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Sediment Measurement and Density Variation in Reservoirs: A Study on Coarse Sediments, Study notes of Literature

The methods used for measuring sediment in reservoirs and the variation in sediment density. the accuracy of various methods, the importance of sediment density in predicting the weight of sediment volumes, and the factors affecting sediment density such as particle size and compaction. The document also includes data on sediment density and particle size for different types of sediments.

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Download Sediment Measurement and Density Variation in Reservoirs: A Study on Coarse Sediments and more Study notes Literature in PDF only on Docsity!

A Study of Methods Used i n

mBaSmmWT m; U U Y 8 1 9 OF Smf MEfT %N ST

Planned and conducted j o i n t l y by

Office of Indian A f f a i r s , Bureau of Ileclarnation

Tennessee Valley A u t h o r i t y , Corpsof Blngineers

Geological Survey, Depastmentof A g r i c u l t u r e

and Iowa I n s t i t u t e of Hydraulic Research

Report Bs. 9 BmSITP OF SmIM&:NT%D m S IN mSERVQ1N E. 8. L m e and Victor A. Roelzer

Published at

S t + Paul U. S. Engineer D i s t r i c t Sub-.Office

W d r a u l i c Laboratory, U n i v e r s i t y of Iowa

Iowa C i t y , Iowa

November 1943

Iri s r a e r t o determine the r a t e at whleh r e s e s v o z r s VIPLI f i l l w i t h

oedlmeri~ x t 1% o f t e n n e c e s s a r ~ to e s ~ l f n a t e the weight, pel urlat volume s f

r,he d e p o s ~~ e d sedlmecit because the q u a n t i t y o f sedlment c a r r i e d by a stream 1s usr*aJ.ly e q r e s s e d i s ; terms 0 % weight r a t h a i tharl volume A t h e t o u g h s L ~ ~ d yof t h i s s u b j e c t h a s never beer1 undertalprer~ arid consequently

thd- esC1mated d e n s l c a e s used cover a wide and i n d i s c r i m a t e range of val

ues All availabke d a t a have beera complied 111 this reporl The r e s u l t s

a.r](i C O ~ I C ~ ~ S L O U SC b r ' a w ~ ~from au a n a l y s ~ s oP the d a t a a r e s

f'o rm 2 p p ~1cab I t to the rleeas sf orgarl a ~ a t i o n s o r individuals i n t e r e s t e d. resarvolr dt?srgi~

Table of' Con tents (^) -- 7

FDU OF CONTEXTS

e^ Bectm-^ ion

f u INTROBUCTIBM I Scope of the project,,,,. , G - , o. ,................................. .1l 2 Purpose of this investigation, , ,.. " , c.............. 12 3 Bcope of this report"... , : ;. 2. , a. , ,.. ,... ,. -........ ,.. 4 Authority and personnel,................................. 14 5 Aehowledgment s.... -... ,,... , , , , " , ~...... , -. ,....... , , 15 11 A r n V I E 1 OF r n L I S r n D L I T g u T m 6 Previously published l i t e r a t u r e , ,. q 1 I I E~mphreysm d A b b ~ t t a. ,.. ,. , , * , 1 7

8 Elephant Butte Reservoir, , ,... I (

9 C o l o r d o River Basin, , , - , 20 10 Texas reservoirs,,, c a. - -. o o , , a , o , , 2 1 k l Mi sssuri Bi ver , ,. , a > 216

12 HiiimS Conservaaey District retarding basins, , , n a o u. 25

1 4 Et~ropea~~investigatioa~s... a c - o n , 2.4 1aaves"cjgat ions of coarse sediments ~n Califsrnia-. , -. 2 8 I? Studies of i n i t i a l density by Trask,. ., -

16 Other investigations, = , , > , a " 3 3 31

111, MSULTS OF STUDY OF A V A I M U DATA 17 Factors influencing sediment density.9o.;. ,.. -. --.. , - ,. ,....... - = 333 I& Analysis of observed densities,,,,. ;. -. a a ~ , 2 ~ ~ ~ : - , ~ ~ , , 9 35 ~. ~ , , , 19 Values of density f o r use in design,. : : , , ,. : ,. , , , , , , , , , , , , , , , (^) *&g

20 Supplementary B a t a 3 0 ~ ~ , , = ~ L , ~, ~ , o~ , o ~~ ~ o,. ~c o o, 0 3 ~.. , ,. s , ,. 2. 0 52

Section v-. R---. 11

%, 1, Lane and Victor A. Koelzer*

1, --The measurement of the q u a n t i t y m d c h a r a c t e r of sediment t r m s p o r t e d by strerams i s rn important a c t i v i t y common t o r i v e r m i n t e n m c e a d development, stream dischasge m e a s u s e ~ e n t , e r o s i o n c o n t r o l , i r r i g a t i o n a d h y d r o - e l e c t r i c development Considerable work i n sediment measurement and m s L y s i s has been done, but t h e methods and a y p w a t u s used L : ~ Y C v a r i e d nideljr and the q u a l i t y of the r e s u l t s r m g e s from very g09d t o very p o o r , 1x1 an e f f o r t t o improve and t o standardize the methods and equipment a cooperative p r o j e c t h a s 'been undertaken by t h e f e d e r a l agencies having problems i n t h i s f i e l d , S i x r e p o r t s covering t h e r e s u l t s of these s t u d i e s , have been issued as f o l l o w s * Report No l--scField P r a c t i c e and Zquipment used i n Sm- ment and neth hods used^ ed%mentu, i n suspendedis^ a^ d e t a i l e d review of sediment sampling^ the from theequip- e a r l i e s t i n v e s t i g a t i o n t o t h e p r e s e n t with d i s c u s s i o n s of t h e advantages sllu disadvantages of t h e various methods and i n s t r u - ments. The requirements of a samples which would meet a l l f i e l d conditions sat i s f a c l o s i l y a r e s e t f o r t h --93quipment Used f o r S m l i n g Bed-Load anad Bed Material". d e a l s mith equipment f o r s m p l i n g bed-load and

bed m a t e r i a l in a manner s i m < l & t o t h a t i n which Beport No. 1

covers suspended load, Suspended^ B e p o r f l o , Sediments',^ 3--- " M a l y t i c a l. covers an^ Studyi n v e s t i g a t i o n of the^ of^ Methods^ s f accuracy^ S w l i n g of v a r i o u s methods of s m p l i n g suspended sediment i n a v e r t i c a l s e c t i o n sf a s t r e a n , based on the l a t e s t developments i n t h e a p p l i c a t i o n sf t u r b u l e n c e t h e o r i e s t o sediment tsansport-,ation. *Professor of Hydraulic Engineering, S t a t e U n i v e r s i t y of Iowa and

A s s i s t a n t Engineer, U o 3 , Engineer O f f i c e , L s u i s v i l l e , Kentucky, formesly

J u n i o r Engineer, U o %.Geologic& Survey, r e s p e c t i v e l y ,

1" 2 "- - ---- ------ Section 2

---^ Report,.^ Ro^4 l'Me^ l2lods^ of^ Analy^ ~ l n gSediment^ Samplesf',^ de i , r i b e ~dnd c i ~ o c u c n e smaiy netbods developeci f o r determining the s i z e o f small p a r t i c l e s i n sediment a n a l y s e s D e t a i l e d i n

s t r u c t i o n s a r e ga veri f o r many of the cornon methods i n use for

clet,err:iining t h e p a r t i c l e s i z e and the t o t a l coizcentration of sediment 1x3 sLtaLples a s developed by agencies doing e x t e n s i v e work i n t h e s e f i e l d s , tfLabora"cry I n v e s t i g a t i o n s of Suspended Sedi,- r n e n f l w l e r s " , d e s c r i b e s investiga"cons of t h e e f f e e t of vari--

ous intake condi t i o n s 0 x 1 the r e p r e s e n t a t i v e n e s s of sediment s m - -

pbes the f i l l i n g c h a r a c t e r i s t i c s s f slow f i l l i n g samplers utjder v a r i o u s conditions, Report Mo , I - "A Study o f ;tee Methods f a r S i z e Analysis of ~uspend-t Samplesfi g i v e s account of a study t o develop methods of s i z e a n a l y s i s more s u i t a b l e to t h e c o n d i t i o n s usu- a l l y rnet 1x1 suspended s e d i m e n t s t u d i e s , I t d e s c r i b e s a simple

form of a p p a r a t u s developed m d g i v e s d e t a i l e d procedures f o r

i t s u s e , Two addi t ~ o n a lr e p o r t s now i n p r e p a r a t i o n v r i l l be issued s h o r t l y on Lhe f o l l o a z n g s u b j e c t s Report--- 110, 6 "The Design of Improved Types s f Suspended Bob.lm@n"Lmplers~~d e s c r i b e s t h e development of v a r i o u s t y p e s asl" Lrkune integrating smunplers s u i k b l e f o r t a k i n g v e r t i c a l l y i n Legrated sarn,uLes i n f l o a l n g streams and o t h e r s f o r Lakialg time--

integrated r,anpl e s at a fixed p o i n t , D e t a i l s o f the b e s t forails

developed are g i v e n ---Report No,^ 8-- '~Measuremene^ s f^ Ihe^ Sediment Discharge^ s f Strezmasft, d e s c r i b e s the most e f f i c i e n t methods and equipment t o bo used i n making sediment measurements under various con- d i t i o n s e n c o w t e red i n n a t u r a l s t r e m s The scope of the p r o j e c e h a s been broadened somewhat i n o r d e r t o eanb~aee Che s1Ct~dy of Bedi~exltderisi t y described i n t h i s r e p o r t , as t h e

s u b j e c t covered was o f considerable importance to the agencies involved

aBnd t h e m a t e r i a l w a s a v a i l a b l e without f u r t h e r e f f o r t ,

2 , Purpose of t h i s i n v e s t i g a t i o n - I n aetesmlaling the economic f e a s i b i l i t y of a r e s e r v o i r p r o j e c t i r ~a sedimerlt b e a r i n g stream, one s f

the mast i m p s r t m ~problems is to malee an e s t i m a t e of t h e l i f e of t h e

1 !-I- "* ----------- (^) - Sect i o n 4

t - i ~ioat ~n d e t a i E ax" a l a r g e m o t m t o f h i t h e r t o unpub%ished d a t a (^) an sedi- aunt d e n s i t i e s md s i z e c o q o s i t i o n , vhich should be useful. i n m y f u r. -

t h 2 2 "aLudics which nay be made sf t h i s s u b j e c t ,

A f t e r the o r i g i n a l d r a f t of t h i s study was completed, c o n s i d e r a b l e

aors s r i g i n % % d e t a i l e d d a t a c o l l e c t e d by the So i l Conservation Service

be&?me a v a i l a b l e , but, l a s ~ f o r t m a l e h y ,i t was i n p o s s i b l e t o d i g e s t these

d a t a and co1~1parethem w i t h the conclusions reached from the e x m i n a t i o n o f the e a r l i e r d a t a , In the time a v a i l a b l e i t mas p o s s i b l e o n l y t o pre- ,jarde t hess d a t a i n d e t a i l i n t a b u l a r f o r n , tvherre t h e y w i l l be a v a i l a b l e

1 1 0 ~ ' ~ U L I Z Z - ~st~dies,as given i n Tables 1% a ~ dl 2

A u t h o r i t y =d persomel--The F e d e r d (^) agencies p a r t i c i p a t i n g i n

the geiAtsaa1 s t ~ d yof ftMeLh~ds Used i n Measurement and h d y s i s of Sedi-

nacr:%,f,s&a in S t r e m ~ ,! ~a r e : the Corps of E x i n e s r s , the Geologies% Sur

u s ; y , the Bureau of B e c L m t i o r , , the O f f i c e s f Indian A f f a i r s , the Flood

C su, t-01 Ctssrdinating Cornit t e e of t h e Depatment of A g r i c u l t u r e , the

'Y', X L R O M S ~ ~Vallegr Autk~ority, The work was l a r g e l y c a r r i e d OIL by personnel

i ~~x~i~iskaadby these w e n e f e s under the d i r e c t i o n o f P r o f G I 3 '@' Wme of

l , f ~ e $ 0 ~ ~ 3 I n s t i t u t e of B y d r a d l ~ Research a s s i s t e d by the s t a f f of the l o ~ : , ; ~ @j ty Sub OZffee of "ce Corps of Engineers Among those engaged or^ ~ l l i eworBr were P o C - Benedict, C. be B o y l l , M - D. Dubrow, 6 B..Borne, 'b he Koelzer, P* M e gobhe V , J c Palmer, F. W , Barker, D E R h i n e b r t , ;uad W P , 8 , S t a n l e y o The p r e s e n t r e p o r t was f i r s t assembled as a p e r s o n a l

p z v j e c L b y the a u t h o r s , but as t h e m a t e r i a l w a s of g r e a t i m p o r t a c e t o

~iaeagencies involved and, s i n c e p u b l i c a t i o n w i t h t h e s e s t u d i e s v o d d preserve a great p a r t of t h e value of the r e p o r t b y e n a b l i n g "ee d e t a i l e d

Section-- 5 - - - ---- -----

d a t a "e be p ~ ~ b l i s h e dI n fuJ 1, i t was decided t o i n c o r p o r a t e t h i s s t u d y as

a p a r t a f t h e major i n v e s t i g a t i o n ,

-^ s--Mu~kl.^ of^ the^ q u m t^ i t a t i v e^ d a t a^ on^ d e p o s i t e d^ sedi-

mentvahich have been used ixa t h i s r e p o r t s e r e obtained from m p u b l i s h e d

records of the W e S , Geological Survey, c o n s i s t i n g of t h e r e s u l t s of wit

weighto m d p a r t i e b s s i z e malysss of numeroue s a a p l e s taken from d e p o s i t s along the Colorado River its trlbuCLaries;4 by T, D, C o l l i n s , C. 9. Ilsward, and S , M e Love, Considerable d a t a v e r e f u r n i s h e d a l s o by the

Missouri Rives D i v i s i o n o f eke Corps of Bngineers v ~ h i c h had been eonpiled

by nf. L. 6. Straub. An^ a r t i c l e^ by^ 0exls(2~),^ t r a n s l a t e d f o r^ t h i s^ study

by t h e U , 8 , Bsterways Xxpsriment S t a t i o n Research C e n t e r s , gave a g r e a t

deal o f da"c from European s t u d i e s on t h i s s u b j e c t. A n m b e r o f sampler:

w e r e c a % l e c l e d from t h e Iowa m d Cedar R i v e r s by t h e Iowa I n s t i t u t e o f Xtydraulic Wesearch, These vmro analyzed by 5 , C. Kennedy, of the U. 3 ,

Xngbnwof Dspartrraealt, who also ~mdf;a preliminary review o f t h e p r e v i o u s

1 i t e r a t u r s on t h i s aubjecL SmpLes sf t h e d e p o s i t s i n t h e 3ngLersood mi$

Bermax1town retarding "basins sf t h e %imi Conservmcy D i s t r i c h n e r e f u r -

nished by C o H, E i f f s r t , Chief Engineer, ,and C. 3. B e m e t t , E n g i ~ e e r , of that o r g a n i z a t i o n , A barge c o l l e c t i o n of ~mpu'blishedd a t a was a l s o f u r - nished by the S o i l Conservation Service o f the U. S. Departmerbt of Agri-

c u l t u r e. Q t h e r d a t a were obtained from t h e p u b l i c a t i o n s of the $ o i l Con-

s e r v a t i o n Berviee, and " c h e U , 5. h r e a u o f R e e l m a t i o n , and from M s. A. D * Lewis, D i r e c t o r of I r r i g a t i o n , Union of South A f r i c a. Many v a l u a b l e sug- g e s t i o n s mere made by C a r l B , Brow.., % $ e d of the R e s e r v o i r S e c t i o n , Sedi-

mentation D i v i s i o ~ bof t h e S o i l Conservation S e r v i c e , 9k1e geneyous cooper-

6 , Previously published li terature--The f i r s t phase i n the study consisted of a thorough review of the previously published information

dealing with t h i s subject, Beferences %.rerefound scattered i n engineer-

ing L i t e r a t u r e , and t o a i d fukure i n v e s t i g a t o r s a bibliography i s added

at the end s f t h i s r e p o r t , I t was found t h a t unit veights varying from

3Q to 125 l b s , p e r cu. f t , have been used by various engineers i n e s t i - -

mating r a t e s of reservoir f i l l i n g. En the foSlowing paragraphs the im.- portant information from these a r t i c l e s i s summarized,

  1. % 3 u ~ h r e y sand^ Abbott--The*^ e a r l i e s t record^ found^ of^ any estimate

of the d e n s i t y of deposited sediment was made i n 1861 by H ~ p l l r e y sand

Abbott who, used a value of 120 Lbs, p e r cu, f t , f o r the unit weight of

material deposited by the Mississippi River.

8, E l e p h a t Butte Reservoir--The Elephant Butte Reservoir,which w a s constructed between 1910 anti 1916 on the Rio Orande River in New ldexico , probably has r e c e i ved more study from the standpoint of sedimen- t a t i o n t h w m y other r e s e r v o i r , Because the sediment Load of t h i s

e t r s m i s extremely heavy, amounting t o as much as 22 per cent by weight,

i h w a s recognized e a r l y t h a t e x t e n s i v e deposition would occur i n the r e s e r v o i r , and s t u d i e s of sedimentation mere therefore p a r t of the in-. v e s t i g a t i o n m d design of the p r o j e c t. The f i r s t study seems t o have been made by T?. II. F o l l e t t of the U. 3. Geological $urvey(5).- On the b a s i s of a single s q l e consisting o f a g - i n , cube taken under c a r e f u l l y

selected conditions, he c o n c l d e d that the u n i t meight of deposited ma-

    1. 8 ..~ Section PI

tepi;zi_ J L L the proposed Elephant Butte Reservoir would be 53 l b s , p e r cu. f ' c - a~d. that an average of 19,739a c r e f t , of sediment would be deposited & k ~ i. u c i 1 1 y lt, i s i n t e r e s t i n g t o note t h a t a Eater survey of the s i l t i n g of the ilicphnrit DutLe Reservoir indicated(') t h a t it was f i l l i n g at the r a t e of 20,000 acre f t. p e r y e a r , Concerning these r e s u l t s , Hemphill ('1 s a y s ,

J'YooXIett made no e s l i m t e of the silt r o l l e d abomg the bottom of the

stream, but s t a t e d h i s b e l i e f t h a t it might p o s s i b l y mount t o as much as

25 per cent of t h a t suspended, Accepting t h i s r a t i o as a maximum, the L ~ J S U L L ~o f the survey gave aurait value of 65 l b s , of d r y silt p e r cu,

f t , sf d e p o s i t , It i s believed t h a t they ( t h e 3 i o Grmde sediment reo-

o r a d s ) ware accurate enough t o i n d i c a t e f a i r l y that suspended s i l t i n the kliblo Gcande rvibk form d e p o s i t s containing from 55 t o 65 bbs, p e r c u e f t.

O T o i a t f t

w aCutXy o f the sediment deposited i n %he b a s i n was made by R. R ,

g d 3. i n ~ 9 1 6 ,who measured the d e n s i t y of three

~ ~ t ~ a ~ ~ p l c sof sediauaent and f o m d d r y weights of 88 t o L O 1 Iba. p e r cu. f t ,

I ~"r,ll311. average o f 92 I b s , per CU, f t , Sieve m a l y s e s o f t h e s e s m p l e s

~ h , + ~s i z e s ranging f r o m 76 t o 88 per cent (average 8 1 p e r c e n t ) p a s s i n g Cne ;)03 mesh s f e v e md p ~ a c t i e a l l ya l l passing t h e LBO-mesh s i e v e , The water inflow i n t o the Elephant Butte Reservoir has been measured

aC Sari Marsial, a s h o r t d i s t a n c e above the r e s e r v o i r s i n c e before storage

nas s t a r t e d in the b a s i n , Continuous sediment observations were made i n

1913 a d from 1925 t o d a t e , Based on the inflow and sedimene records,

esttmaates of the d e n s i t y of t h e sediment mere made by t h e I n t e r n a t i o n a l Boundary Comission from 1925 t o 1935 and by the Sedimentation Division

(^20) ---- "- - -- --- Section 9

t l i l i d - osraissicara is pl~obablyvalid, The International ]e3oundary Csm-

v a :;b9 0x1 e s t imata neglects the storage sf sediment above spillway level,

cl;L tirzstecl by "Lie $oil Conservation Service at 14,323 acre ft. This is

j ( 5 p t r cent sf the storage used for the total period and l1,8 per cent

r3i" the storage used f o r the 1925 to 1935 p e r ~ o d ~The error is therefore

betryrcen 3,8 and lL 8 per cent It is reasonable to assume that most sf

L!w, sct%inaen"cabove spillway level was deposited in the latter part of the

p d " i. ; d , since during anuch of the early part of the period the reservoir

was S'EIling up, and bklerefsre at a low level Assuming that 18,000 sf

L L I ) $ , 32 j acre fL, were deposited in the 1925 to 1935 period, the in-

c i ~ ~ s i o r ~of t h i s volume in the 1925 to 1935 estimate would lower the sedi-

man% d e n s i t y f r o m 70,2 Lo &4*5I b s , per cu, P t , h o t h e r part of the d4f-

:s:ionbc ill tila densities computed by the two organizations is probably

UP: I(:, Lhe shrir~k~agei r b the sediment ~ i t htime, The assumption is made

i,i~,:C "tit? 0 CPero~rce in "che sedimen"c~rcsJ.tame in 1925 m d 1935 is "che space

'st,$ 1ci.~;-d ibg i,he sediment which cans in during this period" Actually the;

&, d ~ , i l ~ n Cr c e ~ ~ p f s erketoovlly this space but also the space made available

) 1 a g e o f the sedineb%%deposited before 1925 which took place dur

i r l g Ghe 192"30 1935 period. The true volume of the 1925 to l935 sedi-

I t s therefore greater than that estimated md the true density is

Cl~crc Pace Lees khan estlmted, Knowledge sf the rate sf compaction in

r o t,e: ("voi rs f s i l l sxrf f f cient to estimate closely how much difference in

c? e l \ b i t y the csqact5on vouXd make, but it might m o ~ m tto several Lbs,

1 ) 9 1 eu, Et,

.$,L&$ River Basin Considerable data have been collected in

Sset ion 10 2 1

the v a l l e y of the C o l o r d o River i n Arizona a d California. The U. S.

Bureau of RccLwnation used(7) a u n i t weight of 100 l b s. p e r ou. f t. i n

studying the deposited material i n the I n p e r i a l Canals, F o r t i e r and

s l a n s y i 6 ) thought t h i s value was too high f o r material c a r r i e d i n sus-

pension as the material sampled and analyzed i n determining t h i s f i g u r e

was l w g e l y t r m s p o r t e d a s bed-lo&.

Table l i s a s (^) r y proposed by Stevens (16) of a number of samples

of sediment deposits %&en i n the region s f %he GsLor&o River by F o r t i e r

aBlmey,

TUU %

DIHSITY OF Sm$UMS% DBPOSITS FROM VICINITY OF C O L Q W Q RImR

Bed Silts, I q e r i a l Canals, 1925

Bsd Sf lLs, Imperial CmaEs , k9%7-%g

OiPa River s i l t bare;

S e t t l i n g b a s i n s sf fallowing I m e r i a l

Valley m n i c i p a l water systems :

EL Gentro , Calif o r n i a

Imperial, C a l i f o r n i a

Calexieo , C a l i f o r n i a

Iqerimen"e1 basin at R a k e r City

Density l b s ,

p e r cu. f t.

A large number of s m p l e s have been taken from the Colorado River region

by the U. S Q GeoEogicd Survey, the d a t a f o r which a r e given i n Tables 8

and 9.

$ 8 , Texas resewoirs--Table 2 gives d a t a taken. from surveys of

naaeraezs r e s e r v o i r s i n Texas ( b y ' ) i n 1929 by the U. S. Department of

k r i c u l t u r e. This t a b l e gives the dry u n i t weight of the deposited sedi-

ment m d a l e s Lhs p e r c e n t w e of moisture i n the s ~ b e aa s taken. The

Section 10 2 3

report sn t h i s study gives a g r e a t deal of valuable d a t a , of which the

fo l l o ~ i n gparagraphs swvmari ze the rno re i q o r t a n. t finding s o

''It should be kept i n mind tha, the average ultimate

weight of the d r y material per cubic foot of deposit depends

on the function m d operation of the r e s e r v o i r , In a reser--

v o i r used f o r flood c o n t r o l s n l y , the water i s stored tempo-

sari12 , m d the deposited ~ n a t e r i a l, subJected to shrinkage during long periods of time, (^) has , r a v e r w e ultimate weiglit s f d r y i n thernaterjal average r e s e r v o i r f o r storage of water^ per cubic foot^ of^ deposit approximating f o r f u t u r e u s e ,^90 I b s , ;

dry periods m d increased demand f o r water result, la lowering

of the water surface and the exposure of the s i l t deposit f o r

periods of time r e s u l t i n g i n an average ultimate weight of d r y

m a t e r i a l per cubic f o o t of deposit qproximatjng 70 l b s , ; and

i n a power reser-voir, where the head. is maintained p r a c t i c a l l y

consLmt, e q o s u r e m d the r e s u l t i n g s h r i n k ~ edo not take p l a c e , cubic f o o tm d theo f depositaverage iLpproxInaatesultimate weight 38 (^) l b s ,of the dry m a t e r i a l per

weight^ "The r a t i o s^ wrieer, of^ s i l ta f t e r samples^ c a r e t u ~ l y and the measurements of^ considering^ the^ volume-exposed md sdmerged d e p o s i t s i n r e s e r v o i r s , has s e l e c t e d 70 I b s , as the a v e r w e ultimate weighs sf d r y material per cubic f o o t of d e p o s i t , f o r cora~rertiu~gu n i t s by weight i n t o u n i t s by volume,

This s e l e c t i o n was made with a knowledge of the indeterminable

v o l m e of vegetable m a h e r i u : %lac form of logs and brush which moves d o m the s t r e m a during r i s i n g stages. Since much of t h i e material is waterlogged m d t r a v e l s unobserved dovmstream

below the water s w f a c e , i t i s impossible Go estimate the

voltme, Such material w i l l be deposited where it v ~ i l lbe pre-

served i n d e f i n i t e l y if kept submerged wftb w a t e r o n Regarding the results of these s t u d i e s on Terns r e s e r v o i r s , Hemp-

head sf^ !!Exposed r e s e r v o i r s ,^ b a r s^ ofaverwed^ coarse 9 2s i l t , I b s ,^ ofsuch dry^ a s materialis^ found t o at 1 cu.the

f t , of d e p o s i t , while f i n e r s i l t i n mush the same Location

averaged 82 l b s , S m p l e s Prom "ce surface o f d e p o s i t s near the middle of r e s e r v o i r s averaged 55 Zbs. of d r y m a t e r i a l t o each suUb%ilergsd cu, f t .deposits Smp1es i n ofo l d the f i n e s t materialr i v e s c h w e l s i n r e s e r v o i a * ~talcen from theaver- w e b g l l b s , of dry material t o 1 cu, f t o i s i n t e r e s t i u g t o note t h a t if the average s i l t y i e l d , i n tons per &;quare mile, from "ce a r e a a'b0ve t h i s r e s e r v o i r (C&e Worth) i s c o q s a b l e t o t h a t of the nearby

9 r! i a o s drainage, as shown by the records at Glenrose, the de- p o t ~i Q 'in I h e reservoPr eonlains l e s s than 60 l b s p e r cu, f t. s t

i f 3 .6. ~ i c i r l e ' " ) s t a t e s t h a t the d e n s i t y of d e p o s i t s i n the gedina

f i c s e i v o l r a f t e r I j years o f operation averaged 30 kbx p e r cu, f t , , but 5

, y c t t ~ ~l e t t e r , owing t o exposure t o the suaz and a'ccnosphere i n t h i s period,

had increased to 6 ~ I b s~ 6 p e r cu f t , IIe e s t i m a t e s t h a t .an average vaP-

~ic-:o f / O I b s , per cu fL, shou.ld be used i n r e s e r v o i r s i n which the s e d i -

IXIO~ILJ~positsare subject to a l t e r s a l e webting and drying

L L & r i Dr, % , C , Straub w l e a thorough study sf the i i c ~ ~ $ i i t jo f sediment carried. by the Missouri River f o r t h e Missouri River 3 i v 2 sioa of the U, S o Engineer Departmeu~t A combination of' smples; gaL1iared i n the course of f i e l d operations were separated i n t o various

t , r ; , r C e k i ranging from clw t o pebble gravel and each grade was aIloned to

& r : C b l c i n still water wader i d e a l i z e d conditions, The fol%ov~ing t a b l e

d j s i 1 , vs3r; t h e wait msights and other p e r t i n e n t d a t a from these studies;,

4 n ~ m ~ b e sof samples ere taken fron the s e t t l i n g basins; o f the Em-

W ~ W C i t y , K;insas, waterworks and analyzed f o r u n i t weights; m-d p e r cent

of arside, The wa"cr was p q e d from the Missouri River and hence the

serilrnen t was d e f i n i t e l y suspended, The r e s u l t s a r e given i n the %oL%ow