The agricultural sector is a major freshwater consumer and around 70% of the world’s freshwater withdrawal is for irrigation [1
]. Although irrigated agriculture constitutes only 20% of the total cultivated land, it contributes around 40% of the total food produced worldwide because irrigation can help increase yields of most crops [4
]. Demand for freshwater has been increasing continuously with growing world population and economic development. It is anticipated that water withdrawal, especially for agriculture, will increase by 50% in developing countries by 2025 (base year 2000), and 18% in developed countries [5
]. The World Water Development Report (WWDR) has also reported that the global water consumption of agriculture is predicted to increase by 19% or to reach to 8515 km3
per year by 2025 [3
]. Moreover, the water shortage is further exacerbated by the increase in variability of water distribution due to the impacts of climate change. Hence, water resource management is an essential issue for satisfying the increasing demand of agriculture with rising population and consequent increased demand of food. In addition, the proliferation of bioenergy and biofuels derived from crops promises to increase stress on water, an already scarce resource in many countries. This is of particular concern to Thailand, which has a large agricultural base for food for local consumption and export as well as for feed and biofuels.
Thailand is recognized as one of the leading countries in agricultural commodities’ exports. Since the country’s climate is tropical, i.e.
, exhibiting hot and humid conditions throughout the year, a variety of crops, fruits as well as perennial trees can be grown nationwide. The agricultural sector shared about 12% of GDP and accounted for 38% of the total employment of the country [6
]. Thailand is ranked as the world’s 6th largest rice (paddy) producer but the 3rd largest rice exporter. Thailand is also the world’s largest cassava producer and exporter contributing about 70% of the world market share. It is the second leading sugar exporter though still relatively small as compared to the outstanding sugarcane producer Brazil. In addition, Thailand is also the key producer of the other agricultural commodities, e.g., palm oil, natural rubber, maize, beans, fruits and vegetables [7
]. The promotion of biofuels derived from domestic feedstocks, e.g., cassava, sugarcane and oil palm by the Royal Thai Government over the past decade has spurred the demand for energy crops which in turn could lead to the increased competitive pressure on water resources in some regions since the freshwater resource is unevenly distributed along the country. Thus, the information regarding water resource availability and crop water requirements in each region across the country is essential for water resource planning to satisfy the increased demand for food, feed, and biofuels production in the future.
Water footprint (WF) has been introduced as a method to indicate the water use and impacts of production systems on water resources measured as the total volume of freshwater used to produce products [8
]. WF divides the water use into three components, i.e.
, green, blue and grey water which are specified geographically and temporally [10
]. The green water footprint refers to the volume of rainwater consumed during the production process of a product. This is particularly important for agricultural and forestry products, where it refers to the total rainwater evapotranspiration plus the water incorporated into the harvested crops and wood. Blue water footprint refers to the volume of surface and groundwater consumed (evaporated and incorporated) into the production of a product. Grey water footprint refers to the volume of freshwater required to assimilate the load of pollutants based on existing ambient water quality to comply with the defined water quality standards [11
]. The concept of green and blue WF assessment has been widely applied in many studies concerning water use, especially for food and agricultural products [12
]. WF analysis has led to a better understanding of the virtual water requirement of agricultural products which can in turn be used to evaluate the implication of agricultural trade. In addition, green/blue and direct/indirect WF distinctions can help the identification of “hotspots” linking the water use and the source of water.
Nevertheless, focusing only the volumetric WF indicator does not directly provide information on the actual impacts of water use [16
]. This is because the impacts of water use in regions of water abundance cannot be directly compared to water use in regions of scarcity. It is necessary to consider the water scarcity or water stress issues at the point of water use which will generally vary based on a number of factors, e.g., geographical and climate conditions, environmental, social, economic and political factors [17
]. To date, a number of metrics have been proposed to assess and map the geography of water scarcity globally. These include, for example, indicators based on human water requirements, the ratio of population to the renewable water supply, and the most common one, the ratio of total annual freshwater withdrawal to hydrological availability or namely “Withdrawal-to-Availability” (WTA) [18
]. Water scarcity assessment methodologies have been further developed for more accurate assessment of global water scarcity and for the assessment of water use impacts especially those combining WF and hydrological water availability, e.g., blue water footprint scarcity [19
], water stress index [20
] as well as some others proposed in the life cycle assessment (LCA) community [21
For Thailand, the studies on WF and the impact assessment of water use by combining WF and the water stress index are still in the preliminary stage. There have been some studies in the recent past evaluating the volumetric water consumption of field crops, e.g., sugarcane, cassava and maize [25
]. However, those studies are site specific and lack consideration of the impacts of water use due to the different water scarcity situation in each region. This study therefore aims to (1) assess the water footprint of ten staple crops for food, feed and fuel production in Thailand by considering the country-wide scale; and (2) evaluating the water stress situation in different regions and watersheds of Thailand and the water deprivation from those ten crops in Thailand. The results from the combination of water footprint and water stress assessment are used to recommend the appropriate measures for enhancing water resource use and efficiency for future food, feed, and fuel crops production in Thailand.
2. Staple Crops Cultivation in Thailand
Agricultural land accounts for around 41% of the total land area of Thailand or about 21 million hectares [7
]. Thailand is divided into five regions including North, Northeast, Central, East, and South covering all 76 provinces. The cultivation patterns and water use by the staple crops in different regions will be different depending on their respective geographical and climate conditions. Table 1
shows the planted areas of the ten studied crops classified by regions. Rice is grown nationwide and has the largest plantation area covering around 70% of the plantation areas of the total ten studied crops. Rice can be classified into two types, i.e.
, major and second rice. Major rice refers to the rice grown during the wet season (i.e.
, May–October), while, the second rice refers to the rice grown in the dry season (November–April). The largest major rice plantation areas are in the Northeastern region. However, they do not have second rice due to the lack of irrigation system. Second rice is mainly grown in the North and Central regions which are well irrigated. In addition, the Northeastern region is also the main region for cultivation of field crops like cassava and sugarcane. Oil palm is widely grown in the Southern region where the climate is rainy and humid. This region has about 86% of the total oil palm plantation areas of the country. Figure 1
shows the actual cropping calendars for the various crops in different regions of Thailand. This will be used for the calculation of crop water requirement. The dry and wet seasons have been defined by the Royal Irrigation Department (RID) as running from November through April and May through October, respectively.
Plantation areas of the 10 studied crops classified by region.
Plantation areas of the 10 studied crops classified by region.
|Studied crops||Plantation areas in 2011 (hectare)|
The proliferation of food, feed, and biofuels derived from crops promises to increase stress on water in Thailand which has a large agricultural base for food for local consumption and export as well as for feed and biofuels. The study combined the water footprint and water stress index of different regions and watersheds of Thailand to determine the crop water requirement, irrigation water requirement and water deprivation in different regions and watersheds of the country. The water requirements for growing the ten staple crops in different provinces, regions and watersheds across the country have been evaluated. The results indicated that per hectare, the perennial trees like oil palm, pineapple and coconut have higher water footprint as compared to the field crops like rice, maize, cassava and sugarcane. However, per ton of crop, mungbean has the highest water footprint, followed by the oil palm, coconut, peanut and rice, respectively. Nevertheless, there are huge variations of the water footprint or crop water requirement from crops grown in different regions due to climate and geographical conditions. Cultivation of mungbean requires the highest amount of irrigation water followed by soybean, peanut, oil palm and second rice, respectively.
Based on the current cropping system of Thailand, the Northeastern region needs the highest amount of irrigation water. Rice (paddy) farming requires the highest amount of irrigation water, i.e., around 10,489 million m3/year followed by maize, sugarcane, oil palm and cassava. The key provinces that require a high amount of water for staple crops cultivation are Nakhon Ratchasima, Khon Kaen, Nakhonsawan, Suphanburi and Prachuapkhirikhan. The results from impact assessment of water use for crops cultivation indicated that major rice cultivation bring about the highest water deprivation, i.e., 1862 million m3H2Oeq/year; followed by sugarcane, second rice and cassava cultivation with about 944, 925 and 598 million m3H2Oeq/year, respectively. The watersheds that have the highest risks on water competition due to the crops production are the Mun, Chi and Chao Phraya watersheds. The high risks come from the second rice cultivation. For biofuel crops, sugarcane cultivation is the major source of water stress in Mun, Chi and Thachin whereas cassava causes high water stress in Mun, Chi and East Coast Gulf watersheds. Recommendations have been proposed for reducing crop water demand and for sustainable crops production in the future of Thailand.