Water and Management Precipitation Input

Water and Management Precipitation Input crimpOne of the key issues in flood management is knowledge of the e genuinelywhere-confidence input into catchments for hydrologists knowledge of this serves to mitigate hazardous and environmental catastrophes, it is thus dogmatic to adequately determine hastiness input with appropriate and applicable statistical bastards. The objective of this study is to determine the actual downfall input and kick up the most appropriate method of determining hurry input for the good exemplar catchment provided.Standard and commonly used methods of obtaining the aral precipitation input over a catchment expanse from rainfallwater gauge measurements at the precipitation station be the Arithmetic pixilated, Thiessen Polygon, Isohyetal, and the Hypsometric methods. These methods serve as good approximations where the topography of a catchment is flat, if the gauges are uniformly distributed and the individual gauge catches do non differ ext ensively from the mean.Arithmetic meanThis is the simplest form of giving a value of the bonnie rainfall over a certain area, and works well downstairs the following conditionsWhen the catchment area is sampled by many uniformly spaced rain gaugesWhen the area has no marked diversity in topography (Davie, 2008)Applying this measurement tool to the arithmetic meanThere are 7 rain gauges with the mean value being 27.14The total catchment area is = 456km456 cardinal square meters,27mm = 0.027 metersSo 456,000,000 x 0.027m = 12,312,000 m3Thiessen PolygonsThe method was devised by an American engineer, the method provides for the non-uniform distribution of gauges by determining a weighting factor for each gauge. This factor is ground on the size of the area within the drainage basin that is nearest to a experiencen rain gauge. These areas are new(prenominal)wise known as irregular polygons.The method is straightforward and easy to useThe catchment is divided into polygons by line s that are equidistant mingled with pair of adjacent stationsThe lines/polygons are bisectedWorkout the area of each polygon by counting the squares within eachSums up the areasCompare to arithmetic method to confirm the twain are the kindredConvert the individual polygonal areas to million sq meters and compute by the converted precipitation rain gauges for simulationo 178,000,000 x0.055 =9,790,000 erst this is d mavin add them alto sether to go down the total volume of precipitation input within the catchment.Isohyetal methodThis considered nonpareil of the most accurate methods hitherto as one will often find the method is military issue to individual abilities and the knowledge of the general catchment. (Shaw, 1994)The method is more complicated than the commencement ceremony iiTo derive of an accurate estimation of the rainfall input one must first find the distance between dickens rain gauges in mm and eventually interpolate and extrapolate the line to give the adj acent rainfall levels, which can later be plotted vertebral column onto the catchment sheet.i.e. method of summation soak up the equidistant line between the dickens rain gaugestake for example the distance in mm between gauge A and B8.5cm-convert to mm- 85mmfind the going between the two rainfall gauges 55-30=25now to work out the a of 85, one would divide 85/100 and multiply this by 25 =21.25Which is after a of the equidistant line between the two rainfall gaugesThis invention can be used to derive the 2/4 apex, the point etc. By simply doubling the 21.25 figure you arrive at the 2/4 or 50% point and then to put down the 75% point adds 21.25 to the 50% point.One must now plump on the quartiles between the rainfall gaugesThis is done by using the difference (25) calculated earlier.Half of this gives 12.5 which when added to the first gauge, or gauge B (30mm) you work 42.5.Half of 12.5 gives 6.25, which when added to 30 gives 36.25, and so on until it matches against the adjacent measuring line.(* bring out supplementary sheets to see for techniques and further explanation)-once this is done plot the rainfall set using the adjacent measurements and join lines of equal rainfallThen establish to count the areas between the isohyets and find the average the two.Convert the individual areas to million sq meters and multiply by the converted average precipitation values for example31,000,000 x 0.059 = 1,829,000 cm3Do the same with all the values add them to get the total volume of precipitation input.Hypsometric MethodThe method uses catchment topography and the rainfall measurements to derive of a total weighted precipitation input. It fairly accurate all the same is in addition dependant on the abilities of an individual, whilst drawing the hypsometric curve. The hypsometric curve allows for adjacent precipitation values to read from the graph. The area underneath the curve of precipitation gives the area of an individual gauge, and can be calculat ed thereafter in the same system as the previous two methodsAnalysis/ConclusionIt is dupe from the results that the arithmetic mean is the likely to be less(prenominal) accurate than the other 3 methods, this is due to the catchment having qualities, such as topography and well distributed gauges which are characteristics that turf out desirable to the other tercet methods.I have averaged the precipitation inputs to get a more accurate figureAveraged 15,027,250 Total volume cm3It has been very difficult to observe a trend of between the methods, however three major patterns have been observed, the arithmetic mean varies much from the Thiessen weights and other two weights, showing that on one level the arithmetic mean is less accurate and takes the values into a much broader scale, whereas the other three methods are much more specific. The relation between the weights is very spread because the precipitation input is governed by various factors and complex activities, and each m ethod also demands certain qualities within a catchment for it to be applied appropriately, take for example the Isohyetal method which is subjective to individual abilities and knowledge of the catchment area, which in this case is not entirely possible, given the limited background information.ReferencesDavie, T., (2008) Fundamentals of Hydrology Volume 1 of Routledge fundamentals of physical geography series, 2, illustrated, Routledge, pp28-30Brooks, K. N., (2003) Hydrology and the management of watersheds, ed.3, illustrated, Wiley-Blackwell, pp30-34ASCE (1996) Hydrology handbook, Iss. 28 Vol. 28 of cartridge clip Life Complete Gardener, American Society of Civil Engineers Publications, pp 40-48Shaw, E.M., (1994) Hydrology in Practice, Taylor Francis, illustrated, tertiary ed., pp208-212