‘ , A sum OF THERUNOFF OF THE SACANDAGA RIVER SPRENG OF 1936 THESES FOR DEGREE OF C. E; William Burns Hanlon 1937 Ina-“:1: . A ; - / 5&6 as. ma? :1, caayyw {—- w J 4 k-.- x X , \ SQ!“ (1'1“ L1. 55.“ ”I". J ‘5" L l 5211/ A M or m RUN-OFF 03' m SACANDAGA mm SPRING or 1936 Thesis for degree of 0.3. William Burns Hanlon 19 37 SYNOPSIS An analysis of the sources of the stream flow and the re- lationship oi’ their associated factors during the spring of 1936 forms the basis of this paper. Use has been made of the following data: amount of water available in the snow cover at the start of. and early in, the melting period; precipitation; temperature; and stream flow. All of the data were collected in or adjacent to the basin of the Sacandaga River above the gaging station near Hope, New York. Above the gaging station, the river is practically free from artificial regulation but its flow is affected slightly by natural storage in lakes. The watershed located on the slepes of the Adirondacks comprises an area of M91 square miles which is almost entirely wooded, largely with coni- fers. Ihe tepography is irregular and rugged with steep slopes producing rapid run-off of the rain falling on the area. Starting on March 1, when the stream flow was low and prob- ably dne ”to flow from ground water and from natural storage in headwater lakes. the measurement of precipitation and stream flow is recorded until June 10. On this latter date, the stream flow was the same in amount as on March 1. Conditions directly effect- ing the stream flow on these dates are presumed to be identical. thus all of the flow in the interim would have been produced by precipitation and melting snow. The term run-off as used in this paper includes all flow past the gaging station regardless whether 1. 10551.11»: it reached there by surface or underground flow. As the ini— tial and terminal flows are identical. the need for dividing run- off further is obviated in so far as total figures for the period are concerned. . Where run-off exceeds precipitation the difference has been used in combination with temperature data to determine melt- ing characteristics of the snow. INTBDDUCTION A blanket of snow on the ground may be considered to be a reservoir holding in store a certain quantity of water. Ihen conditions become favorable to melting. the snow will be Convert- ed into water which is subject to several courses: return to the atmosphere through evaporation, replenishment'of the ground water table, or to occur as surface run-off. As melting occurs at moderate temperatures and before plant growth is advanced the evaporation losses are relatively low. At the same time the ground is often frozen and thus conducive to a high rate of sur- face mn-off. It is realized that generalizations relating to snow and its melting are difficult owing to the wide geographical differences within the belt of snow occurrence. the importance of snow as a source of run-off is, of course, dependent upon the amount of the snow. In some areas practically all of the precipitation occurs as snow, while there are others which have no snow. However. in areas where snowfall is of an ‘ appreciable amount and occurs intermittently over a period of time it becomes of great importance as the precipitation for several months may be stored Up. and then released. sometimes suddenly with resulting high flows and often floods. depending upon conditions attendant to the melting. As the efforts to control and use water more efficiently have increased. the importance of prediction of the amount of water to be expected has become more pronounced. If one knew in advance emctly what amount of water would be available during a certain period definite and exact plans could be made for use of the water. To assist in filling this need for predictions, the use of snow surveys has been deve10ped. Probably the most exten- sive use of snow surveys in this country is in the Sierra Nevada Mountains where the snow cover at high altitudes provides the major source of water for irrigation and other uses at lower eleva- tions. am measurements although they have probably always been used in a general way for forecasting spring run-off have only more recently been put upon a more definite basis by the develop- ment of new methods and equipment. This has promoted a more wide- spread use of snow surveys so that now they are quite generally used. in some form. throughout the entire snow belt. Although one may detemine by snow measurements the poten- tial supply of water in the snow. the amount which actually occurs as run-off is probably dependent upon many different factors. De:;pite the increasing use of snow-fall data in fore- casting, relatively little investigation has been made of the actual melting and the effect of the different factors upon which it is dependent. Some early work along this line was done by R. E. Horton:L and more recently by George D. Clydea. It is this scarcity of data on melting which has prompted the author to bring together the various data included within this paper and to attempt by correlating them to learn from actual field observations what effect precipitation, temperature. and the resulting melting of snow had upon the flow of the Sacandaga River near Hope. NJ. during the spring of 1936. It is felt that althougi the observations were made in one river basin and include but one melting season, some of the observed features may apply to snow melting in general. 1 The Melting of Snow, Monthly Weather Review, December. 1915 2 Change in Density of Snow Cover with Melting. Monthly leather Review, mgust. 1929 Effect of Rain on Snow Cover. Monthly Weather Review. Aug-lat: 1929 SNOV SURVEYS As the name indicates. a snow survey is an examination of the condition and amount of the snow covering the area included in the survey. flee general procedure is to determine the depth. water content, and from the se. the density of the snow cover at a number of representative point s. flue points at which the determinations are to be made must be carefully chosen in order that they will be free from drift- ing and from local variations. To minimize the effect of drift- ing. long courses with as many as fifty observations. fifty to one hundred feet apart, are established at each chosen location. {the measurements are averaged to give the mean at the point. A course sheltered by hardwood trees on reasonably level ground is usually very good. Evergreens will prevent the snow from reach- ing the ground, and. even though not covered with snow at the 1 Much material regarding apparatus and procedure used in snow surveys was obtained from the following publications: Church. LE. Principles of Snow Surveys as Applied to Forecasting Stream Flow. Journal of Agricultural Re- search, Vol. 51, No. 2 Proceedings of the Western Interstate Snow Survey Con- ference. Feb. 18. 1933; June 28. 1933 Cullings. E. S. The Adirondack Snow Survey. Transac- tions of the American Geophysical Union, Reports and Papers. Hydrology. 1936 time of the survey, may be the cause of spotty results owing to snow falling unevenly through them. The main pieces of equipment are a snow-sampling tube and a weighing scale. me tube is usually of duraluminmn or some other light-weight metal, about three inches in diameter. and of sufficient length to exceed the maxim depth of snow. The tube is equipped with a steel cutting edge of slightly smaller diameter than the tube. The cutter used by the Adirondack Slow May has a diameter of 2.655 inches so that ten inches of water will weigh two pounds. A romovable hardwood plug is fitted into the Upper and of the tube to give a surface to bear on when forcing the tube down through the snow. lhere long tubes are required a cutting edge resembling a milling cutter is used and the tube provided with an adjustable handle by which the tube and cutter may be ro- tated and forced down through the snow. The tube should be graduated in inches on the outside so that the depth may be read- ily observed when taking the snow sample. A spring scale with a revolving hand is used. A scale which shows one revolution for each two pounds is very convenient for use with a tube equipped with a 2.655 inch diameter cutting edge. By dividing the dial in- to one hundred parts. each division equals 0.1 inch of water, and the water (but cut may be read directly in inches and tenths with- out involving a conversion figure. In making a determination, the tube is first weighed (be- fore each trial) to allow for any ice or snow Which may have stuck in or to the tube. The tube is then forced down vertical- 1y through the snow. making sure that it goes clear to the ground surface. Iith the cutting edge on the ground surface the depth of snow is observed and entered in the notes. The tube is then withdrawn carefully bringing with it the sample. 'Usually a layer of grass. soil. or litter will be brought up al- so. This material must be removed. taking care that none of the snow sample is lost. The tube and.sample are then weighed and this value recorded. subtracting the initial weight of the tube from that of the tube and sample, of course, gives the weight of the snow.1 Using the tube and scale described above the re- sult is obtained.directly in inches of water. Dividing this by the depth of snow gives the density. In general there are two systems of using snow survey data in the prediction of runpoff. the percentage or normal system. and the system of areas. In the percentage system.the same courses must be used each year. .After observations have been made for a few years, a normal water content value is estab- lished for each course. It has been found that the run-off from an area. in.percent of normal, agrees very closely with the water content also in percent of normal of the snow on the area at the start of the melting season. Thus. by determining the mean percent of normal snow cover over the basin, the percent of normal run-off from the snow field is obtained. 'lhis method has been used with success in the western semi-arid areas where the streams are fed almost entirely by the snow melting at higher altitudes. Where the altitude of the basin varies widely, discrepancies in prediction are introduced by winter melting in the lower portions. For this reason, it is well to divide the basin into altitude zones. assigning representative courses to each zone. Usually. three zones are sufficient. the elevation of the gaging station or point on the stream where the water is to be used being the lower altitude limit and. of course. the summit of the watershed the upper. The area of each zone is then determined by planim- storing and a normal determined for each zone. The expected run- off from the whole basin is computed by combining the individual percentages of normal for each zone using their relative areas as a basis of weighting to procure a man for the entire basin. i he snow survey for the first year cannot be used for a predicticn of the run-off for that year as no normals are avail- able. For the next year. however. the results of the first year may be used as the basis of a provisional normal by making allow- ances for the general character of the first year. As more years of record are obtained the normals will become more definite. he accuracy of this system of prediction. from its very derivation. is dependent upon the normality of all conditions affecting melting mid run-off. 'llie absence of fall rains with the resulting dry ground and extremes. either high or low, in the rate of melting, have a minor effect. The most disturbing factor. however. is a lack of nomal precipitation during the melting period. Seasons of low precipitation show a marked shrinkage in the resulting run-off. In the Sierra region. the initial prediction of the run-off for the period April throng: July is made from the percentage of normal measured on April 1. As the season progresses. the prediction is revised or adjusted as conditions demand. By the middle of May the final estimate can usually be made. Over a period of nineteen years during which sixty-three forecasts were made for several Nevada basins about two-thirds were within ten percent of accuracy and all were within thirty-one percent. Nearly one-half were within five percent. In the method of areas. an attempt is made to compute the actual amount of water stored in the snow cover. The most accu- rate manner of using .the snow survey data is to plot the water content at each course on a map of the area mid draw in the isohyetals. the lines of equal water content. Die area of each division is obtained by planimetering. The areas are then com- bined with their respective depths and the total amount of water computed. Often this refinement is not applied. but the average of the individual observations is applied to the whole basin. This method predicts. after making allowances for losses. the minimum total spring run-off to be expected. The run-off from snow is. of course. supplemented in humid regions by rainfall in varying amounts, which. as yet cannot be definitely predicted. The value toward efficient Operation of storage reservoirs by having advance notice of the minimum amount of water that may be expected is large. SNOW SURVEY DATA The records of ten snow survey stations and three snow stakes have been used. These are well distributed over the drainage area and provide a good determination of the amount of water stored in the snow blanket over the basin. A survey was made between February 28 and March 2. 1936. at which time no melting had occurred. This survey furnishes a good starting point as following it there was little precipitation in the form of snow before melting started. In Figure l are shown the locations of the points and the method of computing the amount of water in the snow cover. Edie points were first plotted with the water content noted. Isohye- tals were then drawn in by interpolation between points guided somewhat by topographic considerations. The areas between isohyetals were then determined by planimetering. It has been assumed that the mean depth of water on each area was the direct 10. "C 7 ',r ' yo ong . Nanrcom , r‘ ‘ an «sums firefly/e sweetest ‘7’ ”i I ~ / / 1L 1 o‘er/Cher t B Carin I " . I, a||.Ch-i-;- :e '11 u m‘ ImonBr'idg 593a”; . ’ Port. ‘ 1 ' Core‘1 ‘ ’2 In”! ' { ll 1‘ .1' . r 1.1,? ‘ L ’ ' lv‘f'~""’"*-L}’ & 7‘ I "Kr" ’ Jo f’ \ s ‘) " ’ ‘ a’ O t ' are cm % t1“ - ""'i "" 153' “ .Jtmc \ . ._' - l I . I - ’ .' 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Tmm sees. seen 3 9m. 56 n.mm 3:: ensues: m 0mm. mam new 38.. sens sH mam. 2.4. «Am 833 Sn. we ode 38.. see some 3 mam. om.» TR 2333 83 m mama Se m. m 38.. ea mama 9e «rim awn ea a mount an onosH v hops: Am muons dogwood. . on Ho #08 Ho I08 season eeneeH Me semen senez sheets asses; me semen eeeeneo aeras S nose: a nose: .. mm refines mgamthozm ho mZOHHq>mammo EH4 whomaHafiE HEB loan .3 mega H .9! 594a .nean of the limiting depths. for example. area D between the 6' inch and 7 inch lines was presumed to have a mean depth of 6.5 inche 3. Determination of Water in Snow on March 2. 1936: No. Area in Mean Depth SQ. In. inInches A 0037 I 9.5 = 3. 515 3 1.61% x 8.5 = 13.9110 9 2.19 I 7.5 = 16.1t25 D 2.26 x 6.5 - 1h.690 E x 5.7 = s,u93 Total 7.95 57,063 Mean depth 3 7.3? 2 7.18 inches of water The mean of the depths of water at the ten survey courses gives 7.0“ inches. his clase agreement would indicate that with well distributed courses as is the case here, the isohyetal method of computation is an unnecessary refinement. PBEOIPI TATION The records of precipitation at four stations in or near the drainage basin of the Sacandaga River above Hepe. New York. were used. The records at Speculator and North Creek were fur- ll. nished by the New York Power and 1:1th Comoration; those at . Rape and 'Hoffmei star are regular Weather Bureau cOOperative stations and the records are published in Climatological Data. Each of the precipitation stations is equipped with a standard Weather Bureau non-recording gage Operated. supposedly. accord- ing to the standard Weather Bureau instructions.1 The gages are of the standard tme consisting of a round metal can over which is mounted a funnel shaped tap about eight inches in diameter with a sharp vertical edge. The rain falls on or into the funnel and runs into the can. The diameters of the can and funnel are such that one inch of rain will give a depth of ten indies in the can. The depth of water in the can is detemined with a measuring stick which indicates to the near- est one-hundredth of an inch the amount of rain. An outer can of about the same diameter as the funnel is provided as an over- flow tank and support for the funnel. he gage should be visited each day. the depth of rainfall measured. the can emptied, and the gage again placed in position. The gage is supposed to be visited late in the afternoon each day. he rainfallmeasured at this time is given as the precipitation for the day but actual- ly is the precipitation occurring in the past twenty-four hours. 1. Instructions for Cooperative Observers. U. S.Dept. of Agriculture. 1927 12. Gages of this type as generally Operated give no information on the intensity or duration of the storm. Frequently gages are read at some other time. especially in the morning. Often discrepancies in the time of occurrence of a rain at more than one station are due to this cause. It is evident from the com- pari son of precipitation and run-off that the four stations here used were visited in the morning. In Figure 3 where precipi- tation is plotted on the day on which it was recorded. the precipitation shown on March 28 must have occurred shortly after the gage was visitedpon March 27. he same is diown but less noticeably on March 12. 17. and 18. Hawever. this study is con- cerned mainly with the amount of precipitation rather than the time of occurrence. so no adjustment in time has been made. he four records were combined into a composite record of the average rainfall over the area. he four stat ions were lo- cated on a map (see Figure 2) and connected by straight lines. At the mid-points of each of these lines perpendiculars were erected to divide the basin into four portions. It is presumed that the precipitation recorded at a station prevailed over the area adjacent to the station. Each partial area was planin- etered to determine what portion of the total area it provided. he four records were listed for each day and each multiplied by its percentage of the total area. The four partials thus obtained were then added to give the composite record. 13. WM (ruck Pursues 2. M09 «slow/M6 Loan-nod at zest/PITA? T/on/ c1727 T/OA/J 44/0 WEN/co OF ”6761-! TIA/6 Pectin/Tarme/ 0474. TABLE NO. 2 comm PRECIPITATION 111 THE summon RIVER BASIN 11301711 HOPE. 1936 bps Hoffmei ter oculato North Cree Total Obs'd sci Obs'd 15% Obs'd 51% Obs'd 100% 1.06 .012 o o o o o .012 2.06 .012 o 0 o o o o .012 a .39 .078 .38 .057 .h3 .219 .15 021 .375 . 9 .098 .057 .219 021 .395 5 .098 .057 .219 021 .395 6 .098 .057 .219 021 .395 7 .098 .057 .219 .021 .395 8 .h9 .098 .057 .219 .021 .395 9 .83 .166 .68 .102 .219 .23 .032 .519 10 1.93 .386 .102 .219 .032 .739 11.386 .102 .219 .0 2 .739 12 3.06 .612 1.93 .211 1.66 .897 1.03 .1 1.817 1 3.26 .652 1.79 .268 .8u7 1. .33 .186 1.953 1 3.52 .70h 2.19 .328 1.98 1. 010 l. .200 2.2u2 15 3.57 .719 - .328 1.010 .200 2.252 16 .67 .73h 2.63 .399 2.20 1.122 1.55 .217 2.h67 17 .77 .85h 3.39 .508 g.h5 L 760 2.57 .360 .h82 18 5.79 1.158 'éfi .622 .75 2.122 .57 .500 .702 19 6.18 1.236 n .gg6 5.17 2.637 .13 .578 5.087 20 6.no 1.280 1.30 . 5 2.637 1.16 .62n 5.186 21 6.51 1.302 n. 61 .692 5.67 2. 892 1.51 .636 5.522 22 6.81 1.362 .692 2.892 1.99 .685 5.6 1 :3 1.362 n.68 .702 2.892 .685 5. 1 1. 2 .702 2.892 .685 5.6111 25 7.10 1. 20 11.93 .790 5.92 3.019 5.29 .7111 5. 920 1.920 .710 3.019 6.02 .8h3 6. 022 27 7.20 1.hho 5.70 .855 3.019 .8h3 6.157 28 8.nn 1.688 6.11 .916 6.77 3.953 .8u3 6.900 1.688 .916 3. h53 .8u3 6. 900 1.688 .916 3.h53 .8u3 6. 900 31 8.65 1 730 6.58 1.087 6.77 3 953 6. 22 .871 7.1h1 TABLE NO. 2 km ffme ter Mal Obs'd 20$ .06 2 .06 3:33 27 7.20 28 8.99 23 8.55 .012 .012 .078 .098 .098 .098 .098 .098 .166 o 382 .38 .612 .652 .7 .859 1.158 1.236 90 1.280 1. 302 1. 362 1.362 1. 2 1. 20 1.920 1.990 1.688 1.688 1.688 1.730 Obs'd 15 O O .33 .68 O 42-: U C 5343E6é5‘ {3:3 .58 e e \D 0‘ ox u 0:1 mm r : :rfrum mww 5'8 .057 .057 .057 .057 .057 .057 .102 .102 .102 .219 .268 .328 - .328 .399 .508 .622 .636 . 5 o 692 .692 .702 .702 .790 0 7% .855 .916 1.66 1.98 2.20 .95 .75 5.17 5.67 5092 3.953 6.22 North C eek Obs‘d l o o 0 o o o .219 .15 .021 .219 .021 0219 .021 .219 .021 .219 .021 .219 .021 .219 .23 .032 .219 .032 .219 .o 2 .897 1.03 .1 .897 1.33 .186 1.010 1. 3 .200 1.010 .200 1.122 1.55 .217 1.760 2.57 .360 2.222 .57 .500 2. 37 .13 .578 2.637 9.96 .629 2.892 9.59 .636 2.892 9.99 .685 2.892 .685 2.892 .685 3.019 5.29 .791 3.019 6.02 .893 3.019 .893 3.953 .893 3.953 .893 3.953 .893 CUMULATIVE PRECIPITATION IN THE SACANDAGA.RIVER.BASIN ABOVE HOPE. 1936 eth Obs'd 51% Total "SIRE! .012 .012 .375 .395 .395 .395 .395 .395 .519 .739 .739 1.817 1.953 2.292 2.252 2.967 .982 .702 5.087 5.186 5.222 5. 1 5.61%. 5. 691 5.920 6.022 6.157 6.900 6.900 6.900 7.191 1131: NO. 2 (Continued) CUMULATIVE PRECIPITATION IN 1111: SACANDAGA RIVER BASIN ABOVE HOPE. 1936 E92; Hoffmeister §peculator‘ North Cr 9]: Tot Obs'd. 53% Obs'd. 23% Obs'd. ‘ffi Apr. 1 0 0 0 0 Not used 0 0 7.191 .13 .069 .22 .051 .96 .110 7.371 .85 .950 .67 .159 .110 7.855 .950 . .170 .110 7.871 .950 .170 .110 7.871 2.63 1.399 2.57 .591 1.98 . 55 9.981 2.93 1.553 2.62 .603 1.73 . 15 9.712 3.36 1.781 3.05 .702 1.95 .968 10.092 1.781 .702 .968 10.092 3.95 1.828 3.19 .722 2.12 .509 10.200 3.60 1.908 3.39 .780 2.36 .566 10.395 3.79 2.009 3.57 .821 2.73 .655 10.626 3.86 2.096 .821 2.86 .686 10.699 2.096 .821 .686 10.699 9.0 2.136 3.73 .858 3.02 .725 10.860 1.33 2.300 .2 .975 3.38 .811 11.227 2.300 9. .998 .811 11.250 2.300 9. 7 1.028 .811 11.280 2.300 1.028 .811 11.280 2. 00 1.028 .811 11.280 9.53 2. 1 5.03 1.157 3.53 ..897 11.596 9.63 2.959 1.157 3.67 .881 11.633 2.959 1.157 .881 11.633 2.959 1.157 .881 11.633 2.959 1.157 .881 11.63 9.67 2.975 1.157 .881 11.653 2.975 1.157 .881 11.659 2.975 1.157 .881 11.659 2.975 5.15 1.189 g.71 .890 11.690 9.85 2.570 5.66 1.302 .01 .962 11.975 TABLE 190. 2 (Continued) CUMULATIVE PRECIPITATION IN THE SACANDAGA RIVER BASIN ABOVE HOPE, 1936 H0132 Hoffmeister eculator- North Creek Tot Obs'd 20$ Obs'd 15$ Obs'd 51% Obs'd 19% 100 May 1 0 0 o 0 0 0 0 11.975 2 .10 .020 .02 .003 .19 .097 .78 .109 12.209 3 .79 .158 1.81 .272 .91 .969 1.08 .151 13.020 .158 .272 .969 .151 13.020 5 .158 .272 .969 .151 13.020 6 .82 .169 . .272 .969 .151 13.026 7 1.01 .202 2.08 .312 .969 1.25 .175 13.128 8 .202 .312 , .969 .175 13.128 9 .202 .312 1.91 .719 .175 13.383 10 2.07 .919 2.18 .327 .719 , .175 13.610 11 .919 .327 , .719 1.85 .259 13.699 12 .919 .327 1.57 .801 2.25 .315 13.932 1 2.33 .966 2.90 . 60 2.57 1.311 2.91 .337 1 . 9 1 2..5 .990 3.30 . 95 1.311 2.72 .381 19.652 15 .9907 .995 1.311 .331 19.652 16 2.59 .518 3.50 .525 1.311 2.87 . 2 19.7 1 17 .518 .525 1.311 2.95 .913 19.7 2 18 .518 .525 1.311 3.01 .921 19.750 19 2.69 .538 9.23 .639 1.311 .921 19.879 20 2.99 .598 9.61 .692 3.30 1.683 3.91 .977 15.925 21 .598 .692 1.683 .977 15.925 22 .598 .692 1.68 .977 15.925 2 .598 .692 3.38 1.72 .977 15.966 2 .598 .692 1.729 .977 15.966 25 .598 9.69 .696 1.729 .977 15.970 26 .598 .696 1.729 .977 15.970 27 3.02 .609 9.79 .718 1.729 .977 15.998 28 3.17 .639 .718 3.60 1.836 3.77 .528 15.691 29 .6 9.82 .723 1.836 .528 15.696 30 3.21 . 2 9.87 .730 1.836 .528 15.711 31 .692 ' .730 1.836 .528 15.711 Elie record at Hoffmei star for April appears inconsistent with the other records. Evidently. the stations was not visited each day and the total rainfall for several days given when it was visited. The monthly total from comparison with others also seems too low. After some investigation, it was decided to disregard the Hoffmeister record entirely during April using only the Rape, Speculator. and North Creek records in the same manner as all four were used during March and May. Precipitation records are given in Table 2. WWW Few temperature stations are equipped with recording thermometer equipment. most being supplied with two thermom- eters, one which indicates the maximum and the other the mini- mum temperature which has occurred since the thermometers were set. They are commonly installed in the vicinity of a rain gage and are visited coincidently with it. At Conklingville. 17 miles west of the Hope gaging sta- tion. the Hudson River Regulating District maintains a record- ing thermometer or thermograph. This instmment has a drum which is rotated by a spring driven clock and to which a paper chart is attached. As the drum revolves a pen actuated by the thermometer unit traces a continuous record of the temperature. The thermograph is housed in a standard Cotton-region shelter. 19. The temperature at Conklingville is fairly representative of that prevailing over the basin above Hepe but may be a trifle warmer. Being the only recorder record near the area being studied it was used directly. No themometers are installed at the four precipitation stations. A continuous record or fre- quent readings are necessary to any study which required data on the duration of certain temperatures as an ordinary thermometer station gives only the extremes. From the thermograph charts the mean temperature for each two hour period was tabulated. For each day the total degree hours above 320 3'. (degrees above 320 1: duration in hours. for. example. a temperature of 35° over a period of 9 hours = (35-32) x 14 2 12 degree hours) were comted from the tabulation of temperature. Robert E. Horton has comput ed1 that to melt one inch of congealed water would require 19.9 inches of rain at 92° F. It has also been determined by Horton2 and George3 that one degree day 0 will melt 0.16 inches of ice or one degree day F will melt 0.09 inches of ice. Equating these values it is found that the l The Melting of aiow. Monthly Weather Raview, December. 1915 2 Transactions of the Awericsn Geophysical Union. Section of Hydrology. 1932. 3 Change in Density of Snow Cover with Melting, Monthly Weather Raview. 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V. . . . 7 . . \x e. ._I\ .I. 1 . _ - J 17- I ’ both that from the surface and that from ground water. During periods of no precipitation the flow from ground water will cause the run-off minus precipitation quantity to increase in the same fashion as will melting snow. The need for ground water data is again made evident. At the lower end of this graph the ground water level probably stayed nearly constant so that this portion of the graph is a good indication of the rate of melting. The plotting of April 1J4. 7-8. indicates that snow re- mained then and that the water table was not being lowered. . Using the slope of the curve March 18-22 a rate of 2.57 inches per 700 degree hours which is equal to 0.00367 inches per degree hour. or 0.089 inches per degree day. his compares favorably with the values of 0.090 and 0.089. respectively. determined by Horton1 and Clydea. The upper end of the graph is complicated by flow due to loweringof the water table so that it is impossibleto tell when the melting ceased. 0f murse. the difference between run-off and precipitation must have been supplied by melting mow but the time required for melting it is indefinite. Using April 15 l B..E.Horton. Proceeding of American GeOphysical Union. 1932 2 George D. Clyde. Change in Density of Snow Cover with Melting. Monthly Weather Review. August, 1929 23. as the date upon which the melting of the snow was completed would.mean that 7200 degree hours had.been required. No satis- factory explanation for the inconsistent plotting of the period April 5-10 has been derived. It appears fliat the high flow of’MarCh 18 was due almost entirely to rain. Evidently. active melting did not produce run-off until March 19. Had more warm weather preceded.the rains of‘MarCh 17 and 18. the flood flow would.undoubtedly have been mush greater. It is conceivable that under certain extreme conditions practically all of the snow could.be melted within a very few days. possibly accompanied by rain With.6$h treme flood conditions resulting. All of the graphs in which the precipitation data were used are step-like in shape and.not smooth. .As his runpoff from a certain rain does not occur simultaneously'with.the rain the run-off minus precipitation gueph shows some reverses. This lag in runpoff is somewhat compensated for by the nature of the records. the runpoff being computed on a.mid-night to midpnight basis while the precipita- tion was determined presumably on a late afternoon to late afterb noon basis. A.plotting of precipitation as ordinate against run-off as abscissa7(Figure 6) shows the runpoff and precipitation to be about equal until March 18. From there on to April 29 run- off exceeds precipitation but gradually approaches it. After 91/ 1 * - — - ‘— 1 1.. i . . F/éUEE Mo. 6. ~ ” ‘ ‘ 624.014 0F EMA/«OFF .oA/D PEEC/P/TflT/OAA _____ _ J, was mam/6 JA/o n/ 0A! rm: (7190 mm 47' 077727 0F 20.56/00. .5 j?‘ 7 7 . J PLoi'TED camauvxugnr ‘ ‘ w 33 'P l 7 ‘ ‘20 a: 6 l E ‘ ' ‘ ‘ ”~81qu V/ g f . . . ' 35 1 1 . 11 mi . ,p ‘ ' ' ’ ' ; .~ § lo . 3 = f 3 f - _ e3 2‘ ” “ ' “ 9 - 5 ~ - - - -— f 7:7. 5 - - - - a. / _ 1- h! flfltj. A ' 1 11 ’ :_ ’14 (E: /Q//o____o__ 3/ / ,3 ~ ~ _ _ ~ 4‘” ’ 7 / V‘ _ _ _ _ _ / 6” , _ __ 7“ " '9 + ' ’r 1 1 1 v? - - _ _- _ 10 - — 11 Iv \tl IS 0( fl 7 _ - 1 1 - 11 12 ")6 ”A ‘Vv — t - - 1 1 1- 1 1 11 1 I} /O .111.- _ _ _._ J __«__ ____ _g_ 5 1 _ 11 1 1.111 . . _ -11 ”4" -_ 1 _ _ j "i * __ : 5171:1171—11— ,Qz/M— OFF, /V #JCHES ____________ 11 11 1 11...- 1 _ 1T. 1 * 111111.:1:1~#111 ,0 A? 4’ a? /9 AZ A! /é “7 “* ' n “25‘ ” ‘ 22 a! - April 29, precipitation for tie most part exceeds the runpoff. This plotting is merely a different method of showing the same effects as are shown in Figure M. This study has dealt with temperature alone, except as corrected for the melting effect of’precipitation, as the melting agent with no attempt made to give consideration to direct insola- tion. or solar radiation. It has been the author's observation that in unwooded and exposed areas insolation is an important factor in melting. Frequently with the temperature as low as 25° melting has been noted there the sun's rays fall directly and nearly vertically on the snow surface. Such melting, however, produces little run-off as the released water will be again con- gealed if and when it reaches a shaded area. .As the melting rate is low'much of fine water will be held.in the snow by capil- lary action or enter fine ground by infiltration. Also melting of this type is of an intermittent nature occurring only near mid-day when the sun's rays strike the snow surface nearly vertically. The area herein studied is largely wooded.which fact would.minimize the effect of direct insolation except in so far as it affected.the temperature of the air and.to this extent was considered in the temperature records. 25. CONCLUSIONS This study has covered only a relatively small area during one melting season. Although the results definitely apply to the Sacandaga River Basin, the study is not considered sufficiently comprehensive to Justify the statanent of definite principles. which would be applicable generally in other localities. Some of the more evident, and probably general, tendencies are summarized as follows: 1. Little melting of snow occurs until the snow cover throughout its depth has reached a rather unstable condition through the absorption of heat such that the addition of a little more heat will cause much of the snow in its unstable condition to be converted into water. a. Rain falling on the snow cover appears very quickly as run-off if enougi warm weather, sufficient to warm the snow blanket so that the rain will not be congealed in the snow. has preceded the precipitation. 3. The amount of run-off exceeded the amount of water available as observed by the snow surveys and the precipitation records. This indicates that the records of rainfall, as collected in scattered gages of the type in general use, give results which are too low. The results of the snow survey are considered of higher accuracy than the rainfall records. 26. ’4. Records of the fluctuations of the ground-water table are necessary to any complete study of precipitation and run- off. 5. After melting of snow has started it proceeds at a rate of 0.09 inchee per degree day 1‘. above 32°. About 2000 degree hours or 83.} degree days were necessary to promote active melting. 6. Warm temperatures are much more potent than is rainfall as a melting agent. 27. mmgg The data for this paper were callected while the author was employed by the United States Geological Survey. Albany. New York,.Arthur W.lHarrington, District Engineer. whose coopera- tion is appreciated. Thanks are due E. B. Shape, Hydraulic Engineer. Hudson River Regulating District for use of snow sur- vey and temperature records, and to Seton.R. DrOppers. Hydraulic Engineer, New York Power and Light Co. for part of the precipita- tion records. The author is grateful to Wm. P. Cross, Assistant Engineer, U. 5. Geological Survey for suggestions and discussion. 1x001 USE ONLY, ‘ ~ _- 5 ~-. bio“! ‘ ”'TIIITIin‘n STATE UNIVERSITY LIBRARIES ||||||l| |||||||1 1293 03014 8497