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<br />EM 1110-2-1405
<br />31 Aug 59
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<br />loeated with respect to principal rainfall zones, mass curves for the recording stations may indicate
<br />jillpTlsiti(,s that are f('presf'ntative of the type of storm involved, and may aid in interpolating mass
<br />rainfall eurvcs for intrrfficdiatc non-reeording prt'ripitation stations.
<br />c. U.S. \\:('uU](,1' BUf{'fill data for Ilont'l'('ordillg precipitatioll stations, Including 1I0t('S n'garding
<br />tinH's of }H'ginning and ('tiding of rainfall, ("Ioudij]('ss, r1i,,(.(.tioll Rlld vrlo('ity of wind Dlld otlH'" pprtillrnl
<br />noh's, an' PIllprp.! on t1\(. ObSI'I'VI'I'S original I'(>('ord, .Although all of thes(' notes an' not publish('d
<br />hy tll(' \\'put.ht'f' Bun'au tlIpy an' filpd permuJH'utly at tlH' ~atiollallh'('ords \VralhC'I' Cptll('I', Ashevillp.
<br />'\"orth ('ar-olina. ('opips of ttH'S{' I'f'("onls g'pll('rnlly firp filE'd lo('d.LI' for varying periods of tim(' at officf's
<br />of tll(' 'Vputhf'T' Burpall Statp Climatologist. In importunt 51 If(Ii'~'s' 1'hps(' \VpatlH'r Bul'puu data should
<br />hp supph'mf'TltP(j from thp follO\vitlg' sour('I'S:
<br />Published and unpublished records of State, municipal, and other public water supply
<br />and consr-rvation agencies;
<br />Files of private organizations interestcd in water pO\\Ter, water supply, etc.;
<br />FilC's of local newspapers, and records maintained by residents in the storm area.
<br />ri, A group of four to six neighboring stations, that are located in regions of reasonably similar
<br />topography, and that appear to have been suhjeeted to similar meteorological conditions during the
<br />storm, is splce-ted. The a{'('umulative rainfall at successive recording times is plotted for each of these
<br />stations 011 a transpaJ'l'Jlt form to permit comparisons witll groups of curves plotted on other sheets,
<br />Similar plottings are made for other groups of stations surrounding the first group.
<br />(~, The mass rainfall eurvcs arc completed hy interpolating the curves between established points
<br />in su('h a manner as to rcAe'('t rl'asonable consistency with the period of rainfall at nrighhoring station~,
<br />,,,"ith frontal and eonvp(,tivc adivity as df'tl'rminpd from ill'?teorological analyses, and allY additional
<br />data that are availahlp in Ow sp('('ifie instance, .such data are seldom entirely consistent; consequently,
<br />th(' most logical intl'rprdations must be d('cidpd upon a~: the study progrE'sses.
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<br />7. HYETOGRAPHS. The term "h.,.('tograph" is used herein to rder to the p;raphical representation
<br />of uv(>rag'p rainfall and rainfall-<'xcf'SS ratf's, or volumE'S, \, ~-f'r speeifird areas during successive units of
<br />t imp during' u. storm. The' IISP of hydographs is convcni('nt ill ('onnection with the analysis of Aood
<br />hydrog'mphs. Examplps an' shown in plate's Xos, :l, 6, and 16.
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<br />CO:YIPONEKTS OF NATGRAL HYDROGRAPHS
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<br />8. GENERAL. a. For th(' purpose of analysis, natural hydrop;raphs may he suhdivided into three
<br />typps of tlow, naml'lyn'-
<br />Surfuc'l' J'unoff, OT' the watpr rpaching surfacE' channels by the overland route;
<br />Subsurfa(',' storm flow, or the portion of infiltrated water that passes through the shallower horizons
<br />of th{> soil to r('aeh df'fin"d stream chanrH'ls within a relatively short time after a storm, without.
<br />having readwd th!' main groundwater table; and
<br />Groundwatrr flow, or tlip water contributed as underground flow from the groundwater ta,ble
<br />1'I"f'utcd b.y infiltration antp('('df'nt to the runoff period under study, supplemented by any recharge
<br />r('sulting from d",'p p"lIetration of infiltrated water during the period under study.
<br />b. Until r('('C'ntly it has b('('n common practice to consider strram Aow as made up of surface runoff
<br />and grollIldwatt'r How. Howrvrr, several invrstigators have observed evidences that an appreciable
<br />quantity of watrr that f'ntprs ill(' ground by infiltration during a storm emerges as a direct contribution
<br />to stream flow within a r('lativel~' short time, and before the water could he expected to have penetrated
<br />to thf' grollndwu.trr table and rral'lH'd thl' stream as base flow.f), 11 This phenomenon is most evident
<br />in tIH' Grf>ut Plains re'gion and in cprtuin basins in thr midwestern and western United States, but may
<br />be ohs('I'vpd to varying dep;rees in other seelions of the country. (See USGS WSP 772, p. Il3.)
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