msu-ceco/aec_v1 · Datasets at Hugging Face

text stringlengths 0 1.09k
0.25 0.6 4.6 9
0.125 0.3 11.5 7
TABLE 2.
Performance characteristics, site ST
Inflow Run Application Distribution
rate length efficiency* uniformity
gpm mile % %
37 0.5 76 78
43 0.5 83 82
56 0.5 86 84
Assumes recirculation of surface runoff.
Does not account for soil variability.
TABLE 3.
Subsurface drainage, surface runoff, and set times for site BU
Flow Run Subsurface Surface Set
rate length drainage runoff time
gpm feet inches inches hours
18 1,440 3.3 0.2 17
720 0.8 2.1 8
480 0.4 4.3 6
25 1,440 4.5 0 14
720 0.9 1.9 6
480 0.5 4.1 4
34 1,440 4.3 0.1 10
720 1.1 1.7 4
480 0.6 3.5 3
TABLE 4.
Performance characteristics, site BU
Inflow Run Application Distribution
rate length efficiency' uniformity
gpm feet % %
18 1,440 58 69
25 1.440 51 66
34 1,440 54 67
.
Assumes recirculation of surface runoff.
Does not account for soil variability.
Their effects on uniformity due to soil variability are unknown.
However, shorter run lengths may improve this uniformity if there are substantial differences in soil texture.
One UC study found that compaction of nonwheel furrows may reduce differences between wheel and nonwheel furrows.
The two-year study reported here entailed gathering irrigation data to field-verify computer models of the performance of a furrow irrigation system.
Information was collected for three furrow inflow ratesinflow and outflow, advance times, depth of flow and furrow cross-sectional shapes-and field length and slope.
This information, coupled with the computer model, was used to assess the potential of upgrading measures to reduce drainage.
This field, clay loam with a saline high water table, consisted of a half-mile run length with a 0.16% slope.
Furrow inflow rates used for the evaluation were 37 gpm , 43 gpm, and 56 gpm.
Data were collected for the preirrigation, first seasonal irrigation in June, and the last irrigation in August.
Smaller furrow inflow rates were used for the last irrigation.
Soil moisture depletion was about 6 inches, and there was about 2.5 inches of drainage at the normal inflow rate for the half-mile run.
Reducing the run to 1/4 mile lowered the drainage volume by 60% to about an inch.
A further reduction to 1/8 mile reduced drainage to about 0.4 inch, or 16% of normal.
Increasing the furrow inflow rate also reduced subsurface drainage.
For the halfmile run, the drainage volume for 43 gpm was about 64% of the normal, while that of 56 gpm was about 56%.
A key to drainage reduction when changing run lengths or furrow inflow rates is to reduce the set time, or overirrigation will occur.
Normally, it takes about 22 hours for water to infiltrate 6 inches in the lower end of the field.
About 12 hours are needed with a 1/4-mile run.
Set times have to be adjusted for increased furrow inflow rates or there will be more subsurface drainage and surface runoff.
A major problem with furrow irrigation is that losses as subsurface drainage and surface runoff are competitive: Reducing one increases the other.
Shortening the run increases the surface runoff, particularly for runs of less than 1/4 mile.
Surface runoff can be returned to the distribution system, recirculated on the field being irrigated, or used on downslope fields.
If the runoff is recirculated, it has to be used to irrigate for a set independent of the district supply, or the surface runoff will become subsurface drainage.
Cutback irrigation, in which the inflow rate is reduced after advance to the end of the field, can reduce surface runoff.
It can present problems in dealing with surplus water, however, unless the district flow rate into the field can also be reduced.
The effect of these drainage reduction measures on performance characteristics is shown in table 2.
Uniformity due to intake time differences and application efficiency increased considerably when the run length was decreased to 1/4 mile.
Further decreases improved performance only slightly.
Analysis of the other irrigations showed that most of the subsurface drainage came from preirrigation.
Little drainage occurs after preirrigation because of the seasonal decrease in the soil infiltration rate.
The basic infiltration rate of the preirrigation was about 0.15 inch per hour, compared to 0.07 and 0.02 inch per hour for the June and August irrigations.
Run length at the BU site, a sandy loam soil with a high water table, was 1,440 feet with a 0.11% slope.
Furrow inflow rates of 18 gpm , 25 gpm, and 34 gpm were used during the evaluation.
Only the first seasonal irrigation was evaluated.
Soil moisture depletion was assumed to be 4 inches for this analysis.
Under normal conditions, subsurface drainage was about 3.3 inches.
Reducing the run length by half reduced subsurface drainage by 76% to about 0.8 inch.
Run lengths a third of the original run reduced drainage by 88%.
As with site ST, surface runoff increased at an increasing rate as the run length decreased.
This site, however, required much shorter run lengths to substantially reduce drainage than site ST did, mainly because of its higher intake rate.
At 18 gpm, the set time must be reduced to about 8 hours when reducing the run by half.
Furrow inflow rates had little effect on subsurface drainage and surface runoff.
As the inflow rate rose, the intake rate became higher due to an increased wetted area of the furrow.
This behavior offset any drainage reduction benefits of a higher uniformity of intake times along the furrow.
Reducing run lengths increased the uniformity of the intake times from 69% to 86%, and the application efficiency from 58% to 89%.
The effect of the furrow inflow rate on the intake rate at site BU was not found at site ST.
There, the same intake relationship
with time was found for all inflow rates, because most infiltration apparently OCcurred through cracks in the soil.
Thus, the intake rate appeared to be independent of wetted area.
Once the cracks sealed, there was little additional infiltration and any effect of different wetted areas on the intake rate could not be detected.
Surge irrigation is another way to reduce drainage in furrow irrigation systems.
This method, reported in the September-October 1987 issue of California Agriculture, requires about one-third less water for advance across the field than does continuous-flow furrow irrigation.
UC studies in the San Joaquin Valley revealed a potential reduction of 30% to 40% of current drainage volumes where the infiltration rates were relatively high.
Level basin irrigation has been successfully used to reduce drainage in Arizona's Wellton-Mohawk Valley.
A UC demonstration showed the method to have potential for substantial drainage reduction in areas where large district flow rates are available and land leveling is economically feasible.
Basin lengths should not exceed 1/8 mile.
These results show a good potential for subsurface drainage reduction in furrow irrigation systems.
The most effective measure is to reduce run lengths.
Reductions of 60% to nearly 80% appear possible by cutting the run length in half.
The effect of increasing the furrow inflow rate depended on the soil type.
Reductions of 30% to 40% appear possible with surge irrigation.
At site ST, preirrigation was the major source of subsurface drainage, and reduction measures only needed to be carried out during that irrigation.
At site BU, however, the large amount of subsurface drainage during the first seasonal irrigation suggests that drainage may be generated throughout the irrigation season, requiring seasonal implementation of these measures.

0.25 0.6 4.6 9

0.125 0.3 11.5 7

TABLE 2.

Performance characteristics, site ST

Inflow Run Application Distribution

rate length efficiency* uniformity

gpm mile % %

37 0.5 76 78

43 0.5 83 82

56 0.5 86 84

Assumes recirculation of surface runoff.

Does not account for soil variability.

TABLE 3.

Subsurface drainage, surface runoff, and set times for site BU

Flow Run Subsurface Surface Set

rate length drainage runoff time

gpm feet inches inches hours

18 1,440 3.3 0.2 17

720 0.8 2.1 8

480 0.4 4.3 6

25 1,440 4.5 0 14

720 0.9 1.9 6

480 0.5 4.1 4

34 1,440 4.3 0.1 10

720 1.1 1.7 4

480 0.6 3.5 3

TABLE 4.

Performance characteristics, site BU

Inflow Run Application Distribution

rate length efficiency' uniformity

gpm feet % %

18 1,440 58 69

25 1.440 51 66

34 1,440 54 67

.

Assumes recirculation of surface runoff.

Does not account for soil variability.

Their effects on uniformity due to soil variability are unknown.

However, shorter run lengths may improve this uniformity if there are substantial differences in soil texture.

One UC study found that compaction of nonwheel furrows may reduce differences between wheel and nonwheel furrows.

The two-year study reported here entailed gathering irrigation data to field-verify computer models of the performance of a furrow irrigation system.

Information was collected for three furrow inflow ratesinflow and outflow, advance times, depth of flow and furrow cross-sectional shapes-and field length and slope.

This information, coupled with the computer model, was used to assess the potential of upgrading measures to reduce drainage.

This field, clay loam with a saline high water table, consisted of a half-mile run length with a 0.16% slope.

Furrow inflow rates used for the evaluation were 37 gpm , 43 gpm, and 56 gpm.

Data were collected for the preirrigation, first seasonal irrigation in June, and the last irrigation in August.

Smaller furrow inflow rates were used for the last irrigation.

Soil moisture depletion was about 6 inches, and there was about 2.5 inches of drainage at the normal inflow rate for the half-mile run.

Reducing the run to 1/4 mile lowered the drainage volume by 60% to about an inch.

A further reduction to 1/8 mile reduced drainage to about 0.4 inch, or 16% of normal.

Increasing the furrow inflow rate also reduced subsurface drainage.

For the halfmile run, the drainage volume for 43 gpm was about 64% of the normal, while that of 56 gpm was about 56%.

A key to drainage reduction when changing run lengths or furrow inflow rates is to reduce the set time, or overirrigation will occur.

Normally, it takes about 22 hours for water to infiltrate 6 inches in the lower end of the field.

About 12 hours are needed with a 1/4-mile run.

Set times have to be adjusted for increased furrow inflow rates or there will be more subsurface drainage and surface runoff.

A major problem with furrow irrigation is that losses as subsurface drainage and surface runoff are competitive: Reducing one increases the other.

Shortening the run increases the surface runoff, particularly for runs of less than 1/4 mile.

Surface runoff can be returned to the distribution system, recirculated on the field being irrigated, or used on downslope fields.

If the runoff is recirculated, it has to be used to irrigate for a set independent of the district supply, or the surface runoff will become subsurface drainage.

Cutback irrigation, in which the inflow rate is reduced after advance to the end of the field, can reduce surface runoff.

It can present problems in dealing with surplus water, however, unless the district flow rate into the field can also be reduced.

The effect of these drainage reduction measures on performance characteristics is shown in table 2.

Uniformity due to intake time differences and application efficiency increased considerably when the run length was decreased to 1/4 mile.

Further decreases improved performance only slightly.

Analysis of the other irrigations showed that most of the subsurface drainage came from preirrigation.

Little drainage occurs after preirrigation because of the seasonal decrease in the soil infiltration rate.

The basic infiltration rate of the preirrigation was about 0.15 inch per hour, compared to 0.07 and 0.02 inch per hour for the June and August irrigations.

Run length at the BU site, a sandy loam soil with a high water table, was 1,440 feet with a 0.11% slope.

Furrow inflow rates of 18 gpm , 25 gpm, and 34 gpm were used during the evaluation.

Only the first seasonal irrigation was evaluated.

Soil moisture depletion was assumed to be 4 inches for this analysis.

Under normal conditions, subsurface drainage was about 3.3 inches.

Reducing the run length by half reduced subsurface drainage by 76% to about 0.8 inch.

Run lengths a third of the original run reduced drainage by 88%.

As with site ST, surface runoff increased at an increasing rate as the run length decreased.

This site, however, required much shorter run lengths to substantially reduce drainage than site ST did, mainly because of its higher intake rate.

At 18 gpm, the set time must be reduced to about 8 hours when reducing the run by half.

Furrow inflow rates had little effect on subsurface drainage and surface runoff.

As the inflow rate rose, the intake rate became higher due to an increased wetted area of the furrow.

This behavior offset any drainage reduction benefits of a higher uniformity of intake times along the furrow.

Reducing run lengths increased the uniformity of the intake times from 69% to 86%, and the application efficiency from 58% to 89%.

The effect of the furrow inflow rate on the intake rate at site BU was not found at site ST.

There, the same intake relationship

with time was found for all inflow rates, because most infiltration apparently OCcurred through cracks in the soil.

Thus, the intake rate appeared to be independent of wetted area.

Once the cracks sealed, there was little additional infiltration and any effect of different wetted areas on the intake rate could not be detected.

Surge irrigation is another way to reduce drainage in furrow irrigation systems.

This method, reported in the September-October 1987 issue of California Agriculture, requires about one-third less water for advance across the field than does continuous-flow furrow irrigation.

UC studies in the San Joaquin Valley revealed a potential reduction of 30% to 40% of current drainage volumes where the infiltration rates were relatively high.

Level basin irrigation has been successfully used to reduce drainage in Arizona's Wellton-Mohawk Valley.

A UC demonstration showed the method to have potential for substantial drainage reduction in areas where large district flow rates are available and land leveling is economically feasible.

Basin lengths should not exceed 1/8 mile.

These results show a good potential for subsurface drainage reduction in furrow irrigation systems.

The most effective measure is to reduce run lengths.

Reductions of 60% to nearly 80% appear possible by cutting the run length in half.

The effect of increasing the furrow inflow rate depended on the soil type.

Reductions of 30% to 40% appear possible with surge irrigation.

At site ST, preirrigation was the major source of subsurface drainage, and reduction measures only needed to be carried out during that irrigation.

At site BU, however, the large amount of subsurface drainage during the first seasonal irrigation suggests that drainage may be generated throughout the irrigation season, requiring seasonal implementation of these measures.