Abstract. Soil loss due to surface erosion has been a global problem not just for developing countries but also for developed countries. One of the factors that have greatest impact on soil erosion is land cover. The purpose of this study is to estimate the long-term average annual soil erosion in the Lam Phra Phloeng watershed, Nakhon Ratchasima, Thailand with different source of land cover by using the Universal Soil Loss Equation (USLE) and GIS (30 m grid cells) to calculate the six erosion factors (R, K, L, S, C, and P) of USLE. Land use data are from Land Development Department (LDD) and ESA Climate Change Initiative (ESA/CCI) in 2015. The result of this study show that mean soil erosion by using land cover from ESA/CCI is less than LDD (29.16 and 64.29 ton/ha/year respectively) because soil erosion mostly occurred in the agricultural field and LDD is a local department that survey land use in Thailand thus land cover data from this department have more details than ESA/CCI.
Soil erosion plays a vital role in reducing reservoir capacity. The Lam Phra Phloeng (LPP) dams were built for flood protection and irrigation. However, they have experienced reservoir sedimentation, and the capacity of the reservoir has decreased. The surrounding soil surface was easily eroded and transported by heavy rainfall and surface runoff to streams and eventually into the reservoir. Understanding this soil erosion and sedimentation is necessary for preventing further decline of reservoir capacity and water management. This research aims to estimate long-term average annual soil erosion and predict sediment yield in the reservoir due to climate change. The methodology is determined soil loss parameters and sediment yield using the Universal Soil Loss Equation (USLE) with the Sediment Delivery Ratio (SDR). The USLE and SDR methods differed from field data, with an average absolute error of 4.0%. The Global Climatic Model, Institute Pierre Simon Laplace-Climate Model version 5A (IPSL-CM5A-MR), with Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5, was downscaled and analyzed to forecast future rainfall in the watershed. The high intensity of rainfall contributed to higher soil erosion, in RCP 8.5. Interestingly, the high and very high-risk areas increased, but the moderate risk area declined, indicating that the moderate risk area should be a priority in land management. However, the heavy rainfall and high slope gradient led to a slight increase in the soil erosion in some areas because the land covers were evergreen and deciduous forest. The prediction of sediment yield was positively correlated with the intensity of rainfall in the central part of the watershed, because the rainfall and runoff led the sediment to the river and streams, indicating that the land cover should be managed to prevent capacity decline.
Although useful in flood prevention and as the source of water for irrigation and consumption, reservoirs could nevertheless not merely create negative social impacts for those living near them but also wreak havoc on the environment following their construction. These environmental and social impacts should be addressed especially in the Northeastern part of Thailand where their history revolving in salt mines and traditional salt production. The attitude questionnaires were used in this study to assess the impacts of a reservoir operation in a saline soil area on the social changes in 8 aspects. It was found, based on more than 160 replied questionnaires, that even if most respondents saw that the reservoir improved their standard of living in several aspects, a number of the respondents expressed concerns that their traditional way of life and ancient salt production method were disappearing. These people did express their concerns for their own safety, their worries about their community future, and hopes for better future of their own and that of their children.
This research has investigated the geotechnical properties of abandoned open pits in Thailand’s eastern province of Chachoengsao that could become targets for illegal industrial waste dumping. Out of a total of 11 districts, this research focuses on two districts, i.e. Plaengyao and Panom Sarakarm, due to the proximity to industrial estates and abundance of open pits. The findings reveal a very low permeability rate of Plaengyao’s surface soil, indicating that no open pits should be used as dumping sites as contaminants are captured by and deposited in the surface soil. Clay liner and surface drainage are needed to be considered for Landfills in Plaengyao district. In contrast, the surface soil of Panom Sarakarm district is of high permeability and thereby renders the utilization of open pits environmentally harmful since the dissolved contaminants can leach through the ground and pollute groundwater.
There are numerous water resource development projects in the Nam Kam River Basin of Nakhon Phanom province in the northeastern part of Thailand. The Nam Kam River Basin is one of the Greater Mekong’s tributaries and covers an area of approximately 3,440 square kilometers. The operation of the development projects situated along the basin must be in a manner that avoids salt solution diffusing into the nearby areas and protects the existing irrigation systems and reservoirs from large amounts of salt seepage. Since saline soil, salt crusts and ancient land salt pits have been found on the ground surface of the Nam Kam Basin, the purpose of this research is to investigate the saline areas by interpreting the satellite images. The interpreted satellite images were mapped and the results were validated against the actual field data. The salinity of soil and water was measured by the electrical conductivity meter and laboratory testing. The preliminary investigation of the study area showed two groups of the saline areas: saline soil spots and ancient land salt pits. Certain difficulties remained in the interpretation of the satellite images, such as the inability to classify the degree of salinity with accuracy and the outdated data in the areas with human involvement. The saline soil spots occupied by landowners are mostly improved for agriculture; on the contrary, the ancient land salt pits are operated only by a few villagers during the summer. Even though in summer 2012, the local office of Royal Irrigation Department flooded the ancient salt pits to protect them from salt farming, the villagers continue producing salt, thereby causing salinity to spread more widely. The study reveals that monitoring of salinity of the water and soil is necessary and is currently carried out jointly by academics, the local community, and agencies responsible for the irrigation projects in the study area.
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