CIVIL 5 SEMESTERHydrology &Water Resources Engineering

PANKAJ KUDECHA:- 130180106052PATEL MAULIK:- 120180106043CHAUDHRI DINESH:- 120180106083PATEL RAJ :-120180106095SHARMA HARSH :- 120180106095

GUIDED BY:PRO.P.M.BARIY

GOVERNMENT ENGINEERING COLLEGE , DAHOD

Non-Recording Gauges: Manually ObservedFor 24-hour collection, a standard rain gauge is typically used. This is a hollow metal tube with an open top that collects precipitation. The observer uses a ruler to measure the depth of the water in a small inner tube. In the winter, the small tube is taken out, and snow falls directly into the large tube. Then, snow is melted down and poured into the small tube to be measured.

It is a rain gage which does not provide the distribution of amount of precipitation in a day. It simply gives the amount of precipitation after 24 hours (daily precipitation

Recording Gauges:Tipping Bucket: Automatically tips when a certain amount of precipitation accumulates inside of it. Total precipitation is determined by the number of tips. Weighing Gauge: Tall and typically cone-shaped. It collects all types of precipitation continuously into a bucket. Its weight presses down on a scale, and every 15 minutes, a hole is punched in a ticker tape or a marking is made on paper by pen to record the bucket's weight. This is useful for hourly collections. Optical Gauge: Measures precipitation rate proportional to a disturbance to a beam between a light-emitting diode and a sensor.

~50 types of National Standard gauges (Sevruk et al., 1989)

Yugoslav StandardDannish StandardGerman UnshieldedNipher-ShieldedVarious Designs: German, Polish, Danish, HungarianStandard in 30 countries: used 30,000 locations world-wide

National Standard since 1870 (inception of NWS): the NWS 8 non-recording gauge~7,500 locations in US (~1,340 elsewhere)1940: Alter Shield Introduced currently about 200 shielded gauges (Western US)Unshielded gauge has large wind-induced undercatch

278 primary stations (1st order)Mainly at airportsStaffed on 24-hr basis by paid employeesHourly precipitation measured at 241 stations, the rest are daily8000 cooperative stationsStaffed mainly by volunteersHourly precipitation measured at ~2600 stations, the rest are daily

Gauge Type and Shielding Inhomogeneous in time and spaceTrend towards Recording Gauges Relocations frequently occur1st order stations located mainly at airportsInhomogeneous in gauge density: low gauge density in Western US and mountainous areas difficult to support higher resolution griddingThe unshielded 8 has large wind-induced undercatch, especially for solid precip

Sevruk, 1982

Wind-Induced Undercatch Snow: 10 to >50%Rain: 2 to 10%Wetting Losses2 to 10%Evaporation Losses0 to 4%Treatment of Trace Precipitation as ZeroSignificant in Cold Arid RegionsSplash-out and splash-in1 to 2%Blowing and Drifting Snow??

Consists of a receiverbucket supported by aspring or lever balance orany other weighingmechanism. The movement of bucketdue to its increasingweight is transmitted to apen which traces therecord on a clock drivenchart.

The rise of float with increasing catch of rainfall is recorded. Some gauges must be emptied manually while others are emptied automatically using self starting siphons. In most gauges oil or mercury is the float and is placed in the receiver, but in some cases the receiver rests on a bath of oil or mercury and the float measures the rise of oil or mercury displaced by the increasing weight of the receiver as the rainfall catch freezes. Float may get damaged by rainfall catch freezer

Obstruction (ideally in a clearing surrounded by trees)Occult Precipitation: fog drip and rimeObserver Errors: random, systematic, and grossErrors due to differences in observation time (ideally midnight)Instrument MalfunctionSpecific to Recording Gauges bad calibrationTampering / VandalismObservation Record Inhomogeneity changes in instrumentation, site, and local environment

Goals:To determine reduction coefficients relating the catch efficiency of different gauge typesReference Gauge: IPRGSnowdown Gauge with Alter ShieldResults: Inconclusive poor reference gauge

Goals:Evaluate wind corrections factors for rainfallCorrect systematic errors in different parts of the world60 gauge sites in 22 countriesReference Gauge: PitSnowdon Gauge Negligible wind lossesResults: Errors as a function of wind speed and precipitation intensity

Urban Horticulture Center Gauges: Steve BurgesTipping Bucket GaugeBelfort with Weighing MechanismNovalynx Collector

National Climatic Data Center (NCDC):15 minute, hourly, daily, monthly precipitation (also other surface observations)~6,000 precipitation stations with daily dataMainly US but some non-USNo gauge undercatch correctionsGridding of this data without prior corrections will cause time and space inhomogeneities

NCEP CPC Global Summary of Day (GSOD) data archive~15,000 stations worldwide with daily precipitation, wind speed, temperature, 1979 through 2001Archived at NCARExchanged on the Global Telecommunications System (GTS)Incomplete records, reporting errors, incorrect time interval reports, unrealistically large reportsInhomogeneous in time and space even within each countryInhomogeneous gauge densitySome Former USSR reports include corrections for wetting losses (although done incorrectly)

Global Historical Climatology Network (GHCN)~7,500 stations worldwide with monthly precipitation (also temperature data available)Through 1990Created from 15 data sourcesExtensive QA/QC and adjustments for station inhomogeneities based on metadata informationNo gauge undercatch corrections

Uniformity of Station DensityGlobal precipitation higher density in more developed countriesGauge Type UniformityIf not uniform, station data should be first be corrected for undercatch specific to each gauge typeStation Representation Do the stations used for gridding adequately represent the precipitation spatial patterns?US stations mainly at airportsStations located in valleys orographic effects

REFERENSE :Hydrology & Water resources Engineering Atul Prakshan

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