IJERD – International Journal of Environmental and Rural Development (2011) 2–1

Research article
erdInfluences of Land Use during the Puddling Period on
Water Balance and Quality in a Rice Farming Area
MOHAMMED KAMRUL HASAN
Hokkaido University, Sapporo, Japan
Email: hasan@env.agr.hokudai.ac.jp

YAMAMOTO TADAO
Hokkaido University, Sapporo, JapanNAGASAWA TETUAKI
Hokkaido University, Sapporo, Japan
Received 3 December 2010

Accepted 28 January 2011

Abstract The study was carried out on the Shinotsu Canal agricultural watershed of
Hokkaido, Japan from 2003 to 2008. This study was conducted to evaluate the nutrients
fluxes after using irrigation into the paddy fields and the effectiveness of the paddy fields
in removing nutrients load of the Shinotsu Canal watershed. Upper part of the Shinotsu
Canal is dominated by paddy field and lower part is dominated by upland field. Water
samples were collected with an automatic sampler at pump station (inflow) and end ofdrainage channel (outflow) of both block, and measured volume of inflow and outflow at
puddling period (May). The concentration of suspended solids (SS) was determined bygravimetrically through suction filtration, total nitrogen (TN) and total phosphorus (TP)were determined by UV spectrophotometric methods, respectively. Water balance ishigher at lower part of Mihara drainage block (MDB) than upper part of Tsukigata
drainage block (TDB) due to high percentage of upland that caused losses of water byleakage and percolation. TN, TP and SS concentrations in drainage water are higher in
MDB than that of TDB. The net loads of TN and TP are showed negative and lower valuesin TDB whereas MDB is positive and higher values, due to a combination of nitrificationand denitrification, sedimentation reactions and sorption by soil is more in high percentageof paddy field in TDB. TN, TP and SS concentrations outflow load and net load are
decreasing from 2003 to 2008 due to changed of water management by progress of pipeline. From the viewpoint of reducing the outflow of nutrients, it may be stated that the
paddy field dominated area showed good performance in purification function for
nutrients compounds.
Keywords land and water use, water balance, puddling period, water quality, Hokkaido

INTRODUCTION
In Japan, paddy fields cover 55% of the land used for agriculture. They require abundant water andaccount for 95% of the total agricultural water demand (Tabuchi and Hasegawa, 1995). Paddy
fields therefore play a significant role in the overall agricultural watershed. Most paddy fields arelocated along lower reaches of rivers, use rivers as their main source of water, and discharge theiroutflow back into the river. The Shinotsu Canal watershed has a significant role in agriculture in
Hokkaido, Japan. Water quality of the Shinotsu Canal is influenced by nonpoint source pollutantsarising from land-based agricultural activities (Hasan et al., 2010). In some paddy fields along thelower parts of the Ishikari River basin in the Shinotsu Canal, irrigation water is reused as means ofmaximizing water utilization, and the water may contain higher levels of pollutants from surface
and subsurface drainage compared with usual irrigation water. Several researchers have reported
that cyclic irrigation may increase the hydraulic retention time of nutrients, and thereby, enhance© ISERD

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IJERD – International Journal of Environmental and Rural Development (2011) 2–1

water purification in paddy field districts (Feng et al., 2004, 2005; Takeda and Fukushima, 2006).
Cyclic irrigation may not only save water but also reduce the concentration of nutrients inagricultural areas (Kudo et al., 1995). The ability of cyclic irrigation to reduce nutrient load is
directly proportional to the quantity of water reused (Kaneki et al., 2003). Tong and Chen (2002)
examined the hydrologic effects of land use in Ohio and observed a significant relationshipbetween land use and stream water quality, especially with respect to nitrogen and phosphorus.
In irrigation practices, especially puddling and transplantation period (May), require abundant
water during the whole irrigation period (May to August) in paddy fields, and have strong influenceon the water environment. Furthermore, many studies on nutrient fluxes in paddy fields have been
outperformed in the irrigation period, but the flow of nutrients out of paddy fields has not beenstudied adequately in Hokkaido in instances of abundant water use. Therefore, this study aimed toassess the influences of land use and water management on water balance and quality during thepuddling period at the Shinotsu Canal watershed in Hokkaido.
MATERIALS AND METHODSThe  investigation  was  performed  in  the  Shinotsu  Canal  in  the  Shinotsu  district  (43°57′N,  141°4′E),  which is located at southern Ishikari River basin in west-central Hokkaido prefecture in northern
Japan (Fig. 1). The Shinotsu Canal is 23 km long and passes through 10,864 hectares ofagricultural watershed where the main cultivated crops are rice, wheat, corn, onions, and vegetables.
Agricultural irrigation is controlled by five pumping stations from upstream to downstream. The
lower stream pumping stations provide irrigation water derived through drainage channels from theoutflow or runoff from upstream paddy fields. The study area comprised the Tsukigata drainage
block (TDB) in the upper stream and Mihara drainage block (MDB) in the lower stream of the
Shinotsu Canal (Fig. 2).The soil is peat-dressed mineral soil, and most land is flat. The annual
average precipitation is 1024 mm, most is in the form of rain occurring from July to September.
The  annual  temperature  ranges  from  a  minimum  of  −7.4°C  in  January  to  a  maximum  of  23°C  in  August. Fertilizer is applied to paddy fields in this region (N, 60–75 kg/ha; P, 80–90 kg/ha) during
puddling to transplantation period (May) and the flowering stage (middle of July).
Sampling points
Tsukigata irri. areaN

Mihara irri.area
Paddy field

Ish

ika

ri

Ri

Sh

in

ve
r

ot

su

Ca

na
l

Upland0

Fig. 1 Location map of study areakm

5Fig. 2 Investigated area of Shinotsu

Inflow and outflow water samples (composite water samples) were collected from TDB and
MDB. Composite water samples (two mixture samples obtained at intervals of 6 h for 24 h) werecollected with an automatic water sampler (ISCO Model 3700) during the puddling andtransplantation periods (May) in 2003, 2004, 2006, 2007, and 2008. Inflow water samples werecollected at each pumping station, and outflow samples were collected at the end of the TDB and
MDB drainage channels. Inflow water volume of TDB and MDB were calculated from data on© ISERD

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IJERD – International Journal of Environmental and Rural Development (2011) 2–1

pump discharge and water level in the delivery tank; these data were collected from the
management office of the Tsukigata and Mihara pumping stations (Shinotsu-chuoh Land
Improvement District). Outflow water volumes were calculated from continuous records of waterlevels using an automatic water gauge, and flow velocity was measured when the water was
sampled. Channel renewal (open to pipe) data were collected from the Shinotsu-chuoh Land
Improvement District. Precipitation was estimated from the Shin-shinotsu and Tsukigata rainfall
records using the Automated Meteorological Data Acquisition System (AMeDAS). Areas of paddy
fields and uplands in the study watersheds were calculated using GIS Arc-View software from
1:25,000 scale digital maps. The concentration of suspended solids (SS) was determined
gravimetrically by suction filtration, and total nitrogen (TN) and total phosphorus (TP) were
determined by UV spectrophotometric methods. The concentrations of SS, TN, and TP were
determined as described in the Japanese Industrial Standard (JIS).
RESULTS AND DISCUSSION
The Tsukigata and Mihara irrigation and drainage blocks were investigated from 2003 to 2008, andthe areas of their paddy fields and upland fields were calculated. The Tsukigata pumping station
irrigated 1948 hectares in the upstream agricultural watershed of the Shinotsu Canal (Table 1).
TDB forms part of the irrigation area for Tsukigata pumping station and covers an area of 743
hectares (Table 1). Mihara pumping station lies in the downstream agricultural watershed of the
Shinotsu Canal and irrigates 2018 hectares (Table 1). MDB is part of the irrigation area of Mihara
pumping station and covers 747 hectares (Table 1). During the study period, the paddy field area
was greater in TDB than in MDB, but the upland field area was greater in MDB than in TDB. A
high percentage of the paddy field area was found in TDB (41–46%). In contrast, the percentage of
upland was higher in MDB (56–63%) than in TDB (30–36%). TDB was dominated by paddy fields
and MDB by upland fields; land use pattern did not change substantially during the study period.
80

Pipe line (km)Government

Hokkaido

District and others

60
40
20
0
2003

2004

2006

2007

2008

2003

Tsukigata

2004

2006

2007

2008

MiharaFig. 3 Renewal of pipe line at Tsukigata and Mihara irrigation block
The form of irrigation channels is an important factor in water management in the agricultural
watershed of the Shinotsu Canal. The pipeline irrigation channels are constructed from open
channels in the Tsukigata and Mihara irrigation blocks. Lengths of the pipeline irrigation channelsof the Tsukigata and Mihara irrigation blocks were calculated for every year from 2003 to 2008,
except for 2005. The total pipeline length in the Tsukigata irrigation block was larger than that in
the Mihara irrigation block for every year (Fig. 3). Pipelines are constructed as part of projects
operated by the national government, the Hokkaido prefecture government, and the Shinotsu-chuohLand Improvement District. The length of pipeline constructed under the national government
project was constant during the study period, whereas the length of pipeline constructed under the
Hokkaido project increased from 2003 to 2006 in both blocks. Pipelines constructed under otherprojects gradually increased in length from 2003 to 2008 in both blocks. The condition of thesepipelines is evaluated at each drainage block. The water balance of each block was calculated using
Eq. (1):
Water  balance  =  total  inflow  −  total  outflow                                                                          

(1)where total inflow is the volume of pumped water plus precipitation, and total outflow is surface
plus subsurface drainage water per day. Inflow and outflow water volumes of TDB and MDB were
calculated for the years 2003 to 2008. Irrigation water is distributed from about May 7 every year
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IJERD – International Journal of Environmental and Rural Development (2011) 2–1

in the Shinotsu district. Average daily inflow water volume was greater for MDB than for TDB for
every year. In contrast, outflow water volume of MDB was lower than that of TDB. Inflow andoutflow volumes gradually decreased due to increasing pipeline length in both blocks. The form of
irrigation channel is changing gradually from open to pipeline, and farmers now control irrigationwater for each paddy block to ensure proper water utilization. In contrast, the land use pattern ofeach block did not change significantly during the study period. The water balance of MDB was
higher than that of TDB for every year (Fig. 4), because the percentage of upland was higher in
MDB than in TDB, and paddy fields were scattered. Abundant water was therefore lost from the
paddy fields to adjacent uplands by leakage and percolation. Water balance in TDB and MDB did
not change significantly during the study years except in May, 2006 at MDB (Fig. 4).
50

Inflow

Water balance (mm/d)

40

Precipitation

Outflow

Balance

30
20
10
0
-10
-20
-30
2003

2004

2006

2007

2008

2003

2004

2006

TDB

2007

2008

MDB

Fig. 4 Water balance of TDB and MDB
15

15
(MDB)

Discharge weighted m ean

10

TN (m g/L)

5

10

2003

2004

2006

2007

2003

3

2007

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

2006

2008

(MDB)

2

TP (m g/L)

1

2

1

2004

2006

2007

2003

2008

2004

2006

2007

Inflow

Outflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow
2003
1200

Inflow

0

0

2008

1200
(MDB)

(TDB)
900

2003

2004

2006

2007

2008

2003

2004

2006

2007

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

0

Inflow0

Outflow

300

Inflow

300

Inflow

600

Outflow

600

Inflow

SS (m g/L)

900

Outflow

TP (m g/L)

2004

3
(TDB)

SS (m g/L)

Inflow

Inflow

2008

Outflow

Outflow

Inflow

Outflow

Inflow

Outflow

Inflow

Outflow

Outflow

Inflow

0

Inflow

0

5

Outflow

TN (m g/L)

(TDB)

2008

Fig. 5 Concentarions of TN, TP and SS in TDB and MDB in May
The discharge weighted mean concentrations of TN, TP, and SS of inflow and outflow waterof TDB and MDB in May for every year are shown in Figure 5. The box plots of TN, TP, and SS
concentrations represent 75% and 25% quartiles, medians, and weighted mean values for TDB and
MDB. Mean TN, TP, and SS concentrations were higher in outflow than in inflow water in bothdrainage blocks. Variations in TN, TP, and SS concentrations were larger in outflow than in inflow
water. These variations are thought to be caused by agricultural activities, i.e., puddling and© ISERD

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IJERD – International Journal of Environmental and Rural Development (2011) 2–1

transplantation. In the initial stages of rice cultivation, abundant irrigation water is used in paddy
fields for puddling, and it mixes with soil and fertilizer. Nutrient-rich flooded water is released
through surface drainage before transplantation. A high load of pollutants accumulates throughsubsurface drainage and is subsequently discharged into drainage ditches. The concentrations of
nitrogen and phosphorus in drainage water increase during puddling and transplantation, and also
when fertilizer is applied (Takeda et al., 1997; Feng et al., 2004). Several studies of water quality
indicators in drainage water from paddy fields in Japan showed that the concentrations of thesecontaminants increased significantly during puddling periods (Kondoh et al., 1992). Also, nutrient
concentrations are generally higher in drainage water than in irrigation water (Takeda et al., 1997).
In the present study the concentrations of TN, TP, and SS in outflow water were higher in MDB
than in TDB due to the land use pattern, i.e., low percentage of paddy fields in every year (Table 1).
Outflow discharge was lower in MDB than in TDB during the study period (Fig. 4), and nutrient
concentrations were decreased by the high outflow discharge in the TDB drainage. Tabuchi and
Takamura (1985) reported that outflows from paddy fields contained much less pollutants thanupland fields because nutrients are easily absorbed by soil particles in paddy fields. The
concentrations of TN, TP, and SS showed large variation due to puddling, transplantation, andinitial use of fertilizers, which runoff by surface and subsurface drainage from paddy fields in both
blocks. Nutrient concentrations of drainage water increased rapidly when the puddling process
began, and high concentrations continued to be present during subsequent farming activities.
The net outflow nutrient load is one of the most important factors to consider when evaluating
the role of paddy fields in reducing levels of pollutants from agricultural watersheds (Tabuchi and
Takamura, 1985). The net nutrient load associated with irrigation is defined as the outflow nutrient
load minus the inflow nutrient load (e.g., Takeda et al., 1997). The net load indicates increase or
decrease in the nutrient load discharged from the paddy field when irrigation is compared withdrainage water. A positive net load indicates that the paddy field area is a nutrient source, whereasa negative value indicates that the area is a nutrient sink, i.e., nutrients are absorbed by the paddy
soil. The nutrient load is the product of average nutrient concentration and water flow volume. The
daily nutrient load is calculated using the L-Q power Eq. (2):
L = aQb(2)

where L is the load in kg ha−1 d−1, Q is the flow rate m3 ha−1d−1, and a and b are coefficients. Thus,
the net nutrient load, Lnet (kg ha−1d−1) is given by the following Eq. (3):
Lnet = aQoutb–a′Qin b′(3)

TN, TP, and SS loads were greater in MDB than in TDB for every year except for the outflow
SS load of MDB. The net TN and TP loads were negative and lower values were found in TDB
than in MDB (Table 2), because TDB contained a higher percentage of paddy field than MDB,
causing greater nitrification and denitrification, sedimentation reactions, and sorption by soil.
Misawa (1987) and Shiratani et al. (2002) reported that paddy field areas in Japan caused net
removal of nutrients due to a combination of nitrification and denitrification, sorption by soils, andsedimentation reactions.
Table 2 Nutrients loads of TDB and MDB in May
Table 1 Land use of research areas
TDB
MDB
-1

Upland (ha)Paddy (ha)Study block
Irrigation block (ha)Drainage block (ha)
2003
2004
2006
2007
2008
2003
2004
2006
2007
2008

Load (kg ha )Tsukigata1948
743
303 (40.8%)308 (41.5%)311 (41.9%)
310 (41.7%)
343 (46.2%)
269 (36.2%)
264 (35.5%)
261 (35.1%)
262 (35.3%)
224 (30.1%)

Mihara2018747
161 (21.6%)
208 (27.8%)
184 (24.6%)
188 (25.2%)
177 (23.2%)
467 (62.5%)420 (56.2%)
444 (59.4%)
440 (58.9%)425 (56.9%)

TN

TP

SS

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Year

2003
2004
2006
2007
2008
2003
2004
2006
2007
2008
2003
2004
2006
2007
2008

Inflow
10.25
10.13
9.54
10.03
10.06
1.54
1.23
0.84
1.04
1.12
105.39
96.53
92.51
90.35
88.08

Outflow-11.86-11.48
-9.21
-9.27
-9.49
-1.24
-1.15
-0.48
-0.47
-0.55
112.35102.00
56.57
53.90
50.83

Netload
1.61
1.36
-0.33
-0.77
-0.57
-0.31
-0.08
-0.36
-0.57
-0.57
6.96
5.47
-35.94-36.45-37.26

Inflow Outflow Netload
18.21 -23.94
5.73
15.35 -17.29
1.94
14.68 -33.53
18.85
13.76 -15.66
1.90
13.30 -13.28
-0.02
2.51
-3.78
1.26
2.06
-2.83
0.77
1.98
-5.07
3.09
1.81
-2.93
1.12
1.75
-2.25
0.50
61.33
26.22
-35.1048.68
24.99-23.69
49.42
56.20
6.78
40.67
23.97
-16.7033.09
21.04-12.05IJERD – International Journal of Environmental and Rural Development (2011) 2–1

Net SS loads were negative in both TDB and MDB. TN, TP, and SS loads decreased between
2003 and 2008 due to changes in water management activities, i.e., progress in pipeline
construction. However, progress in pipeline construction reduced outflow water volume, which
affects the outflow and net load of nutrients. Water discharge is closely related to nutrient load. Ourdata on net nutrient loads indicate that areas dominated by paddy fields promote the purification
mechanisms for nitrogen and phosphorus compounds in the water environment of agricultural
watersheds.
CONCLUSION
In this study, we evaluated the land use pattern, renewal of irrigation channels by pipeline
construction, water balance, water quality, and mass balance of nutrient loads in drainage blocks.
The data on land use pattern indicated that TDB is dominated by paddy field areas whereas MDB isdominated upland fields. The water management system changed from open channels to pipelines
in each block during the study period. Water balance was higher in MDB than TDB because MDB
had a larger proportion of upland, which caused greater losses of water by leakage and percolation.
The concentrations of TN, TP, and SS in outflow water were higher in MDB than in TDB, because
pollutant outflow from paddy fields was much less than that from upland fields. Paddy fields act topurify pollutants such as nitrogen and phosphorus. The net loads of TN, TP, and SS were negativein TDB, where the lower values indicated nutrient uptake by TDB paddy soil, whereas MDB paddy
fields had positive loads and higher values; i.e., they were nutrient sources. By reducing theoutflow of nutrients, blocks dominated by paddy fields showed good purification performance fornutrient compounds. The reasons for this were the relatively low nutrient concentrations in
irrigation water and the change in the water management system in TDB. Upstream (TDB) water istherefore cleaner than lower stream (MDB) water because of the effects of agricultural land use andthe water management systems of the Shinotsu Canal watershed.
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