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<br />e <br /> <br />. <br /> <br />e <br /> <br />. <br /> <br />e <br /> <br />EM 11111-2,1405 <br />31 Aug 59 <br /> <br />located with rcspeet to principal rainfall zones, mass C'urves for the recording stations may indicate <br />iiltensitirs that are rpprpsrntativc of the type of storm involved, and may aid in interpolating mass <br />rainfall euI've'S for intprmcdiatc non-recording prN'ipitation stations. <br />c. U.S. \,,"('atfH'1' BUff'llLl data for nOIlJ'{'('~)rdillg pr(>('ipitatioll statiolls, Jlwlllding nolPS regarding <br />tinws of lH'~irlllillg and PlIding of rainfall! ('!owlillPSS, dirpd,ioll and v(lloc'ity of wind nllt! othrf (H'I'tillrnl <br />lIol('s, un' (>Jl1(,rt'd 011 tll(' obs('rvpt's original n>('ord. Although all of thPSf" notf'S arp not puhlished <br />hy tht' \\'('uthpr Bun'au ttH'Y UI'P fiktl w'rmallr[dly ut tlH' :\atiollal Rel'onls WputIH'l' ('('ntpl', AshC'villp, <br />~ol'lh ('aroElla. (lopips of tll{'sf' ('('cords g{,llpntll,v al'{' filNlloceJL\- for varying IWl'iods of time at officps <br />of tll(' \Vpal}H'r BUJ'{'au Stat(' ('limatologist. In irnportunl stlfdi('s these \Vpjltll(\r BuI'PUU datu should <br />bp supph'rn('ntf'd from t lip follo\villg sour{'('s: <br />Puhlished and unpublished records of State, municipal, and other public wa.tpr supply <br />and conservat.ion agencies; <br />Filps of privalr organizations interested in water pO\\Cer, water supply, etc.; <br />Filrs of local newspapers, and records maintained by residents in the st.orm area. <br />rl. A group of four to six rwighboring stations, that are located in regions of reasonably similar <br />topography, and that apppar to have he en subjeeted to similar meteorological conditions during the <br />storm, is splccted. The accumulative rainfall at slu'cessive recording times is plotted for each of these <br />stations on a transpa['(~nt form to permit comparisons witll groups of curves plotted on other sheets. <br />Similar plottings are made fOf otlH'r groups of stations surrounding the first group. <br />(~. The mass rainfall (~UfVeS are complr-tcd by interpolating the curves between established point.s <br />in such a matltlf'r as to reOrcl f'('asonahlc consistellcy with the period of rainfall at neighboring stations., <br />with frontal and ('Ollv('(,tiv(' adivity as dC'terminf'd from m~tcorologit'al analysr-s, and any additional <br />datn that an~ availahlf' in the sp<'('ific instanef'. Such data are seldom r-I1tirf'ly consistent; consequently, <br />th(' most logi,:'a.l intprprPlatiolls mllst br de('idrd upon a~~ the study progrrsses. <br /> <br />7. HYETOGRAPHS. The lPrm "hy(.to~raph" is used hen.in to refer to the ~raphieal representation <br />of avC'ragl' rainfall and rainfall-('x('pss mtps, 01' voluml's, ~,~Tef spceifircl areas during successive units of <br />tinll' during 11 storm. Thr IIse of hy('tographs is convenif'llt ill rOlwpction \l..ith HI(' analysis of flood <br />h.nlrogmphs. Exampl('s art' showll in plates .'\os. :l, 6, and 16. <br /> <br />CO:\IPONENTS OF KATURAL HYDROGRAPHS <br /> <br />8. GENERAL. a. For the pmpose of analysis, natmal hydrographs may he subdivided inlo three <br />tyP('s of flow, namply- <br />Surfa('p runoff, or the watrr reaching surfact' channels by the overland route; <br />Sunsnrfaer storm flow, 01' Ihr portion of infiltrated water that passes throngh the shallower horizons <br />of thr soil to rr-SI,ch d('fiIlrd stream rhann('ls within a rE'latively short time after a storm, without <br />having rrach('d the main groundwater table; and <br />Groundwatf'r flow, or thp water contributed as undHground flow irom the ground\vatE'r table <br />en'uted by infiltration antp('('dpnt to the runoff period under study, supplemented by any recharge <br />I'(.sulting from deep penplration of infiltrated water during the penod under study. <br />h. Cntil f{'('f'ntly it has bPPIl ('ommon practice to consider strpam flow as made up of surface runoff <br />and grouIHlwatE'r flow. How{'V{'r, sevr-ral invpstigators have observed evidences that an appreciable <br />CJuantity of watpl' that ('ntel's tlip ground by infiltration during a storm pmerges as a direct contribution <br />to strram flow within a fplativr-Iy short time, and bf'forc the water could be expectf'd to have penetrated <br />to tll(' groundwc.tpr table and r('ached till' stream us base ftow.ll. II This phenomenon is most e\Tident <br />in tlH' Gl'rut Plains f('gioTl and ill ('{'rtain basins in tht' midwestern and western United States, but may <br />he onsP!'vpd to varying d('~r..es in other sections of the eounlry. (See USGS WSP 772, p. 113.) <br /> <br />3 <br />