Laserfiche WebLink
<br /> <br />~ <br /> <br /> <br />All streams 1101'.' at dll!erenl rates and with dll/erenl volumes of water at various limes. <br />WhaT might 3ctounl for such changes? Rainfafl, temperature, se;non, <br />topography of the land, slope of the stream bed. <br /> <br />Take a fIeld trip loa stream. Select a stretch which is fairly Slrau'Jhl and even flowing <br />Mark 3 check points. one at either end and one exactly In the middle. Using a float <br />la 2" styrofoam batl works well). drop It in far enough abOve the fIrst check point <br />loallow II to reach full velocity. Time ils progress tram Point A 10 Band B 10 C, <br />Usmg an average between the two. calculale the velocity in feel I second. Next <br />measure Ih.. depth and width 0' the stream in several locations (.1, 112. etc) <br />and avera(,,'.: jhem to lind thearea Consullthe following table for the <br />velOCIty coelliclerll and complete the formula, <br /> <br />Averageslream <br />dep1h In teet <br />1 <br />2 <br />3 <br />4 <br />5 <br />6 <br /> <br />Veloclly <br />coefllClenl <br />66 <br />68 <br />.70 <br />72 <br />" <br />.76 <br /> <br />Veloclly{'1 /second) <br />X Coelflcient X <br />Arealdeplh X width) <br />::: Volume/second <br />tmeasured In cubIC 'eell <br />second)_ One cubIC 1001 <br />containS 7,48 gallons <br /> <br />Return a1 a later lIme and measure again Old the <br />Ilow Increase or decrease? <br /> <br />::::::- <br /> <br />____0---..:;:: <br /> <br />=c <br /> <br /> <br /> <br />o <br /> <br />Although the <br />tormula appears <br />complicated, It is <br />not 100 dllficult il each <br />step is taken in order and <br />carefully calculated. For <br />e_ample. the following <br />computations were used 10 <br />determine Ihe Slream llow <br />illustrated on this page, <br /> <br />VElOCITY <br />A - B = 25leel in 10 seconds <br />8 - C = 25leel in 14 seconds <br />50 24 =2.lfl/sec <br /> <br />AREA <br />_1 20" deep X 60" Wide <br />_2 27" X 63" <br />113 33'. X 69" <br />_4 24" X 56'. <br />1().4" =26" 248.'=62" <br />T ""4 <br />Area::: 26"X62" ::: 1612 square inChes <br />1612SQ in- 144sq in fSQ 11.= 11 ,2 square leet <br /> <br /> <br />*' <br />II" <br />2' It/see <br />VElOCITY <br /> <br />.68 1428 !t./second <br />X COEFFICfENT = ADJUSTED VELOCITY <br /> <br />1428 <br />ADJ VEL <br /> <br />x <br /> <br />11.2sq It <br />AREA <br /> <br />= <br /> <br />16cutHC feet/second <br />VOLUME/SECOND <br /> <br />What do you think accounted <br />lor the change? <br />The most probable cause of a change would be <br />the presence or absence of rainfall run.off. <br />Other factors mifllt include: irrigation or garden <br />run-off,or sporadic upstreilm Q ~ <br />discharges. <br />#-3 <br />;H- <br /> <br />1f)cu It /sec. <br />VOLUME <br /> <br />X 748gaIS,/CU,IL <br />CONVERSION CONSTANT <br /> <br />::: 120gallons/second <br />STREAM FLOW <br /> <br />FIRST STUDY <br />VElOCITY X COEFFICIENT = ADJUSTED VElOCITY X AREA = VOLUME/SEe <br /> X 748gats,/cu,tt <br />VOLUME CONVERSION CONSTANT = STREAM FLOW <br />SECOND STUDY <br />VELOCITY X COEFFICIENT = ADJUSTED VELOCITY X AREA = VOLUME/SEe <br /> X 748gaIS./cu,tt, = <br />VOLUME CONVERSION CONSTANT STREAM FLOW <br /> -19- ,5 <br />