Park, Edward

Rice serves as a crucial staple food crop for half of the world's population. In the Vietnamese Mekong Delta (VMD), rice production plays a vital role in national food security. However, the majority of the existing intensified rice cultivation schemes in the VMD, which are typically traditional, have rendered many farmers' livelihoods unsustainable due to issues such as land degradation, water pollution, health risks, and low profitability. Therefore, it is imperative to explore alternative sustainable farming systems. This study investigates the benefits of two ecological farming systems, specifically organic rice and rice mixed with lotus, as alternatives to conventional rice farming in the upper VMD floodplain province of An Giang. These two farming systems have demonstrated long-term socioecological and economic advantages. On the one hand, they allow the introduction of rice products to the market at more affordable prices. Additionally, they contribute to improved water quality, improved soil fertility, and increased biodiversity such as bird, fish, and plant species compared to traditional rice farming systems. Although we acknowledge that the availability of floodwater poses a significant constraint for alternative farming systems, the business opportunities and socioecological benefits associated with these systems outweigh the limitations. Our findings provide evidence that ecological farming practices that support rice cultivation represent promising alternatives to sustainable rice production, which can help mitigate vulnerabilities in intensified rice farming systems and can be scaled up for other floodplain provinces in the VMD and beyond.

Sand traps in irrigation networks are typically used in mitigating canal sedimentation. In irrigation networks located in basins of high sediment yield due to the presence of volcanoes, it is essential to assess the vulnerability of sand traps. Using sediment yield at irrigation scheme inlets, sand trap vulnerability can be evaluated. This study aims to understand the vulnerability of irrigation sand traps throughout the Progo–Opak–Serang (POS) Volcanic River Basin, Indonesia, via mapping the sediment yield distributions in the basin. We employed the Revised Universal Soil Loss Equation to estimate soil loss, where the results show that the average soil loss in the POS River Basin is 179.69 tons/ha/year that falls under the category of moderate erosion potential, while the average sediment yield for the whole basin is 51.04 tons/ha/year. Parts of the basin with high yields of more than 180 tons/ha/year were mostly found along the volcanic mountains such as Sindoro, Sumbing, Merapi, Merbabu, and Telomoyo, and the Menoreh Hills. The model demonstrated relatively high performance with R2, NSE, RMSE, and MAE of 0.89, 0.82, 0.14, and 0.11, respectively. Within the POS Basin, Badran, Kalibawang, and Blawong are the three most vulnerable irrigation sand traps, with sediment yield values of 252.83, 178.92, and 63.49 tons/ha/year, respectively; they are all located in sub-watershed outlets. The vulnerability assessment conducted in this study can be used for the decision support system to prioritize irrigation sand traps towards a more effective irrigation system development.

Large-scale sand extraction has had significant and compounding impacts on the riverine environment of the Vietnamese Mekong Delta (VMD). Yet, effective and targeted implementation of regulations and sustainable management remains hindered by scant data availability, limiting a comprehensive understanding of the delta's sand mining scale and extent. This study assessed recent intensifying patterns of sand mining activities in the VMD mainly based on extensive bathymetric surveys carried out across 800 km² of the VMD river channel from 2017 to 2022. Our results revealed severe riverbed deepening across the VMD, with the upper reaches of the Hau (Bassac) River experiencing an average incision of 1.4 m from 2017 to 2022, resulting in sediment losses of 127 Mm³. Similarly, the upper reaches of the Tien (Mekong) River and the Co Chien branch showed incisions of 1.3 m and 0.7 m from 2017 to 2020, accompanied by sediment losses of 139 Mm³ and 87 Mm³, respectively. The observed spatial and temporal variability in incisions, along with widespread sand mining pockmarks along the riverbed profiles, provide strong evidence of the significant contribution of sand mining to changes in riverbed morphology. The progressive lowering of riverbed elevation provides further evidence of the recent intensification of sand mining activities. Additionally, field surveys highlighted the proximity of perceived sites of bank collapse to pitted riverbeds, providing reliable indications of sand mining-induced erosion. Ultimately, we intend for this evidence-based assessment of sand mining activities in the VMD to contribute to informed quantitative assessments of sediment budgets and effective implementation of regulatory frameworks for sustainable sand mining in the future.