CHAPTER IINTRODUCTION1.1 BackgroundIn
the management of water resources with water building design required
an information that shows the amount of water going into the building in
a unit of time known as the discharge of the magnitude aliran.Informasi
river flow help in designing buildings with regard to the discharge
peak (flood) necessary
for flood control and the design of the building is also seen from the
minimum required discharge data for water use, especially in the season
kemarau.Sehingga with the control of water flow data is either in a
state of excess or less had to be taken into account in an effort to
reduce the impact of flooding at the time of discharge maximum
and drought or water deficit during the dry season panjang.Oleh
Therefore, in this study lab streamflow measurements to obtain
information on the amount of water flowing in a river at a certain time.1.2 ObjectivesThe purpose of this lab is to measure the river flow in Cikuda with buoyancy and current meter method.
CHAPTER IILITERATURE REVIEW2.1 Debit FlowIs
the rate of flow of water (in the form of volume of water) that passes a
stream cross section per unit magnitude debti time.In the SI system is
measured in cubic meters per second (m3/sec). Whereas in technical
reports, usually indicated flow in
the form of a hydrograph aliran.Hidrograf aliranadalah discharge
behavior in response to changes that take place in the biophysical
characteristics of a watershed by the watershed management activities
and / or a change (seasonal or annual fluctuations) local climate.2.2 Measurement DebitDirect flow measurement techniques in the field can basically be done through four categories (Gordon et al., 1992):1. Measurement of the volume of river water2. Debiut measurement by measuring the flow rate and determine the cross-sectional area rivers.3. Discharge measurements by using chemicals (dyes) which flowed in streams (substance tracing method).4. Measurement of discharge by making buildings as weir flow measurement (slow flow) or flume (fast flow).In
the second category of discharge measurements, the discharge
measurements with the help of gauge or current meter discharge
measurements are often known as the approach velocity-area method most
widely used and applicable to most of the river flow. Current
meter is a tool associated with propeller-shaped box recorder (monitor
that will record the number of laps for the propeller in the water) and
then inserted into the stream to be measured velocity tail
alirannya.Bagian the tool shaped like a fin rotates due to the movement
of water lairan sunagi.Kecepatan
lairan water will be determined by the number of revolutions per second
is then calculated to be presented in the monitor average speed of
water flow during the time interval tetentu .. Measurements were made by
dividing the depth of the river into sections with leber
berbeda.Kecepatan surface flow in the river each section was measured according to the measurement kedalaman.Ketentuan presented in the following table.
Where d is the depth of the riverOnce the speed of the flow and the extent obtained, river flow can be calculated using the following equation.Q = A VWhere Q is discharge (m3/sec)V is the velocity (m / sec)A river is the area (m2)
In
measuring streamflow note numbers mean flow velocity, stream width,
depth, slope, and shear sungai.Geseran tepid and base edge and the
riverbed will reduce flow velocity at the center of the largest and the
smallest at the bottom sungai.Faktor important Other Noteworthy is the hydraulic radius r (hydraulic radius).R = A / Wpwhere: A cross-sectional area (m2)Wp = circumference basahan (wetted perimeter)
Way
other than by using a measurement tool Current meters, the river flow
velocity measurements can also be done using floating (floating method).
Trick with placing objects that can not be drowned in the river surface
to a certain distance and record the time required by the floating
object moving
from one observation point to another observation point that has been
floating ditentukan.Benda used in this measurement is basically any
object can sapanjang sungai.Pemilihan floating in a stream where
measurements should be on the river with not much current relatiflurus
not beraturan.Jarak between
the two observation points required is determined at least that gives
the travel time for 20 detik.Pengukuran do some Klai so as to obtain an
average speed of surface streams with the following equation.Vper = L / tWhere: L = the distance between the two points of observation (m)t = travel time floaters (seconds)
CHAPTER IIIMETHODOLOGY3.1 Equipment and MaterialsTools and materials used in this lab are as follows:1. Current meter2. Stopwatch3. Meter4. Rope5. Bamboo or cane scale6. Pencil7. Paper8. Objects that can float3.2 Proceduresa. Practical implementation of this procedure for the measurement kecevatan streams using current meter tool are as follows:1. measuring
dimensions of the river covering a wide river, and the width of the
river into segments depending on the state of the river.2. calculate the depth of a river with a stick-scale3. place the current meter gauge at certain depths corresponding water depth (see table 1)4. using a stopwatch, calculate the speed of the river through the numbers displayed in the monitor current meter. Long recording time is 1 minute.5. Repeat up to three times of measurement.6. Perform measurements on segments, ie segments 2 and 37. Calculate the speed of the average river flow at each measurement segment by summing the value of his observations.8. Calculate by multiplying streamflow sectional area of a river with an average flow speed of the river.b. River flow velocity measurement procedure with floating method (floating method) is as follows:1. Measure
the length of the river with a meter that will be used as the path
length of the river benda.Jarak or at least give the travel time for 20
seconds.2. Drop
objects can float at the observation point 1 and the start time
dihitung.Hentikan timekeeper when the object has reached a point of
observation 2.3. Record the time taken by the object.4. Observe the minimum number of times the experiment three times5. Calculate the average time it takes the object during trial.6. Calculate
the speed of the river flow by multiplying the distance between the
observation point with the average travel time rata.Kemudian multiply
the flow rate with a constant rate of 0.75 (rough river bed conditions).7. Calculated by multiplying the broad river discharge and river flow rates obtained from the calculation in step 6.
CHAPTER IVRESULTS AND DISCUSSION4.1 Resultsa. Calculation of cross-sectional area rivers
Extensive A1 = 0.5 (3 x 2.8) = 4.2 m2Broad AII = 3 x 2.8 = 8.4 m2Broad AIII = 0.5 (3 x 2.8) = 4.2 m2The total area of the river = 16.8 m2b. The experimental results with the method of floating methodNo.
Object
Time (second)
Length of river (m)
Speedm / s
1.27Calculation:Q = V x A = (0.75 x 1.27 m / s) x 16.8 m2Q = 16.002 m3 / sCalculation:Q = A x V = 16.8 m2 x 0.53 m / sQ = 8.90 m3 / s4.2 Discussion
Streamflow
measurements made at the lab using two methods, namely floating
(floating method) and use tools meter.Berdasarkan current data and the
calculation of the two methods produce different discharges that much
difference between the two reached 7,101 m3/s.Tentunya case The
second dikarena discharge measurements obtained from two berbeda.Dalam
means in practice many factors that lead to inaccuracies in the
calculation of river flow.
On
the methods of measuring floating, irregular stream characteristics,
both in terms of depth, flow velocity and heavy, making it difficult
medn practitioner in determining the exact location for pengukuran.Hasil
lab using the floating method is obtained relative velocity with a
constant difference, ie
1m / s but the last measurement changed significantly, the speed is
much slower than the previous perngukuran, ie the measurement of the
third object observations obtained two rivers flow velocity reaches 0.92
m / s which is much smaller in a row at 0.37 ;
0.55 from observations 2 and 1 with objects such sama.Hal aliaran due
to irregular water so the occasional object floating on the surface of
the flow of the river basin trapped by the currents that travel from the
observation of objects 1 and 2 is not smooth resulting latency is much of
observation as a tool lain.Penggunaan objects floating in the river
also needs diperhatikan.Hasil observations between objects 1 and 2,
which have different sizes lead to differences in flow velocity in the
observation dapatnya.Pada get 1 objects whose size is smaller than the
object 2 turned
out to have an average speed greater than 2 objects which are larger in
size, the average speed of object 1 reaches 1.32 m / s, while the pace
of objects mencapai1 2, 22 m / s, there is a difference that reaches 1, 1
m / s.Selain it also, at least according to the reference object
observation distance to reach the end point of observation takes 20
detik.Namun lab results there is only one observation that reach more
than 20 seconds remaining less than 20 seconds, it also objects reaches
more than 20 seconds due to trapped in the whirlpool so latency becomes
more lama.Dengan Thus, the observation distance was 22 m was still
lacking for some observations on the state of the river flow velocity of
the river flow, so that the data obtained were less accurate.
Unlike
his thing with the floating method, method of discharge measurement by
current meter of water is more difficult penggunaannya.Pengukuran water
flow rate is not as simple as floating method, in this method, the depth
of the river to be a determinant in the measurement, but it is also the
river should be divided into several parts to get average
speed of the flow of the river at the edge and tengah.Sehingga before
the observation needs to pay attention to several things, the main thing
is the depth of the river, but it also flows should not be obstructed
by an object or a rock is blocking because it would affect the outcome pengamatan.Hasil
observations indicate river flow velocity in the middle of a larger
segment of propagators on the left edge and kanan.Dari observations 1
through 3 in most of the middle segment, which ranged from 0.7 to 0.8,
while on the left and right river
flow reaches a maximum speed of 0.5 m / s.Hal is because at the center
of the relatively smooth surface of the water ssehingga essentially
unobstructed journey, it is different to the one on the edge of the lot
was blocked bebatuan.Faktor-factors that can reduce the accuracy of the
observed data is
the limited equipment available so that the determination of the point
of observation terhamabat by large currents, surface irregular riverbed
disabling carefully situations in depth calculation air.Namun Thus, when
compared with the results of observations with the floating method, the
method proved more accurate current meter with results observations
are far jebih tiny.Moreover also use the tool well enough to
mengghindari various errors in the measurement compared with the method
apung.Debit stream obtained from both observations based methods using
current meter floating and can be used as the information is very
important in the design waterworks.CHAPTER VCLOSING5.1 Conclusion
Based on observations in the River Cikuda Jatinagor can be summarized as follows:1. River flow by measuring the buoyancy method of 16.002 m3 / s.2. River flow is based on measurements using current meters at 8.90 m3 / s.3. River flow measurement using current meter is more accurate than the floating method.5.2 Suggestions
On
the measurement of river flow by buoyancy method should be assessed on
the effect of dimensional objects are used and should be tried before
the observations were made beforehand how objects travel time from a
certain distance to be able to determine the distance of qualified
observations, the travel time of at least 20 objects detik.Untuk measurements
with a current meter measurements place to note that current is not
blocked by stones or other objects so that the speed actually measured
the speed of the river flow.
