Introduction
1. URGENCY OF THEMES
Water is reducing on the volume as well as the quality in most area
in the world. For agricultural water, the volume of water is reduced due
to critical competition of the other economic which using water.
Irrigational water-saving to raise the index of agricultural products
per unit of irrigational water which became extremely important.
Therefore, “research reveal the influence of irrigated-agriculture to
reduce volume of water, reduce consumption volume of water for rice
in Ha Nam area” is very urgent now.
2. OBJECTIVES OF THEMES
- Research on impact of irrigated agriculture to Shallow –open-
dried irrigation to reduce consumption water in order to establish the
scientific basis and practic to establish irrigational procedure .
3. RESEARCH METHOD
- Inheritance: based on some research results, appling to achieve
objective of the project.
- Primary analysis: deperiodining the impact of Shallow –open-
dried irrigation to rainfall as scientific basis for formulating the process
of water-saving.
- Field experimenl: to test theoretical research results.
- Statistical analysis: to handle the experimental results
4. SCOPE OF RESEARCH
The research was conducted within the general theory about the
impact of Shallow–open-dried irrigation, the level of reserves and
irrigation, the volume of irrigation for the region of Ha Nam Province.
Theoretical research is conducted on a database of 24 years (1985-
2008), experimental research was conducted in 4 harvest season (2
1
winter season and 2 summer season) to demonstrate for results of
theoretical research.

processes in rice-soil
Under the influence of water regime on the surface of field,
occured process in rice-soil very diverse. Those processs includes:
changes of dynamics of reduction-oxidation reaction (Eh) changes of
acid of soil (pH) change of mechanical properties, status of exist of
nutrition in the soil and the relationship between reducing output and
irrigation regime.
In the soil, reducing reduction-oxidation reaction (Eh) depends
on the time and nature of submerged land and fertilizer regime. Besides
the dependence on these factors, Eh also depends on rice.
In the soil For pH, when the soil with value of pH > 7, the
process of full water, pH is decreased gradually and approach to value =
7. When the soil with value pH <7, due to the weak phase so pH
increases and gradually and approach to value = 7. time of Flood is long
so, pH is increasing on the value.
The metabolism of nutrients in the soil plays a very important
for the tree. When soil change the phase from anaerobic (flooded) to
Aerobic (dried), Chemical reactions in soil occured according to
direction of oxidation. The nutrients in soluble regime, good for rice
develops.
1.2 Overview of relationship between the lack of water to rice’s output
Theoretical and experimental researchs, practical of agricultural
production shown, the regime of surface water directly affects to the
3
productivity of rice. In general, when dehydrated, evaporation of
reduction affects to rice’s output.
1.3 Overview of effective rainfall in the world
1.3.1 Overview of effective rainfall in the world
In the World had many research on volume of effective rainfall
that was announced. Which notably:

Plan 2: P
hq
= 0,6*P - 10 (for P < 70 mm)
P
hq
= 0,8*P - 24 (for P > 70 mm).
4
Plan 3: P
hq
= a*P - b (for P < z mm),
P
hq
= c*P - d (for P > z mm).
Coefficient a, b, c, d and z are confirmed by user.
Plan 4: P
hq
= P/125 (125 - 0,2*P) for P < 250 mm,
P
hq
= 125 + 0,1*P for P > 250 mm.
1.3.2 Effective rain research in Vietnam
Nguyen Duc Chau (2001) [7] on the basis of experimental
material in Tuy Phuoc district - Binh Dinh in 1998 ÷ 2000 shown using
coefficient of rainfall reached from C = 0.57 - 0.7.
1.3.3 Comments
- The research results in-home and out-home shown that
efficiency closely depended on research area.
- Most of research results in home only stop at results of
experiment that were not provide the way to period line effective
rainfall from the actual rainfall.

• Affects of the Shallow –open-dried irrigation regime to lose
volume of water is also not mentioned in the published research. This is also
a problem need to detail in this thesis.
6
Chapter II
RESEARCH on rule of rainwater distribution
and affecting to effective rainfall,
volume of water, Consumed WATER
2.1 Research on rule of distribution volume of rain-water by the
time of the research area
2.1.1 Some characteristics on research area
Ha Nan is located the south of Hanoi, extend from 20
0
34'18'' to
21
0
18'26'' in the north latitude, 105
0
17'18'' to 106
0
0’28'' in the east
longitude, including 1 city and 5 districts with a total area of 85,958
hectares, population of 785,057 people. Irrigation system is almost by
dynamic.
2.1.2 Distributional rule of rainfall in the research area
Analyzing rain documents of Phu Ly station within 24 years
(1985-2008), results showed that: the distributional rule of rain on
(Table 2-1) with precipitation> 50mm got large proportion (60% for
spring and 82% for harvest season), it is disadvantage for increasing
using coefficient of rainfall.

(2-1)
with: Xhq
j
= X
j
- DR
j

in there: Xhq
j
is a effective rainfall in period from j-1 to j, X
j
is
a actual rainfall in period from j-1 to j, DR
j
is a consumption rainfall in
period from j-1 to j, a
j
, a
j-1
is a surface water layer at period j and j-1,
ET
j
is lose evaporation at period from j-1 to j, S
j
: is a lose by
impregnated in long time in period from j-1 to j,
On base of equation (2-1), with formulas NTX (a
j
=30-50mm),

2
= 0,5 -:- 0,98), remaining
months are not tightly correlated (Table 2-2a,b).
8
Table 2-2a. The statistical parameter relations X
tt
and X
hq
statistic of spring reason in Ha Nam
Month Regression equation
Number
of
example
Correlation coefficient
R
2
I X
hq
= 0,23 X
tt
+ 8,4 24 0,49
II X
hq
= 0,73 X
tt
+ 3,7 24 0,97
III X
hq
= 0,46 X
tt

= 0,2 X
tt
+ 74,6 24 0,36
IX X
hq
= 0,25 X
tt
+ 53 24 0,48
X X
hq
= 0,042X
tt
+ 10,1 24 0,1
2.2.3 The relationship between effective rainfall and actual rainfall
according to reason
Analysis Results on the relationship between effective and
actual rainfall showed that this relationship is less close in both Spring
harvest reasons (R
2
= 0,32 -:- 0,41) ( Table 2-2c).
Table 2-2c. Statistical parameters with correlation X
tt
và X
hq
reasons system in Ha Nam
reason Regression equation
Number
of
example
Correlation coefficient

Number
of
example
Correlation coefficient
R
2
Spring DR = 0,823 X
tt
- 150 24 0,91
Harvest DR = 0,856 X
tt
- 203 24 0,96
2.5 Conclusions of chapter
-Rainfall in Ha Nan with rainstorms > 20mm predominant
absolute on total volume (83% for spring reason and 94% for harvest
season). So if the formula is applied irrigation NTX (30-50mm), will
not take advantage of rainfall which satisfies with the water regime of
the rice. So the rainfall and necessary volume of water is high.
- Although in some cases with correlation coefficient is very
closed (rain under time with X
tt
≤ 20mm; rain under month with X
th
<
30mm) but in general,
-Correlation between the actual rainfall and effective rainfall of
the remain cases are not closed. Therefore, there is no scientific basis to
establish the relationship between the actual rainfall and effective
rainfall on the system of Ha Nam.
10

- ET
J
- S
j
+ (X
j
- DR
j
) (3-1a)
a
min
≤ a
j
≤ a
max
(3-1b)
In there : t is one time of irrigation, ∆t is time of stop between 2
time of irrigation, X
j
is a actual average rainfall which pour out on total
area of irrigation, DR
j
is a average Consumption rainfall on total area of
irrigation. DR
j
is period base on basis of surface water layer at caculated
time. Detail as follows:
DR
j
= X

max
+ a
reserve
– W
j-1
) got a nagetive value.
In case of sowing by order, average values et
j
, S
j
, X
j
và DR
j
are
ajusted by multiply with coefficient K as follows:
K = j/tg khi j < tg,
K = 1 khi tg < j < tst,
K = 1 – j/(tst+tg) khi tst < j < (tst+tg)
In there : tg is time to sow, tst is growth time,
12
On base of soluting equation (3-1), the rainfall and rainfall in zone
under Ha Nam province within 24 years according to different equation of
irrigation are period by WSI software.
3.1.2 Research on effects of irrigational formula to potential of
reducing the volume of Consumption water and the rainfall for rice
field in Ha Nam province
On the basis of meteorological data for weather stations in Phu
Ly. Level of irrigation throught years at the face of field corresponds to
the irrigational formula NTX, NLLT, NLP and the level of reserves

Spring, down 30% compared with NTX) and 2583 m3/hectare (harvest
reason downs 38.6% compared with NTX).
Regarding the relationship between depth of water reserve and
level of irrigation: if the depth of water storega is high so irrigational
13
level is low. Reduction of water level(compared to reserve 50mm)
received in the depth of 100 mm and 150 mm respectively with 21% to
24% (for Spring) and 43% to 53% (for harvest).
Spring reason Harvest reason
Figure 3-3c: Influence of depth of reserve water layer to the irrigational
level
3.1.2.2 Influence of irrigational formula and the depth of water reserve
to potential of reducing the volume of Consumption water.
There is a closely related between the rainfall water and
formula of production increase, between the rainfall water and the depth
of rain water reserve, the volume of Consumption water is reduced from
formula of agricultural irrigation in regular, Shallow–open-Continues to
Shallow–open-dried. The level of Reducing irrigational water reached
about 23% of the harvest reason and about 29% to 30% of spring reason
respective with Shallow–open-Continues and Shallow –open-dried
formulas.
For the relationship between the depth of rain water reserve and
volume of Consumption water, results showed that reduction of
Consumption water between different depths are very different. The
difference between the reserve with 50mm and 100mm are very large,
this difference reached 35% to 70%. In contrast, the difference between
reserve with 100mm and 150 mm is not much. Between these two
levels of reserve, The level of Consumption water reduction from 10%
to 15%.
14

(α/2)(n-1)
: allowed to concludes that 2 statistical samples
is not different with statistical meaning p=

α.
3.2.2 Content of experimental arrangement
Placement of experiment in Liem Tiet, Thanh Liem, Ha Nam.
Experiment time from the Harvest reason in 2005 to Spring Season in
2007.
Experiments with 10 cells, size 1.5 x 1.5 m with 9 watering
formula. Layout cells following experiments:
- Cell No 1: irrigating NTX, reserves 50mm;
- Cell No 2: irrigating NTX, reserves 00mm compared to
surface of filed.
- Cell No 3: irrigating NTX, reserves 150mm compared to
surface of filed;
- Cell No 4: irrigating NLLT, reserves 50mm;
- Cell No 5: irrigating NLLT, reserves 100mm;
- Cell No 6: irrigating NLLT, reserves 150mm;
- Cell No 7: NLP, reserves with 50mm: field dried process as
follows:
+ 10 first days: remain the surface layer about 30-50mm,
16
Figure 3-7: Diagram of cells in experiment at Liem Tuyet
+ To eleventh day to the end of lay branch: irrigating to 50mm,
to dry in nature, when filed dried 5 days (for Spring reason) and 3 days
(for Harvest reason) irrigate to 50mm. 7 to 10 days before the end of to
branch without irrigation.
+ The end Period of to branch (10 days): let’s dry in nature.
+ Period of seat- flowering: irrigate to 50mm, when filed dried

and NLP in all seasons.
+ On the level of rain reserve: between two levels of reserve
are 50mm and 100mm, there is a fairly large variations in consumption
water . The difference according to the trend reduction from 100mm to
50mm.
3.2.3.4 Comparing to results with experimental measurement and
theoretical calculation
a) On level of irrigation
18
Comparing to the irrigation level of the harvest reason in 2005,
harvest reason and spring reason in 2006 and spring reason in 2007
showed the difference in irrigation levels between theoretical and actual
in 4 cases about 6.58%. This is the error is acceptable.
b) On the volume of consumption water
Deviation between the theoretical and experimental results between
irrigation formulas and average level of reserve about 6.77%. This is the
deviation is acceptable.
3.3 Conclusions of the chapter
1) There is a closely related formula irrigation and rain water
reserve depth to water level and water quality standards. The decrease
in water level and water quality criteria to achieve the maximum
applicable rate formula combines NLP reserves 100mm. This is the
basis for selection regimes in irrigated fields to reduce water, reducing
consumption water for irrigation in Ha Nam province.
2) The potential for irrigation to reduce the average area of Ha
Nam for the service (if applicable rate reserve formula and NLP 100
mm) can be reduced by 40% for the irrigation service and over 55% for
Spring reason.
3) The potential to reduce consumption water of the average for
the service (if you apply the same formula applied irrigation and

j-1
+ m
j
+ P
hqj
– (S
i
+ ET
i
) (4-1)
in there : a
j
last field is the surface water layer on (mm), a
j-1
surface water layer is the first field day (mm), m
j
irrigation water is
needed (mm), K
i
is a volume of water was absorbed (mm), DR
i
is water
is removed (mm), P
hqj
is the effective rainfall (mm) in the calculation
period. P
hqj
= X
j
– DR

In full water condition (in period not dry field), compoments E
i
is period by formula:
ET
i
= ETc = Kc x ETo. (4-2a).
In there: ETc: volume of actual vapor water (mm),Kc:
coefficent of plant, ETo: volume of vapor water of standard.
In the field drying period, ET
i
is caculated under formula:
ET
i
= ETc = Ks x Kc x ETo. (4-2b).
In there: Ks is the coefficient of lack of soil moisture depends
on soil moisture. Ks = 1 when soil moisture larger than a certain value
(about 80% moisture saturation), Ks <1 when soil moisture less than
80% moisture saturation. The deperiodination of the Ks are conducted
in experimental.
In the field exposure time, water contained in a section of land
should evaporate soil moisture during this period under saturated
humidity. So to make the initial moisture O
i
to moisture saturation β
bh
,
need for additional water level w. with:
w
j
= (β

j
if a
reserves
- a
j-1
>= P
j
,
P
hqj
= a
reserves
- a
j-1
if a
reserves
- W
j-1
< P
j
,
P
hqj
= 0 nếu a
j-1
>= a
reserves
.
In there: a
reserves

at the time of calculation and actual rainfall.
+ During the Shallow period, moisture is smaller than field’s
moisture, etc. are multiply by multiply the coefficient of lack of soil’s
moisture to the formula ETc
Conclusion and recommendation
A. Conclusion
1. Effective rainfall in calculating of irrigational regime for a
quantity of rice is not only dependent on rainfall distribution rules but
also on the surface water layer at the time of rain. Research results of
relationship between actual and effective rainfall in 2892 rainstorm
during 24 years (1985-2008) of the Ha Nan region showed that between
those two quantities are not tightly correlated statistics. Therefore can
not build Line of actual relation and effect rain of the zone.
2. There is a closely between irrigational formulas and depth of
rain water reserve and volume of consumption water. Level of
irrigational water and consumption water, if Appling minimize Shallow
25