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Estimation of Water Loss from Irrigated Rice Fields

M. A. Rashid
Principal Scientific Officer
Irrigation and Water Management Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh.

Wais Kabir
Executive Chairman
Bangladesh Agricultural Research Council, Farmgate, Dhaka-1215, Bangladesh.

L. R. Khan
Professor
Irrigation and Water Management Department, Bangladesh Agricultural University, Mymensingh.

A. F. M. Saleh
Professor
Institute of Water and Flood Management, BUET, Dhaka.

M. A. Khair
Professor
Irrigation and Water Management Department, Bangladesh Agricultural University, Mymensingh.

Abstract/ Executive Summary:

This study was conducted in the Barind area under Rajshahi district of Bangladesh to estimate the irrigation water loss from irrigated rice fields. The study was carried out during three Boro seasons (the dry months in Bangladesh from December to April) of 1999, 2000 and 2001, and the two T. Aman seasons (the wet months from July to November) of 1999 and 2000. In most irrigation water is lost through different processes from rice fields which need to be quantified to determine the actual water requirements of the crop. In the present study the principal losses of irrigation water were measured directly in rice fields. On an average, the evapotranspiration (ET) rate was 5.1 mm/day and the seepage and percolation (S & P) rate was 4.2 mm/day in Boro season. These two values demonstrated that 55% of the applied water was needed for ET and the rest 45% is lost from the field as seepage and percolation. In T. Aman season, the evapotranspiration and S & P rates were 5.2 and 6.3 mm/day, respectively demonstrating that 45% of the applied water in rice field was needed for ET and the rest 55% was lost from the field as seepage and percolation. Irrespective of seasons and years around 50% of the irrigation water is needed for ET and the rest 50% is lost through S & P annually from the double cropped rice fields. The water productivity was 0.58 kg/m³ of water in Boro season and 0.49 kg/m³ in T. Aman season. The relative water supply (supply: demand) was 1.15 and 0.90 in Boro and T. Aman seasons respectively.

Keywords: Irrigation, Watre losses, Rice, Evapotranspiration, Seepage, Percolation, T. Aman, Boro season

Location: Amtoli, Godagari, Rajshahi.

Start Date: 01-07-1999

End Date: 31-04-2001

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

To estimate the different methods of loss of water from irrigated rice fields.

Methodology:

The field experiment was conducted during 1999 to 2001 to measure crop water requirements and field losses. The principal losses of irrigation water from rice fields are evapotranspiration and seepage and percolation. The tests were carried out at Amtoli area of Godagari thana under Rajshahi district. This is a terrace land to the north-west of Rajshahi city. The soil of the site is less permeable, which represents the typical Barind soil. The textural classes are clay loam and silty clay loam. Rice is predominantly grown in this area. The study area lies at north latitude and east longitude. Here the surface water potential is seasonal and very limited and consequently the area is drought prone. The average annual rainfall is 1645 mm (BMDA, 1995) and surface water availability is also limited. The agricultural development through surface water irrigation is practically impossible in this area. There is no storage facility of surface water for irrigation. Thus, irrigation is mainly dependent on groundwater extraction by means of tubewells. The Barind Multipurpose Development Authority (BMDA) has started exploiting the groundwater resources of Barind area since 1985.A rain gauge was installed at the experimental site at Amtoli. Another rain gauge and evaporation pan (Class A pan) were available at a nearby weather station located at Rajbari, which is about 2 km from the experimental site. The effective rainfall was calculated on the basis of daily field water depth, levee height (10 cm) around the plot and the amount of rainfall on the day.A sloping gauge was also installed in each plot outside the lysimeter to measure the combined ET and S & P from the plot. Each sloping gauge was driven into the soil so that the zero datum of the gauges coincide with the soil surface. The site of the experimental plot was 72 m × 18 m. Field experiments were carried out in 5 crop seasons (three in Boro seasons and two in T. Aman seasons) during 1999-2001. In Boro seasons (the dry months in Bangladesh form December to April) rice was transplanted on 18^th January and harvested on 24^th April and in T. Aman seasons (the wet months form July to November) transplanting was done on 15^th July and harvested on 5^th November. In Boro seasons 45 day old seedlings of BR28 were used while 30 day old seedlings of BR11 were used In the T. Aman seasons. The rice varieties were different in Boro (dry) and Aman (wet) seasons because in this country there are recommended varieties for each season. The same variety is not suitable for all seasons. The recommended dose of fertilizers were applied at the rate of 80N:60P kg/ha. The whole amount of phosphorus and potash were applied during the land preparation and nitrogen fertilizer was applied as top dressing in 3 equal splits.

Source of Information: SAARC JOURNAL OF AGRICULTURE, Vol. 7, Issue 1, 2009, pp. 29-42, ISSN 1682-8348, SAARC Agricultural Information Centre.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the study area the average annual evaporation was 1438 mm and the average annual rainfall was 1710 mm which was not uniformly distributed throughout the year. Most of the rainfall (about 98%) occurred during the period of April to October while the remaining months was almost dry. As a result, the Boro rice was fully dependent on irrigation water. In Boro seasons 55% of the applied water was needed for ET and the rest 45% was lost from the field as seepage and percolation. In T. AMan season these two values were reverse, i.e., 45% and 55%, respectively. Therefore, combining the seasons results finally it could be concluded that irrespective of seasons and years about 50% of the irrigation water was needed for ET and the rest 50% is lost through S & P annually from the double cropped rice fields. Actually, only ET was the true water requirement for rice and S & P were unavoidable losses. Therefore, these losses could be minimized by practicing alternate wetting and drying method of irrigation. Thus, the efficiency of irrigation could be increased. The water productivity was 0.58 kg/m³ of water in Boro season and 0.49 kg/m³ in T. Aman season. The relative water supply (supply: demand) was 1.15 and 0.90 in Boro and T. Aman seasons respectively. Therefore, in T. Aman season the potential demand of water (ET + S&P) was higher than the total water supply.

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