__ v-v.._" an , .. -_U'. m 1"?! Sn! APPr HYDROLOGIC ANALYSIS or A SMALL AGRICULTURAL WATERSHED by Earl Abraham Myers AN ABSTRACT Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering 1960 Approved é:é:;;/fi;é;;:f;::¥éZ1€Z/Z// t] (D (1) de' by As (:82 moi the "er con: Hunk Infi- to be detent Earn a. Abraham pIyerS ABSTRACT Five years of hydrologic data from a relatively flat, 9.3h square mile, predominately agricultural watershed in south-central Michigan were analyzed. The Thiessen uniform depths, the unweighted gage average depths, and the depths recorded at one specific gage were compared. There was very little difference between the Thiessen and unweighted procedures, however the single gage determination was considered inadequate. The amount and peak rate of surface runoff were determined for 15 storm periods. The amount was determined by planimetering the area between the total discharge hydrograph and the assumed straight-line base flow curve. As shown by a composite recession curve, surface runoff ceased approximately 2% days after the hydrograph peak for each storm. In analyzing the rainfall-runoff process, antecedent moisture, moisture accounted for by base infiltration, and the amount of moisture required prior to surface runoff were considered. The fraction of antecedent precipitation considered effective depended upon the season and the number of days prior that the rain had occurred. Initial 3: ob! pea. was the for eXis form WHS( than ‘ e}, \K Earl Abraham 33,58" ”pat the amount required to supply initial infiltration varied with the season, probably more specifically With the .moisture content of the lower soil strata. The unit graph method of estimating flood peaks and amounts was illustrated and discussed. The procedure of combining unit graphs of various lengths was described and used for determining the 1 hour unit hydrograph for the watershed. This unit graph was used for calculating the expected hydrographs which were then compared with four natural hydrographs and Very satisfactory results were obtained. To illustrate the rational formula method, the design peak runoff rate for a once in 25 years frequency rainfa11 was determined. This method compared favorably with the unit graph procedure and was considered appropriate for use on small watersheds where no previous records exist. The Soil Conservation Service's revision of Cook's formula was discussed and illustrated. This procedure was considered appropriate only for areas much smaller than Sloan Creek. HYDROLOGIC ANALYSIS OF A SMALL AGRICULTURAL WATERSHED by Earl Abraham Myers A THESIS Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering 1960 VITA Earl Abraham Myers candidate for the degree of Doctor of Philosophy Final examination: September 7, 1960; 8:00 A.M.; Room 218 Agricultural Engineering Building Dissertation: Hydrologic Analysis of a Small Agricultural Watershed Outline of studies: Major subject: Agricultural Engineering Minor subjects: Civil Engineering Soil Science Biographical items: Born: January 15, 1929; York, Pennsylvania Undergraduate studies: Pennsylvania State University B.S.A.E., 1950 Graduate studies: Pennsylvania State University M.S.A.E., 1952 Pennsylvania State University 1952-195h, 1956-1959 Michigan State University 1959-1960 Experience: 1950-1951 New Departure Fellow, Agricultural Engineering Department, Pennsylvania State University 1951-195u Instructor, Agricultural Engineering Department, Pennsylvania State University 195h-1956 Military leave, Assistant Civil Engineer Facilities Engineering Branch, Rocky Mountain Arsenal 1956-1959 Assistant Professor, Agricultural Engineering Department, Pennsylvania State University 1959-1960 Graduate Assistant, Agricultural Engineering Department, Michigan State University Member of: American Society of Agricultural Engineers American Society of Engineering Education Gamma Sigma Delta, Agricultural Honorary Ig/V rifiw-"H ' 3.. ACKNOWLEDGEMENTS The author expresses his gratitude to Professor E. H..Kidder for the many hours of guidance and discussion time so freely given throughout the writers stay at Michigan State University. Sincere thanks are extended to Dr. A. W. Farrell for providing the opportunity and financial assistance for the pursuance of this program of studies, and to the various members of his staff who helped make this year one of great educational value. a For the generous cooperation of A. H. Eichmeier and A. D. Ash.and their staffs, respectively of the U.S. Weather Bureau and U.S. Geological Survey, the writer is deeply indebted. A special note of thanks is due Mr. R. Z. Wheaton of the Agricultual Engineering Department for his constant interest in the author's program and aid in supplying background information concerning the Sloan Creek Watershed. vi TABLE OF CONTENTS Section INTRODUCTION . . . . . . OBJECTIVES . . . . . . . REVIEW OF LITERATURE. . . . COLLECTION OF DATA . . . . PROCESSING OF DATA . . . . Rainfall distribution . . Hydrograph construction . Recession curve and base flow . . . Runoff . . . . . . . ANALYSIS AND DISCUSSION OF RAINFALL DATA . ANALYSIS AND DISCUSSION OF RUNOFF DATA. . Unit graph method . . . Rational formula method . Cook's method. . . . . SUMMARY . . . . . . . . CONCLUSIONS. . . . . . . SUGGESTIONS FOR FUTURE STUDIES REFERENCES . . . . . . . APPENDIX. . . . . . . . 1. Data for plotting Sloan Creek hydrographs . 2. Thiessen procedure rainfall analysis data . 3. Data for Sloan Creek composite recession curve 109 %. Data for obtaining unit . Data for comparison of calculated and actual _ ? Hr. unit graphs 1 I graphs. . . 85 . 85 . 113 . Fez-w a: —-=r~a»—-—~- -—r—-— war 9-... ”:3de it”? are." m Figure 1. 3. h. 5. 6. 7. 8. 9. 1o. 11. 12. 13. 11.. 15. 16. 17. 18. 19. Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan Sloan LIST OF FIGURES Creek basin . . Creek Creek basin nine Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph Creek hydrograph I C O O O 0 Aug. 9-12, 1956. Aug. 17-20, 1956 Apr. 27-30, 1957 May 1h-17, 1957. May 18-21, 1957. July u-7, 1957 . July 8-11, 1957. July 11-1u, 1957 Nov. lh-17, 1957 Apr. 6-9, 1958 . July 28-31, 1958 May 23-26,. 1959. Aug. 16-19, 1959 Sept. Zl-Zh, 1959 Oct. 6-9, 1959 . Nov. h-7, 1959 . _-.l- basin six gage Thiessen procedure. gage Thiessen procedure Page O 22 23 25 26 27 28 29 3o 31 - 32 33 3h 35 36 37 38 39 r --~;_ «gr- 1; Figure 25. 26. 1 Hr. Sloan Creek unit graphs . 2 Hr. Sloan Creek unit graphs . ix Page .65 .67 LIST OF TABLES Table Page 1. Percentage of watershed ascribed to each gage using Thiessen procedure. . . . . . . . 20 2. Rainfall and runoff data for 17 Sloan Creek hydrographs. . . . g. . . . . . . . h? 3. Sloan Creek rainfall data for 18 storm periods . 50 A. Data used in the analysis of the rainfall- runoff process for the watershed . . . . . Sh 5. Data showing the month by month variation in amount of moisture required prior to runoff and the percent of runoff for each storm period. . . . . . . . . . . . . . S9 6. Data for unit graph from August 17-20, 1956 hydrograph. . . . . . . . . . . . . 61 7. Data for comparison of a 1 hour unit graph calculated from a % hour composite unit graph and the actual 1 hour August 9-12, 1956 unit graph. . . . . . . . . . . 6h 8. Comparison of calculated and actual hydrographs for July ll-lu, 1957 . . . . . 69 9. Calculated and actual peak differences for the selected storm periods . . . . . . . 7O a... INTRODUCTION Peak runoff rates from small-area storms are critical in the design of spillways for dams, drainage systems, flood protection works, culverts, bridges, and storm sewers. Runoff volumes from small areas are also necessary in the design of irrigation systems, flood storage reservoirs, and other water detention and storage structures. Most previous rainfall and runoff data have been secured from either large areas, above 25 square miles, or extremely small areas of several acres or fractional acreages. And for most of these areas only one or at best relatively few recording rain gages have been used. Thus little detailed rainfall data exist on areas of S to 25 square miles in size. This is especially true for predominately agricultural watersheds. It was for the above reasons that in l95h, the Michigan Water Resources Commission; Surface Water Branch, Michigan District Office, United States Geological Survey; United States Weather Bureau office at East Lansing: and the Agricultural Engineering Denartment- kw ,“.,. raw—f7 ,, *7 Williamston in south-central Michigan, from which all the data for this thesis have been secured. The dominant land use of the Sloan Creek watershed was agricultural, with no urban infringement on the area. Nearly 60 percent of the area was cropland, with corn being the major crop. About 12 percent of the area was in pasture and 20 percent either idle or in wood land. The overall cultural picture of this watershed was one of a typical agricultural area. From a U.S. Geological Survey topographic map and detailed field checks on the basin boundaries, the drainage area above the stream gage was determined to be 9.3h square miles. The watershed was approximately four and one-half miles wide by six miles long, see Figure 1. The topography was flat to gently undulating and the channel slopes averaged 10 feet per mile. The main channel, a constructed drainage ditch excavated about 1917, had several small meanderings; however the ditch bottom was generally straight and reasonably clear of debris and woody vegetative growth. The watershed had mainly imperfectly-drained Conover and poorly-drained Brookston loam to clay loam soils with less than five percent of the area occupied by undulating to rolling well-drained, sandy loam Hillsdale and Bellefontaine soils. Also small areas of Brady and Griffin stratified, sorted, poorly-drained sands and LEGEND NWATERSHED BOUNDARY --- WATERCOURSE I U.S.G.S. STREAM GAGE Q RECORDING RAIN GAGEl [j CONOVER-BROOKSTON % BRADY-GRIFFIN Q HILLSDALE — BELLEFONTAINE == ROADS SCALE: 0—! MILE—9 FIGURE I. SLOAN CREEK BASIN "' J,"- I95. gravels occurred along the creek. In June 19511 the United States Geological Survey established the stream gaging station. The equipment consisted of a Stevens A-35 waterstage recorder in a wooden shelter over a welded-steel pipe well and concrete control with 90 degree steel V-notch sharp-crested weir. The operation and maintenance of this station were completely under the Jurisdiction of the U.S.G.S. Six recording rain gage stations were established in April 1956 under the supervision of the United States Weather Bureau, East Lansing office. Three additional stations were installed in April 1958 to give an even better coverage of the area. These gages were installed and calibrated by the Weather Bureau and were serviced by Agricultural Engineering personnel. The Water Resources Commission of Michigan aided in publication of data and supplied matching funds to the U.S. Geological Survey for stream gaging. The Soil Science Department advised on watershed soils problems. The Agricultural Engineering Department was responsible for changing the rain gage charts and helped maintain all field equipment in efficient operation. Another of its functions was to aid in the analysis of the data, under which this thesis was prepared. OBJECTIVES The basic objectives of this study were to collect, process, and analyze the five years of available Sloan Creek watershed rainfall and runoff records. More specifically these objectives were as follows: 1. To determine the adequacy of a single raingage for the watershed. 2. To compare the various methods of evaluating the average depth of rainfall of a small watershed. 3. To choose an applicable procedure for separating surface and base flow so the volume of runoff can be determined. h. To study the specific watershed characteristics which have the greatest effect on the runoff process and if possible to determine their Specific values for the Sloan Creek watershed. 5. To determine the applicability of various methods of estimating flood peak rates and/or volumes of discharge for watersheds of this size with or without prior hydrologic records concerning them. REVIEW OF LITERATURE A "small watershed" may refer to any area from a fractional acre to several hundred square miles in size. As implied in the Introduction, small watersheds in this thesis refer specifically to areas of 5 to 25 square miles. Very small watersheds pertain to areas from this size down to a fraction of an acre, while large watersheds refer to areas larger than 25 square miles. Rainfall and runoff records concerning large watersheds have been secured for a long period of time, mainly by the U.S. Weather Bureau and the U.S. Geological Survey. The early, published records contained only daily average stream discharge and raingage data, thus only areas over 500 square miles could be adequately analyzed. (10) As recording rain gage and stream gage records became available, areas much smaller than these were given more consideration. In 1917 the Miami Conservancy District gathered data on many large-area storms in connection with the design of flood-protection works for the Miami River above Dayton, Ohio. In 1931 this study was expanded to include depthearea-duration curves for 250 of the greatest storms in eastern United States. The Corps of Engineers in cooperation with the Hydrometeorological Section.of the Weather Bureau, in 1937, undertook a study of about 1000 major storms Which occurred in all parts of the United States. The data from this study were more detailed and supersede the Miami Conservancy work. (2h) Since 1930, much experimental work has been in progress on watersheds ranging from a few acres to several square miles in size. These experiments were designed primarily to determine the effects of land use and of conservation practices on runoff. The procedures on and the results of many of these studies are summarized by Krimgold (12,1h) and Cardwell (h). The previous references verify that the size of the watershed affects greatly the approach required for its “analysis, as it affects both the rate of runoff and the manner of its occurrence. 0n larger watersheds, floods reach their crest slowly, remain at flood stage for days, and subside slowly; while on smaller watersheds they crest more quickly, remain at flood stage only a short time, and subside quickly. When large streams overflow, the resulting damage is more extensive because of the larger flood plains and greater length of flood period; but the suddenness of small watershed floods frequently causes a heavy loss of life and preperty. (23) (29) Floods on small watersheds are generally caused by very intense precipitation, which occurs over small areas only. It is usually rains of low intensities covering w... r- w—flrw Th .‘1 H“. I A . .—' - .- 5. 1.5.4- .-e-_ i]. .;‘“.‘n. I 9” f. c *- 3 i. " ’ _. .- ‘5 ' - .111 .fl.‘ i r n I 5-. 1...“: f ‘1 q -- 1y.“- v.5.v‘ . ‘ > I 'P‘..'f d' #1'9’0“9w ms. .01. a“ :3". 1 a: 4““-M “”0 "Y rf'I-I'hltt -fe-.l.’.... .' -Jaw .14 ..1 III .II. 4...“ ‘1 . the entire watershed and lasting for several days which cause floods on large watersheds. Small and very small watersheds may consist entirely of steep slopes and impervious soil, causing a high percentage of runoff and a rapid concentration of flow; while the varied topography and soil of a large watershed usual result in a smaller percentage of the rain running off and in a slower rate of concentration. For example, the June 1903 flood of Willow Creek, Oregon produced 1800 cfs per square mile from a 20 square mile watershed; while the l90h flood on the Illinois River with a drainage area of 27,900 square mile had a flood runoff rate of only h.h8 second-feet per square mile. (23) On very small watersheds the rates and amounts of runoff are influenced primarily by the physical conditions of soil and cover over which man had some control, and thus most attention in hydrologic studies is given to these factors. The channel storage effect for large. watersheds becomes more pronounced and is given the most attention when considering runoff from large areas. (5) During the past ten years much information has been made available concerning large watersheds and also very small areas; however, information concerning the 5 to 25 square mile areas is still very inadequate. Decisions concerning runoff from these small areas, which include nu II in. A i., I so n,,,,,_,j _‘ smaller watersheds, must nevertheless continue to be made. Each year these determinations of runoff must permit more economical design of structures and at the same time assure a high degree of safety. Thus more accurate rainfall-runoff data must be secured. Pickles (23) lists and discusses a number of empirical formulas that have been used for estimating .. future flood flows. He also states, "The paper by Gregory and Arnold and the extensive discussion on it contain the most complete coverage of the subject of runoff formulas of which the author is aware." Most of the previously used empirical formulas have been grouped into two categories by Linsley, et a1. (17) The first category is of the type used by Fuller, Myers, Fanning, and Talbot which has the general form of qp = b Am. That is the peak flow is considered a power of the basin area. The exponents used differ to such an extent that this reference concluded that theses formulas "should never be used for engineering design." The second group is typified by the Burkli-Ziegler formula qp = A c iv/E: In this expression 1 is the expected average rainfall in inches per hour, a is the average slope of the watershed in feet per 1000 feet, A is the area in acres, and qp is in cfs. This type of .v-‘.I—-'"6-- 4— ... A- .«i '- Iig w... .. — b- q 0' ___‘1-- x -. 01‘“- v! s - :9- .v- _. “my —-——. A “T". ..... w _ 3.! ~‘:.--.~ 5 A ‘;'P—’. «I :2; — ‘.... ‘modern.engineering design". After considering all available references and the data available frommthe Sloan Creek watershed, three methods of estimating runoff were chosen. Before discussing these methods however, certain rainfall and watershed factors need to be considered. The major rainfall characteristics required for hydrologic analyses are intensity, duration, amount, and distribution. (2) Direction of storm movement also affects runoff. To analyze this factor, however, requires greater synchronization of raingage timing and longer periods of record than were available for this study. Recording gages supply adequate intensity, duration, and amount of rainfall data. The number and distribution of gages in the raingage network should be such that the rainfall data are congruent with the permissible variation in basin discharge. (16) The equivalent uniform depth of precipitation over a given area may be computed by one of four methods. The simplest is by taking the unweighted mean of the precipitation recorded by the various gages in the area. If the gages are regularly spaced this procedure is frequently as satisfactory as any of the others. The Thiessen procedure makes allowance for irregularities in gage spacing by weighting the amount received by each gage in proportion to the area which the gage represents. 1 - new. . 1‘71: yrs-aw Ram—3' ‘ - _ 11 The gage is assumed to represent all areas closer to it than to any other gage. The isohyetal map makes even greater use of the gage data by taking into account the evidence of other nearby gages and making corrections accordingly. (10) (2h) In the isohyetal method, the human element enters into the drawing of isohyetal lines which account for influences of areal distribution and topography on intensities. The Myers (20) method is a mathematical procedure which assumes uniform areal variations due to storm patterns and uniform changes in precipitation due to differences in elevation, but is always consistent when used to analyze a number of storms over the same watershed. Besides the storm characteristics previously (discussed, the quantity of runoff produced by a storm depends upon the moisture deficiency of the basin at the onset of the rain. Direct determination of the moisture conditions throughout the basin is not feasible, as depression and interception storage, as well as three- dimensional soil moisture measurements are required. (17) Nevertheless, various procedures have been considered for approximating these initial moisture conditions. Thames and Ursic (30) indicated that surface runoff is strongly correlated with storage opportunity in the upper 6 inches of soil.' In this case soil moisture ;_mm-“- F throughout the watershed was determined by a network of fiberglas resistance units. Variations in groundwater discharge at the beginning of storm periods and pan-evaporation data have been used with varying success. At the present time, the most common index is based on antecedent precipitation. (17) If moisture deficiency is broadly interpreted it also includes infiltration. Actually, storm loss is mainly due to infiltration and the infiltration rate at any time depends upon the water available for infiltration and on the infiltration capacity of the soil. If the rainfall intensity is greater than the infiltration capacity the excess water fills depressions and then runs off. (3) The infiltration capacity is extremely variable and has been the cause of much study. Kidder (ll) analyzed the effects of crops and tillage on the amount of infiltration that took place during individual natural storms. His review of literature summarized many factors which affect the infiltration process. Krimgold (l3) quoted from a paper of H. K. House to show "why the records from (very) small agricultural drainage areas with constantly changing vegetal cover, soil moisture, and structure of surface soil show such a great variation in peak rates of runoff which overshadow the relation to intensity of rainfall." Zingg (31) stated, ”The infiltration rate decreased throughout the ,;, V”. “32'. : storm, from a value of 0.12 inCh per hour at the initial time of rainfall excess, to less than 0.01 inch per hour about 15 hours later." The previous data point out some of the variables which must be considered in the rainfall-runoff process. These variables, individually and through interactions, affect the shape of the runoff hydrographs of a watershed, hydrograph being defined as a graph of discharge rate versus time. Each runoff hydrograph consists of three segments, a rising limb, a crest segment, and a falling limb or recession. The shape of the rising limb for any specific watershed is influenced mainly by the rainfall characteristics of the storm producing the runoff, whereas the recession is largely independent of these characteristics. (17) A flood-period hydrograph is usually a hydrograph of surface runoff superimposed on a hydrograph of groundwater discharge. A base flow line, between the point where the rising limb begins and the position on the recession where surface runoff ends, is used to separate these two flows. This line is assumed to be straight if groundwater data for a particular watershed is nonexistent. However, it may be concave downward or upward depending on the particular watershed characteristics. (10) Various methods have been considered for determining the position on the recession curve where surface runoff essentially ends. (9) The methods discussed in th. Processing of Data section were suggested by references (3), (17), and (2h). Pickles (23) recommended using the recession record from a similar, previous period to estimate the groundwater component. A mathematical procedure using unit graph theory to determine the expected values of surface runoff is suggested by Johnstone and Cross (10). These computed values are then compared with the natural hydrograph values and adjustments of time made until reasonable agreement between the calculated and actual rates is reached. This procedure is frequently used when previous recession curve data are not available. The first procedure of estimating watershed runoff to be considered in this thesis is the unit graph method. A unit graph is defined as a hydrograph resulting from 1 inch of runoff from the entire watershed as the result of a uniform rainfall lasting one unit of time. This method was introduced in 1932 by L.K. Sherman and is based on the principle that identical amounts of runoff should be produced from identical rains falling on identical watersheds. Recognizing that identical situations never occur in nature and that reasonable variations are acceptable for practical applications, certain tolerences are permitted. (15) (23) The unit graph principle was used in the approaches of Bernard, McCarthy, and Snyder. Each of their procedures is outlined in detail in reference (10). Their work was all on large areas. Linsley (15) has found unit hydrographs to be applicable to drainage basins in the 5-10 square mile area range. Minshall (19) is presently investigating the use of this method on areas less than 1 square mile in size. The unit graph method is most applicable where a number of years of rainfall and discharge records from recording gages are available. Besides this possible limitation some of the assumptions and other considerations required are discussed in the following paragraphs. For most watersheds variations of i 25 percent for lengths of rainfalls used to develop a unit graph are permissible. (17) The unit length chosen should be short enough to adequately define the hydrograph peak (2h), or be about one-fourth of the basin lag (15). Besides being relatively uniform in length of rainfall, the rainstorm should be evenly distributed over the entire area and of such magnitude that all parts of the watershed contribute to the runoff. The directions and rate of storm movement its intensity, and the season of its occurrence should be similar. (10) It is assumed that the time distribution of surface runoff from a given storm period is independent of concurrent runoff from antecedent storm periods, and that for storms of equal lengths the rates of runoff at corresponding times are in the same proportion to each . “m “mu—u» ,v-ha a—‘n‘w‘ ' ..,- '_-r 7-4:": ‘Fv-v' 7 ‘-__ l .a...‘ other as the total volumes of surface runoff. (10) The composite unit graph from a number of similar storms is considered more applicable than from any specific one. This is because of inaccuracies in the basic data, nonuniform distribution of storms, and departures of drainage basin performance from unit graph theory. (10) All the authorities agree that none of these assumptions are rigorousily correct, but they believe that a maximum variation and peak discharge of 1 20 percent about the mean can be obtained. The rational formula Q = C i A is a very simple formula. It is a very satisfactory formula however, if all the rainfall and watershed characterstics can be properly determined. Sharp (25) has done an excellent job of outlining its two main weaknesses. ”The first of these is the determination of the proper rainfall intensity to use. This will vary with the season of the year, the size of the watershed, the type of storm, direction of travel of rain wave, and many other factors ’-----~ Watersheds, other than those measured by square feet in area, rarely have uniform rainfall intensity even instantaneously over the entire watershed much less for periods of minutes or hours which are the most normal duration of concentration time." "The second is the determination of the coefficient C. This coefficient must be adjusted to accomodate surface storage, detention storage, initial abstracts, rainfall interception, and a varying rate of infiltration. Detention storage varies with land slapes and channel gradients, stream meander, pondage, and other factors. Infiltration may be affected by land use, land treatment, vegetative conditions, antecedent soil moisture, temperature, and other factors." This certainly is true, but without previous rainfall or runoff information for a watershed any other formula must consider these same factors. An example of rational formula use is given in the Analysis and Discussion of Runoff Data section. Cook's method of evaluating runoff for a particular watershed by examining the relief, soil infiltration, vegetal cover, and surface storage characteristics has been modified by Soil Conservation Service personnel. Its latest modification has been recently outlined by Ogrosky (22), who states, "The approach takes into consideration the soil, land use or cover, treatment or practice, hydrologic condition of the cover, soil moisture condition and rainfall.” The field hydrologists are then provided with the range of data which is to be used in a prescribed procedure. This information includes 2000 major soils which have been placed in four hydrologic groups; curve numbers for various combinations of soils, cover, and treatment; a series of curves relating rainfall and runoff; and description of the various soil moisture conditions. The procedure is very exacting; all field men arrive at the same runoff from a given set of data. These values of runoff are probably fairly accurate if the rainfall and watershed conditions were of the "average" type for which the procedure was designed. I LEE-M“ n. -' a = he: at 0 .—A ~— w;$2-‘1‘ . _’_¢n' ‘ “w" COLLECTION OF DATA In determining the specific rainfall-runoff periods to study, it was necessary to use raingage and streamgage records simultaneously. It is merely for convenience that they are here discussed separately. The hourly precipitation from each of the raingage charts was read and tabulated by Weather Bureau personnel. Copies of the tabulated sheets were maintained by the Agricultural Engineering Department. These tabulations were rechecked for arithmetical accuracy and where comparisons between gages indicated possible errors original charts were referred to. These records were satisfactory for the determination of average depth of rainfall over the watershed and for indicating the hourly amounts of precipitation for the runoff hydrographs. The original tracings, however, had to be used for preparing unit hydrographs, as specific lengths, intensities, and uniformity of rainfall are critical in their construction. In securing runoff data it was necessary to refer to the original tracings of the waterstage recorder, as U.S. Geological Survey personnel tabulate only daily average discharges. Their notes for the calculation of 7...... ,_,"_._ "r‘zfi-‘ _ these discharges, however, served as an excellent check on the author's work. Forty five possible discharge peaks were checked. Many were discarded due to frozen ground or to water from melting snow being in the discharge; others were eliminated because the peaks could not be readily separated or there was insufficient data. Assistance of U.S.G.S. personnel in determing the appropriate runoff peaks to use was invaluable. Eventually data were secured for 19 hydrographs, with peak flows ranging from 685 cfs to 3 cfs. Fifteen of them were used for determining the rainfall-runoff process for spring, summer, and fall conditions; two were representative of winter conditions with no snow; one was for exemplifying snow melt runoff; and one was for showing the effect of very light precipitaion during extremely high antecedent moisture. Only sufficient points necessary to obtain a true reproduction of the original hydrograph were secured. These data and an explaination of their derivative are presented in Appendix 1. 20 PROCESSING OF DATA Rainfall distribution According to Linsley, Kohler, and Paulhus (17), the Thiessen method of determing equivalent uniform depth of precipitation will give "essentially the same" results as linear interpolation used with the isohyetal procedure. Since there are no topographic influences which warrant modification from linear interpolation and since the Thiessen method is easier to apply it was used for this watershed. Table 1. Percentage of watershed ascribed to each gage using Thiessen procedure. Gage Six gages Nine gages number percent ggpercent 9.8 7.2 2 19.1 11.0 3 1h.2 12.h h 19.6 1h.8 S 22.9 20.8 6 1h.h lh.1 18 6.0 19 11.1 21 __ A Total 100 . O 100 . O 21 q 3" Figures 2 and 3 show the areas ascribed to the various rainfall gages for the six and nine gage arrangements, respectively. The specific percentages of the watershed assigned to each gage are listed in Table 1. Using the percentages given in Table l, the Thiessen procedure rainfall analysis data were calculated. These data and additional information concerning them are presented in Appendix 2. Hydrograph construction The data of Appendix 1 were used to construct hydrographs for the 19 runoff periods. Figures h through 22 show chronologically these hydrographs with their respective base flow separations. These figures also include the Thiessen hourly precipitation values, each plotted in the center of the hour‘gf its collection. A uniform scale of time for the abscissas was used, but the scales for the ordinates were varied to secure maximum area under the curves. The greater area permitted increased accuracy in the determination of runoff by planimetering. As discussed in the next section, 2% day surface runoff recession curves were used for nearly all hydrographs. Occurrence of another storm before the ending of this period required the lengthening of three hydrographs by using data from similar storms. Typical recessions for the 7 Ur---“ ,A..._ W 533%: 'm""§; o :- . - ”aw”: , v ._ 9-way?!" 7' . .- ~’”‘ _ ___._.. 22 LEGEND N WATERSHED BOUNDARY \ -—- WATERCOURSE ‘ v I U.S.G.S.STREAM GAGE , I Q RECORDING RAIN GAGE ' .. = ._ THIESSEN LINES SCALE: p——L_.x._..g__4 ‘ " FIGURE 2. SLOAN CREEK BASIN SIX THIESSEN PROCEDUM'T ‘8 A (3 E: 23 LEGEND /\.WATERSHED BOUNDARY --- WATERCOURSE I U.S.G.S. STREAM GAGE Q RECORDING RAIN GAGE _ NI __ THIESSEN LINES Q SCALE: o—l MILE—e FIGURE 3. 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NI BSHVHO 30...... umI 43.2.06. / -N IaI xmmmo z<04m m N d.mm30E w II II Ilnlv Ill IIII ls l' III II I ll 0 3'0 NI HOUVHD‘SIO 8 S 30...... mwt ...<:...o< I HI. m3. .3- a mm >42. Ia1 xmmmo Z<0..m .2 umber. 0n 0N ow 3033:! 30.... “90 ougmm< IIIII tn. (recent. 45.2.04 II 0 SI 0 '93:) N‘)’ assvso _.'" e-’ ~ ~.‘- I. ‘p f‘ .“F a. .. d-. ,1 .v.'_"~ -‘a. .* ...- I .‘ Q‘II .ru i new 1 4f” . .5!“ - ‘U K 35 9.9.8-3 ><2 Im1 xmmmo z<0..m 0N vN .9 mane... nN _ 30...... mm1 ..<......o< 14—.- l N V 0 'SZ-J'O NI BSUVHOSIO 0. N. ....\I\I.I _ _ _ . IL $2 .m_-w_.o:< I¢1 xmmmo z<0..m .0. manor... m. o. a. c. _ _ _ _ _ _ _ o I 2 I O N I 9 _j dllOSHd 8 $30 NI BSHVHOSIO 3 l 30....— mmz xmmmo 240.5 s. IIIIIIII III 30...... mmdm owiawmd ..... Iadmoomot. ..<......0< I 20_mmm0mm 4<0_n.>... II _ . r _ I o 9 ‘- . E... , I . § § ‘ss'o NI asaVHOSIO I - o 9 b 2.2.»... .>02 flm1 xmnmmo z<0...w c .m. umber. _ _ _ _ _ . _ _ _ 39 dDE i. ..______ H. zmr v. n. xwwMo z<0..w 304... uwr 4<=b0< I y... 8m..~.ma<-m~.mz xmmmo 240.5 N . . .n — . :m4m00co»: 44Dh04 0n _ mN . 0N _ 5N .NN manor. 0N ..§. 3 3 3 sec NI asawosm fi h3 August 9-12, 1956; October 6-9, 1959; and January 12-15, 1960 hydrographs were obtained from the July h-7, 1957; July ll-lh, 1957; and January h-7. 1955 storms, respectively. Recession curve and base flow A specific point on the recession curve which defines the ending of surface flow is more theoretical than realistic. However, the position where this essentilly occurs can be determined by methods described in the Review of Literature. With the data available for this analysis the use of a typical base flow recession curve was the most appropriate method of estimating this point. Since a sufficiently long, rainless period following a major storm did not occur, a typical recession curve was constructed synthetically by combining short recessions. Figure 23 shows the construction of the composite recession curve from seven individual storm recessions. The data for the individual storms are tabulated in Appendix 3. Curves from the base flow section of the composite recession curve plotted to the appropriate scales were used to determine where surface flow became insignificant. This occurred essentially two and a half days after the peak for all hydrographs except April 27-30, 1957 and July ll-lh, 1957. For these the storm recessions deviated xmmmo 24040 10.... m>m30 20.mmm0mm m..._won.200 .MN manor... «>40 2. m2... - u u 1 q d u u u u u u u 1 * d u u - u u - mzofimuoum Exp—.0 4400.202. K I mine 2933...... £59.28 \ .n x.02mmn.4 2. 0mh4...:m4... m2¢0km 4400.202. 10.... 4...40 ' S 8 'SL—J'O NI BDHVHOSIO 8 IIS materially from the base recessions about three days after the peak. This was due to light showers occurring shortly after the main storm in each case. Linsley, Kohler, and Paulhus (17) suggests, as a rule of thumb, that the time in days N from the peak to surface flow secession may be approximated by N = A0.2 where A is the drainage area in square miles. This formula gave an N of 1.56 days for the watershed. The discrepancy between this value and the two and a half days actually found was probably due to the watershed being long and narrow, being flatter, and having proportionally more surface storage than the "typical" watershed. Our watershed examplifies their statement, "However, N is probably better determined by inspection of a number of hydrographs, keeping in mind that the total time base should not be excessively long and the rise of the groundwater should not be too great". As little is known of the rate at which accretion to groundwater discharge takes place from infiltration, a straight line joining the positions of surface runoff beginning and ending was assumed. This concurs with the authorities referred to in the Review of Literature. Runoff At this point it would be well to make a precise distinction between ”total surficial outflow" and "surface l ,. 1.. e a . ... DH 0 o t 4 ,, I I u ‘ . I .,. l ”u he runoff". According to thnstone and Cross (10), "Total surficial outflow is to be taken as meaning all water moving out of the drainage area in surface streams, regardless of whether it has reached the stream directly from overland flow or indirectly via underground movement". Whereas, surface runoff has a narrower connotation; strictly defined, it is that portion of total surficial outflow (total runoff) from a given drainage area that has come from precipitation which has at no time infiltrated into the soil. The data of Appendix 1 are measures of total surficial outflow. They include certain amounts of base flow which were derived from groundwater. The straight, dashed, base flow line essentially separates that portion due to surface runoff from that due to groundwater. Actually, the portion referred to as surface runoff contains a small amount of water which has infiltrated into the soil surface but has come out again very quickly from seeps or from tile lines. This water is frequently called interflow but is usually so small in comparison that it was not considered in this analysis. Surface runoff, hereafter referred to merely as runoff, is thus that portion between the hydrograph and the base flow line. The volume of runoff can be obtained by multiplying the average hourly ordinate in cubic feet per second by 3600 seconds in an hour and summing over the -ueuuw" Table 2. Rainfall and runoff data for 17 Sloan Creek hydrographs . ea 0 a - un- , 2.1.2:... :33?“ $22“ 323” 8%- ’3}? Date C.F.S. In. Sag. In. 53. In. Hours In. Aug. 9-12, 1956 128 2.15 n.62 288 1330 0.22 Aug. 17-20, 1956 h3 1.19 3.85 lhh 555 0.09 Apr. 27-30, 1957 137 0.67 u.o3 360 1u50 0.2u May lu-l7. 1957 79 0.60 u.oo 216 86k 0.1u May 18-21, 1957 23h 1.80 8.87 576 5110 0.85 July h- 7, 1957 90 2.09 8.00 216 1728 0.29 July 8-11, 1957 61 1.19 9.13 1th 1316 0.22 ' July ll-lh, 1957 685 3.69 7.13 luuo 10280 1.70 Nov. 10-17, 1957 32 1.13 9.59 72 690 0.11 Apr. 6- 9, 1958 27 0.82 8.15 72 587 0.10 July 28-31, 1958 3 1.20 6.83 9 58 0.01 May 23-26, 1959 10 1.07' 10.8h 29 312 0.05 Aug. 16-19, 1959 61 0.8a 6.00 1th 86k 0.1u Sep. 21-2h. 1959 21 1.7a 10.20 AB A90 0.08 Oct. 6- 9, 1959 A76 3.28 7.h0 1152 8530 1.01 Dec. ll-lh, 1959 76 0.73 7.89 216 1703 0.28 Jan. 12-15, 1960 90 1.18 10.n0 216 2250 0.37 duration of runoff. Or it can be determined by planimetering the area between the curves, as each unit of area represents a specific volume in cfs-hours. Since in this study each hydrograph was reproduced to a reasonably large scale it was concluded that planimetering was a satisfactory procedure. Table 2 shows the area of the hydrograph representing surface runoff, the cfs-hours per square inch for the scales used, the runoff, and other associated information for each of the 17 storm periods thus analyzed. The conversion between cfs-hours and inches over the 9.3u square mile watershed area was 60h0. ANADYSIS AND DISCUSSION OF RAINFALL DATA The storms considered in this analysis are essentially of two types; 1. the steady, rather uniform, and widespread rains occurring during the approach of warm fronts with stable air masses; and, 2. the thunder- shower type, which develops in connection with . - convectively unstable air masses or the passage of cold fronts and squall lines. (2) The former type occurs mainly in the early and late parts of the growing season and frequently lasts several days. Most of the summer storms are of the thundershower type, which frequently result in high intensities for short durations, and may produce large runoffs to overload drainage systems. (7) Existing Weather Bureau raingage stations spaced 20 to 30 miles apart serve well for describing storms of the first category. The irregularly distributed and small area summertime storms, however, may pass between these stations. As these storms are important in the design of many water management facilities, especially for small agricultural areas, the dense network of gages in this project were necessary. Rainfall data pertaining to 18 of the storm periods included in this analysis are presented in Table 3. Comparisons of the Thiessen averages and unweighted .- ',. Table 3. Sloan Creek rainfall data for 18 storm periods, essen nwe e average average Gage h _Dag Inches Inches Inche_s_ Aug. 9-12, 1956 2.15 2.10 2.70 Aug. 17-20, 1956 1.19 1.1h 1.70 Apr. 27-30, 1957 0.67 0.67 0.75 May 111-17, 1957 0.60 0.67 0.15 May 18-21, 1957 1.80 1.81 1.80 July h- 7. 1957 2.09 2.10 2.50 July 8-11, 1957 1.19 1.20 1.19 . July ll-lh, 1957 3.69 3.68 h.00 Nov. 1h-17, 1957 1.13 1.10 l.h0 Apr. 6- 9, 1958 0.82 0.81 0.81 July 28-31, 1958 1.20 1.17 1.56 May 23-26, 1959 1.07 1.06 1.13 Aug. 16-19, 1959 0.8M 0.90 0.60 Sep. 21-2h, 1959 1.7h 1.70 2.05 Oct. 6- 9, 1959 3.28 3.20 ‘ 3.92 Nov. h- 7, 1959 0.95 0.97 1.0u Dec. ll-lh, 1959 0.73 0.73 0.85 Jan. 12—15, 1960 1.18 1.19 1.33 51 Everages show that 50 percent of these differ by less than one percent. This agrees with the Weather Bureau's concept that for much work, averaging methods more detailed than unweighted averages are unnecessary. The location of gage h was considered an appropriate single gage position for the entire watershed. Table 3 shows this gage recorded more rainfall than the Thiessen average 13 of the 18 times; several times by over 0.5 inch and one of these being h3 percent larger. As the location and calibration of this gage met all standard specifications, why it recorded consistantly high has been of great concern. EVen greater variation was noted when single gages at different ends of the watershed were compared. The May 15, 1957, storm produced rainfall amounts ranging from 1.36 inches at gage l to 0.26 inch at gage 6. The range for the August 16, 1959 storm was 1.6h inches at gage 2 to 0.23 inch at gage S. The distances between gages l and 6 and 2 and 5 were respectively, h.3 and 3 miles. These data were confirmed by those of reference (6) and indicated that for accurate rainfall information it is imperative that irrigation farmers have their own raingages. The long axis of the watershed was North-South which is perpendicular to the general West to East direction of storm travel. The effect of direction of 52 Storan travel on the peak discharge rate was therefore minimized. This, coupled with only small differences in the beginning time of the rain between gages, made it impossible to measure an effect due specifically to direction of storm movement. It was possible to determine storm centers from the intensity and amount of precipitation recorded by the various gages. However, an insufficient number of storms of uniform size but with different storm centers, prevented adequate determination of their effect on peak runoff rates. . ;‘v' . v I ANALYSIS AND DISCUSSION OF RUNOFF DATA The actual average amount of rain which fell on the watershed and the amount of runoff which it produced are shown in Figures A through 21. This information and other pertinent data used in analyzing the rainfall-runoff process of the watershed are presented in Table h. Only 15 of the 19 hydrographs were considered in this analysis. The December ll-lh, 1959 and January 12-15, 1960 storms occurred after the ground had been frozen and are thus not considered. It was impractical to use the November h-7, 1959 storm period because of the additional rise on the recession due to showers on the afternoon of the fifth. The March 26-April 2, 1960 period was included only to show a late-spring, snow-runoff hydrograph. The 285 cfs peak, due only to melting snow, was the third largest peak- discharge recorded in the five years of data and emphasizes the extreme antecedent conditions which must be considered when estimating design peak runoffs. The total inches of rainfall and runoff for each of the storm periods are listed in columns (2) and (3), respectively. Column (h) is merely the difference between the previous two. This amount of water from the storm having just occurred did not leave the watershed as surface flow and had to be accounted for in some other way. Various methods considered for determining the soil Table A. .Data used in the analysis of the rainfall- runoff process for the watershed. (1) Date Aug. 9-12, Aug. 17-20, Apr. 27-30, May 1h-17, May 18-21, July h- 7, July 8-11, July 11-1u, 'Nov. lh-l7, Apr. 6- 9, July 28-31, Hay 23-26, Aug. 16-19, Sep. 21-2k, Oct. 6- 9. 1956 1956 1957 1957 1957 1957 1957 1957 1957 1958 1958 1959 1959 1959 1959 (2) Rain- fall In. 2.15 1.19 0.67 0.60 1.80 2.09 1.19 3.69 1.13 0.82 1.20 1.07 0.8k 1.70 3.28 Run- f (h) 2-3 In. 0.93 1.10 0.k3 0.k6 0.95 1.80 0.97 1.99 1.02 0.72 1.19 1.02 0.70 1.66 1.87 (5) figfst. In. 0.07 0.00 0.88 0.59 0.65 0.00 0.55 0.50 0.00 0.35 0.00 0.38 0.88 0.00 0.58 (6) Tot mei§%.1nfl. In. 2.u0 1.10 1.31 1.05 1.60 1.80 1.52 2.89 1.h2 1.07 1.19 1.h0 1.58 1.66 2.h1 (7) In. 0.19 0.19 0.25 0.09 0.65 0.25 0.hk 1.13 0.59 0.28 0.19 0.3h 0.19 0.56 1.20 14.23. runogf In. 2.21 0.91 1.06 0.96 0.95 1.55 1.08 1.36 0.83 0.79 1.00 1.06 1.39 1.10 1.21 moisture conditions of a watershed prior to a storm have been mentioned in the Review of Literature. Most authorities recognize the importance of antecedent moisture and feel that antecedent precipitation gives a satisfactory index of its effects on runoff. They also agree that soil 55 moisture usually decreases logarithmically with time during periods of no precipitation. The exact rate of decrease depends mainly on the amount and type of watershed vegetation, the type of soil, and the climatic conditions. Since these are extremely variable any system which gives a reasonable indication of the amount present is all that can be justified. The season of the year effects both the number of antecedent days for which precipitation will effect runoff and the fraction of the antecedent precipitation which will be effective. Ten days of antecedent precipitation were considered to effect runoff for April, May, and November and only five days for July, August, September, and early October. The specific fraction of the rain which was considered effective for each of these preceding days were 0.9, 0.7, 0.5, 0.h. 0.3, 0.2, 0.2, 0.1, 0.1, and 0.1 for the ten day period and 0.9, 0.7, 0.5, 0.3, and 0.1 for the five day period. These depletion rates compare favorably with irrigation concepts, as well as with prior hydraulic analyses. The specific values of effective antecedent moisture computed for the surface eight to twelve inches of the watershed prior to each storm period are listed in column (5). These values added to the moisture of column (h) gave the total inches of moisture in the basin which had to be accounted for at the end of each storm period. ”M 56 These totals are listed in column (6), Table h. Rainfall which did not run off as surface flow during the storm period was considered a combination of infiltration, surface storage, and detention storage. The surface and detention storage of a watershed is reasonably uniform from storm to storm, but infiltration is extremely variable. Infiltration depends not only upon the physical characteristics of the soil and the cover on the soil, but also on such factors as soil moisture, temperature, and rainfall intensity. Since the initial infiltration rate is much more rapid and more variable than the "normally approached constant infiltration rate" they were considered separately. The "constant" infiltration rate was estimated at 1/32 inch per hour for April, May, and November and 1/16 inch per hour for July, August, September and October. The values for each of the two periods were determined from hydrographs which occurred due to low intensity but long duration storms. The May 19, 1957 rain fell at an average of 0.1 inch per hour for the first 17 hours and produced a peak runoff of 2&0 cfs. With approximately 50 percent of the rainfall running off and a small amount going into surface and detention storage no more than about 0.03 inch per hour could have gone into the soil. The December ll-lh, 1959 and January 12-15, 1960 57 storms, by the same procedure of analysis, gave infiltration rates of less than 1/32 inch per hour. These, however, can be Justified due to previously frozen soil. The rise produced in the hydrograph recession by the 0.12 inch of precipitation of November 5, 1959 attests also to the low infiltration rate of the watershed when extremely high antecedent conditions exist. Each infiltration amount of column (7) was obtained by multiplying the appropriate infiltration rate by the number of hours two greater than the length of rainfall. The addition of two hours accounted for infiltration during the time required for overland flow. This moisture was assumed to have gone into the deeper soil strata of the watershed and to be no longer effective watershed moisture. The total effective moisture required prior to surface runoff for each storm is listed in column (8) and was determined by subtracting column (7) from column (6). Total effective moisture included surface and detention storage, initial infiltration, and effective antecedent moisture. The column (8) values of Table h listed timewise, irrespective of the year of occurrence, are presented in column (B) of Table 5. In this manner they more clearly indicate the total effective moisture required to produce runoff from month to month throughout the season. Omitting those with asterisks, the values increased from spring through the middle of August and then decreased from there to winter. As these values depend upon the amount of moisture in the lower soil strata, the specific time they begin to decrease depends upon the amount of fall rain received. Those storm periods marked with asterisks are not appropriate for comparison. The storm of July 28-31, 1958 produced virtually no runoff, as shown in column (C), and thus the watershed had not reached its maximum water holding capacity when the rain stopped. The other three followed previous storms which had increased the substrate moisture; thus required less initial infiltration before runoff began. It was considered advisable to test the previously developed procedure on storms with which the author had no previous knowledge. The storms for testing, therefore, had to come from the spring of 1960 records. The multiple storm periods of April lh-l7, May 19-23, and June 13-16 were chosen, as the records included no individual storm of major consequence. In following the procedure previously outlined the author's estimated peak discharges versus those which actually occurred were as follows: April lh-17, 10-20 cfs versus 39 cfs; May 19-22, 20-k0 cfs versus 18 cfs; and June 13-16, 90-125 cfs versus 31 cfs. The differences for April lh-l7 were caused by the extremely late spring, whereas, those for June 13-16 were due to no prior June records, both of these indicating a lack of knowledge of the moisture content of the subsurface soil layers. Table 5. Data showing the month by month variation in amount of moisture required prior to runoff and the percent of runoff for each storm period. m_ L m (A) (8) (C) Prior to Runoff Runoff Date Inches Percent Apr. 6- 9, 1958 0.79 11.8 Apr. 27-30, 1957 1.06 35.8 May 18-17, 1957 0.96 23.8 May 18-21, 1957 0.95 87.0 ‘May 23-26, 1959 1.06 8.8 July 8- 7. 1957 1.55 13.7 July 8-11, 1957 1.08* 18.3 July 11-18, 1957 1.36* 58.0 July 28-31, 1958 1.00* 0.8 Aug. 9-12, 1956 2.21 10.3 Aug. 16-19, 1959 1.39 17.0 Aug. 17-20, 1956 0.91* 7.7 Sep. 21-28, 1959 1.10 8.7 Oct. 6- 9, 1959 1.21 83.0 Nov. 18-17, 1957 0.83 10.1 For specific reasons see text. m *These values are not appropriate for comparison. 7 c I ‘ l 0 ¢ . . 3 J. I _ ' ‘ u . ..I 't I 1 5.. -§.‘ '.‘ ,3 .' ,..“_ .... ., ,1 11, PT .H.r.‘1‘r_rM-..._. ._ , . . 60 Unit graph method As stated previously a unit graph is a hydrograph which results from a one inch runoff from the entire watershed. It also implies the fulfillment of the other specifications stated in the Review of Literature. This rarely or never occurs in nature. However, since a perfect procedure is not available, this and other methods will be discussed as reasonable approximations. A study of the rainfall and runoff records revealed five periods of reasonable conformation to unit graph specifications. Original raingage charts were used in the preparation of all unit graphs. Two of the rainfall periods were each % hour in length, two were 1 hour, and the other was 2 hours. This proved very convenient in the selection of the unit time. The procedure of obtaining a unit graph is explained by using the August 17-20, 1956 data as listed in Table 6. Columns (2) and (3) show the total surficial outflow and base flow, respectively. Values for both of these columns were obtained from the curves of Figure 5. The surface runoff presented in column (8) is the total flow minus the base flow. The actual depth of runoff over the entire watershed from this storm was 0.0919 inch. If I inch had run off, each value of column (8) would have been 10.9 times as large and the values would have been as recorded in 61 Table 6. Data for unit graph from August 17-20, 1956 hydrograph. ‘1’ ASE}... 3.5.2.! 1.2%! $32. flow flow off graph Timg_» C.F.S. C.F.S. C.F.S. C.F.S. 18- 2 1.2 1.2 0.0 0 3 2.0 1.2 0.8 9 8 6.1 1 .2 8.9 53 5 3h 1-3 32-7 356 6 83 1.3 81-7 858 7 39 1.8 37.6 809 8 35 1.8 33 .6 366 10 27 1.5 25.5 278 12 22 1.5 20.5 223 15 18 1.6 16.8 179 18 15.8 1.7 13.7 189 21 13.1 1.8 11.3 123 28 11.8 1.9 9.5 103 19- 8 7.8 2.0 5.8 63 12 6.8 2.1 8.7 51 28 8.9 2.6 2.3 25 20-12 3.6 2.9 0.7 8 18 3.1 3.1 0.0 0 a This column is essentially data secured from standard U.S.G.S. rating tables where values above 10 cfs are considered only to the nearest whole number. JV 62 columns (5). The graph of discharges from column (5) plotted against time give a unit graph. Data for the unit graphs from the periods of August .9-12, 1956; May 18-17, 1957; July 877, 1957; and August 16-19, 1959 are tabulated in Appendix 8. Due to nonuniform distribution of storms and departures of drainage basin performance from unit graph theory, it is common practice to derive the unit graph for a watershed from a number of storms. The two % hour unit hydroglaphs are shown in Figure 28. The peaks were made to coincide in time as recommended by Johnstone and Cross (10). The magnitudes of the peaks differed by less than 10 percent which is considered excellent for unit graph work. If a unit graph of % hour duration is added to itself lagged by % hour the resulting hydrograph represents the hydrograph for 2 inches of runoff in 1 hour. If the ordinates of this hydrograph are divided by 2 a unit graph of 1 hour results. This is the procedure which was used to convert the composite of the % hour unit hydrographs to a 1 hour unit graph. The data for this procedure are tabulated in Table 7. The composite unit graph is shown with the 1 hour unit graph from the August 9-12, 1956 storm in Figure 25. The peaks of these two hydrographs differ only by approximately 20 percent which is still satisfactory. 63 $3.55 .52: xmmmo 240.5 .m: No: 8 av ¢N N. em “#52“. 02m... :2: 9.3: _I III/_I/I_ _ _ _ _ _ _Ka— , Ba. 2..-: >42 III 1 . 82.8.: .22 ..... a 4 1..— _ —— M mm=f_-=-_____ 8 § 'S'J'O NI 398VHOSIG § Table 7. Data for comparison of a 1 hour unit graph calculated from a % hour composite unit graph and the actual 1 hour August 9-12, 1 6 unit graph. ompos e n grap u e a cu a e c ua Hours % hour shifted 1 hour 1 hour 1 hour from unit graph % hour unit graph unit graph unit graph peak C.F.S. C.F.S. C.F.S. C.F.S. C.F.S. - 3% 0 0 0 0 - 3 8 0 8 2 - 3 23 8 27 13 7 - 2. 2 23 65 32 - 1% 182 g2 228 112 67 - 1 322 l 2 508 252 - t 801 322 723 361 253 O 881 801 882 881 + 3 855 881 936 868 578 + 1 855 888 + 1% 808 829 833 816 878 + 2 379 808 783 391 + 2% 351 379 730 365 365 + 3 3 351 675 337 + 3% 30 3 630 315 268 + 8 288 306 598 297 + 8% 272 288 560 280 232 + 5 256 272 528 268 + 8 186 + 8% 179 186 365 182 167 +18 102 +18% 99 102 201 100 103 +32 87 +32% 85 87 92 86 55 +88 23 +88% 21 23 88 22 26 +50 18 +50% 12 18 26 13 18 +55 8 +55% 6 8 18 7 6 +60 0 0 O 0 0 "7"? W..- .J‘. ‘ ‘ ., r * h . ~ . i "'0 I D O o . vuAb mInEmo ._._ZD xwwmo 240.5. .m: _ .nN wmboi 00 0? @n VN N. 0 3‘2 20mm mm—DO: _IIIIT: _ _ _ _ _ _ 1 _ I/I/ * I. II __ I / _.‘ ll — /.., __ ll- // n§ [SN 1" _ .. 4 a, l 4.! Icon I y 18.. __/ :35 :2: l I we .I utmousoo a: S. :2: .. [08 . e8. .~_.m 583 In--- ._._ . , c I. _ _ _ _ _ _ _ _ ._ _ _ _ loom o 9 'S'J'O NI 398VHOSIO 66 The data for the conversion of the composite of the two 1 hour unit graphs to a 2 hour unit graph are listed in Appendix 5. This 2 hour unit graph was compared with the 2 hour unit graph of the July 8-7, 1957 storm in Figure 26. The peaks of the two 2 hour unit graphs differed by 57 percent which was considered too great for use in this study. The discrepancy between the magnitudes of the peaks was due to the nonuniformity of the rain. Each of the six gages showed that the storm of July 8-7, 1957 was composed of three bursts of rain rather than a continuous one. The storm period of August 16-19, 1959 was also discounted due to nonuniformity of rain. In this case there was much variation in the intensity at each gage, as well as amounts from gage to gage. From the previous unit graph data it was considered reasonable to use the 1 hour composite unit hydrograph to check several actual storms periods. This unit time compared favorably with Linsley (15) who states, "In general, the unit duration should probably be in the order of 25 percent of the basin lag", basin lag being the time from the centroid of rainfall to the hydrograph peak. An hour interval was also very convenient for making computations and using regularly tabulated rainfall data. Comparison of the calculated hydrograph and actual . 9, . mIm 8 I a“ . 7 .. 5 Appendix 1 Continued Corr. Stage Corr. Stage charge Dis- Timp Feet Feet Feet C.F.S. 28 21-12 28 22- 8 3.11 0 CG Le/V 2.89 2.88 +.08 +.08 8-13 18 19 21 22 23 28 5- 1 3 13 21 28 6-10 16 28 7-12 18 1.69 1.68 .91 .19 .70 .83 .50 .88 .81 .18 .98 .92 .77 .68 ha “3 [U R) IV R) IV R) \A u) k» u: k» n) r0 +.01 3.19 3.06 2.97 2.92 1.70 1.69 1.92 2.20 2.71 B-hh 3.51 3.89 3.82 3.15 2.99 2.93 2.78 2.69 .55 +.01 2.56 .80 +.02. 2.82 .33 +.02 2.35 53 39 32 28 1.1 1.1 2.8 5.5 18 82 90 88 79 88 33 29 21 18 9.6 8.0 fl Corr. Stage Corr. Stage charge Dis- Time Feet Feet Feet C.F.S. 28 July 8-11. 1957 8- 1 5 8 9 10 11 12 13 18 _16 28 9-11 28 10-12 18 28 11- 2 11-2 2.30 +.02 2.32 2.29 +.02 2.31 2.27 2.85 2.96 3.00 3.07 3.16 3.18 3.22 .3-28 3.20 3.07 2.90 2.66 2.88 2.39 2.35 2.38 +.02 July ll’lhe 1957 2.29 2.87 2.98 3.02 3.09 3.18 3.20 ~ 3.28 3.26 3.22 3.09 2.92 2.68 2.50 2.81 2.37 2.36 2.38 +.02 2.36 H I, 01}, 7.2 6.8 11 33 36 52 58 58 61 56 82 28 17 12 9.3 8.8 8.2 8.2 1—--e. I . Lahfl 3:1- ‘ 1 . . m“ "-32-.- ..wee' ' .~‘ ’ h:".-‘ ' he 1‘. ' .- ‘I-O ' I ’ JI L4 .- "€.‘ :00 0 '~ 1." A J v ‘ .Wflt‘ "3 F ll 4.. H'fls 9. '1 0v 9:“- It "it? . - 1.... rw‘-O.-.Et: ‘10-...“ _ “‘b'fi. ' Wine-Till: It 11.9. 3 .. ' —- rv-qr-r—mu‘e pap . 3:11-31" * Appondix 1 Continued Stage Corr. Stage charge Time Feet Feet Feet C.F.S. Corr. 8 2.52 +.02 2.58 S 6 8 10 11 13 18 15 16 l7 18 19 '21 22 28 3L22— 1 3 5 6 8 2.80 2.78 .13 .28 .26 .23 3.23 3.50 5.20 5.95 6.50 7.33 7.17 6.22 5.76 5.25 8.78 8.60 8.32 3 3 3.31 , 3 3 2.82 2.80 3.15 3.30 3.33 3.28 3.25 3.25 3.52 5.22 5.97 6.52 7.35 7.19 6.28 5.78 5.27 8.80 8.62 8.38 10 '8-18 +.02 8.16 Dis- 13 23 22 88 65 69 63 60 6o 91 333 885 582 685 656 895 820 380 270 283 201 175 Corr. Stage Corr. Stage charge Time Feet Feet Feet C.F.S. Dis- 18 3.68 -.02 3.66 109 21 3.57 " 3.55 28 3.53 " 3.51 13- 2 3.50 ' 3.88 12 3.29 ' 3.27 28 3.18 ' 3.12 18-12 '3.08 ' 3.02 28 3.02 -.02 3.00 November 18-17, 1957 18- l 1.77 none 1.77 8 1.79 ” 1.79 9 1.93 " 1.93 12 2.19 " 2.19 15 2.55 ' 2.55 18 2.72 ' 2.72 21 2.86 " 2.86 23 2.96 " 2.96 28 2.97 ' 2.97 15- 2 2.95 " 2.95 8 2.90 ” 2.90 7 2.82 " 2.82 12 2.67 none 2.67 95 90 87 62 85 36 38 1.5 1.6 2.8 5.8 18 19 25 31' 32 30 27 23 17 \ P ) I I . 7, . \ k I O- 'I y 1 llllll APpend ix 1 Continued «_.‘—- ‘ Corr. Dis- Stage Corr. Stage charge Stage Corr. Stage charge Time Feet Feet Feet C.F.S. Time Feet Fget Feet C.F.S. 2m. 2585 none 2.85 ..10 9-12 2.20 none 2.20 5.5 - 16—12 2.33 " 2.33 "7.6 21‘ 2.17 none 2.17 5.1 ' .28 2.28 n 2.28 6.1 July 28-31, 1958 3 17—12 2.17 none 2.17 5.1 28- 7 1.82 none 1.82 0.3 April 6-9, 1958 13 1.81 " 1.81 0.3 (Ba. 8 1.98 none 1.98 2.8 18 1.56 ” 1.56 0.6 17 1.97 " 1.97 2.7 15 1.75 ' 1.75 1.8 19 2.05 ” » 2.05 3.5 16 1.75 , 1.75 1.8 21 2.15 " 2.15 8.8 17 1.72 , 1.72 1.2 23 2.36 ” 2.36 8.2 18 1.90 " 1.90 ‘ 2.2. 2.71 " 2.71 ' 18 20 1.96 . 1.96 2.6 7- 1 2.85 " 2.85 28 22 1.99 " 1.99 2.8 2.88 ' 2.88 26 28 2.03 ” 2.03 3.3 8 2.90 " 2.90 27 29- 2 2.00 " 2.00 2.9 8 2.87 " 2.87 26 8 1.95 " 1.95 2.5 10 2.88 " 2.88 28 6 1.90 ' 1.90 2.2 12 .2.80 , 2.80 22 9 1.88 ” 1.88 1.8 18 2.68 n 2.68 17 12 1.78 " 1.78 1.5 28 2.56 " 2.56 18 15 1.73 " 1.73 1.3 8.. 6 2.86 " 2.86 11 18 1.70 " 1.70 1.2 12 2.37 " 2.37 8.8 28-' 1.66 . 1.66 1.0 28. 2.28 none 2.28 657 30- 6 1.63 none 1.63 0.9 Fr" Appendix 1 Cbntinued 91 Corr. Dis- Corr. Dis- Mfi? $22? $32? 813%??? 13E. 322%?" 332? 32:? 8’33??? 12 1.61 none 1.61 0.8 August 16-19, 1959 2.8 1.58 " 1.58 0.7 16-12 2.23 none 2.23 6.0 3:L-12 1.56 , 1.56 0.6 18 2.21 " 2.21 5.6 18 1.58 none 1.58 0.6 17 3.07 " 3.07 80 Fltlzr 23-26, 1959 18 3.17 " 3.17 .51 33- l 1.81 none 1.81 1.7 20 3.26 " 3.26 61 8 1.81 " 1.81 1.7 22 3.18 " 3.18 52 8 1.87 ," 1.87 2.0 28 3.11 " 3.11 88 12 2.03 " 2.03 3.3 17- 3 3.00 " 3.00 38 18 2.28 ’ " 2.28 6.7 8 2.87 " 2.87 26 21 2.36 " 2.36 8.2 12 2.77 7 2.77 21 28 2.81 " 2.81 9.3 18 2.65 " 2.65 16 3311- 3 2.83 " 2.83 9.9 28 2.55 " 2.55 13 5 2.88 " 2.88 10.2 18-12 2.81 " 2.81 9.3 10 2.83 " 2.83 9.9 28 2.38 " 2.38 7.8 13 2.82 " 2.82 9.6 19-12 2.28 " 2.28 6.7 18 2.80 " 2.80 9.0 20 2.23 none 2.23 6.0 28 2.37 " 2.37 8.8 September 21-28, 1959 5355-12 2.31 " 2.31 7.2 21- 7 1.61 none 1.61 0.8 28 2.28 " 2.28 ~ 6.1 17 1.60 " 1.60 0.7 =3€»-12 2.19 " 2.19 I'5.8 19 1.76 n 1.76 1.8 20 2.16 none 2.16 8.9 22‘ 2.03 none 2.03 3.3 Appendix 1 Continued ‘ 92 .1... 32:8 32:2” 335%; 2:78? 3:28 .222:- SEEE‘; 312%? 28 2.21 none 2.21 5.6 10 8.81 none 8.81 272 222-. 2 2.80 ' 2.80 9.0 11 8.83 " 8.83 275 6 2.70 " 2.70 18.0 12 5.15 ' 5.15 322 7 2.75 " 2.75 20.0,. 13 5.55 " 5.55 383 9 2.77 " 2.77 20.8“ 18 5.77 " 5.77 818 11 2.76 ” 2.76 20.6 15 5.85 " 5.85 831 12 2.78 " 2.78 19.6 16 6.13 ' 6.13 876 18 2.69 " 2.69 17.9 17 5.85 " 5.85831 17 2.62 " 2.62 15.6 20 5.08 ' 5.08 312 20 2.58 ' " .2.58 12.7 28 8.50 " 8.50 225 23:3— 2 2.83 " 2.83 9.9 7- 6 '8.00 “ 8.00 153 12 2.33 " 2.33 7.6 12 3.68 * 3.68 111 28 2.20 " 2.20 5.8 18 3.89 " 3.89 88 2211-12 2.15 " 2.15 8.8 28 3.38 “ 3.38 75 28 2.09 none 2.09 8.0 8-12 3.20 " 3.20 58 c><=tober 6-9, 1959 22 3.12 none 3.12 85 ES- 1 2.26 none 2.26 6.8 November 8-7, 1959 8 2.30 ” 2.30 7.0 8- 1 2.06 none 2.06 3.6 2.88 " 2.88 10 6 2.05 " 2.05 3.5 2.78 " 2.78 20 9 2.11 n 2.11 8.2 3.75 " 3.75 120 11 2.88 " 2.88 10 8.68 none 8.68 286 12 2.87 none 2.87 26 CDNIO‘UI I“ fi—“RJ f Appendix 1 Continued rr—fi: Wm Stage Corr. Stage charge Stage Corr. Stage charge Time Feet Feet Feet C.F.S. Tiflet Feet Feet C.F.S. 13 3.01 none 3.01 35 18 2.60 none 2.60 15 18 3.17 " 3.17 51 19 2.81 " 2.81 22 15 3.25 " 3.25 60 21 3.13 " 3.13 86 16 3.26 " 3.26 61 23 3.38 " 3.38 70 17 3.26 " 3.26 61 28 3.38 " 3.38 75 18 3.25 " 3.25 60 12- 1 3.39 ' ” 3.39 76 21 3.20 " 63.20 58 ‘ 2 3.38 " 3.38 75 28 3.18 " 3.18 87 6 3.28 " 3.28 63 55.12 2.98 " 2.98 33 11 3.18 " 3.18 52 18 2.91 " 2.91 28 28 3.00 " 3.00 38 20 2.90 8 2.90 27 13-12 2.85 " 2.85 25 28 2.92 " 2.92 28 28 2.78 " 2.78 20 (5. 3 2.91 " 2.91 28 18-12 2.62 " 2.62 16 12 2.80 " 2.80 22 20 2.57 none 2.57 18 28 2.68 " 2.68 17 January 12-15, 1960 7-12 2.57 none 2.57 18 12-1 1.97 none 1.97 2.7 11-6 2.18 none 2.18 5.2 7 2.00 " 2.00 2.9 11 2.18 " 2.18 5.2 12 2.17 " 2.17 5.1 13 2.20 ” 2.20 5.5 15 2.85 ” 2.85 28 15 2.25 " 2.25 6.2 18 3.27 " 3.27 62 17 2.83 none 2.83 9.9 20 3.85 none 3.85 83 Appendix 1 Continued aorre BEB- _ 'U’Corr. Dis- ' T1... 322? 333" 322? 8’3??? n... 322? 322'? $22? 8*}??? 21 3.50 none 3.50 89 28 3.85 none 3.85 138 22 3.51 " 3.51 90 29- 8 3.70 " 3.70 118 28 3.89 " 3.89 88 9 3.57' " 3.57 97 13- 2 3.86 " 3.86 88 12 3.65 " 3.65 108 5 3.86 " 3.86 88 15 8.12 " 8.12 170 9 3.33 " 3.33 69 17 8.75 " 8.75 262 12 3.23 " 3.23 57 18 8.90 " 8.90 285 28 3.01 " 3.01 35 20 8.78 " 8.78 267 73L11-11 2.87 " 2.87 26 28 8.28 " 8.28 192 28 2.81 none 2.81 22 30- 8 8.00 “ 8.00 153 March 26 - April 2, 1960 7 3.90 " 3.90 180 23(5-12 1.90 none 1.90 2.2 9 8.08 "’ 8.08 168 27-12 1.93 " 1.93 2.8 12 8.35 " 8.35 202 18 2.32 " 2.32 7.8 15 8.50 " 8.50 225 28 3.00 " 3.00 38 18 8.36 " 8.36 208 2213- 3 3.31 n 3.31 66 28 3.98 '" 3.98 150 7 3.50 " 3.50 89 31- 6 3.69 " 3.69 113 10 3.85 ” 3.85 83 12 3.51 ” 3.51 90 12 3.51 " 3.51 90 28 3.31 " 3.31 66 15 3.70 " 3.70 118 1-28 3.16 " 3.16 50 18 8.11 " 8.11 168 2-28 3.07 none 3.07 80 20 8.21 none 8.21 182' 95 Atppendix 2 Thiessen procedure rainfall analysis data. The hourly precipitation for each gage was read and ‘tabulated by Weather Bureau personnel following standard erather Bureau procedure. These values were multiplied lxy the percentage of the watershed area each gage represented, according to Thiessen procedure, and listed on the following pages. The right hand column thus shows the average weighted depth of rain for each hour and at the end of each storm period indicates the equivalent uniform depth of rain over the watershed. As the March 26-April 2, 1960 runoff period was included only to show the effect of snow runoff, the small amount of rain which fell during the end of this period was not included. It should also be noted that the average hourly precipitation values of less than 0.01 inch were not shown on Figures 8 through 21. 96 APpendix 2 Thiessen procedure rainfall analysis data. _.‘ agenumeran wege nceso ran an Time 1 2 J 1+ 5 6 Inches Aaxigust 9-12, 1956 59-13 0.076 0.33h 0.173 0.333 0.389 0.27h 1.579 in 0.078 0.029 0.109 0,186 0.092 0.01u 0.5u8 15 --- --- 9:993 0.010 0.005 _0.003 9:922 0.15u 0.363 0.326 0.529 0.086 0.291 2.1u9 August 1.7-20, 1956 18- 2 --- --- --- --- --- 0.007 0.007 3 0.029 0.229 0.171 0.2u5 0.1h9 0.1u8 0.971 u 0.002 0.008 0.0u8 0.088 0.030 0.003 0.179 22 --- --- --- --- 0.014 0.01u 0.028 0.031 0.237 0.219 0.333 0.193 0.172 1.185 11pr11 27-30, 1957 227- 9 0.001 --- --- .-- --- --- 0.001 10 0.033 0.075 0.06h 0.090 0.105 0.065 0.u32 11 0.012 0.023 0.016 0.039 0.037 0.019 0.1h6 12 --- 0.002 --- 0.002 --- 0.003 0.007 1n 0.001 0.002 0.003 --- --- --— 0.006 15 0.00u 0.006 0.00u 0.002 0.009 --~ 0.025 16 0.002 --- 0.001 0.00u --- --- 0.007 17 --- 0.002 --- --- --- --- 0.002 18 ~ 0.001 0.00u 0.00u --- 0.007 0.00u 0.020 Appendix 2 Continued ‘ :Gag? number an we 0 no es 0 rs n F5171- - Time _ 1 3 j j 6 _Inches 20 9;993 ‘Qéggg 0.006 0.00 --- 0.001 0.018 0.057 0.120 0.098 0.1u5 0.160 0.093 0.673 May 111-17, 1957 117.211 0.001 --- --- 0.0011 --- 0.006 0.011 15- 1 0.133 0.177 0.092 0.081. 0.0178 0.036 0.570 2 --- --- --- --- 0.016 --- ' 0.016 3 .:::_. _:::_. _:::;. _:::_. 2122é..2;QQl .2;222 0.138 0.177 0.092 0.088 0.066 0.0u3 0.600 May 18-21, 1957 318-20 0.001 --- --- --- --- --- 0.001 21 0.00u 0.006 0.003 0.00u 0.002 0.00u 0.023 22 0.006 0.011 0.006 0.010 0.011 0.006 0.058 23 0.00u 0.017 0.018 0.022 0.023 0.025 0.109 2a 0.010 0.019 0.013 0.018 '0.025 0.016 0.101 :19— 1 0.011 0.017 0.013 0.020 0.021 0.013 0.095 2 0.002 0.006 0.007 0.008 0.011 0.007 0.001 3 0.012 0.019 0.011 0.018 0.011 0.007 0.078 a 0.003 0.010 0.006 0.005 0.002 0.007 0.03u 5 0.022 0.0uu 0.036 0.053 0.066 0.083 ‘ 0.26u 6 0.01u 0.029 0.020 0.020 0.021 0.01u 0.122 7 0.01h 0.029 0.020 0.02h 0.018 0.019 0.12u 8' 0.017 0.027 0.020 0.02u 0.021 0.016 0.125 _.._.- Appendix 2 Continued 98 Time :56 numzer an 1‘16 6 no 38 0 1'2 11 1112;23- 9 0.005 0.011 0.009‘ 0.012 0.009 0.007 0.053 10 0.011 0.021 0.018 0.027 0.032 0.023 0.131 11 0.008 0.019 0.018 0.020 0.018 0.012 0.091 12 0.012 0.019 0.011 0.022 0.023 0.013 0.103 13 0.006 0.015 0.009 0.011 0.018 0.013 0.075 18 0.003 0.00h 0.001 0.008 0.005 0.035 0.055 15 0.002 0.001 0.001 0.006 0.005 --- 0.018 16 0.002 0.008 0.001 0.002 0.002 0.003 0.018 17 0.002 0.002 .0.001 0.001 0.002 0.003 0.018 18 0.001 0,00u 0.003 0.008 0.005 0.001 0.018 19 0.008 0.008 0.001 0.008 0.002 0.008 0.019 20 0.001 0.002 0.001 0.001 0.005 0.003 0.016 21 0.001 0.002 0.003 0.002 0.002 0.007 0.017 22 0.001 --- --- --- 0.002 --- 0.003 23 0.001 --- --- --- --- --- 0.001 an -—- --- . --- 0.002 -—- --- 0.002 0.183 0.385 0.218 0.358 0.362 0.301 1.797 Jun h-7. 1957 14.-18 0.03h 0.076 0.063 0.029 0.083 0.083 0.288 19 0.075 0.097 0.092 0.296 0.263 0.193 1.016 20 0.047 0.097 0.081 0.165 0.232 0.160 0.782 0.156 0.270 0.236 0.190 0.538 0.396 2.086 rmw‘ .. Appendix 2 Continued 99 2&22;7 :86 numaer an 3we g to no 53,0 r: n Inzhgs July 8-11, 1957 8- 5 0.001 --- --- --- --- --- 0.001 0.029 0.025 0.009 0.016 0.009 0.001 0.089 7 0.073 0.1h9 0.09h 0.135 0.1h2 0.09h 0.687 8 0.011 0.027 0.017 0.02h 0.037 0.022 0.138 9 0.011 0.019 0.01h 0.026 .0.030 0.019 0.119 10 0.015 0.029 0.020 0.033 0.03h 0.025 0.156 11 --- --- --- --- --- 0.003 0.003 0.1h0 0.2h9 0.15h 0.23h 0.252 0.16M 1.193 July ll-lh, 1957 11- 2 0.001 --- 0.00h --- --- 0.010 0.015 3 0.033 0.101 0.031 0.0h1 0.03h 0.022 0.262 h 0.009 0.035 0.068 0.096 0.092 0.0h8 0.3h8 6 0.003 0.008 --- --- --- --- 0.011 7 0.007 0.029 0.026 0.029 0.032 0.0h3 0.166 8 0.010 0.019 0.018 0.035 0.057 0.029 0.168 15 0.008 0.010 --- --- --- --- 0.01h 16 0.119 0.193 0.099 0.1h1 0.130 0.073 0.755 17 0.087 0.208 0.121 0.196 0.206 0.092 0.910 18 0.066 0.115 0.078 0.133 0.137 0.066 0.595 19 0.017 0.025 0.0h3 0.075 0.076 0.0h9 0.285 20 0.00h 0.002 0.001 0.00h 0.005 --- 0.016 Appendix 2 Continued 100 m2 280 numzer an we e no ES 0 r: 11 11121123 12-18 0.009 0.008 70.011 0.006 0.005 0.003 0.082 19 --- --- 0.001 0.008 0.002 0.001 0.008 21 0.002 0.010 0.007 0.008 0.009 0.003 0.039 22 0.001 0.011 0.007 0.012 0.011. 0.007 0.052 0.375 0.778 0.515 0.788 0.796 0.886 3.690 November 1h-17, 1957 1n- 5 0.008 0.006 0.006 0.008 0.005 0.008 0.033 6 0.008 0.019 0.009 0.020 0.027 0.010 0.093 7 0.008 0.015 0.006 0.010 0.011 0.007 0.053 8 0.006 0.006 0.009 0.018 0.011 0.012 0.061 9 0.008 0.015 0.009 0.022 0.023 0.012 0.089 10 0.015 0.031 0.018 0.031 0.037 0.021 0.153 11 0.006 0.015 0.007 0.012 0.018 0.010 0.068 12 0.009 0.021 0.009 0.028 0.025 0.016 0-10h 13 0.005 0.010 0.007 0.011 0.011 0.007 0.058 18 0.001 0.002 0.001 0.002 --- 0.001 0.007 15 0.008 0.011 0.006 0.010 0.011 0.007 0.052 16 0.003 0.006 0.008 0.002 0.005 0.001 0.021 17 0.002 0.006 0.003 0.008 0.005 0.006 0.030 18 0.008 0.008 0.007 0.018 0.01u 0.00h 0.055 19 0.007 0.015 0.011 0.037 0.017 0.121 0.031 Appendix 2 Continued 101 Cage mm or an we e no es 0 ra n a 11 Time 1 2 3 5 6 Inches 20 0.00h 0.013 0.01h 0.027 0.021 0.013 0.092 21 0.003 0.00h 0.003 0.010 0.009 0.001 0.030 22 0.001 0.002 --- 0.006 --- --- 0.009 0.09h 0.205 0.129 0.275 0.273 0.1h9 1.125 April 6-9, 1958 6-17 0.012 0.027 0.023 0.037 0.092 0.065 0.256 18 0.029 0.0hh 0.0h1 0.051 0.069 0.035 0.269 19 0.012 0.029 0.020 0.027 0.023 0.019 0.130 20 0.003 0.002 0.006 0.012 0.009 0.006 0.038 21 0.006 0.019 0.007 0.018 0.009 0.007 0.057 22 0.002 0.008 0.006 0.010 0.007 0.007 0.0h0 23 0.002 0.006 0.00h 0.002 0.002 0.00h 0.020 2h 0.001 0.002 --- 0.002 0.002 0.001 0.008 0.067 0.128 0.159 0.213 0.1hh 0.818 j0.107 102 «00.H 0«0.0 0HH.0 H00.0 «0H.0 0m«.0 00H.0 H0H.0 JHH.0 m00.0 «00.0 mmmqm 0H0.0 n00.0 m00.0 0«0.0 0H0.0 W00.0 «00.0 H00.0 0 mm~.0 --- 000.0 000.0 ~«0.0 0«0.0 0H0.0 0«0.0 0H0.0 «H0.0 0 H00.0 «00.0 000.0 m00.0 0H0.0 «no.0 mH0.0 HH0.0 HH0.0 000.0 0 0«H.0 000.0 0H0.0 000.0 HH0.0 Hm0.0 ««0.0 000.0 0H0.0 000.0 0 000.0 «H0.0 m:0.0 ««0.0 mmo.0 000.0 .0m0.0 H00.0 «00.0 0«0.0 m 00H.0 m00.0 000.0 0«0.0 0«0.0 000.0 m«0.0 ««0.0 0H0.0 HH0.0 0 mmo.0 «00.0 m00.0 000.0 000.0 0H0.0 000.0 000.0 000.0 m00.0 m ««0.0 -n- .m00.0 «00.0 000.0 «00.0 m00.0 «00.0 «00.0 «00.0 « m«0.0 -u- --- H00.0 m00.0 000.0 m00.0 m00.0 000.0 «00.0 H -m« . 0m0a .0«-m« 00: m0«.H 0«0.0 0:a.0 0m0.0 0mH.0 00«.0 Hm«.0 HOH.0 HmH.0 0m0.0 wmmqm --- --- --- -u- --- m00.0 -a- . -u- --- 0H 0«0.0 H«0.0 «00.0 am0.0 «00.0 00H.0 0m~.0 «00.0 000.0 0«0.0 ma Ham.0 000.0 000.0 0«0.0 000.0 «0H.0 «00.0 000.0 :m0.0 «20.0 :a-m« 0m0H .Hnuom haze 0””me HN 9H ma 0 m fl‘ m 3 no man om H 08:. noun—3:00 w wacoamw _ 5.0““ 103 000.0 H00.0 --- H00.0 H00.0 «00.0 H00.0 --- H00.0 -u- « -0 . 0m0H .0-0 0000060 0m0.H mm0.0 00H.0 000.0 0:«.0 ««m.0 m0m.0 «H«.0 00H.0 0«H.0 mmmqm wmmwm 000.0 0«0.0 n«0.0 00m.0 000.0 0.0 H 0.0 ««0.0 :« «mH.0 «00.0 «00.0 000.0 Hmo.0 000.0 0H0.0 0«0.0 mH0.0 000.0 m« 000.0 «00.0 000.0 .m00.0 HH0.0 mHo.0 «H0.0 0H0.0 000.0 000.0 «« «0«.0 m00.0 nm0.0 000.0 0m0.0 Hm0.0 000.0 0«0.0 0H0.0 000.0 H« 00H.0 m00.0 MH0.0 m00.0 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J. . ,J ..f. * ..h!.....$ .o\..r0..,.. .- ..H..\..1..1.VLH..‘J?'Mr'r....uol.ly11.nmv£$‘#uiw‘ ...-0:. l.. . . l ..J‘.. 0. “.NN... .\. 109 m.H 0 m.H 0H 0.H m 0.H 0 0.H N 0.H 0 0.H H 0.N 0 0.N om N.N 0 m.N 0N m.N m 0.N 0N 0.N 0 0 m HN 0 m 0 m.m w m.m - mm w.m m. 0 O H O O I N 0.0 0N 0.: 0H N.0 0 mm .0 0 0.: H 0.0 0H H.m. mH N.m m N.m NH m.m 0H 0.m 0H 0.0 N 0.m HH 0 0000 .0 0H 0.0 0H 0.0 H, w.0 0H 0.0 0H 0.0 NH .0 0 0.0 . mH 0.0H HH 0 0: 0.0 0 0H 0H 0.0H 0 mH MH 0m .0m< 0H NH 0H MN 0 .000 0N HH 0N NN 0m HN 0m .000 . no em 0m N0: .0.0.0 0000 .0.0.0 0000 .0.0.0 0000 .m.0.0 0000 .m.0.0 0000 owhano owhugo ownano amnaflo awhano -000x -000 -000 0H0 -000 .ophao scammoooh 000000500 #0000 caoam 000 0000 m H«cnoqu 110 Appendix h Data for obtaining unit graphs. The specific procedure for calculating unit graph values is presented in the Analysis and Discussion of Rainfall Data section. The May lh-17, 1957 data are for a % hour unit graph, the August 9-12, 1956 and August 16-19, 1959 data are for 1 hour unit graphs, and the July h-7, 1957 data are for a 2 hour unit graph. The total flow values as listed under each of these storm periods were essentially all from Appendix 1 data and thus list values above 10 cfs only to the nearest whole cfs. The base flow data were all from the respectiye hydrograph figures, therefore were read to the nearest 0.1 cfs. The tenths were maintained under the surface runoff column because this column had to be proportionally increased to 1 inch of runoff which required a large magnification in most cases. 111 Appendix 1 Data for obtaining unit graphs. O a 386 un- n , O a 839 un- flow flow off graph flow flow off graph gm: cps cps cps cps ' Time cps cps cps cps August 9-12, 1956 May 11-17, 1957 9-12 0.8 0.8 0.0 ' 0 11-21 6.1 6.1 0.0 o 13 2.6 1.0 1.6 7 15- 1 19 6.1 ”12.6 88 11 16 1.1 11.9 67 2 69 6.1 62.6 138 15 57 1.2 55.8 253 2% 79 6.1 72.6 508 16 128 1.3 126.7 571 3 75 6.5 68.5 179 17 107 1.1 105.6 178 6 52 6.6 15.1 318 18 82 1.5 80.5 365 11 31 6.8 21.2 169 19 60 1.6 58.1 261 17 21 7.0 17.0 119 20 53 1.7 51.3 232 21 19 7.2 11.8 83 21 39 2.2 36.8 167 16-12 11 7.6 6.1 15 10-10 26 3.3 22.7 103 21 11 8.0 3.0 21 21 17 1.9 12.1 55 17-12 9 8.3 0.7 5 11-12 12 6.2 5.8 26 15 8.5 8.5 0.0 o 18 9.9 6.9 3.0 11 23 8.8 7.1 1.1 6 :12- 1 8.0 8.8 o 0.0 ~ W“ ”THC—Ht“ ‘--.-r 'r. mn- *4 Appendix 1 Continued O a 886 'un- In 0 a .ase ’un- '1: flow flow off graph flow' flow off graph Time Q§§ __gps CFS cps,gu Time CFS CFS CFS CFS July 1-7, 1957 August 16-19, 1959 1-18 1.1 1.1 0.0 0 16-11 5.6 5.6 0.0 o 19 2.1 1.2 1.2 1 15 6.6 5.6 1.0 7 20 3.6 1.1 2.2 8 17 10 5.7 31.3 210 21 5.5 1.5 1.0 11 18 51 5.7 15.3 318 , 22 18 1.6 16.1 57 19 57 5.7 51.3 359 23 82 1.7 80.3 281 20 61 5.8 55.2 387 21 90 1.8 88.2 308 21 57 5.8 51.2 358 5- 1 88 1.9 86.1 301 22 52 5.8 16.2 323 2 83 2.0 81.0 281 21 11 5.9 38.1 267 3 79 2.2 76.8 269 17- 3 31 5.9 28.1 197 7 65 2.8 62.2 218 8 26 6.0 20.0 110 13 18 3.5 11.5 156 12 21 6.0 15.0 105 21 33 1.5 28.5 100 18 16 6.1 9.9 69 21 29 1.8 21.2' 85 21 13 6.2 6.8 18 6-10 21 6.2 11.8. 52 18-12 9.3 6.1' 2.9 20 16 18 7.1 10.9 38 21 7.8 6.6 1.2 8 21 11 8.0 6.0 21 _ 19-12 6.7 6.7 0.0 0 7-12 9.6 9.6 0.0 o “FT—=3 , Appendix 5 Data for comparsion of calculted and actual 2 Hr. unit graphs. ‘4fimep. ‘980. gr. DouSIe CaIc. ‘1-7 July 57 Hours 1 hour shifted 2 hour 2 hour 2 hour from un. gr. 1 hour un. gr. un. gr. un. gr. pgak C.F.S. ___C.F.S. C.F.S. C.F.S. C.F.S. - 5 o - 1 O O 0 g - 3 10 0 10 5 - 2 9O 10 100 50 11 - l 307 90 397 198 57 0 521 307 828 111 281 + 1 117 521 968 181 308 + 2 365 117 812 106 301 + 3 290 365 655 327 281 + 1 256 290 5%6 273 269 + 5 228 256 1 1 212 255 + 6 208 228 136 218 210 + 7 190 208 398 199 229 + 8 171 190 361 182 218 +11 118 +12 139 118 287 113 171 +17 109 . .+18 102 109 211 105 123 +21 78 ‘ +25 7h 78 152 76 35 +31 51 +32 50 51 101 52 60 +13 26 -+11 21 26 50 25 30 +19 15 +50 13 15 28 11 19 +51 9 +55 7 9 16 8 10 ”-59 1 "~60 O l. l O O Appendix 6 Data for comparsion of calculated and actual hydrographst= omp. u a c. c . Hours unit 3 Run Run Hours from graph hour hour off off from peak CFS CFS CFS CFS CFS gpgak 0 - 6 - 1 o o o 1 - 5 - 3 10 2 o 2 2 - 1 _ 2 90 15 1 16 1 - 3 - l 307 S2 11 63 16 - 2 o 521 88 36 121 80 - 1 + 1 117 75 61 136 88 O + 2 365 61 53 111 86 + l + 3 290 19 13 92 81 + 2 + u 256 13 3h 77 77 + 3 + 5 228 38 30 68 73 + 1 + 6 208 35 27 62 69 + 5 + 7 190 32 25 S7 65 + 6 + 8 171 29 22 51 62 + 7 + 9 161 28 21 19 59 + 8 +10 155 26 19 15 56 + 9 +11 118 25 18 12 53 +10 +12 139 23 17 10 ' so +11 +13 133 22 16 38 17 +12 Appendix 6 Continued (Ramp . Hours unit T31: . Juii 8211;"19S7_—__'"'7Eflifi-'IEFT-‘—‘-_ End. , 3rd . 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