Sustainable rice cultivation in the deep flooded zones of the Vietnamese Mekong Delta

Abstract

Abstract:This paper explains how the management of the full-dyke system in the deep flooded zones of the Vietnamese Mekong Delta affects rice cultivation, and outlines how alternative dyke management strategies could offer more sustainable adaptations in the face of future environmental threats. The current management of the 'full-dyke' network has been successful in promoting triple-cropping rice cultivation, but this practice has prevented sediment deposition on the land surface. River-borne sediments deposited on the delta land surface have high economic value because they are (i) rich in nutrients (potentially 26 million USD/yr of free fertiliser to An Giang Province) and can (ii) help to maintain the Mekong Delta land above sealevel. Without a continuing supply of sediment to the delta, triple-cropping paddies may not continue to be sustainable or profitable for the majority of rice farmers over the next 10 to 20 years. The economic value of sediment as a free fertiliser is particularly important to poor farmers, as without sediment, they run a significant risk of debt due to fluctuations in rice, fertiliser, and other input prices. With incoming loads now declining, sediment must be managed carefully as a resource. Our projections show that the best use of the remaining sediment resource can be achieved by allowing full paddy flooding only in years of high sediment potential, and this would greatly increase the sustainability of rice agriculture in the face of future environmental change. This recommended policy is an option with few regrets, in that its other benefits include maximising groundwater replenishment, ensuring freshwater availability during drought periods (including countering salt water intrusion), cleansing rice paddies of pests and disease, and tempering downstream flooding. If triple-rice-cropping continues to have priority, financial support will particularly be needed to provide help to poorer farmers coping with increases in artificial fertiliser prices.

Impact of water resources variation on winter–spring rice yield in the upper Vietnamese Mekong Delta: A case study of An Giang Province

“…Therefore, the agricultural sector has to spend more money on providing nutrients to the soil (People's Committee of An Giang Province, 2021). This result is also in line with a study indicating that changes in flood water level affect nutrients for the VMD and An Giang Province, and nutrients available from flood water potentially have a value of 26 million USD per year of free fertilizer to An Giang Province (Bui & Nguyen, 2021; Chapman et al, 2017).…”

Disentangling the concepts of global climate change, adaptation, and human mobility: a political-ecological exploration in Vietnam’s Mekong Delta

“…A minority, yet growing amount, of studies no longer solely ascribe changes in the region to climate change, but to broader changes, including land-use challenges, government policy, geopolitical relations, and transboundary water governance issues (Tran, 2020b). The studies establish links between (out)migration and failure to adapt to agricultural intensification (Chapman et al, 2017), land-use change and lack of employment opportunities (Tran, 2019;Tran & James, 2017, and government policy (Danh & Mushtaq, 2011). On the other hand, we found that the majority of the studies (61%) still established a direct relationship between environmental or climate risk and human mobility.…”

Anthropogenic sediment starvation forces tidal dominance in a mega-delta

“…Delta subsidence, driven by compaction of sedimentary strata 13 , is also being accelerated due to increased rates of ground water extraction 14,15 . Furthermore, many large deltas are also sediment starved 16 due to major reductions in the supply of fluvial sediment caused by upstream dam construction 17,18 , rapid and accelerating sand mining 19,20 , and the construction of flood embankments 12,21,22 . Such sediment starvation potentially compromises the ability of deltas to offset rising sea-levels through sediment deposition 1,23 .…”