impact of on-farm water management research on the performance of a gravity irrigation system in...

Agricultural Water Management, 23 (1993) 11-22 11 © 1993 Elsevier Science Publishers B.V. All rights reserved. 0378-3774/93/$06.00

Impact of on-farm water management research on the performance of a gravity irrigation system in

Bangladesh

M.K. Mondal, M.N. Islam, G. Mowla, M.T. Islam and M.A. Ghani* Irrigation and Water Management Division, Bangladesh Rice Research Institute (BRRI), Gazipur,

Bangladesh

ABSTRACT

Mondal, M.K., Islam, M.N., Mowla, G., Islam, M.T. and Ghani, M.A. (1993). Impact of on-farm water management research on the performance of a gravity irrigation system in Bangladesh. Agric. Manage., 23:11-22.

Irrigation coverage increased in the middle and tailend tertiaries in the monsoon season due to proper monitoring, allocation and equitable distribution of water. Farmers used to apply about 40% more water than actually needed for rice cultivation. After a demonstration of water-saving tech- niques, the farmers applied an optimum amount of water for growing rice. Land productivity in the tailend areas of the irrigation system can be increased by an alternative water management approach. About 6.0 t /ha rice can be obtained from timely grown monsoon rice in those areas, where wet season rice can not be grown due to shortage of water. Before 1982, only a few farmers used to grow non-rice crops in the project area. Field demonstration of the selected non-rice crops encouraged them to grow those crops in dry season. Adoption of non-rice crops was increased from almost nil to about 50%. The farmers could not go for a proper production plan due to an erratic and uncertain pumping schedule. A fixed starting and suspension date, which will not change from year to year, will be followed in productive use of water. Consequently, it will create pump suspension opportunities for about 30-40 days during June to August and thus a pump operation cost of Tk. 400 000 or US$ 11 500 per day will be saved.

I N T R O D U C T I O N

Most of the irrigation systems in Bangladesh are performing far below their potential level. Recently, much concern has been expressed about improving the performance of existing irrigation systems. Planners, administrators and donor agencies seem to be shifting attention from building new irrigation systems to the need for improving the performance of the existing ones (Ghani

Correspondence to: M.K. Mondal, Irrigation and Water Management Division, Bangladesh Rice Research Institute (BRRI) , Gazipur 1701, Bangladesh. *Present address: Irrigation Engineer, World Bank, Dhaka, Bangladesh.

12 M.K. MONDAL ET AL.

et al., 1990). There are very few research studies to pinpoint the weaknesses in the major irrigation systems, fewer still that can demonstrate how to effectively alleviate them (Wickham and Takase, 1976 ). Field studies are therefore needed to identify the nature and magnitude of water management problems and to develop methods of improving water management and allow farmers to achieve higher benefits from the use of irrigation water.

The Ganges-Kobadak (G-K) irrigation project is the largest irrigation system in Bangladesh; it started operation in the mid-1960s. Water is being pumped from the river Ganges and allowed to flow through a network of canals under the influence of gravity. The project has a design capacity of 153 m3/s with three main and 12 subsidiary pumps, each having a discharge capacity of 36.80 and 3.54 m3/s, respectively (BRRI-BWDB-IRRI, 1986 ). The irrigation system is composed of two phases, namely phase I and phase II, having a service area of about 46 000 and 90 000 ha, respectively.

Irrigation water is primarily supplied for rice cultivation in wet (March- June) and monsoon (July-November) seasons since the system does not pump water during the dry season (November-February), because at that time the annual maintenance is carded out. The system can irrigate only about one-third of its irrigable area in the wet season due to lower water supply in the Ganges in the beginning of the season (BRRI-BWDB-IRRI, 1984 ). Field studies were, therefore, conducted from 1982 to 1990 to identify the major weaknesses of the irrigation system and find out means to effectively alleviate them, so that maximum benefits can be achieved from the irrigation system. In this paper an attempt is made to highlight the important findings of on- farm water management research and its impact on the performance of the G - K irrigation system.

METHODOLOGY

In November 1981, Irrigation and Water Management personnel of the Bangladesh Rice Research Institute (BRRI) started applied research in the G - K project (phase I) in collaboration with the Bangladesh Water Develop- ment Board (BWDB) and the International Rice Research Institute (IRRI). Research sites comprised of the service areas of nine tertiary canals belonging to three secondary canals - the fourth, ninth and eleventh secondary of Kush- tia main canal (S4K, S9K, and S11K). They represent the head, middle and tailend reaches of the main canal, respectively. Similarly, three tertiaries were selected from each secondary representing the head, middle and tailend reaches of the secondary. The tertiaries were: T3, T9, T18 of S4K; T3, T6, T10 of S9K; and T2, T6, T10 of $11K (Fig. 1 ).

Water availability was measured by staff-gauge and current meter method at the main, secondary and tertiary canals and by V-Notch weir at the farm

IMPACT OF ON-FARM WATER MANAGEMENT RESEARCH 13

Fig. 1. Schematic diagram of the Ganges-Kobadak Project, Bangladesh, showing selected secondary canals, and tertiary canals and their service areas.

level. Rainfall and evaporation were measured by Tru-check rain-gauge and USWB class A evaporation pan, respectively.

Fifty plots were selected in each tertiary area to moni tor farmers' cropping activities. Cropping pattern trials were conducted at each tertiary taking 10 × 10 m area from the farmers' existing plots with recommended inputs and other management practices.

RESULTS AND DISCUSSION

Water availability and irrigation coverage Irrigation water was measured for the selected tertiaries in both wet (March-

June) and monsoon (July-November) seasons. Measured discharge was 5- 72% more than the designed in the tertiaries T3 and T9 of S4K and was less than the designed value in other tertiaries (Table 1 ). It was observed the head tertiary of each secondary canal received more water than the middle and tailend tertiaries. Also, water delivery was always higher in the monsoon season in comparison to that in the wet season.

In the wet season, irrigation coverage in T3 and T9 of S4K was sharply increased at the beginning of the applied research activities (1983-84), pos- sibly due to more intensive care of the project personnel in those areas (Table 2 ). There was no significant improvement in irrigation coverage in other tertiaries except in T6/S11K. The main reason was that water supply was cut- off in different tertiaries in different years for successful implementat ion of the rehabilitation program that was launched. In the monsoon season, irriga-


TABLE 1

Design and measured discharge for the selected tertiaries of the G - K project

Secondary Tertiary Design Measured discharge in % of design canal canal discharge discharge*

(m3/s) Wet season Monsoon season

S4K T3 0.159 144.7 171.7 T9 0.142 133.1 104.9 TI8 0.292 35.3 82.5

S9K T3 0.345 91.3 95.9 T6 0.354 55.1 66.4 TI0 0.190 59.5 67.9

S I l K T2 0.207 74.4 87.0 T6 0.266 31.2 43.6 TI0 0.207 - 54.1

*Discharge data presented based on water stage of the season (av. of 1984-90 ).

TABLE 2

lmgated area in percent of irrigable area

Season Location Irrigable area 1982" 1983-84 1985-87 1988-90 (ha)

Wet T3/S4K 112 55.4 85.3 64.0 58.9 T9/S4K 98 66.3 83.7 68.4 67.0 T3/S9K 428 34.1 30.8 35.8 27.3 T6/S9K 466 29.4 26.5 23.7 16.8 TI 0/S9K 186 22.6 23.7 19.4 3.9 T2/S 11K 216 43.1 45.8 41.5 45.7 T6/SI IK 285 1.4 3.2 2.1 17.7 Total 1719 31.9 34.0 34.7 29.9

Monsoon T3/S4K 112 85.7 89.3 100.0 86.0 T9/S4K 98 86.7 87.8 87.8 93.2 T I8 /S4K 96 30.2 37.0 38.9 34.4 T3/S9K 428 61.7 64.4 64.9 65.6 T6/S9K 466 45.9 50.5 45.6 53.9 T10/S9K 186 52.7 71.6 69.2 73.7 T2/S11K 216 91.7 91.9 84.7 66.7 T6/SI IK 285 32.6 41.1 45.4 56.1 T 1 0 / S l l K 241 71.0 97.5 54.6 50.2 Total 2128 58.6 66.9 62.0 61.4

*Benchmark year.

tion coverage increased considerably in the tertiaries of T I 8/$4K, T6/S9K, T 10/S9K and T6 /S 11 K; but improvement in other tertiaries was not as high as the above tertiaries (Table 2 ). Like the wet season, the rehabilitation pro-

IMPACT OF ON-FARM WATER MANAGEMENT RESEARCH

TABLE 3

Actual water delivery in percent of planned delivery

15

Season Location 1983-85 1986-87 1988-89

Planned Actual Planned Actual Planned Actual (days) (% P) (days) (% P) (days) (% P)

Wet

Monsoon

T3/S4K 43 226 30 237 30 187 T9/S4K 41 241 30 133 30 107 T3/S9K 46 152 31 132 31 81 T6/S9K 40 102 31 119 31 74 T10/S9K 38 84 31 56 31 32 T 2 / S I I 1 K 38 121 31 116 31 77 T 6 / S l IK 41 85 31 - 30 93

T3/S4K 36 236 35 177 35 146 T9/S4K 38 287 35 86 35 114 T18/S4K 40 245 35 63 35 120 T3/S9K 35 211 35 74 35 174 T6/S9K 37 176 35 103 35 157 T I 0 / S 9 K 36 97 35 54 35 120 T2 /SI 1K 36 239 35 220 35 171 T 6 / S I 1 K 41 137 35 - 35 186

gram also affected irrigation coverage in this season. Comparatively higher percentages of irrigation coverage at the upstream

areas in the wet season were attributable to more days of irrigation water delivery than the programmed one (Table 3). Actual flow duration in both seasons was much higher than the programmed flow up to 1985 in S4K area and the gap became narrower afterwards. The planned water delivery was improved and remained stable after 1985 which indicated the impact of research activities in this area. The actual water delivery did not significantly improve over time because of the rehabilitation activities; but a sign of improvement was observed during the monsoon seasons of 1988-89.

F a r m level water use It was observed at the beginning of the research program that the farmers

of the G - K project practiced the continuous flowing (wild flooding) water application method for rice cultivation. They used to apply water throughout the rotation period, resulting in excessive loss of water at headends of the system.

An attempt was made to measure and document water used by the farmers for rice cultivation both in the wet and monsoon seasons. A measured volume of irrigation water (50-70 mm water per rotation) was applied to all research management plots in 1984 to demonstrate rice cultivation without continuous irrigation practice. Water required for land preparation was 237 and 261


mm in the wet and monsoon seasons, respectively. Water requirement during the growing period was much higher in the wet season ( 1900 mm) than in the monsoon season ( 1360 ram), because of higher rainfall at the later part of the wet season. Rain water was considered because at the system level rainfall and irrigation water application is inversely related. It was observed that when there was sufficient rainfall, farmers were reluctant to apply irrigation water in their farms.

Farmers of the study area keenly observed yield and water application re- lationships of the research plots. Yield of research management (RM) plots was higher than those of the farmers' managed (FM) plots (BRRI, 1985 ). In 1985, farmers of the study farms agreed to supply about 50-70 mm irrigation water once in each rotation. During land preparation, they applied 16% more water than the RM farms. Water used for land preparation showed a declining trend afterwards (Table 4). Land preparation water requirement is most important especially in the wet season (usually no rainfall in the beginning of the season) because in most cases, it dictates the command area of the irrigation system. Water required for land preparation in the monsoon season was almost similar under both management levels (Table 4) due to well- soaked land prior to the season.

In 1985, water required for growing rice was about 28% higher under FM than RM farms in both the seasons. After that, farmers applied 4-10% more water in their farms than those managed by the research group (Table 4). Farmers of the study plots and their neighbours accepted the technology and as a result, field level water use efficiency in the monsoon season increased from 1985 and finally reached 100% in 1989 (Ghani and Mondal, 1990).

Yield maximization in water-shortage location The G - K irrigation system can irrigate only about one-third of its irrigable

area in the wet season because of higher water demand for rice than the monsoon season and lower water supply in the Ganges in the beginning of the

TABLE 4

Water used for land preparation and growing period under recommended and farmers management practices

Season Period 1985 1986-87 1988-89

Recomm. Farmer Recomm. Farmer Recomm. Farmer (mm) ( % R M ) (mm) ( % R M ) (mm) ( % R M )

Wet Land prep. 248 116 248 !12 232 105 Growing 1289 128 1308 110 1456 104

Monsoon Land prep. 215 92 211 107 204 105 Growing 1297 127 1348 105 1169 106


season (BRRI-BWDB-IRRI, 1984). It was observed that the project author- ity included a small percentage of the command area for irrigation in the wet season even at the tailend of the system. For this reason, the farmers at the tailends suffered more often from unreliable water supply in both the seasons. In most cases, they have to forego their plan to grow wet season rice often with investment loss (BRRI-BWDB-IRRI, 1984).

Tailend areas of the system like T10/S 11K experienced delayed and inadequate water supply during the wet and monsoon seasons and from unwanted excess water supply in the later part of the dry season. In 1982 and 1983, farmers from this area failed to harvest wet season rice due to inadequate water delivery. Unreliability in water delivery schedule, in most cases, com- pel the tailend farmers to transplant monsoon rice late and as a consequence, they usually harvest the crop late. Due to the delayed harvest, cultivation of non-rice crops in the dry season was delayed. Again, the water delivered for seedbed preparation in the 1983 wet season, flowed over the fields and dam- aged all non-rice crops that were about to harvest within a week or two (Mon- dal and Ghani, 1990).

To mitigate the sufferings, an attempt was made to maximize monsoon rice yield in T10/S1 IK area. For this, water delivery from the mid-through tailend sections of S 11K was cut-off in wet season by erecting a cross-dam (after monsoon rice harvest ) at R3 / S 11K (Fig. 1 ) with a view that irrigation water, pumped for seedbed preparation, would not cause damage to standing non- rice crops and farmers of T 10/S 11K area can harvest their crops safely. The dam was open in the last week of May for monsoon season's seedbed preparation. Proper water delivery was scheduled in the middle of June, when water demand for the upstream section was minimum (wet season rice was at the ripening stage and needed terminal drainage).

Modern rice was transplanted in the first week of July in the monsoon season of 1984, which was about a month ahead of the upstream farmers' cropping schedule. Replicated trails in farmers field of T 10/S 11K area produced about 6.5 t /ha rice (Mondal and Ghani, 1990).

The farmers of T 10/S 11K area grew mostly kheshari (Lathyrus sativus L. ) and gram (Cicer arietinum L. ) in the dry season of 1984 and were able to harvest about 1.4 t /ha grain. Total grain production was 5.4 t /ha, which was almost double that of the total production before 1984 (Table 5 ). The farmers were pleased with this arrangement and accepted the approach whole- heartedly. They adopted the rice (local)-rice (modern )-pulse cropping pattern and obtained 6.5 and 3.8 t /ha grain in 1985 and 1986, respectively. The farmers of the other locations (like T 10 / S 11 K) could benefit if they followed this approach.

Residual soil moisture utilization It was observed during a benchmark survey in 1981 that most of the land

remained fallow during the dry season because of difficulty in plowing the

18

T A B L E 5

Year ly to ta lproduct ionof~odgra incrops in T I 0 / S I I K area

M.K. MONDAL ET AL.

Period Year Wet Monsoon Dry Total grain production

Rice Rice Non-rice ( t / h a )

( t /ha ) ( t /ha) ( t /ha)

P~-approach 1982 - 2.97

1983 - 2.72

Post-approach 1984 1.06 2.96

1985 1.41 4.46 1986 0.00" 2.88

1.39

0.63

0.88

2.97

2.72

5.41

6.50 3.76

*Flood damage caused by excessive rainfall.

TABLE 6

Yield ( t /ha ) of popular non-rice crops in the dry season

Year Kheshari Gram

RM FM RM FM

Wheat Onion

RM FM RM FM

1982-83 1983-84 1.32

1987-88 0.99

1988-89 0.65 1989-90 0.20

Mean 0.79

Fertilizer use N

(kg/ha) P K

1.93 1.51

1.18 1.28 1.02 0.76 0.45 0.40

0.50 2.03 1.92 0.19 0.60 0.56

0.66 1.26 1.08

1.50 1.11 - -

- - 8.21 8.28

- - 6.45 6.34 - - 7.68 6.99

1.50 1.11 7.46 7.20

80 30 45 33 60 34 44 46

40 19 29 30

RM = recommended management; FM = farmer's management. Source: Mondai et al. (1990) .

land after the harvest of monsoon rice. In the dry season of 1982-83, performance of wheat and gram was evaluated under rainfed conditions in different locations of the project. Average yield of wheat was 1.5 and 1.1 t /ha and that of gram was about 1.9 and 1.5 t /ha, respectively, under RM and FM levels (Table 6). The yield of wheat was not really low. In the potential wheat growing areas of Bangladesh, wheat yield varied from 2.0 to 3.0 t /ha under irrigated environment. When compared with other wheat growing countries of the world, the yield is really low; maybe because of the shorter growing season coupled with a higher temperature at the flowering stage of wheat. Similar trials with kheshari and gram were conducted in 1983-84. Kheshari was included in the trial because this leguminous crop has got an added ad-

IMPACT OF ON-FARM WATER MANAGEMENT RESEARCH

TABLE 7

Adop t ion o f different non-r ice crops in the dry seasons

19

Year Adop t ion o f crops (%)

Khesha r i W hea t G r a m On i on Pea Lentil Oil seed Total

1983-84 7.3 3.8 0.7 8.4 - - 1.6 21.8 1984-85 27.8 11.1 5.3 8.2 0.9 - 0.7 54.0 1985-86 22.9 11.1 11.1 8.7 3.3 - - 57.1 1986-87 9.1 13.6 19.8 8.4 4.2 1.1 - 56.2 1987-88 18.7 5.3 7.3 15.3 2.2 1.8 - 50.6 1988-89 21.0 3.3 16.0 6.9 4.7 - 2.4 54.3 1989-90 13.0 12.3 3.8 15.8 2.3 0.8 2.0 50.0

Mean 17.1 8.6 9.1 10.2 2.9 1.2 1.7 41.9

Source: Monda l et al., 1990.

vantage that it can be sown on the standing rice field as a relay crop. There- fore, moisture availability does not pose a major problem for this crop.

Farmers of the project area took keen interest in growing pulses in dry season. Therefore, trials were discontinued from 1984-85 to 1986-87. During this period, inspire of conducting trials, farmers' cultivation practices were monitored throughout the project area. It was observed that kheshari was the most popular non-rice crop in the project area (Table 7). Gram and wheat were also among the major non-rice crops. From 1987 to 1988 and 1989 to 1990, production trials were conducted with onion along with kheshari and gram. Yield of onion varied from 6.45 to 8.21 t /ha under RM and 6.34 to 8.28 t /ha under FM levels, with an overall 3.3% increase under RM practice (Table 6) and was attributable to only intercultural practices such as weeding.

Residual soil moisture is used in significant proportion in the G - K area for growing non-rice crops following monsoon rice. Kheshari, onion, wheat and gram were the most popular grown non-rice crops. Coverage of these crops increased from 1984 and remained almost steady up to 1990 (Table 7). Crop yields vary significantly from year to year due to differences in the amount of rainfall, planting time and inputs used (Bhuiyan, 1990). The percentage of farmers who grew non-rice crops using residual soil moisture did not vary much between 1984 and 1990, but the number of farmers who grew a partic- ular crop varied widely over the years. About 50% of the farmers cultivated non-rice crops after 1984 which was mainly due to the demonstration of non- rice crop cultivation during the periods of applied research in this area.

Pump operation schedule and suspension opportunity Pump starting and suspension dates of the irrigation system for the last 20

years indicated that pumping has been started at various times between the


last week of December to the first week of May (Ghani et al., 1990) mostly because of the management problems. But in most cases, it was in the months of February and March. It was observed that irrespective of the pump starting date, the pumps were shut down around the middle of November. This rela- tively stable suspension date indicated that farmers were not sure of water delivery schedule and could not adapt successful cropping schedule with the availability of water. Therefore, establishment of a reliable water delivery schedule is necessary in order to improve the performance of the irrigation system.

It was observed that pumping was seldom suspended even during the heavy rainy period. Results of applied research pinpointed the opportunity of pump suspension for about 30 to 40 days during the rainy months of June through August (Ghani, 1987), when wet season rice remains at the maturing stage (needed terminal drainage) and land preparation for the monsoon rice is underway.

The project management showed keen interest and implemented the sug- gested strategy in 1990 and were able to suspend pumping water for 26 days during June to August (Ghani et al., 1990). Pump suspension is very important not only for proper rainwater utilization but also for saving very high operation costs of about Tk. 400 000 or US$11 500 per day.

CONCLUSION AND RECOMMENDATION

Supply of irrigation water was less than the designed flow in the mid through tailend sections of the G - K project. Again, actual flow duration was much higher at the upstream section than the programmed one before the research program started in the G - K area. The actual and programmed water delivery situation was slightly improved during 1988-89. But the achievement was not satisfactory because of the rehabilitation activities interrupted irrigation water delivery in many sections. Therefore, more intensive care should be given in water allocation and distribution through proper monitoring to achieve maximum benefits from the irrigation system.

The farmers of the project area used to apply about 40% more water than required for growing rice before 1985. Due to the demonstration of the water- saving technique, they applied an optimum amount of water for rice cultivation. As a result, farm level water use efficiency increased both in the wet and monsoon seasons.

For productive use of water, delivery should be limited to the upstream sections only in the wet season. In water short areas, an early delivery should be made in order to maximize rice yield in the monsoon season as well as total production from the system.

Cultivation of non-rice crops has increased significantly using residual soil


moisture. Farmers can harvest about 1.0 t /ha grain from these crops, which may play an important role in the food supply of the country.

Farmers can not go for a successful crop production plan because of an erratic pump operation schedule. If a fixed pumping schedule is followed, there is a possibility of pump suspension for about 30 to 40 days or even more during June to August. Consequently, a significant amount of pump operation costs of Taka 400 000 or US$11 500 per day can be saved. This saving may help in operation and maintenance activities of the irrigation system.

ACKNOWLEDGEMENTS

Sincere thanks are extended to the staff members of the Bangladesh Rice Research Institute, the Bangladesh Water Development Board, the Interna- tional Irrigation Management Institute, the International Rice Research In- stitute and to the cooperating farmers of the G-K Project. Sincere apprecia- tion is extended to Mr. Md. Arifur Rahman and Mr. Md. Abdul Maleque for typing the manuscript.

REFERENCES

Bhuiyan, S.I., 1990. Technical Farm Level Issues in Irrigation for Rice-Based Farming Systems: An Intercountry Synthesis. Paper presented at the Intercountry Workshop on "Irrigation Management for Rice-Based Farming Systems", IIMI, Colombo, Sri Lanka, 12-14 Novem- ber 1990.

BRRI, 1985. Annual Internal Review Report for 1984. Agricultural Engineering Division, Ga- zipur, Bangladesh.

BRRI-BWDB-IRRI, 1984. Applied Research for Increasing Irrigation Effectiveness and Crop Production. First Progress Report, BRRI, Gazipur, Bangladesh.

BRRI-BWDB-IRRI, 1986. Applied Research for Increasing Irrigation Effectiveness and Crop Production. Second Progress Report, BRRI, Gazipur, Bangladesh.

Ghani, M.A., 1987. lmproved Water Management for Rice Irrigation Systems in Bangladesh. Unpublished Ph.D. Thesis, Utah State University, Utah, USA.

Ghani, M.A. and Mondal, M.K., 1990. On-Farm Water Management for Rice-Based Farming Systems in Bangladesh. Paper presented at the Intercountry Workshop on "Irrigation Man- agement for Rice-Based Farming Systems", IIMI, Colombo, Sri Lanka, 12-14 November, 1990.

Ghani, M.A., Hakim, M.A. and Mondal, M.K., 1990. Water Management for Rice Irrigation Systems in Bangladesh. Paper presented at the Intercountry Workshop on "Irrigation Man- agement for Rice-Based Farming Systems", IIMI, Colombo, Sri Lanka, 12-14 November, 1990.

Mondal, M.K. and Ghani, M.A., 1990. Water management approach for tailend areas of the Ganges-Kobadak project. Bangladesh J. Agricult. Engin., 4: 33-40.

Mondal, M.K., Ghani, M.A., Rashid, M.A., Islam, M.N., Hassan, M.N., Molla, H.R., Khan, A.K., Mowla, G., Islam, M.T., Joarder, N.J., Islam, M.R. and Bhuiyan, S.I., 1990. Water Regimes and Crop Diversification. Paper presented at the Workshop on "Applied Research for Increasing Irrigation Effectiveness and Crop Production" BARC, Dhaka, Bangladesh.


Wickham, T.H. and Takase, K., 1976. Some Management Issues in Irrigation Development. Paper presented at the CPDS-UPLB-NWRC-NIA Workshop on Water Resources, UPLB, Los Banos, The Philippines.

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