US> to the* proper ZLeorAlaAXd-ty standards, oven ^liougli the b«)Bt possible oopy was used for preparing trie master floho • PNRI-H:
t
RADIOLOGICAL IMPACT ASSESSMENT OF THE
HYDROLOSICAL CHARACTERISTICS OF THE
AREA AROUND PRR-1
BY
L. R. DE LA PAZ and M.V. B. PALATTAO
1989 Radiological Impact A«s»»»m«nt Philippine Nucl»«r R»»»arcb In»titut« TABLE OF CONTENTS PAGE
INTRODUCTION 1 MATERIALS AND METHODS 1 Probable Maximum Precipitation (PMP) Typhoon Rainfall Model Statistical Estimates of PMP DISCUSSION OF RESULTS AND IMPACT ASSESSMENT 4 Ground Water Effects of Accidental Release of Radioactivity on Streams and the Ground Water Typhoon 5 Probable Maximum Precipitation 7 Probable Maximum Typhoon 7 Effect of PMP on PNRI Compound and its Drainage System 8 Evaluation of Reactor Bay Drainage System 8 REFERENCES 9 TABLES 1-5 10
FIGURES 1 - 9 22 RADIOLOGICAL IMPACT ASSESSMENT OF THE HYDROLOB1CAL CHARACTERISTICS OF THE AREA AROUND PRR-1 by L.R.de la Paz and M.V. Palattao Radiological Impact Assessment, PNRI
ABSTRACT The hydrologic characteristics of the PRR-1 site are discussed. A study of the rainfall and typhoon behaviour in the areas around the site is made and the maximum precipitation characteristic is computed, with the Probable Maximum Precipitation calculated as 1383.9mm. The possible effects of accidental release of radioactivity on streams and waterways &re discussed. An evaluation of the PNRI drainage system is made.
INTRODUCTION An important factor that must be considered in siting a research reactor is the hydrologic characteristics of the area. ANSI/ANS-15.7 (1977> <1> lists the following assessments that should be made: a. Effects of accidental releases of radioactivity into nearby streams, lakes or water tables b. Seismically induced floods, for sites along streams, rivers and lakes c. Effects of probable maximum flood, seiche, surge or seismically induced floods as may be induced by dams d. Hazards of tsunami, river blockage, diversion in river systems or distant or locally generated sea waves. The succeeding sections discuss these factors as they are applicable to the PRR-1 site.
MATERIALS AND METHODS Tabulations and frequency distributions were prepared from data obtained from the Philippine Atmospheric, Geophysical and Astronomical Administration (PAGABA) < 2,3.) Probable Maximum Precipitation Two methods arm used to calculate the Probable Maximum Precipitations the typhoon rainfall model and the statistical method.
Typhoon Rtinfj&l.l Mod>4. the typhoon ramfmll model makes use of a simplified typhoon windfield and the concept of conservation of moisture contents. The amount of rainfall within any circular area is assumed to be equal to the net differential between the moisture content of the inflow at the lower level and the outflow at the upper layer. From this model a profile representing the line of maximum rainfall within the storm is constructed. After assuming that the maximum rainfall intensities occur at a distance of 28 nautical miles from the typhoon center, rainfall intensities along the 28 mile line from the typhoon center and parallel to the direction of its forward motion may be calculated and plotted, to give a profile of maximum rainfall. By moving this profile over a location at a certain assigned storm speed, the maximum point rainfall may be calculated.
To further maximize the rain-fall pattern, the lowest reasonable 24-hour overland speed for a typhoon in the site area is determined. For the PNPP-1, a determination of the speeds of all the typhoons which traversed the rectangular area bounded by 117 to 127 degrees east longitude and 9 to 21 degrees north latitude for the last 32 years was made.The minimum overland speed of 3 knots was then used as the forward speed to move the typhoon intensity profile. The PMP values were calculated from this model for the duration of 1,3,6,12 and 24 hours. Since the PRR-1 is well within the area covered by the assumptions used in the PNPP-1 model,and since all other assumptions of the typhoon model are not site specific, the results of the maximization can be applied to PRR-1 (4).
Statistical Estimates, of PMP The statistical procedure developed by Mersfield (5> was used. A modified frequency distribution:
*m - *r> + km sn '• eqn.l)
where : xm = maximum observed rainfall
xn and sn = mean and standard deviation of the series
km ~ statistical variable
The statistical variable has been determined from climatological data mainly from the USA. Hersfield plotted the values of the statistical variable for different rainfall intervals as a function of the mean annual rainfall. This i» shown in figure 2. From this table the value of 5.5 was obtained for the statistical variable.
The values of the mean and standard deviation of the aeries need to be adjusted for events of rare magnitude, which affect their values. Extreme rainfall amounts of r&rm magnitude and occurrence with expected period of say 500 years, mrm often found to occur at some much shorter time, (e.g. 30 years) than expected. Such events are called outliers. Hersfield plotted the effect of outliers on the mean and standard deviation of the series. These are shown in figures 3 and 4.
Another adjustment is necessary for sample size. The frequency distribution of rainfall extremes is skewed to the right so that there is a greater chance of getting a larger than a smaller extreme as the length of observation increases. This correction is shown in figure 5.
Precipitation data cover fixed time intervals. For example the 24-hour rainfall may be observed from 8:OOam to BsOO am of the next day. Such data rarely yield the true maximum observational amounts for the period indicated. Data will show for example that the annual 24-hour amount is most often much less than the annual 24-hour amount determined from intervals of 1440 consecutive minutes unrestricted by fixed hour intervals. In the case of the data used in the paper, to compute the maximum 24-hour precipitation during typhoons, these were recorded every 6-hour interval and a correction factor of 1.0O5 was utilized.
Finally,in order to convert point rainfall data to areal rainfall a depth-area correction curve is used. This is shown for various time intervals in figure 7.
The statistical model was used on the 24-hour maximum rainfall data associated with tyhpoons making use of the ratios t
xn-m Bn-m
and .
x sn
where : xn_RI * the mean without the highest value
>;n - mean of all values sn-m *" standard deviation without the highest recorded value
sn =• standard deviation of all values
To correct for outliers , the PMP was then calculated using equation 1.
Maximum Rate of Runoff
The maximum rate of runoff was calculated using the equation from M.J.Hammer <6)t
0 • 0.278 CIA where : Q • maximum rate of runoff in cu.m/sec. C • coef"icient of runoff whose value is dependent on the type and character of surface I « average rainfall intensity in mm/hr. A = drainage area in sq. km.
DlSCUSSION OF RESULTS AND IMPACT ASSESSMENT Ground water sources The PRR-1 site lies west of the Marikina Valley and is underlain by a geologic formation known as the Guadalupe Formation, consisting of an Alat conglomerate and a tuffaceous member referred to by Teves and Gonzalrs (7) as the Diliman member. the Diliman member is water—laid and bedded or stratified. One way of describing the water bearing property of soil types is through the use of transmissivity values. Transmissivity values for some areas close to the PRR-1 site <8> are available and they range from 135 sq m./day at the Veteran's Memorial Center (2000 m away) and in Constitution Hill (5000 m away) to 22 sq.m./d at the ABS/CBN Compound (2200 m away). In contrast, the most productive zone is the alluvium of Marikina Valley at Pasig where transmissivity ranges from 250-500 sq. m./d. The Diliman area should give values ranging from 100-250, sq.m./d which is typical of the water—bearing beds of the Guadalupe Formation. In fracture zones associated with faulting, much higher values may occur.
It may be noted that some areas around the PRR-1 site are not yet serviced by the Metropolitan Water and Sewerage System (MWSS), and therefore have to rely on ground water resources for their water supply. There is a very rapid growth of population in the area and this will cause rapid withdrawal of the ground water resources. At the same time the rapid build-up of housing units, the cementing of roads, grounds and other areas which are points of ground water recharging, will greatly diminish the ground water sup pi J/ for the area. The PRR-1 however, relies on the Metropolitan Water and Sewerage System (MWSS) for its water supply and should not be seriously affected by a diminshing ground water supply. There are plans currently being put into effect of connecting the areas around Tandang Sora, about 1 km. from the PRR^l to the MWSS. This will reduce incursions into the ground water reservoir of the area.
If facts ef Ac£idjBMfl_ Release of Ra_djoac£.i vity on iferearps and the ground W#Jter Two types of accidents may be postulated that could have some impact on the streams and ground water around PRR--1.These are* 1. Radios!otope releasee to the atmosphere around PRR-1. The design basis accident, in which a fuel rod fails in air is the most serious postulated accident that will result in an atmospheric release. 2. Radioisotope releases through the reactor water systems. One of the most serious accident of this type i«5 a loss-of-coolant accident. In the first type, the design basis accident assumes that only halogens and inert gases may escape from the reactor building to the environment. All other fission products that may be released from the fuel will be unable to escape from the reactor room because of plateout on the cold surfaces on the walls of the reactor building. The Eu-U-ZrH fuel of the TRIGA has been shown, by experiments, to have very low release fractions even with completely unclad fuel (9).
The inert gases are insoluble in water and will be dispersed and diluted by the atmospheric sink. The halogens on the other hand, are water soluble and may be washed down by rain to be eventually found in the streams and rivers in the vicinity of the PRR-1. However, all the fission product halogens are •hort-lived, with half-lives ranging from 86 sees, to 8.05 days. Hence, 1-131 included, these radioisotopes pose no serious long- term contamination of the streams and surface waters. In the second instance, radioisotopes accidentally released to the reactor water systems, will go to the reactor sump pit, especially if a portion of the water system is also breached a multiple failure occurrence which is a very unlikely event. In this case the automatic pump draining the sump pit intD the environment may be deactivated if the radioactivity content of the water is above allowable limits. Further the drain pipe itself can be plugged to contain the contaminated water within the reactor buliding. If part of this water is spilled into the environment, inspite of the above safety actions, the contamination will spread into the grounds surrounding the reactor building, and part of it may reach the Cuiiat Creek through small gullies and streamlets especially if the accident occurs during the rainy season. The amount however is expected to be small since most fission products will be adsorbed by the soil nearest to the reactor building and within the FNRI compound. Contamination of the ground water is held unlikely as adsorption arid ion-exchange processes in the surface and top soils are expected to retain these radioisotopes. Typhoons Typhoons arm common occurrence in the Phi 1ippines.Data of the last 40 years indicate an average of approximately 20 weather disturbances a year. The months of July to October have the highest typhoon frequency, as shown by table 1 and figure 1. Mo significant trending is shown between the decades studied.
During the period 1948-1987, a total of 542 tropical storms and typhoons entered the Philippine Area of Resposibilty (PAR). Of these, 30.0% were tropical storms, with maximum wind speeds between 64-118 kph, 26.0% were typhoons with maximum wind speeds in excess of 200 kph, of which six exceeded 300kph. Please see table 2. As shown in this table, however the Philippines was fortunate that six howlers with maximum winds exceeding 300 kph did not cross the country and that 53.8% of those whose maximum wind speeds were between 200-300 kph did not affect the country.
Of interest to PRR-1 operations is the frequency of typhoons which pass within 100 km. of the reactor site. The. 40- year record shows an average of 1.4 weather distrubances a year. Of these, 46.2 % are typhoons, 31.4 % are tropical storms and 22.2 V. are tropical depressions. Table 3 tabulates these weather distrubances. It will be noted from this table, that of the 25 typhoons which passed approximately 100 km. from Metro Manila, only 10 exceeded the 20O kph wind speed. Only one exceeded the 250 kph wind speed, typhoon Sprung with maximum wind velocities of 275 kph recorded at Virac, Catanduanes. not at the Metro Manila stations.
A study of the amount of precipitation induced by the weather distrubances is shown in table 4. For the 40 year period, 1948-1987, the highest maximum 24-hour precipitation was that induced by typhoon Trining on October 17, 1967 which gave a 24- hour .precipitation of 979.4 mm as recorded in Baguio City. The 40-year average maximum typhoon associated precipitation is 487.6 mm.
It will be noted in table 4 that 20% of the weather distrubances which induced the maximum 24-hour precipitation for the year, did not even cross the country and that the Baguio station registered the highest 24-hour rainfall, 45% of the time.
On the other hand, the heaviest rainfall in the Metro Manila area as registered in the 40-year period was associated with typhoon Lois in August 35, 1952, which gave a precipitation of 353.0 mm for a 24-hour period. Table 5 gives, the 24-hour rainfall data associated with weather distrurbanc.es exceeding 100 mm for the period 1948-1987 for the Metro Manila area. As shown therein, 50% of the high 24-hDur precipitation in Metro Manila were due to either tropical depressions or to storms many of which (54,5 %> did not cross the Philippines.lt will be further noted from the 1985-1986 data, that precipitation in the Manila International Airport is higher than that recorded in Port Area for the same 24-hour period. For the single yaar where precipitation is recorded in ail three stations for Typhoon Oyang, the MIA scation gave the highest reading followed by Port Area. The Quezon City Science Garden recorded the lowest rainfall value. Probable Maximum Precipitation The Probable Maximum Precipitation calculated by the Typhoon Rainfall Model ( Maximization of Typhoon Emma), for the duration of 1,3,6,12 and 24 hours are 102,297, 571, 1064, 1566 mm respect i vely. On the other hand the statistical estimate of PMP gave an adjusted true maximum 24-hour precipitation of 1383.9 mm. No adjustment was made for areal precipitation as the PRR-1 site precipitation was considered as a point PMP. The statistical estimate compares well with the 1566 mm value obtained by maximizing Typhoon Emma. A study of table 5 shows further that the highest precipitation recorded in the Metro Manila area during the 40-year period studied was 321.4 mm recorded at the Manila International Airport ( now Ninoy Aquino International Airport ) in 1986 in connection with Typhoon Oyang. The Science Garden recorded 178 mm during that typhoon.
Probable Maximum Typhoon The Philippines is located in the typhoon belt and is subject to severe tropical cyclones, which generally travel in an east to west direction, deintensify while crossing the Philippines and often reintensify in the South China Sea.In terms of wind intensity therefore, the east coast of' the Philippines experiences the most severe typhoons. The Probable Maximum Typhoon is defined as a hypothetical typhoon having the combination of characteristics which will make it the most severe that can probably occur in the region under consideration. The typhoon should approach the region under study, along a critical path and at an optimum rate of movement. The Probable Maximum Typhoon
Effect of PMP_ on PJJRJ. CompotiD^ and its Draijnge §.ys_ts?a» The PNR1 drainage system consists of a number of open canals and pipes connected to a main 24" drainge pipe, 180 m long and sloping at an angle of 20 degrees.Using the equation of M.J. Hammer, the maximum runoff from the PNRI compound was computed using the following assumptions : Coefficient of runoff * 0.4 Average rainfall intensity 3 1566 mm/day. Drainage area = 62,500 sq.m. or 0.062 sq. km. For conservatism in the estimates, the PMP was used in the computations as the rainfall intensity . On the other hand, the coefficient of runoff used was that for single dwellings since the PNRI site contains both open grasslands and areas occupied by buildings and paved roadways. The upper limit for single dwellings was used for conservatism. The drainage area used was the total •T9m occupied by the PNRI, a site 250x250 m. The calculated maximum runoff was 560 1/s. This rate of runoff will require a pipe whose diameter is approximately 420 mm. or about 16.5 inches. The 24" main drainage conduit of +he PNRI can therefore readily drain the site provided that the connecting canals and pipes are free from clogs, dirt and other obstructions.
Evaluation £f the Reac.tpr. Bay Drainage System Access to the reactor bay »r9» may be achieved through four entrances. Of these, only the truck entrance door is directly subject to flooding from outside. The slightly elevated area around the truck entrance with a surface area of 70 y. 70 m was considered In the evaluation. This area consists of asphalted access roads about 4.3 m above the lowest level of the truck entrance. Between the reactor building and the ARC laboratories, and along the eastern boundary of the truck entrance is a grassland, the runoffs from which can also flow into the truck entrance from a secondary side passageway. This portion is covered by the 70 x 70 m surface area considered above. Please see figure 8. Using °MP values, and assuming a coeffcient of runoff of 0.6 which is -\n average of that between parks and playgrouns end paved stree s, the maximum runoff was calculated as 51.1 2/sec.
There ar«» drain pumps that are operated to pump the water that may be at the truck entrance in case of very heavy rains. The capacity of these pumps is 300 gal/min or IB.9 1/sec. With this capacity the pumps will not be able to cope with PHP rainfall. It may therefore be necessary to devise means by which excess waters may be diverted from the passageways leading to the truck entrance.
Assuming that humps and canals ara built to divert the water falling on the roads around the reactor truck entrance, and the passageway on the northwest end of the ARC building, the effective area that may drain into the truck entrance may be reduced to 2200 square meters. The maximum run-off from this are is 18.3 1/sec and can be drained by the installed pumps.
REFERENCES
1. ANSI/ANS-15.7-1977 American National Standard. Research Reactor Site Evaluation
2. Tropical Cyclone Summaries from 1948 to 1978 Philippine Atmospheric Geophysical and Astronomical Services Administration. ISSN Ol15-2505. U.D.C.551.2 <914) December 1978.
3. Tropical Cyclone Summary. Yearly data 1979-19S7. National Weather Q-f-fice. Tropical Cyclone Warning Center, PAfciASA.
4. rinal Safety Analysis Report. Philippine Nuclear Power Plant i.l, vol.3
5. WMO Operational Hydrology Report No.1 Manual for Estimation of Probable Maximum Precipitation. 2nd Ed. WMO No. 332 (1986).
6. Mark J. Hammer. Water and Water Technology. SI Version . J. Wiley and Sons, New York, 1977.
7. Juan S. Teves and Mauro L. Gonzales. Geology of the University Site-Balara Area, Quezon City.
B. Interim Report (MWSS). Ground Water Development. Manila Supply Project II. Electrowatt Engineering Services, Ltd. and Engineering Beoscience, Inc. 1981.
9. Fin.il Safeguard Report for Philippine Open Pool Reactor. General Electric. April,1 1960. *
iitvm F«WWC< m m PHILIPPINES
WWH : PERIODS
: 1948-195? t 1958-19*7 t 19M-1972 I 1978-191? i 101M.
JANUARY b 6 8 2 22
FEWUARV t 5 3 J 13
HARCH 2 9 I 4 11
iiPRll 5 J 4 4 16
M'I 4 13 1 e 32
JUNE 16 IS 16 is 62
Jtfir 22 44 31 32 129
AUGUST JO 37 29 40 136
SEPTEflBER 29 29 «; 30 121
OCTOBER 25 21 24 33 103
NOVEMBER JO 19 20 22 91
KCENCR 19 13 9 18 59
I01AL 190 209 185 211 795
io IMLE 2
cuKiFicftiiM of m\w. DISIUMMICES tmm imw wt miwrn
OKA OF RESPQKMIiLltt IW*»
.EAR IropiCit IrofUUl fyphoeo Scvtrc typhMn UepreiMon Stori tIB-199 kph 206-299 k>h SWItfk 1DTAL
1946 I & U - • 20
1«49 14 7 1 22
IVW) 5 . 5 1* 14
r 1931 J J i - 13
1952 13 4 & 3* 28
195 J 9 5 4 1* ' 19
1-04 e 4 ? 1* • IB
W35 i t * • l' 1* 15
!?5o IS 4 6 • **M> 26
1957 s 4 4 1* 15
1*56 5 J 4 •V J* IB
1*5? 2 4 A I*.* 18
19M 4 6 6 2* 1* 19
I»tl 9 10 •1 I'M1 25
1942 S 10 3 21 •
lit; i 7 U
19&4 I • II 7 4«Md 1* V)
1 IVfcS 8 5 5 A. i\ 11 t'tSft Ir&fii*: tropiiil ijJti&Wi fteprmift* St©r» U8-JW Irjrfc TOfM
t£> a
s it it* 4
5 15 *V ?!
It.'t n 7 V ir;> 7 5 •17
P.'T- V 6 12
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l'V8'.: 23
12 table 2: tfaor J e< 3)
(EAR tropical Tropical typhoon Stvtrt Typhoon B»p»M*H* Stora I1B-M k»t> 200-2?* k»h 30*) k»h ICIM.
mi * a a t*t 4. 5 9 tJ
7 d £ 1983 J tl 5 jS2 M 23
1W 5 a 3 iV 20
t
:m 2 4 12 *S|« 21
i?i7 2 2 7 *3d 16
TOTALS- 253 239 20b «,*4b«#£»3»d 4* ?95
FftEUU£»Li 0.32 0.3 0.26 - .Ml O.ll
i H»i r.tr «r«t«t. tud rid ;roi5 Ui» country
'.;•>$ !'j'. .'6V5 tl.fr MUfiiri- out lfiljcui !.«*.»
:! ;•'.>'. •:•:.'•! I.Mr U.-J.'r. lU't li<'.<•'">)'f *.«j '.M 13 TA8LC 5 UFHOONS tWICH PASSED WITHIN 100 Kit Of KE1R0 MANILA • EAR HO. OF HEATHER DISTURBANCE ryPHOOHS IROPICAL STORMS i TROPICAL DEPRESSION TOTAL 1948 i - WW 1950 l 195$ - 1952 2* 195J - 1959 • 1955 • l»5i 2 1^57 - 1958 - 1959 - »9W> 1 1941 - 1962 - 1963 - 1964 2 MS - 1966 'i 196; 1 14 IMU 3 tr** 2 of 3): . «CM ; m. OF NEftTK ft I1STWIMCE : iimm : IWICM. S10WS t 1MNCM. BCWE»1W : 10TM. !»*• »W - - • 1*70 2b 1 - 3 mi i i - 2 1*72 JC - -• I 1973 NONE 1974 J J - 2 1975 - J - *. 197* - 1977 11 - 2 im i* - * i 2 t 19» 2 2 4 Iflt Jf - I 1982 t' 2 J 4 1983 • - 2 2 J9I4 - I98S J 1 15 TMLE 3 (»•* 3 of 3) • YfMt : ». * «M«t iinmmE : FVfNWB t TMncntTIM : TUfltA KMEfSIM i TBI* • Ittk . — in? 2* 7 2 fOTM. 29 17 12 54* AVlMK 0,42 0.43 1.3 1,4 Typhoon* Msitw wiot optt* trMttr thM III ion. Tropic*) Storo-Miiow nintf opart 44-111 kph Tropicol OOtrtuioo-tixiOM •iotf optf* up to W kpk ibiioji !i*J flkitifoj ». Typhoon Trix 213 kph ot Lef#Hi City b, lyphoon Stoino, 275 tph it Vtroc, CotowhoMt Typhoon Tolino, 200 kph it Rift c. Typhoon Conoiftf 204 kpff ottitttei City tf. Typhoon kfcDinf. 200 kph ot Viroc t. Typhooo TtyM| 230 kph ot Vlrtc • . Typhoon nodi no, 2*0 kph Port 9, Typhoon Norainf 220 kph l»i h, Typhoon SiunQ 240 kph lt|i*pi typhoon Horoifti 240 kph Htcon It WHU4 mm imm mm » mm mmmm \m-\Hi im MI.24-MU MIX ItfMM KAlttft MIltKIWI NU. ft PUKE itfttwrn MM mmmn KMMUflf 1941 554.0 vm C !.».*W.»-22 u - m. raw. 1949 191.2 MHT,G.R. C 1.KTTV-RC9 II MMTWR, nmN 1990 471.1 MUTOC, C T.MI1A-KT.2 n 1991 754.0 MR,m. C T.LNIM-M. 13 m TNKNMI 1952 534.0 tlACM, C 1 .wPwf "WW* ™ 5* CKJIM 1953 94*.* MW1D c 1.C0MH0V.17 140 mmi 1954 3*1.0 ILM»M| c I.MUV-NQV.t 152 mimm 1955 3W.9 MWIO t m UME-iEfT.23 10 MMIO 1954 309.5 VIMH,I.S. nc f.MM'MW. 14 5* IMM 1957 423.2 MUt.BUElttl i ~ " 1.X11-MV.12 129 VIMC, CMMNMII 1958 491.9 ViMC T.UHMhNT.29 US VIMC, CMMflUMEl »F* F FFFHT»W^WW 1959 317.9 C MllM-MLII ' 212 19*4 32*. 0 IM.ZMMIES c r.LOUHXUJ *5 MtUHR mi 494.1 LMnVf JvNf NC T.EIS1E-JUL13 »; WWIU 19*2 409.0 WfiVflVf 1 >nt C 1 »tmWw*fnlP» J9 103 LAQM 19*5 *7*.0 MLER,BUEZM C UlMW-KCH 112 MHIMTI* J 9*4 9*2.0 MIUSO C TJMIMHIt.' HO MWJO 19*5 5*1.0 MIU10 C rjiUHMr if 17* (UMMMO II ill i 17 1 ' Uble 4: \V» t£f» WU.24-W. KLftCt UfHOWt Uttltftl ftlSIINCTIN HAJ. MS PUtt HEASUKB m* mmimi aw HUMMM 1*44 2St.ft M6UID C I.KLMIN6-K1.I7 195 *Wrt»|WW»* :**? 979.4 MfiUID C r.IRlllIW-0C1.17 2«? *mi ms 649.4 IA6U1D C MITMB-JUL.Zi ts? VIIM 196* 649,4 M6VID C umm-m.2k IS? V1MN 1969 512.2 • M6U1D G \.tim-M. 24-27 222 MRS 1970 437.7 IM DC ui.mtm-MM.ii 95 MK8 -KM.t 1971 379.5 MMJID C 1.WSW6-MI.I? 190 MIC0 19)7 479.* M6U1D NC f.ftftlM-JUl.17 27J wmm 1973 379.7 IA6U1D C MUMWHKU 150 »N»1 1974 S7B.8 BttUld c I.KHIN6-0CT.2B 269 p*m : 1975 ' 2*1.o BMCQ c t.HAWCHfG MAX 21 241 MSCD l?1S 605,1 6MSU1D c , t.&l&ftH6Jt)t 24 150 ISA '.ill m.o BftSCQ c :.60RIM6-JUL 24 150 cw.*r/w VOi 534.2 9A&UI0 c I.S.MDIN&-MJG.22-26 \m 290.fr ftMSLON C I.S.KKW-MH 12-26 185 ItECM I960 730. J mm ' c I.MMM-IPT. 15-2? 165 MKHLON 1981 467.4 ctuhim c U0IWB-M 26-2? 145 flUUUMM 1912 567.1 CM.AYM DC h\iim-M 26-2? 1*0 ROM \w; 475.0 TWAMI C 1,WR)W-M ?•)) 1J0 ™tw fatlt 4i trap ] tf 3) im WIt24HSa met lifWJHI nw mtnctm IM. m UNI mm\m) •Ml tmmn ntu • \m MNI hi.mimm.v-u n w.i c 11* S44.S mm K I.MLim-M 27-J? Itf im TOt.t MM! c l«MLI«w0*ML •** 2IB mi 341.0 VIMC K T.t.ltll»m 17-21 lit C - CrtMM tat mUwiMft i IX • Eftttrrf Ml tat M Mt CTMt tit rHUiMtm I* II - Iratical ntrtttiM H IS • TrMiul Start , T - TyaMtt It MILE 5 NKffllMIM EUEE9IK W m.M tt. IN REIN fgJIA 1940-1907 YEAR FftECIMIftUON DATE KAMI 01S1UMANCE . PATH NM. FtftCE IM) n.s. Kernel 1952 333.0 MM. 25 I. LOIS C 52 RAMI tw 119.1 JUNE » I.I. ME 20 C - 1958 239,01111*1 JIM.T 14 MINNIE NC 241 EMI OF TtNMOMMO 19*0 229 (RIM MY 27 I.S.LUCILLE C 42 N.I.CENTMN, OFFICE 19M 227.9 JUNE 29 • NPPPHN9^^N7 c 127 INFMfTA 1*6.0 M.V 17 MUMW c IR WERNATIR I9*» 142.1 KfT.4 T.C0M NX ft MM10 1970 113.7 SEFT.2 19 *# WWW HP NC 52 MK8 1974 150.9 MMMO I,S.REI1R» NC W mcff •WW 1973 123.4 OCT.II IvltmWRS^ C 47 MW1B 197* 255 (RIM MRMQ T.MTANI NC 220 OVER WHEN 1977 234.4 MV 25 T.O.IfNINO NC 55 OVER RATI! 193.0 WO. 19 T.S. Ill** HC 95 OVER RATER 152.1 KPT. 12 T.t.NMCIW NC 55 OVER RATER 1978 257,4 Mil,13 r.S.HULIW HC 85 f ^NNrHfW 1 NrbrfrW 274.5 0CT.7-14 T.YM1W C 145 VlRftC 1979 223.0 MM. 9-15 T«rmnfff * 140 ftECM 1980. 210.0 NOV.1-7 T.ftMIM C 240 MKO 20 UU»5t «n»2if2} rut manuxm Wwl fUO •.I. mi 1*1.2 ML1S-M 1.1 K tit im I22.2WIM miMt !.l C US HI IM9 3IMM1M MI2S-2I T.I B MS 2».imn • tm 32l.4tH*> MKM OCI.5-1 T.I»VfMI. I I7MIK. n •ft* M • » W% ft*rra I •MJNMM af mm af MMMI , aart a* far r rat*all fftfaNlatl,lfM .| 1 I ,'l I 1,1 0.2 9A 0,1 ** 1,0 W*n ?lf«rt 4.-AdjutCMtit •* standard deviation of annual aarlaa for aaximm ataarvad rainfall (Haratifiald,lf tla) 24 20 W 40 10 • # laacth. «t vaaati (jr'aava) Figure 5 *A4i««tMnt af MM «M stand*** {avlati** af mmil aarlaa far langtk •* »•«•»« f*aranfi«14,If il ,J r 0 4 I ..12 tl SO 31 ffuavtr af atMrraUfaai «aiif M|«rt e>!A4JttfbM«t of flxatf intai*il araelaleatlon Moonta for t»i»par af a Warva clonal wnltavithia ttia intarral (Vaiaa.lt Ml l * i* c s i& 1 •-£*- 1 ? • I * r \ 200 400 MO •00 tooo \ t Arts tkm*> Mgwt* 7rO«vt1f-«r«at <. er' .tna-rtoactlon, curves for wester* United ftetM - •'. tUf Weather B»res*,lttO) 1001 | J "J |—T • 12 It Our alien fhourt) Figure .•-MMfisuv 4e»tft-^«r«tleit curve (Huff, IftTJ