MEDIDAS ESPECÍFICAS PARA LA SEPARACIÓN DE LOS RESIDUOS EN OBRA

5. MEDIDAS PARA LA SEPARACIÓN DE LOS RESIDUOS EN OBRA

5.2. MEDIDAS ESPECÍFICAS PARA LA SEPARACIÓN DE LOS RESIDUOS EN OBRA

3. Determining effective rainfall from formulae

3.1 Renfro Equation 3.1 Renfro Equation

3.2 U.S. Bureau of Reclamation Method 3.2 U.S. Bureau of Reclamation Method

3.3 Potential Evapotranspiration/Precipitation Ratio Method (India) 3.3 Potential Evapotranspiration/Precipitation Ratio Method (India) 3.4 USDA, SCS Method

3.4 USDA, SCS Method 3.5 Empirical Relationships 3.5 Empirical Relationships

A number of empirically determined formulae can be used. They have been developed under a given A number of empirically determined formulae can be used. They have been developed under a given set of conditions which may be very different from those under which they are to be applied. Their set of conditions which may be very different from those under which they are to be applied. Their use elsewhere therefore remains doubtful.

use elsewhere therefore remains doubtful.

3.1 Renfro Equation 3.1 Renfro Equation

Renfro, as quoted by Chow (1964), suggested the following equation for estimating effective Renfro, as quoted by Chow (1964), suggested the following equation for estimating effective rainfall:

rainfall:

ER = E R ER = E Rgg+ A+ A

ER = effective rainfall ER = effective rainfall

Rg = growing season rainfall Rg = growing season rainfall A = average irrigation application A = average irrigation application

E = ratio of consumptive use of water (CU) to rainfall during the growing season (Table 4) E = ratio of consumptive use of water (CU) to rainfall during the growing season (Table 4)

The E value implies degree of rain likely to be utilized in meeting consumptive water needs. The The E value implies degree of rain likely to be utilized in meeting consumptive water needs. The greater the E value, the higher the value of

greater the E value, the higher the value of effective rainfall. For example, if effective rainfall. For example, if rainfall during the four rainfall during the four month growing season is 400 mm, consumptive use of water is 700 mm, and average irrigation

month growing season is 400 mm, consumptive use of water is 700 mm, and average irrigation application is 100 mm, then the effective rainfall i

application is 100 mm, then the effective rainfall is equal to 0.60 x 400 + 100 - 340 mm. The methods equal to 0.60 x 400 + 100 - 340 mm. The method is empirical and may not suit ma

is empirical and may not suit many situations.ny situations.

Table 4: RATIO E

Table 4: RATIO E FOR USE IN ESTIMATING EFFECTIVE RAINFALL IN RENFROFOR USE IN ESTIMATING EFFECTIVE RAINFALL IN RENFRO EQUATION (Chow, 1964)

EQUATION (Chow, 1964) CU/R

CU/R gg EE CU/R CU/R gg EE 0

0 0 0 2.4 2.4 0.720.72 0.2 0.10 2.6 0.75 0.2 0.10 2.6 0.75 0.4 0.19 2.8 0.77 0.4 0.19 2.8 0.77 0.6 0.27 3.0 0.80 0.6 0.27 3.0 0.80 0.8 0.35 3.5 0.84 0.8 0.35 3.5 0.84 1.0 0.41 4.0 0.88 1.0 0.41 4.0 0.88 1.2 0.47 4.5 0.91 1.2 0.47 4.5 0.91 1.4 0.52 5.0 0.93 1.4 0.52 5.0 0.93 1.6 0.57 6.0 0.96 1.6 0.57 6.0 0.96 1.8 0.61 7.0 0.98 1.8 0.61 7.0 0.98 2.0 0.65 9.0 0.99 2.0 0.65 9.0 0.99 2.2

2.2 0.69 0.69 // I I

3.2 U.S. Bureau of Reclamation Method 3.2 U.S. Bureau of Reclamation Method

A method described by Stamm (1967), is recommended for arid and semi-arid regions and uses mean A method described by Stamm (1967), is recommended for arid and semi-arid regions and uses mean seasonal precipitation of the five driest consecutive years. Percentage marks are given to increments seasonal precipitation of the five driest consecutive years. Percentage marks are given to increments

of monthly rainfall ranging from greater than 90 percent for the first 25 mm (1 in) or fraction thereof, of monthly rainfall ranging from greater than 90 percent for the first 25 mm (1 in) or fraction thereof, to 0 percent for precipitation increments above some 150 mm (6 in), as is shown in Table 5.

to 0 percent for precipitation increments above some 150 mm (6 in), as is shown in Table 5.

Table 5: EFFECTIVE PRECIPITATION BASED ON

Table 5: EFFECTIVE PRECIPITATION BASED ON INCREMENTS OF MONTHLYINCREMENTS OF MONTHLY RAINFALL (U.S. BUREAU OF

RAINFALL (U.S. BUREAU OF RECLAMATION METHOD)RECLAMATION METHOD) Precipitation increment range

Precipitation increment range PercentPercent Effective precipitatEffective precipitation accumulated - ion accumulated - rangerange mm For example, if monthly rainfall during the past five years in the

For example, if monthly rainfall during the past five years in the month of July is 100; 125; 250; 225month of July is 100; 125; 250; 225 and 175 cm, the mean is 175 cm. From the table, the effecti

and 175 cm, the mean is 175 cm. From the table, the effecti ve rainfall value for the month of Julyve rainfall value for the month of July will be 120.6 mm. The method does not take into account the type of soil, nature of the crop and will be 120.6 mm. The method does not take into account the type of soil, nature of the crop and frequency and distribution of rain. Nor does it consider degree of aridit

frequency and distribution of rain. Nor does it consider degree of aridit y. The method is noty. The method is not considered satisfactory.

considered satisfactory.

3.3 Potential Evapotranspiration/Precipitation Ratio Method (India) 3.3 Potential Evapotranspiration/Precipitation Ratio Method (India)

This simple semi-empirical method is used in some projects in India. A ratio of potential This simple semi-empirical method is used in some projects in India. A ratio of potential

evapotranspiration, taken as 0.8 of the U.S. Class A pan data, to the total rainfall for a certain group evapotranspiration, taken as 0.8 of the U.S. Class A pan data, to the total rainfall for a certain group of days during the growing season is computed. The number of days in a group is based broadly on a of days during the growing season is computed. The number of days in a group is based broadly on a soil type or soil moisture properties as wel

soil type or soil moisture properties as well as general weather conditions or evapotranspirationl as general weather conditions or evapotranspiration rates* The maximum number of days in a group is 15 during warm weather and 30 during cool rates* The maximum number of days in a group is 15 during warm weather and 30 during cool weather for crops other than rice. The lower the water holding capacity of the soil and/or the higher weather for crops other than rice. The lower the water holding capacity of the soil and/or the higher the evapotranspiration rate, the shorter the period in the group. This is shown in Table 6.

the evapotranspiration rate, the shorter the period in the group. This is shown in Table 6.

Table 6: NUMBER OF DAYS IN

Table 6: NUMBER OF DAYS IN A GROUP FOR DIFFERENT SOIL TYPES ANDA GROUP FOR DIFFERENT SOIL TYPES AND CLIMATIC CONDITIONS

CLIMATIC CONDITIONS Crop

Crop Mean monthly ETpMean monthly ETp (mm/day) (mm/day)

Soil texture and water storage capacity (mm/m).

Light (below

Rainless periods are deleted from the calculations. The ratios are expressed in a percentage for each Rainless periods are deleted from the calculations. The ratios are expressed in a percentage for each period. So the maximum value of

period. So the maximum value of the ratio cannot exceed 100. The monthly the ratio cannot exceed 100. The monthly means are thenmeans are then computed and from these the grand mean ratio is obtained for the

computed and from these the grand mean ratio is obtained for the entire growing season. Preciseentire growing season. Precise knowledge on soil properties or aridity is not essential. There can be some under or over estimation knowledge on soil properties or aridity is not essential. There can be some under or over estimation depending upon the distribution of rainfall, but the error is small. This method is good for broad depending upon the distribution of rainfall, but the error is small. This method is good for broad planning purposes. It is rapid and inexpensive.

planning purposes. It is rapid and inexpensive.

A sample calculation for the case of a heavy soil in a warm season is shown below. Of the total A sample calculation for the case of a heavy soil in a warm season is shown below. Of the total rainfall of 670 mm during the growing season, 80 percent is effective ac

rainfall of 670 mm during the growing season, 80 percent is effective ac cording to this method,cording to this method, Period

Period Potential Potential evapotransevapotranspirationpiration (mm)

In the case of rice, instead of the evapotranspiration value, total water loss, which is In the case of rice, instead of the evapotranspiration value, total water loss, which is evapotranspiration plus percolation losses, is used for computation.

evapotranspiration plus percolation losses, is used for computation.

Taking crop characteristics into account, necessa

Taking crop characteristics into account, necessary correction can be further applied for undesirablery correction can be further applied for undesirable or destructive kinds of rainfall such as

or destructive kinds of rainfall such as those causing lodging, or flower or fruit drop.those causing lodging, or flower or fruit drop.

3.4 USDA, SCS Method 3.4 USDA, SCS Method

The U.S. Department of Agriculture's Soil Conservation Service has developed a procedure for The U.S. Department of Agriculture's Soil Conservation Service has developed a procedure for estimating effective rainfall

estimating effective rainfall by processing long term climatic and soil moisture data. Aby processing long term climatic and soil moisture data. A comprehensive analysis was made by perusing 50 years of precipitation re

comprehensive analysis was made by perusing 50 years of precipitation re cords at 22 experimentalcords at 22 experimental stations representing different climatic and soil conditions. The soil moisture balance was worked out stations representing different climatic and soil conditions. The soil moisture balance was worked out for each day try adding effective rainfall

for each day try adding effective rainfall or irrigation to the previous day's balance and subtractior irrigation to the previous day's balance and subtracti ngng consumptive use. To avoid a high degree of complexity, neither the soil intake rate nor rainfall consumptive use. To avoid a high degree of complexity, neither the soil intake rate nor rainfall intensities are considered in this method.

intensities are considered in this method.

From total rainfall and monthly consumptive use, effective rainfall values

From total rainfall and monthly consumptive use, effective rainfall values were computed (Table 6).were computed (Table 6).

The values were based on a 3 in or 75 mm net irrigation application, which is equal to the available The values were based on a 3 in or 75 mm net irrigation application, which is equal to the available storage capacity in the root zone at the time of irrigation application. To convert this data to other net storage capacity in the root zone at the time of irrigation application. To convert this data to other net depths, factors were worked out which are shown in Table 7. For example, a crop of

depths, factors were worked out which are shown in Table 7. For example, a crop of wheat grown onwheat grown on sandy loam has a net depth of irrigation application of 50 ram. With a mean consumptive use for the sandy loam has a net depth of irrigation application of 50 ram. With a mean consumptive use for the month of December of 100 mm and a mean rainfall of 75 mm, the effective rainfall will be 52.7 x month of December of 100 mm and a mean rainfall of 75 mm, the effective rainfall will be 52.7 x 0.93 = 49 mm.

0.93 = 49 mm.

The monthly effective rainfall cannot exceed the r

The monthly effective rainfall cannot exceed the rate of consumptive use. If it date of consumptive use. If it does, the lower valueoes, the lower value of the two is taken.

of the two is taken.

Table 7: MULTIPLICATION FACTORS TO RELATE

Table 7: MULTIPLICATION FACTORS TO RELATE MONTHLY EFFECTIVEMONTHLY EFFECTIVE RAINFALL VALUE OBTAINED FROM TABLE 8 TO

RAINFALL VALUE OBTAINED FROM TABLE 8 TO NET DEPTH OF IRRIGATIONNET DEPTH OF IRRIGATION APPLICATION (d), IN mm

APPLICATION (d), IN mm d mm

d mm factorfactor d mmd mm factorfactor d mmd mm factorfactor 10.00 0.620 31.25 0.818 70.00 0.990

Table 8: AVERAGE MONTHLY EFFECTIVE RAINFALL AS RELATED TO MEAN Table 8: AVERAGE MONTHLY EFFECTIVE RAINFALL AS RELATED TO MEAN MONTHLY RAINFALL AND MEAN MONTHLY

MONTHLY RAINFALL AND MEAN MONTHLY CONSUMPTCONSUMPTIVE USE IVE USE (USDA, SCS)(USDA, SCS) Monthly mean

Monthly mean rainfall mm rainfall mm

Mean monthly consumptive use mm Mean monthly consumptive use mm 25

25 5050 7575 100100 125125 150150 175175 200200 225225 250250 275275 300300 325325 350350 Mean monthly effective rainfall mm

Mean monthly effective rainfall mm 12.5

240 240 300

300 175 175 190 190 203 203 215215

325 at

287 287

198 213 224 198 213 224 350

350 200 200 220 220 232232

375 at

331 331

225 240 225 240

400 at

372 372

247 247

425 250

at at 412 412 450

450 25 25 50 50 75 75 100 100 125 125 150 150 175 175 200 200 225 225 250250 3.5 Empirical Relationships

3.5 Empirical Relationships

3.5.1 Crops other than rice 3.5.1 Crops other than rice 3.5.2 Rice Measurement in rice 3.5.2 Rice Measurement in rice

Several methods of estimating effective rainf

Several methods of estimating effective rainfall for irrigation schedules are all for irrigation schedules are in vogue in differentin vogue in different countries. They are based on long experience and have been found to work quite satisfactorily in the countries. They are based on long experience and have been found to work quite satisfactorily in the specific conditions under which they were developed.

specific conditions under which they were developed.

3.5.1 Crops other than rice 3.5.1 Crops other than rice India

India

For a given area, effective rainfall is taken to be equal to 70 percent of the average seasonal rainfall.

In another method, effective rainfall is

In another method, effective rainfall is taken as the mean value of rain, with ttaken as the mean value of rain, with the excess ever 3 in. inhe excess ever 3 in. in one day and 5 in. in 10 days omitted.

one day and 5 in. in 10 days omitted.

Effective rainfall has als

Effective rainfall has also been taken to be equal to the lowest monsoon rainfall occurring in threeo been taken to be equal to the lowest monsoon rainfall occurring in three out of four years.

out of four years.

The Damodar Valley Corporation divided the 'Kharip season' (June to November) into ten-day The Damodar Valley Corporation divided the 'Kharip season' (June to November) into ten-day periods. During these periods, rainfall which exceeded the water needs of the predominan

periods. During these periods, rainfall which exceeded the water needs of the predominant crop wast crop was considered as ineffective and the rest as effective.

considered as ineffective and the rest as effective.

Khushlani (1956) suggested that rainfall during the life cycle of t

Khushlani (1956) suggested that rainfall during the life cycle of t he crop in a bad year (one with lowhe crop in a bad year (one with low rainfall) should be considered as the effective rainfall.

rainfall) should be considered as the effective rainfall.

In determining the water requirement of sugar cane

In determining the water requirement of sugar cane under Bombay Deccan conditions, Rege et alunder Bombay Deccan conditions, Rege et al (1943) considered that rainfall received only after

(1943) considered that rainfall received only after five days from the irrigation date was effive days from the irrigation date was effective.fective.

The rainfall received within five day after irrigation was treated as ineffective.

Sastry (1956) suggested the following equation for estimating rainfall usable by crops under Andhra Sastry (1956) suggested the following equation for estimating rainfall usable by crops under Andhra Pradesh (central part of South India) conditions,

Pradesh (central part of South India) conditions,

Y = usable rainfall, per days for a given period Y = usable rainfall, per days for a given period

= mean dally rainfall

= mean dally rainfall C = a co

C = a constant, which determines the confidence limit of the minimum statistical averagenstant, which determines the confidence limit of the minimum statistical average d = standard deviation of the dally rainfall

d = standard deviation of the dally rainfall

Estimates of usable rainfall in various periods of the monsoon season can be arrived at by selecting Estimates of usable rainfall in various periods of the monsoon season can be arrived at by selecting suitable confidence limits and statistical methods for calculating the standard deviation.

suitable confidence limits and statistical methods for calculating the standard deviation.

Burma Burma

During the wet season, rainfall of less than 0.5 in. is considered as ineffective. Above this figure, 63 During the wet season, rainfall of less than 0.5 in. is considered as ineffective. Above this figure, 63 percent of the amount greater than 0,5 in. is con

percent of the amount greater than 0,5 in. is considered affective rainfall. Baring the dry season,sidered affective rainfall. Baring the dry season, rainfall of less than 1 in.

rainfall of less than 1 in. is considered as ineffective. Above this figure, 65 percent of is considered as ineffective. Above this figure, 65 percent of the amountthe amount greater than 1 in. is considered as. usable by the crop (Kung, 1971). This approach would appear to greater than 1 in. is considered as. usable by the crop (Kung, 1971). This approach would appear to be rather arbitrary.

be rather arbitrary.

Thailand Thailand

Of the November rainfall 80 percent and of the December to March rainfall 90 percent is considered Of the November rainfall 80 percent and of the December to March rainfall 90 percent is considered an effective (Kung, 1971)

an effective (Kung, 1971) 3.5.2 Rice Measurement in rice 3.5.2 Rice Measurement in rice

Rice thrives under conditions of abundant water supply, hence the practice

Rice thrives under conditions of abundant water supply, hence the practice of land submergence.of land submergence.

Depth of flooding is governed by the variety grown and its height, the height of field bunds and Depth of flooding is governed by the variety grown and its height, the height of field bunds and availability of water. The water requirements of

availability of water. The water requirements of rice include evapotranspiration and percolation.rice include evapotranspiration and percolation.

Measuring effective rainfall is thus more complicated. Different empirical methods used in different Measuring effective rainfall is thus more complicated. Different empirical methods used in different countries are outlined bel

countries are outlined below (Kung, 1971).ow (Kung, 1971).

India India

In one method, a percentage of total rainfall varying from 50 to 80 percent is assumed effective.

In a second method, rainfall less than 0.25 in (6.25 mm) on any day is considered as in

In a second method, rainfall less than 0.25 in (6.25 mm) on any day is considered as in effective*effective*

Similarly any amount over 3 in (75 mm) per day, and rainfall in excess

Similarly any amount over 3 in (75 mm) per day, and rainfall in excess of 5 in (125 mm) in 10 daysof 5 in (125 mm) in 10 days is treated as ineffective.

is treated as ineffective.

Japan Japan

For submerged rice the year having the lowest rai

For submerged rice the year having the lowest rainfall over the past 10 to 15 years is senfall over the past 10 to 15 years is selected.lected.

Depending upon local conditions, an amount of 50 to 80 mm is considered as ineffective. The rest i Depending upon local conditions, an amount of 50 to 80 mm is considered as ineffective. The rest i ss all effective. A daily record is kept of soil water in the field.

all effective. A daily record is kept of soil water in the field.

For non-submerged rice a method using daily readings is also used. The daily rainfall

For non-submerged rice a method using daily readings is also used. The daily rainfall efficiency isefficiency is assumed to be 80 percent. Daily rainfall of less than 0.5 x ET is not effective. Also, if the sum of assumed to be 80 percent. Daily rainfall of less than 0.5 x ET is not effective. Also, if the sum of effective rainfall and the

effective rainfall and the residual moisture from the previous day exceeds a residual moisture from the previous day exceeds a predetermined value, thepredetermined value, the surplus is disregarded. A sample calculation of computation for a 12 day period is shown below for surplus is disregarded. A sample calculation of computation for a 12 day period is shown below for non-submerged rice. In this example ET = 3.7 mm/day, available soil Water = 30 mm.

non-submerged rice. In this example ET = 3.7 mm/day, available soil Water = 30 mm.

In document ANEXO 7. GESTIÓN DE RESIDUOS (anejo nº11 del proyecto). (página 21-32)