Zorkeflee Abu Hasan
Study Area and Problem Statement:
Paddy fields are found majority in the Asian regions where it contributes staple food i.e. rice which are consume by almost half of the world's population in this region. Paddy fields have multifunctionalities or multiple roles (e.g. food production and security, flood control, water purification, social economic improvement, preservation of soil erosion, cultivation of ground water, habitats of aquatic animals, reduction of nitrogen content in irrigation water, climatic mitigation agro and eco-tourism and amenities, cultural and education, etc..) which are important to the stakeholders.
This study is part of Malaysia's continuous support to the International Network of Water and Ecosystem of Paddy Fields (INWEPF) in promoting the benefits of paddy cultivation beyond rice production. The Malaysian INWEPF Chapter, through Agriculture Drainage and Irrigation Division of the Ministry of Agriculture and Agro-based Industry Malaysia, has initiated this study to provide scientific evidence of such multi-functionalities of paddy fields in Malaysia.
REDAC (through USAINS Holdings Sdn Bhd) was appointed by Ministry of Agriculture and Agro-based Industry Malaysia to conduct this study, concentrating on the capacity of paddy fields in providing flood, sedimentation and erosion control. The 8-month study will be conducted in selected paddy plots in Pendang, Kedah, which is under the Muda Irrigation Scheme, operated and managed by Muda Agricultural Development Authority (MADA).
Scope of Work:
The scope of this study includes:
To study the effectiveness for the flood, soil erosion and sediment control of paddy fields under the context of sustainable paddy cultivation.
To produce guideline or standard format on the planning aspect to execute this study or task.
Multi Functionality of Paddy Fields:
Multifunctionality of paddy field has been widely studied in developed rice-growing countries such as Japan, Korea and Taiwan. However, very few if any, of such study have been conducted in Malaysia, or the South East Asia region. Table 1 summarised some of the multifunctionalities of paddy field documented by several literatures. Among some widely acknowledged functions of paddy fields include flood control, erosion control and water purification. Monetary evaluation suggested that these multifunctionalities of paddy field could provide millions in benefit of the people and government. These saving come from mitigating possible flood, land slide hazard, and mitigating draughts, as showed in Table 2.
|Function:||Masumoto (2003)||Matsuno et al. (2006)||Huang et al. (2006)||Kim et al. (2006)|
|Water Cycle Control||
|Environmental Load Control||
|Social and Cultural Formation||
Table 1: Multifunctionality of paddy fields
Table 2: Monetary evaluation of Multifunctionality of Paddy Fields
(Kim et al., 2006)
The study will be conducted in two parts to examine the flood and sediment control capacities of paddy fields. In each part, the functions will be examined in two scales, namely micro (local) and macro (regional) scales. Finally, the flood and sediment control capacity will be determined, and the findings will be compiled and documented as a guideline for paddy fields flood and sediment control assessment and management practices. Figure 3 illustrates the proposed work flow for the study.
In order to determine flood control capacity of paddy field, two assessments will be carried out. First, a plot water balance model will be established at 3 selected plots within study area to examine the capacity of paddy field in reducing rainfall runoff. Field works will be carried out to survey the plots, determine soil infiltration rate, and hydraulic parameters. It is expected that flood control capacity will vary due to seasonal changes (soil condition) and farmer's practices. This study will also look into these factors. Second assessment will determine how paddy plots collectively perform as floodplains in order to mitigate regional flood. A hydraulic model will be used to examine the effect of having paddy field floodplains in Pendang area.
As for sediment control, there will also be two assessments to be carried out. Firstly, the plot level sediment control of paddy field will be determined. As water enters paddy plots through irrigation canal in normal operation condition, it will flow through the plot and exits at the outlet of the plot into agricultural drainage. There will be expected change of sediment content due to the change of flow regime during this period. Several factors which will affect this change include flow, farmer's practice, and crop growth stages. The sediment control relationship to these factors will be determined. Second assessment involves determination of sedimentation capacity of paddy plots in regional scale. As river flood occurs, paddy fields as floodplains will attenuate flood flow, thus encouraging settlement of larger particles. This phenomenon will be simulated using sediment transport computer model.
The final output of the study will include the assessment of flood and sediment control in the Pendang paddy fields as a representation of Malaysia paddy cultivation practice in general. The study is also expected to identify factors influencing flood and sediment control capacity of paddy fields including plot physical condition, crop growing stages, and farmer's practices.
Finally, the methodology applied in this study will be properly compiled and improved at the end of the study to provide guidelines for any future paddy field multifunctionality evaluation, particularly for flood and sediment controls. Suggestions to optimise flood and sediment control capacities will also be documented to maximize values of paddy cultivation.