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<br />GENERAL PROCEDURE FOR GAGiNG STREAMS <br /> <br />11 <br /> <br /> <br />I <br /> <br />/ <br /> <br /> <br />Figure 1o.-Equipment for fluorometer testing of waler samples in the field. <br /> <br />c'ontl'ol the stug-e-disC'hal'g-e relation is impor- <br />tallt. TIlt" den'lopl1lellt of stagl'-disehul'p:e <br />t'llt'n':-; wht'l'p mort' than Olll' ('olltJ'ol is (>ffecti\"e <br />:llHl tlw 11l1llllJPl' of lllpaSllI"PHH'lIts is limited <br />~Pll(>l'ally I'Nlllin.:.;. jlldp:lllent ill interpolating <br />lJptWl'PIl lllp<lSlll'l'ments and in extrapolating: <br />beyond tilt' hi.!!lwst lltl'HStllVlllenb;. This ju(lg:- <br />lIll'llt is pal'ti('1l1arly n(,(,(>s:--:i\l'Y where. thp controls <br />an' 1101' 1lt'1'I111\l1Pllt and Ylll'iollS disehul'g-e meas- <br />1l1'PI1Wnts l'l'pl'esent llitfl'rent posit.ions of tlU' <br />~tagll_(lisehal'p:e L'lll'YC. <br />Rtag'('-di~('harge l'platiolls arc developed from <br />a g-l'aphi('.l1 illlHlysis of tilt' data plotted on eitlwl' <br />rt.C'tallp:lllar-c()onlinatl' or l(lgal'itllmie- plotting <br />papPI'. .\ p:o()(l allaly~is of tlw data requires :t <br />kllowlpdp:l' of the ('hal'ill'tpI'isti('s of the channel <br />and a kllO\y]('(}g-p or OPPll-('It:Ulllel hydraulics. <br />Tlw lli:-;('h(\I't..!.'l~ lllea:o;ItI'PIlH'llb availahle for the. <br />;lll:dy:"i:-; ra1'l.1y dpfhH' a lI11iq!H' stag..'.dischart!(' <br />1'(~latioll 1I('('a1l:O;('. of l'h:IIlg'l's ill tlw ('hanllpl dur- <br /> <br />ing the period represented by the measure- <br />ments. The determination of the proper shape <br />of the rating curve and it!'; position at various <br />tinlcs requires considerable enginee.ring knowl- <br />('dg-e, experience, and judgment. In general, a <br />hase stage-disehal'~e relation is used, and devia- <br />tions from this relation with time (shifts) are <br />determined by consideration of the plotting of <br />individual diseharge measurements. These <br />shifts, in the form of a stage adjustment, are <br />then nsed with the base rating in computing <br />tIle discharge record, <br />The stability of the stage-diseharge relation <br />p:overns the nnmhel' of discharge measurements <br />that are neces.sary to define the relation at a.ny <br />time. If the channel is stable, one measurement <br />:L month is g'cnerfilly sufficient; in sand-channel <br />st.I'l';llns~ three measurements a week may be <br />""quirt'll because of the mndom shifting of the <br />~tI'ealU channel. <br />