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Rice Production and Water use Efficiency for Self-Sufficiency in Malaysia: A Review
Abstract
Rice is one of the most important staple foods for world’s population ranking third after Wheat and Maize in terms of production and consumption. Asia accounts for over 95% of global rice production with Brazil, ranked ninth as the only non-Asia nation among the World’s top ten producers. China (194.3 million tonnes) and India (148.3 million tonnes), ranked first and second respectively are by far largest producer of rice, producing half of the World’s rice. Malaysia is currently ranked 25th with a production capacity of 2.4 million tonnes and fairly constant cultivable land of about 0.7 million hectares since the 1980s. even though the land area for rice production has remained rather constant, rice productivity has been increasing every year from 2.1 in 1961 to 3.6 tons ha-1 in 2008 with an annual increase of 2.0% per year or about 28,000 tonnes per year. This has not in any way guaranteed self-sufficiency as over 700,000 tonnes or 30% of its rice needs were being imported from their neighbouring countries annually. The study therefore, examines rice production with respect to growing population for self-sufficiency in Malaysia. This is considering past trends in rice production, water use efficiency, eating habits and prosperity level by 2015.
... The statistic shows that around 250 million hectares, about 17% of total agricultural land worldwide is irrigated today, this amount is almost 5 times more than the early of 20th century and hence it is about total 40 % of paddy crops is contributed worldwide [4]. Irrigation plays an important role in helping to boost the agricultural yields, at the same time it also stabilizes the food prices. ...
... In year 2009, total 57% of paddy is harvested from irrigated area, 28% are from rain fed low land area and 11% from highland while 4% from others area. Studies shows that irrigated paddy was contributing about 75% of overall paddy production [4]. During the irrigation period, the amount of water which used to apply on crops is usually more than the amount that the field need. ...
... LCA has been incorporated into the ISO 14046 environmental management system, serving as an important tool for environmental management. The growing concern about sustainable food production and consumption has prompted much more research on the LCA of agricultural production activities [4,7,13,[15][16][17]19]. In this study, we describe the application of LCA to investigate environmental impacts of the rice production system in the Muda Granary area and offer several suggestions to minimize negative impacts on the environment. ...
Rice is a crucial part of everyday Malaysian diet. The demand for rice in year 2030 is projected to be around 533 million ton of milled rice and known to be a high-water consuming crop. It is mainly cultivated in Kedah of Malaysia under irrigated conditions. It is responsible for the environmental degradation due to inefficient use of factors of production, low yield as well as being grown under ponded conditions. Therefore, this study was designed to assess the environmental impacts of rice production in Muda Granary Area in Kedah using life cycle assessment (LCA) approach. Data was collected from Muda Agricultural Development Authority (MADA) and one of rice milling’s factory in order to identify the environmental impacts with different phase of production. It was observed that different production practices and different levels of input consumption contributed to the different environmental impacts. The LCA considered the entire system required to produce 1 kg of rice. All impact assessment categories were considered and the sensitivity analysis was performed to test the cut-off criteria set for the chemical input by increasing the solvent input to 15% and including trace amounts of heavy metals. Results from ReCiPe impact assessment methods concur that the top impact categories are rice plantation compared to rice milling and land preparation phase. These include climate change, eutrophication, ecotoxicology, and water depletion. As a result, it is concluded that the fertilizers used were excessive and should be examined further. The study concludes that the greatest impacts of rice production in a Muda Granary area in Kedah are from rice planting phase. It is learnt that the quantity of fertilizers used were excessive and must be looked into. The results of the study will likely provide a good basis for future LCA research on paddy cultivation, especially in terms of nutrient management.
... Apart from being the staple food for Malaysians, paddy serves as a primary income source for farmers and agricultural workers in Malaysia (Omar et al. 2019;Firdaus et al. 2020). An estimated agricultural land in Malaysia was 645,000 ha, used to cultivate the paddy (Akinbile et al. 2011). Since 2018, more and more lands have been developed for paddy farming in Malaysia to meet the country's high rice consumption demand (Malaysia Population 1950-20212021. ...
... Due to the heavy metals' nonbiodegradable characteristics, excessive use of agrochemicals, including lead (Pb), cadmium (Cd), and copper (Cu), causes environmental pollution and, more seriously, contamination of the paddy soil and grains themselves (Rudzi et al. 2018;Irshad et al. 2023). Using tainted irrigation water and soil for rice production is a problem since they contain heavy metals that can be transferred from the roots of the paddy into the grains (Akinbile et al. 2011). ...
As the Malaysian population grows, there is a high demand for rice, the main staple food in this region. This has caused the overuse of agrochemicals that contain heavy metals and the utilization of contaminated groundwater to increase paddy yield, posing a risk to humans. This study reviewed the accumulated heavy metals in paddy fields of Malaysia's Selangor, Kedah and Sabah states and further calculated the consumption risks of rice grains from the selected areas. The study revealed that paddy soil in Ranau Valley (Sabah), Kota Marudu (Sabah) and Tanjung Karang (Selangor) showed presences of Cu and Cd in high concentration, respectively, creating higher potential to be uptake by paddy roots. These findings also revealed that Ranau Valley (Sabah) paddy grains contained high Cu and Cd concentrations, while Sabak Bernam (Selangor) contained high Pb concentrations. Further, a higher Cd concentration was reported from the Ranau Valley (Sabah), while the higher Pb concentrations were reported from the samples collected from Sabak Bernam (Selangor), Tanjung Karang (Selangor) and Kubang Pasu (Kedah). Based on the health risk indices calculation in this study, carcinogenic and non-carcinogenic health risks in all study areas except in Kubang Pasu (Kedah) and Langkawi (Kedah) are likely to occur due to Cu mining activities, ultrabasic soil contamination, utilization of contaminated groundwater and rock phosphate fertilizer and vehicular emission. Regular assessment of heavy metal content and consumption risks of paddy is essential to ensure the paddy field is free from contamination and will help protect the ecosystem and human health.
... Rice (Oryza sativa L.) constitutes one of the most important staple foods of over half of the world's population and globally, it ranks third after wheat and maize in terms of production but first in terms of global consumption [1]. It is a globally important cereal crop and the primary source of food for more than 3 billion people living mostly in Asia and Africa. ...
... Some of the design considerations for the drip irrigation system are stated for clarity. The slope of the field was about 2% as estimated by Akinbile, et al. [1]. The soil type was also verified as sandy clay loam through standard laboratory tests. ...
Abstract
The study investigated performance effects of biochar concentrations and fertilizer types on drip irrigated upland rice
for two seasons. A Randomized Complete Block Design (RCBD) comprising of four levels of biochar application (0 t/ha, 5
t/ha, 10 t/ha and 15 t/ha) and four fertilizer types (Liquid Organic Fertilizer, NPK 15:15:15, poultry manure, and control)
with drip irrigation system and thrice replicated was conducted. Agronomic parameters such as plant height, stem girth
width, leaf area, number of leaves, yield and others were measured. Treatments NPKB15, PMB15 and LOFB15, in that
order, performed better than F0B15 and F0B0 in all the agronomic parameters in the two seasons. These parameters
also performed well according to the biochar concentrations - B15, B10, B5 and B0 in that order. Highest average yield
of paddy and processed rice of 6.31 t/ha and 6.20 t/ha in season 1 and 6.36 t/ha and 6.21 t/ha in season 2 respectively
were recorded in NPKB15 while liquid organic fertilizer recorded highest average rice yield of 3.51 t/ha and 2.54 t/ha in
season 1 and 4.55 t/ha and 4.08 t/ha in season 2 respectively in LOFB15. Lowest values were recorded in Zero Fertilizer
(control) in all parameters. There was at least 50% increase in paddy and processed rice yields in all the treatments
when compared to the control F0B0. NPK fertilizer at biochar concentration of 15 t/ha, which gave the best result. in rice
agronomic and yield responses is recommended as the best treatment for rice production.
Keywords
Desirability, Soil Improvement, Field capacity, Rice yield, Food security
... Rice is Asia's largest water user, accounting for more than half of all irrigation water demands [1]. In Malaysia, the largest freshwater withdrawal of more than 75% is for irrigation in the agriculture sector and is mainly confined to irrigated rice production [2]. ...
Continuously flooded rice systems are a major contributor to the greenhouse gases (GHG) emissions in the agriculture sector in Malaysia. Intermittent irrigation has been recommended to replace conventional rice water management to save water and reduce GHG emissions without compromising rice yields. This study was conducted in two growing seasons at Malaysia’s largest rice granary area to determine the effectiveness of different water management practices on conserving water, mitigating GHG and maintaining rice grain yields. Three water management treatments were continuous flooding (CF), saturated and wet conditions from transplanting to heading and flooding until maturity (S-F) and continuous saturated and wet conditions (CS). The results showed that S-F and CS reduced water inputs between 15.0-16.8% and 32.0-34.0% as compared to CF, respectively. Water-saving treatments mostly did not significantly affect the plant's physiological performance, plant growth parameters, growth rate, grain yield and yield parameters. The results indicated that soil saturated and wet conditions provided adequate soil moisture content for the plant’s requirement similar to flooding conditions. Maintaining soil at saturated and wet conditions during the vegetative stage reduced 24.18-39.76% of methane emissions. However, maintaining soil at saturated and wet conditions throughout the growing season reduced 34.52-55.08% of methane emissions. In conclusion, intermittent irrigation could be an effective adaptation technique for simultaneously saving water and mitigating GHG while maintaining high rice grain yields in rice cultivation systems.
... In Asia, where around 90% of rice is grown, the water problem poses a long-term threat to the viability of irrigated rice systems and food security. Therefore, there is a need for the development of more efficient irrigation methods [47][48][49]. AWD has gained popularity as a water-saving irrigation technique, offering increased WUE by reducing water input while potentially increasing grain yield. Several countries, including China, Vietnam, India, Nepal, Indonesia, and the United States of America, have successfully implemented AWD system. ...
Rice serves as a fundamental sustenance for approximately half of the global population, particularly in Asia. Nevertheless, the cultivation of rice demands a substantial water supply, and the challenges associated with water deficits have been exacerbated by irregular rainfall patterns induced by global warming. Consequently, there is a critical need to reassess irrigation techniques to effectively tackle these issues. In this comprehensive review, the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) method was employed to systematically explore literature on irrigation techniques aimed at fostering sustainable water management in rice cultivation systems. The primary components of the framework encompass water consumption and water-related characteristics, soil-related characteristics, and plant-related characteristics, encompassing relevant components and indicators. Two alternative irrigation methods, namely alternate wetting and drying (AWD) and saturated soil irrigation (SSI), have been proposed to enhance water use efficiency (WUE) in rice cultivation compared to traditional continuous flooding (CF). These alternative irrigation methods do not adversely affect rice yield, both quantitatively and qualitatively. Furthermore, these alternative irrigation approaches have the potential to mitigate greenhouse gas (GHG) emissions, particularly methane emissions, in rice production. This review underscores the significance of data on alternate irrigation systems, providing valuable insights for researchers and policymakers in formulating strategies that align at every level for practical implementation. This is crucial as it is relevant to multiple organizations and stakeholders. Moreover, in the face of inclement weather conditions resulting from climate change, the study's findings indicate that research on farmers' adaptation, plant stress, and resilience within the rice cultivation system is still in its nascent stages. This highlights the pressing need for further exploration and advancement in these areas to develop effective strategies for coping with the challenges posed by climate change. ARTICLE HISTORY
... Among other food crops, rice is arguably the most important crop for guaranteeing food security and tackling global poverty (Diagi et al. 2021). It is consumed by over 50% of the world's population (Akinbile et al. 2011;Seck et al. 2012;Rathna Priya et al. 2019). Rice is the second most consumed food item in Nigeria, accounting for approximately 10.5% of its caloric intake (Food and Agriculture Organization [FAO] 2019a) and 6% of household expenditure (Johnson et al. 2013). ...
The Nigerian government is committed to sustaining rice production to meet national demand. Nevertheless, political tension and climate-induced stressors remain crucial constraints in achieving policy targets. This study examines whether climate change and political instability significantly threaten rice production in Nigeria. First, we employed nonparametric methods to estimate the country's rainfall and temperature trends between 1980Q1 and 2015Q4. Second, we employed the autoregressive distributed lag (ARDL) technique to examine the effects of climate change and political instability on rice production. The results show that while temperature has an increasing pattern, rainfall exhibits no significant trend. The findings from the ARDL estimate reveal that rice production responds negatively to temperature changes but is less sensitive to changes in rainfall. In addition, political instability adversely affects rice production in Nigeria. We argue that Nigeria's slow growth in rice production can be traced back to the impact of climate change and political tension in rice farming areas. As a result, reducing the overall degree of conflict to ensure political stability is critical to boosting the country's self-sufficiency in rice production. We also recommend that farmers be supported and trained to adopt improved rice varieties less prone to extreme climate events while supporting them with irrigation facilities to facilitate rice production.
... In terms of fertilizer loading, the per-ha consumption of fertilizer was found, in 2003-2004, to be approximately 100.2 kg (http://www.fao.org/3/a0257e/A0257E05.html, accessed on 28 December 2022). India is considered to have the largest land area (about 44 million ha) occupied by rice cultivation, which contributes approximately 21% of global rice production [1]. About two billion people in Asia are considered to draw 61-70% of their energy requirements from rice and its derivative by-products (FAOSTAT Database, 2014). ...
Potassium (K) is a critical nutrient for crops, as it is a major constituent in fertilizer formulations. With increasing concentrations of K in agricultural soil, it is necessary to understand its movement and retention in the soil. Sub-surface modeling is an alternative method to overcome the exhausting and uneconomical methods to study and determine the actual concentration of K in soil. HYDRUS-1D is considered an effective finite-element model which is suitable for sub-surface modeling. This model requires the input of ground-station meteorological (GM) data taken at a daily timestep for the simulation period. It can be a limiting factor in the absence of ground stations. The study compares K predictions in surface and sub-surface soil layers under Boro rice cultivation obtained with the usage of different meteorological datasets. Thus, the main hypothesis of the study was to validate that, in the absence of GM data, satellite-based meteorological data could be utilized for simulating the K concentration in soil. The two meteorological datasets that are considered in the study included the GM and satellite-derived NASA-Power (NP) meteorological datasets. The usage of a satellite meteorological product at a field scale may help in applying the method to other regions where GM data is not available. The numerical model results were validated with field experiments from four experimental fields which included varied K doses. The concentration in soil was assessed at the regular depths (0–5, 5–10, 10–15, 15–30, 30–45 and 45–60 cm), and at various stages of crop growth, from bare soil and sowing, to the tillering stages. The concentration of K was measured in the laboratory and also simulated through the optimized model. The modeled values were compared with measured values statistically using relative root mean square error (RMSER) and Nash–Sutcliffe modeling efficiency (E) for simulating K concentration in the soil for the Boro rice cropping pattern with both GM data and NP data. The model was found most suitable for the 0–30 cm depth on all days and for all treatment variations.
... As a result, rice is one of the world's greatest water users as mentioned by Chapagain and Hoekstra (2011), as it is also the most important component of South Asian food composition and the world's most important crop. Akinbile et al. (2011) found that around 250 million hectares, or 17% of total agricultural land, is irrigated today, almost five times more than what was irrigated in the early twentieth century, contributing 40% to global paddy production. Agriculture yields are boosted by irrigation, and this helps stabilize the modern economy. ...
As water is essential for rice cultivation, growing more rice with less water can be a challenge. A water footprint (WF) is an inclusive measure of freshwater use that can be used to evaluate the impact of human water consumption on both water volume and distribution. In the present study, WF was opted as an indicator for direct and indirect water consumption calculation of rice production at Muda Area, which is the largest rice granary in Malaysia for five consecutive years from 2011 to 2015. The boundaries were set based on resource input and output within the Kedah River basin. A life cycle assessment (LCA) framework analysis was applied, and the WF efficiency of agricultural water resources was discussed to represent its upgrading units. In addition, the findings from this study were cohesively related to energy and food components. The paddy plantation assessment showed that a very large amount of fresh water around 2500 L/kg was used in the paddy plantation. This unique study is the first of its kind to assess the mediation effect of WF in the area between climate factors and crops among Muda irrigation schemes in Malaysia and determine sustainability. In a changing climate, this study illustrates how WEF factors interact with WF and has significant implications for food security, crop production, and malnutrition. This research is essential for knowledge purposes and agricultural development in Malaysia. Consequently, it can become the baseline for other agricultural activities in Malaysia.
The identified problem revolves around establishing the water requirements for rice seeding, growth, and maturity in hot climatic conditions. This study reviews the net water requirement for rice growth or production under various climatic conditions in the Cross River Basin. It was observed that the water requirement from seeding to harvest varies from location to location, maintaining a FAO range, as postulated by Brouwer et al., 1986, ultimately falling between 450mm to 700mm for hot weather.The methodology used for investigating the Net Irrigation Water Requirements for rice growth to maturity involves the application of New_Clim Location and CropWater software. These tools were utilized to compute Reference Evapotranspiration (ETo) and Crop Water Requirements (CWR) for the net irrigation water requirements of rice, respectively. The data were obtained from meteorological stations within the Cross River Basin. In rainfed conditions, no water stress is practically observed throughout the entire crop cycle, affirming that no irrigation system is needed in such a specific climate. This study uses data generated through New_LocClim as input into CropWat, which, among other factors, determines the net water requirement for rice growth and production. Consequently, the results obtained from the use of the CropWat model in determining rice water requirements for Obudu, Nkari, Ikom, and Ijegu-Yala were 633.7 mm, 397.9 mm, 303.0 mm, and 548.4 mm, respectively. The water requirement of only two locations, Obudu and Ijegu-Yala, fell within the FAO-suggested range of 450 mm to 700 mm (Brouwer et al., 1986) for hot climates, while Nkari and Ikom LGAs did not comply with Brower et al., 1986 postulation due to their location in a relatively less hot climate.
Rice contributes significantly to global food security and is a major food crop for half of the world’s population. Sixty-five traditional and improved rice genotypes were collected and grown in pot conditions to evaluate the presence of genetic diversity. Analysis of variance showed significant differences among the genotypes for all traits. The phenotypic coefficient of variation was higher than the genotypic
coefficient of variation for most of the traits. Correlation analysis revealed significant positive and negative correlations among the traits. Principal component analysis showed that the first two principal components of the considered traits pointed out a wide variation among the genotypes. The dendrogram of cluster analysis grouped 65 rice genotypes into eight clusters. Data from this study provide
the presence of sufficient genetic diversity among the traditional and improved rice genotypes which can be employed in future rice breeding programs for either varietal improvement or development of new varieties.
The ever-increasing demand and competition for the finite water resource worldwide call for more efficient use of water in
all sectors, including firstly agricultural food production. One important consideration is the existence of a limit to the
amount of biomass a crop can produce per unit of water consumed. This article analyzes the theoretical background and the
experimental evidence for the conservative behavior of the efficiency in water use by crops to produce biomass, i.e., biomass
water productivity (WPb), under variable environmental conditions. Particularly, WPb is approximately constant for a given crop species after normalization for evaporative demand of the atmosphere and air carbon
dioxide concentration. A stepwise scaling up approach, from leaf to canopy, is undertaken to underline the processes involved
at the different hierarchical levels of biological organization that lead to the conservative behavior of WPb. Starting at the leaf level, the basic gas exchange equations are outlined to demonstrate that the normalized photosynthetic
WPb at the leaf scale is proportional to the ambient CO2 concentration. New experimental evidence in support of that conclusion is presented for several C3 and a C4 crops. Additional factors are introduced to assess photosynthetic WPb at the canopy scale, including the extent of radiation capture and the role of respiration. The composition of biomass was
then considered in the analysis of WPb over a season. The paper highlights the need to normalize WPb for differences in climate, specifically, in evaporative demand of the atmosphere to extrapolate WPb values between climatic zones, and in atmospheric CO2 concentration to account for changes in CO2 with time, when looking at the past and into the future. Two procedures for normalization for differences in evaporative
demand are presented, and a procedure for normalization for changes in CO2 concentration is derived for the leaf scale and shown to be applicable to canopy scale. Some knowledge gaps and research
needs are pointed out and the potential offered by the near constancy of normalized WPb in crop simulation modeling is emphasized.
As the competition for the finite water resources on earth increases due to growth in population and affluence, agriculture
is faced with intensifying pressure to improve the efficiency of water used for food production. The causes for the relatively
low water use efficiency in agriculture are numerous and complex, including environmental, biological, engineering, management,
social, and economic facets. The complexity of the problem, with its myriads of local variations, requires a comprehensive
conceptual framework of the underlying physical and biological processes as the basis to analyze the existing situation and
quantify the efficiencies, and to plan and execute improvements. This paper proposes such a framework, based on the simple
fact that the overall efficiency of any process consisting of a chain of sequential step is the product of the efficiency
(i.e., output/input ratio) of its individual component steps. In most cases of water use, a number of process chains, both
branching and merging, are involved. Means to integrate the diverging and converging chains are developed and presented as
equations. Upscaling from fields to regions and beyond are discussed. This chain of efficiencies approach is general and can
be applied to any process composed of chains of sequential steps. Here the framework is used to analyze the systems of irrigated
and dryland crop production, and animal production on rangeland. Range of plausible efficiencies of each step is presented
as tables, with values separately for the poor and for the good situation of circumstances, management and technology. Causes
of the differences in efficiency of each step, going from water delivery to soil water extraction, transpiration, photosynthesis,
and conversion to crop biomass and yield, and to animal product are briefly discussed. Sample calculations are made to demonstrate
how modest differences in the efficiencies of the component steps are manifested as large to huge differences in the overall
efficiency. Based on an equation quantifying the impact of changes in efficiency of component steps on the overall efficiency,
it is concluded that generally, it is more effective to made modest improvements in several or more steps than to concentrate
efforts to improve one or two steps. Hence, improvement efforts should be systematic and not overly concentrated on one or
two components. The potential use of the same equation as the point of departure to optimize the allocation of economic resource
among the component steps to maximize the improvement in the overall water use efficiency is elaborated on. The chain of efficiencies
framework provides the means to examine the current levels of efficiency along the pathways of agricultural water use, to
analyze where inefficiencies lie by comparing with the range of known efficiency values in the tables presented, to assess
the potential improvements that may be achieved in various parts and their impact on the overall efficiency, and to aid in
the optimal allocation of resources for improvements.
Yields of dryland (rainfed) wheat in Australia have increased steadily over the past century despite rainfall being unchanged,
indicating that the rainfall-use efficiency has increased. Analyses suggest that at least half of the increase in rainfall-use
efficiency can be attributed to improved agronomic management. Various methods of analysing the factors influencing dryland
yields and rainfall-use efficiency, such as simple rules and more complex models, are presented and the agronomic factors
influencing water use, water-use efficiency, and harvest index of crops are discussed. The adoption of agronomic procedures
such as minimum tillage, appropriate fertilizer use, improved weed/disease/insect control, timely planting, and a range of
rotation options, in conjunction with new cultivars, has the potential to increase the yields and rainfall-use efficiency
of dryland crops. It is concluded that most of the agronomic options for improving rainfall-use efficiency in rainfed agricultural
systems decrease water losses by soil evaporation, runoff, throughflow, deep drainage, and competing weeds, thereby making
more water available for increased water use by the crop.
At present and more so in the future, irrigated agriculture will take place under water scarcity. Insufficient water supply for irrigation will be the norm rather than the exception, and irrigation management will shift from emphasizing production per unit area towards maximizing the production per unit of water consumed, the water productivity. To cope with scarce supplies, deficit irrigation, defined as the application of water below full crop-water requirements (evapotranspiration), is an important tool to achieve the goal of reducing irrigation water use. While deficit irrigation is widely practised over millions of hectares for a number of reasons - from inadequate network design to excessive irrigation expansion relative to catchment supplies - it has not received sufficient attention in research. Its use in reducing water consumption for biomass production, and for irrigation of annual and perennial crops is reviewed here. There is potential for improving water productivity in many field crops and there is sufficient information for defining the best deficit irrigation strategy for many situations. One conclusion is that the level of irrigation supply under deficit irrigation should be relatively high in most cases, one that permits achieving 60-100% of full evapotranspiration. Several cases on the successful use of regulated deficit irrigation (RDI) in fruit trees and vines are reviewed, showing that RDI not only increases water productivity, but also farmers' profits. Research linking the physiological basis of these responses to the design of RDI strategies is likely to have a significant impact in increasing its adoption in water-limited areas.
The spatial and temporal impacts of climate change on paddy irrigation water demands in South Korea have been modelled and mapped. The outputs from a general circulation model (HadCM3) for two selected scenarios (A2, B2) of the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) and for two time periods (2050s and 2080s) have been downscaled and applied to a baseline climatology (1961–1990) developed by the International Water Management Institute. A GIS was used to map spatial changes in irrigation water requirements.
The simulations showed that although future average rainfall is expected to increase substantially (25–53%), average effective rainfall will only increase slightly (2–8%), leading to only slight reductions in paddy irrigation requirements (−1 to −8%). Assuming cropping patterns and farming practices remain unchanged, total volumetric irrigation water demand decreases by 4–10%. However, the spatial variations are substantial.
Combining these results with previously forecast increases in the available water resources under the SRES A2 scenario, the ratio between available water resources and volumetric irrigation demand would increase significantly. However, most of the increased rainfall falls after the peak demand period. Potential adaptation strategies such as constructing more storage reservoirs can be considered where water shortages still occur. Copyright © 2010 John Wiley & Sons, Ltd.