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Slide 1

Start Precipitation as the Input

Slide 2

Some Huge Rainfalls

Slide 3

Precipitation As Input Precipitation is by and large "pre-handled" Uniform in space and time – never! Gages - Recording & non-recording Radar Satellite Derived QPF

Slide 4

The Basic Process… . Essential for a solitary bowl Focus on Precipitation Excess Precip. Display Excess Precip . Bowl "Steering" UHG Methods Runoff Hydrograph Excess Precip . Stream or potentially Reservoir "Steering" Downstream Hydrograph Runoff Hydrograph

Slide 5

From A Basin View Excess Precip. Abundance precip. is consistently dispersed! Abundance Precip. Demonstrate Basin "Steering" Unit Hydrograph Runoff Hydrograph Stream "Directing"

Slide 6

Precipitation ... essential "input" for the hydrologic cycle (or hydrologic spending plan). … The examples of the precipitation are influenced by expansive scale worldwide examples, mesoscale designs, "regional" designs, and smaller scale atmospheres. … notwithstanding the amount of precipitation, the spatial and transient circulations of the precipitation effectsly affect the hydrologic reaction.

Slide 7

Precipitation … In lumped models, the precipitation is contribution to the type of normal values over the bowl. These normal qualities are regularly alluded to as mean elevated precipitation (MAP) values. … MAP's are assessed either from 1) precipitation gage information or 2) NEXRAD precipitation fields (MAPX).

Slide 8

Precipitation (cont.) … If precipitation gage information is utilized, then the MAP's are generally computed by a weighting plan. … a gage (or set of gages) has impact over a range and the measure of rain having been recorded at a specific gage (or set of gages) is doled out to a region. … Thiessen, isohyetal, and the reverse separation squared are a portion of the more mainstream strategies.

Slide 9

Precipitation Issues for the Hydrologist Characteristics of precipitation in or on my basin(s)! Amount – How much would we say we are getting? Space – Where will it fall? Time – When will it fall (and where)? Respectability of the Data – Is this information substantial?

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Characteristics Convective, Frontal, Orographic, and so forth…

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Convectional Storms.... Rainstorms are the great case. Warm clammy air is quickly lifted - making it precarious. As the transports it cools and precipitation shapes. As the precipitation falls - it cools the air This is the reason you may feel extremely cool blasts of air amid those hot summer days when a rainstorm kicks up.

Slide 12

Urban Areas & Thunderstorms... It has been accounted for that urban ranges may add to the improvement of storms because of the nearness of a warmth source and the regularly darker zones.

Slide 13

Orographic Effects..... Territory can likewise bring about lifting - which is a noteworthy segment in the precipitation component. The mountains give a lifting instrument to the warm advecting sodden air.

Slide 14

Orographic impacts

Slide 15

Local Effects – e.g. the Great Lakes... Do lake impact occasions change the volume of Lake Superior?

Slide 16

Ice.... Hail, Rime, Sleet, and Graupel Very hard to quantify Antifreeze or warmed gages

Slide 17

Snow, A Few Brief Points ..... Snow or snowfall achieves the ground to frame the snowpack . Snowpack is by and large reported as snow profundity. We should likewise consider the snow water proportional or SWE - WHY? NOAA Photo Library

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SWE.... SWE is accounted for as a proportion - i.e. 10:1 Meaning 10 inches of snow equivalent 1 crawl of water - when liquefied. We additionally report this as thickness. 10:1 would be a thickness of 10% or 0.1. At the point when is the snowfall most thick and slightest thick. At the point when is the pack most or slightest thick? NOAA Photo Library

Slide 19

Measuring Snow and SWE... Snow gages Snow tubes Radar - VERY troublesome!! - WHY?????

Slide 20

Quantity Measuring the Precipitation

Slide 21

Rainfall..... Precipitation differs in both space and time This is alluded to as spatial and worldly fluctuation. Precipitation sums fluctuate significantly

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Measuring Precipitation.... For the most part utilize rain gages Measure profundity What are the issues with rain gages? Point scope... Obstruction - wind, trees, and so on... What number of others would you be able to name? Radar

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Standard Gage (non-recording)

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Fisher & Porter Tipping Bucket

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Slide 26

Precipitation Gage Networks An arrangement of gages Design Issues: thickness area quality (of information) gathering & transmission handling, documenting, overseeing

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Factors Affecting Density Purpose of Network – Desired Quality/Precision/Accuracy Finances – Installation and UPKEEP! Nature of Precipitation – rain, rain + snow, orographic, convective, and so forth.. Availability to name a few.....

Slide 28

Network Densities Many studies Brakensiek et al., 1979 – Brakensiek, D. L., H. B. Osborn, and W. J. Rawls, cooridnators. 1979. Field Manual for research in Agricultural Hydrology. USDA, Agricultural Handbook, 224, 550 pp, represented.

Slide 29

Spatial Characteristics Where will it fall and in what capacity will I utilize it?

Slide 30

Precipitation in Models … In lumped models, the precipitation is contribution to the type of normal values over the bowl. These normal qualities are frequently alluded to as mean flying precipitation (MAP) values. … MAP's are evaluated either from: 1) precipitation gage information or 2) NEXRAD precipitation fields (MAPX).

Slide 31

Precipitation (cont.) … The MAP's are typically ascertained by a weighting plan. … a gage (or set of gages) has impact over a zone and the measure of rain having been recorded at a specific gage (or set of gages) is appointed to a territory. … Thiessen, isohyetal, and the opposite separation squared are a portion of the more famous techniques.

Slide 32

Calculating Areal Averages.... Number juggling Isohyetal Theissen Inverse Distance

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Slide 34

Thiessen technique is a strategy for areally weighting precipitation through graphical means.

Slide 35

Isohyetal technique is a strategy for areally weighting precipitation utilizing forms of equivalent precipitation (isohyets).

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Inverse-Distance Squared Used to figure normal precipitation anytime in light of close-by gages. The heaviness of the adjacent gages is dependant on the separation from the indicate each of the close-by gages. Gage A Gage B d A d B d C Gage C

Slide 37

Radar Precip. as Input Radar gives a decent picture of where it is down-pouring - may show how to alter the Unit Hydrograph for moving and halfway region storms! May likewise give great gauge of the amount, BUT Will vary from gages in all out bowl normal. Verifiable records depend on gages! This makes alignment rather troublesome.

Slide 38

WSR-88D Weather Surveillance Radars - 1988 Doppler 1 st WSR-88D destinations introduced in 1991 right now, there are more than 160 radars set up. Ought to ideally give scope to an extensive rate of the United States. Ideally utilized in light of the fact that under numerous conditions, the helpful scope of the radars changes impressively.

Slide 39


Slide 40

Nexrad is a technique for areally weighting precipitation utilizing satellite imaging of the power of the rain amid a tempest.

Slide 41

Temporal When will fall and where?

Slide 42

Temporal Distributions Gages record information at interims - 10 min., 15 min., 60 minutes, 24 hour, etc.... Models utilize the information at 60 minutes, 6-hour, and so forth... Should either total or disaggregate precipitation amounts.... i.e. Join 1 hour values into a 6-hour esteem... Not an issue! On the other hand... Break a 24-hour esteem into 6 hour values... A great deal more troublesome!

Slide 43

Temporal Disaggregation 24-hour gage 3.6 inches add up to 1 hour gage with 2.2 aggregate inches and the accompanying circulation: Distribute the 3.6 inches utilizing the breakdown of the hourly gage

Slide 44

Intensity, Duration, & Frequency Intensity, span, & recurrence Duration - the timeframe over which the rain falls. Power - the rate at which the rain falls or the sum/span. Recurrence - the recurrence of event - i.e. How uncommon is this tempest? - We'll return to this..... General connections: the more noteworthy the length, the more prominent the sum the more prominent the span, the lower the power the more continuous the tempest, the shorter the term, and; the more regular the tempest, the less the force

Slide 45

Let's Look at an Example First… Let's figure the Rainfall/Runoff proportions for the Little J at Spruce Creek.

Slide 46

The Situation… .

Slide 47

1996 Totals

Slide 48

Some Issues How to handle the missing information Which bowl averaging system to utilize. Gage Average Thiessen Isohyetal Inverse Distance Weighting

Slide 49

Missing Data Filling in missing information is a noteworthy issue. For this situation, we are filling it in space – not time. There are numerous approaches to fill in this information: Averaging close-by stations Weighting (averaging is an uncommon case) Isohyetal

Slide 50

The Missing Data Averaging = 57.06 inches Weighting would rely on upon nearby learning and would require formation of verifiable connections between the greater part of the neighborhood gages. Isohyetal would suggest that the esteem is more like 62 to 63 inches – see next slide For this practice we will utilize 60 inches.

Slide 51


Slide 52

Now Lets' Find Basin Average Arithmetic Averaging Thiessen Isohyetal IDW

Slide 53

Gage Average I utilized Excel to normal the gages. The little worksheet is appeared at the privilege - >

Slide 54

Thiessen Polygons

Slide 55

Thiessen Wts. (%)

Slide 56

Combine % w/Totals Replace w/60.0

Slide 57

Thiessen - Final Computations

Slide 58

Isohyetal Approach

Slide 59

Isohyetal Areas

Slide 60

Combine % and Precip. Values

Slide 61

Inverse Distance Weighting Need directions of every gage Need directions of bowl centroid or purpose of intrigue