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Assessing the effects of dike protection systems on rice cropping patterns and water quality in An Giang province, Vietnam
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| Title: | Assessing the effects of dike protection systems on rice cropping patterns and water quality in An Giang province, Vietnam |
| Other Titles: | ベトナム、An Giang省における稲作パターンと水質に対する堤防保護システムの影響の評価 |
| Authors: | HUYNH, VUONG THU MINH Browse this author |
| Keywords: | Water quality parameters | | multivariate analysis | | rice phenology | | water infrastructure | | rice cropping pattern mapping | | SAR backscattering |
| Issue Date: | 25-Sep-2019 |
| Publisher: | Hokkaido University |
| Abstract: | The Vietnamese Mekong Delta (VMD)is one of the largest rice-growing areas in Vietnam, andexports a huge amount of rice products to destinations around the world. Rice is grown under the irrigated triple and double-rice cropping systems,andalso under the rain-fed single-rice cropping systemin the Vietnamese Mekong Delta (VMD). These rice cropping systems are adopted according to the geographical location and water infrastructurein place. Dike-protection systems have been built to prevent floodingin orderto support agricultural intensification since the early 1990s. Thus, double and triple-rice cropping systems have been dependenton the semi-and full-dikesystems. However, only a small number ofstudies have been conducted to evaluate the effects of rice cropping system on water quality in the context of dike development. This study aimed to value the impact of dike systemon spatio-temporal variation of surface and ground water quality. We used multivariate statistical analyses andgroundwater quality index based onFuzzy-AHP with the Triangular Fuzzy Number method. The LULC was generated using Support Vector Machine (SVM) classification of Sentinel-1A data. Weconducted fieldworkin An Giang province of the VMD, from March 2017 to March 2018.The overall accuracy of the classification was 80.7% with 0.78 Kappa coefficient. Therefore, Sentinel-1A can be used to understand rice phenological changes as well as rice cropping system distribution using radar backscattering. The assessment of surface water quality results show the mean concentrations of COD, NH4+, NO3-, PO43-, EC, and turbidityin surface water inside full-dikeas compared tooutside full-dikeand inside semi-dikein both seasons. Moreover, surface water located in secondary canal inside full-dike system was considered as "hotspot" surface water quality with low GQWI unit. Besides, the high concentrations of PO43-were detected in most of the primary canals where residential areas and local markets settled leading to increase PO43- concentration; However, NO3-was mainly found to be higher in secondary canals where chemical fertilizers used for rice intensification inside dike-system were increased. The effect of dike system ongroundwater quality was not very clear in this studysince groundwater quality depends on characteristicsof aquifersand unused well management. Dikeinfrastructures are useful for preventing flooding; however, changes in cropping system have resulted which adversely affect maintenance and surface water qualityand challenging task for the protection of ground water quality in the long-term in the study area. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第13740号 |
| Degree Level: | 博士 |
| Degree Discipline: | 環境科学 |
| Examination Committee Members: | (主査) 准教授 藏崎 正明, 教授 沖野 龍文, 教授 渡邉 悌二, 助教 Ram Avtar, 名誉教授 大崎 満 |
| Degree Affiliation: | 環境科学院（環境起学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/77151 |
| Appears in Collections: | 課程博士 (Doctorate by way of Advanced Course) > 環境科学院(Graduate School of Environmental Science)
学位論文 (Theses) > 博士 （環境科学）
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