Negative externalities from agriculture have critical impacts on the environment in tropical regions, particularly in Asia. Pervasive agricultural system has major influences on land, water, and climate through intensified land degradation, sedimentation, and water contamination problems, as well as increasing the frequency and severity of natural disasters (e.g., landslides and floods). They also affect environmental services such as carbon sequestration, and biodiversity. In order to mitigate these issues, payment for environmental/ecosystem services (PES) is highlighted as an alternative approach to compensation mechanisms with high potential for environmental recovery not only for local areas/users but also for climate change adaptation. We will conduct a reliable research in which human actions are seeking better economy through agriculture, and considering the planning and dissemination of technology developments that incorporate the three factors of water, food production and energy at the basin level. Accordingly, we will establish the continuity of a framework for pursuing a proper research. We will also prepare an infrastructure for water, food, and energy which is an absolute prerequisite to the development of an environmentally advanced basin model in Asia. To carry out this central challenge, we will collaborate with many organizations such as universities, national institutes, and ministries in Asian countries. This special issue is published as examples of study on “Development and dissemination of environmentally advanced basin model in Asia”. We hope this issue will help more people to understand the importance of these studies.
Food security has become a serious concern recently in Southeast Asia. The reduction of agricultural land because of economic development is decreasing the food supply. Simultaneously, due to rapid population growth, the food demand is increasing. Therefore, to ensure a stable food supply, it is important to estimate the supply capability of rice, which is the staple food in most Asian countries. In this study, a crop model (SIMRIW-RS) that can combine remote sensing data with a crop model (SIMRIW) was used to estimate rice yield at a regional scale. This model was applied to the estimation of rice yield in paddy fields located in the suburbs of Vientiane, Laos. Satellite (COSMO-SkyMed)-derived data for leaf area index (LAI) were integrated into SIMRIW-RS, and the transplanting date detected by COSMO-SkyMed was used to set the starting date of the simulation. Results were verified by surveying farmers. Transplanting dates were detected with high accuracy in all but a few fields. On the basis of the results of regression analysis between actual LAIs and the corresponding backscatter coefficients of COSMO-SkyMed, we suggest that COSMO-SkyMed can estimate LAIs at early growth stages when LAI is small. The results of yield estimation after integrating the LAIs derived from COSMO-SkyMed data into SIMRIW-RS indicated that the estimation accuracy of the rice yield was improved compared with the estimation result without adjusting parameters in the model, and this held so long as LAI was retrieved with high accuracy by satellite data. However, when LAI could not be estimated accurately, integration has the potential to worsen the model’s accuracy compared with the estimation result without any such readjustment. This study therefore indicates that SIMRIW-RS has the potential to estimate rice yield accurately when the LAI of rice is estimated with high accuracy from satellite data.
To evaluate rice production and management on a regional scale, a simulation model combined with remote-sensing is recommended. This study aimed to develop a simulation model for use with remote-sensing (SIMRIW-RS) to evaluate the field-to-field variation in rice production on a regional scale. This model was developed based on a simulation model for rice weather relations called SIMRIW and its derived models. The model consists of 6 components (water budget, nitrogen uptake, phenological development, leaf area index (LAI) growth, dry matter production and yield formation) and has 2 representative field parameters and 5 representative cultivar parameters. The parameters that were determined with the data from previous field studies seemed to be reflected with field and cultivar characteristics, and differences in the rice growth and production among the fields and cultivars were well explained by the model. The application of the model on a regional scale using remote sensing is discussed.
Rice is the most important crop in Lao People's Democratic Republic (Lao PDR). The improvement of its productivity is strongly recommended, but information about its growth characteristics in farmers' fields is limited. This study evaluated the dynamics of the leaf area index (LAI) and analyzed the relationship between the rice productivity and soil in farmers' fields in Vientiane province, Lao PDR. Because the LAI in the farmers' fields increased almost linearly, a straight-line regression was used for the analysis. The rice yield in the farmers' fields ranged from 63.8 g m-2 to 411.8 g m-2 and correlated with the LAI during the later growth stage. The variability in the LAI was explained by the LAI growth rate but rarely by the effective accumulated temperatures from the estimated transplanting date. The LAI growth rate was associated with the nitrogen and carbon content in the soil. These results suggest that the rice productivity in farmers' fields is governed by the soil fertility through LAI growth, and that LAI monitoring is an effective tool to evaluate the production.
The recent rapid population and economic growth in Southeast Asia has brought about drastic socio-economic changes, such as urbanization and an agricultural shift. Urbanization consists of concentrating a population from a rural to an urban area and expanding urban areas, which pushes farmland outward. The current development diagram generates and accumulates disaster risk as an extensive risk; however, the relationship between developmental progress and the increase in disaster risk must be determined for sustainable development to be achieved. We assessed the effects of land-use changes driven by economic growth on sedimentation in a river reach of the upper Citarum River basin in Indonesia. The land-use changes in the 20 years from 1990 to 2010 were driven by economic growth and urbanization around Bandung city and are typical for Southeast Asia. Urbanization was characterized by expansion of the urban area, replacement of paddy fields, and cultivation of forest into upland fields for cash crops. As a result, sediment runoff from the hillside to the plate increased from 0.17 Mton year-1 to 0.24 Mton year-1, and sediment deposition on the plate increased from 0.11 Mton year-1 to 0.13 Mton year-1.This amount corresponded to about 30% of the sediment dredged for flood control in 2013. These results indicate that the land-use changes had a direct impact on humans under the heavy rainfall and a wide plate with steep hillside characteristics of Southeast Asian islands. We revealed the relationship between developmental progress and increased disaster risk. The results suggest that forest cultivation and the increased flood risk in the urban area were directly connected through land-use driven by rapid economic growth and urbanization.
Human population growth has led to increases in energy and food production, use of fertilizers, and wastewater flows. Enhanced availability of nitrogen is a cause of eutrophication of rivers, lakes, and estuaries worldwide. In this study, Citarum River Basin, West Java, Indonesia was selected as a target area, supplying 80% of domestic water to Jakarta Metropolis. Meteorological and hydrological data from 1996 to 2009, and spatial data such as topography, land use, soil properties were collected for model simulation. Conceptual nitrogen balance model, which has three nitrogen pools, was developed and combined with rainfall runoff model. Proposed model was applied to the Citarum River Basin and simulated river discharge and nitrogen load in 1 km×1 km resolution to check the model applicability. By using the model, spatial distribution of nitrogen loading in whole basin level was estimated and histograms of nitrogen load from different land use also evaluated. The results provide a first insight into the magnitude and the spatial distribution of nitrogen loading in Citarum River Basin.
Many of the water sources in Lao PDR are used for drinking and other domestic purposes. There are few reports on the domestic water availability in Lao PDR, which is composed of quality and quantity. The aim of this study was set to determine actual domestic water use and quality conditions during the rainy season in Vientiane, Laos to reveal seasonal variations in domestic water quality. In the target region, the supplied water and the deep and shallow well water were used for the domestic water sources. The different sources were taken depending on the purpose. On the whole, the quality of the supplied water was much better than that of the deep well water, which contrasted with the residents’ understanding. The quality of the shallow well water varied in the rainy season due to a dilution effect on many items except NH4+, TP, PO43- and coliform bacteria. Some shallow well with a very high NH4+ concentration implied contamination from a leaking sewer through the groundwater. The shallow well water used in the kitchens of some households may have bad health effects because of coliform contamination.