32.31:o 740 1.;. 1.;. iU 11: :uin G1.750 740 maximum of nielting of has passed. The lowr 1;. $1 33, wn snow ll.iOI! G?, ha! 740 river falls rapidly as soon as the crest has passed. It is 6 !K) 13, IGII 33, iSU 63,2E’l not unusual for the declinc to eqiial 30,000 second-fcet ~ __ - the first day and 20,000 second-feet the second and third days. WATER SUPPLY IN CALIFORNIA. By ANDREW H. PALMER. TABLE1.-Rating tublt-LjorGrmi Kiiw at Elgiri, LTid, mar C;reab Riwr, [Abstmct: Journd of Geography, New York, Vol. xviii. NO. 2 (Fch.. 1Y19.)] b‘tnh. The author discusses both the present and the future water su ,ply problem, with special reference to California. D1.s- Differ- 11 (:ace The e ect of the great latitude ancl topogra hic varia- h:iz. charge. enre. height. k - -- tion in the State is very niarlred on the rainf d-the real. Fret. sa.-f/. Sa.-/,. Fwl. source of water power. The rainfall of California pre- 6. UI 9.40 sents some astounding contrasts. In the Mohave Desert, 6.10 ?E 6.20 3 Yo0 for esnnnple, the average annual xecipitatioii is only 1 6.30 4’ 200 9. io 4’ wl to 3 inchcs, while in ortions of tL e Sierra ru’evades the 6.40 9.w9.90 6.50 4: ,Po0 E annual aniount escee s 100 inches. 6. Bo 5 100 B 6.70 5’ 420 33 It has been found that in the ccntrd Sierras up to 6.80 5: im 6.90 6,120 5,000 feet elevation tlie average annual rainfdl increases 7.00 6500 5 10.40g+; at the rate of S.5 inches for each 1,000 €eet.2 Fortu- 7.10 6: 900 7.20 7 320 jz I 10.50IO. riu nately, niuch of the precipitation at the higher elevations 7.30 i,740 7.40 8,180 is in the form of snow, thereb storing u) water for 7.50 s 620 power and irrigation purposes Airing the 11ong rainless 7. Bo 9: (kjo 7. i0 9, Frlo :::E summers so characteristic of the Pacific coast States. 7. 8u 10, ooo 11.2011.30 7. 90 10.5w) 3 After taking up the natural controls of water power, 8.00 11 m namely, climate, topography, geology,ve etation, and arti- mz mz 11.4011.50 8.10 11: 500 5oo 6. a0 12 OM) 11.m ficial agencies (dams, reservoirs, etc.), t% e writer gives a 8.30 1”’ 500 11.70 of 8. M li‘ ooo 11.u) brief his tory hydro-elec tric development in California. S. 50 13: 5M) 11.90 In conrlusion, he discusses water power in relation to 8.60 14.100 12. 00 8.70 14,iMI 12.10 irrigation, flood control, and cit water supply. S. 50 15.300 12.20 all R. 90 15.900 12.30 Thus, it is quite evident t tat of the principal 9.00 16 500 12.40 factors entering into the problem of water power and 9.10 17: 100 12.3 9. 20 17, 700 12. tul supply, climate, particularly precipitation, demands the 9.30 18,300 E 12.io first considera tion.-H. L. - I The above table Is not apptirable lor ice or ohstrurted ch:mnel conditions. It is 1 Qce McAdie A. Ci., The RainIall 01 California, Univ. of Cal. pubs. in Gecpaphy, based on three disrharge measurements .made durinc 1910 and the forin or previous Berhiley Calii vol I No 4 February 1914. curves: one diwharge measurement belug made June 13, 1909. gage 15.15 feet, and is 2 Henri. A. J.’: I&e hhecipitati& with altitude, MONTHLYWEATHER REVIEW, not well defined. January, 1919,47: 33-41. (2 e.) 135518-194

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