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• Publicado : 9 de noviembre de 2010

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2.1) Rain gauge X was out of operation for a month during which there was a storm. The rainfall amounts at three adjacent stations A, B and C were 4.2, 3.7, and 4.9 in; respectively. The averageannual precipitations amounts for the gauges are X=36.5, A=42.1, B=37.1, and C=39.8. the delta x and delta y values respectively for each station are X – 0, 0; A – 3, 7; B – 4, 6; and C -5, 9. Using aweighted average, estimate the amount of rainfall for gauge X
2.3) Compute the mean annual precipitation for the watershed in the following figure using the arithmetic mean, the thiessen polygonmethod, and isohyetal method. The gauge readings for gauges A-K are: 29.79, 34.97, 25.6, 24.27, 24.6, 42.61, 42.35, 15.51, 39.99, 43.04, and 28.41.
2.4) Compute the mean annual precipitation for thewatershed in the figure for the problem 2.3 using the arithmetic mean and the Thiessen polygon method. The gauge readings for a gauge A-K respectively are: 28.1, 33.7, 25.6, 23.9, 24.6, 40.7, 41.3, 37.2,38.7, 41.1, and 29.3.
Development exercise number 2.3
ARITHMETIC MEAN:
P=P1+P2+P3+…Pnn
P= 24.27+ 42.35+ 15.51+ 39.99+ 43.04+ 28.416
ℙ= 32.26 inch.
In this answer we can’t to use allprecipitations. Because this method doesn’t have present the station out-off the watershed.
For this reason we can to use only six precipitations.
THIESSEN POLYGON METHOD
GAUGE N° | AREA % Φ | PRECIP-IN β| Φ * β |
1 | 0.04 | 29.79 | 1.19 |
2 | 0.03 | 34.97 | 1.05 |
3 | 0.04 | 25.6 | 1.02 |
4 | 0.07 | 24.27 | 1.7 |
5 | 0.05 | 24.6 | 1.23 |
6 | 0.06 | 42.61 | 2.56 |
7 | 0.11 | 42.35 |4.66 |
8 | 0.05 | 15.51 | 0.78 |
9 | 0.21 | 39.99 | 8.4 |
10 | 0.19 | 43.04 | 8.18 |
11 | 0.15 | 28.41 | 4.2 |
TOTAL | 100% | | Σ= 34.97in |

ISOHYETAL METHOD.
ISOHIETAS | PRECIPITACIONMEDIA ENTRE ISOHIETA P | AREA ADIMENSIONAL ENTRE ISOHIETA £ | £ * P |
15.00 – 25.00 | 21.46 | 0.143 | 3.06 |
25.00 – 30.00 | 27.93 | 0.10 | 2.7 |
30.00 – 35.00 | 34.97 | 0.17 | 5.9 |
35.00 –...