Adaptation to saline intrusion for agriculture farming transformation in the coastal Ben Tre province, Vietnam

This study aimed to evaluate the adaptive capacity (AC) of agriculture farming transformation to improve for the adaptability by saline intrusion of those culture systems in the coastal Ben Tre province. The primary data was collected by questionnaires in three coastal districts of Ba Tri, Thanh Phu and Binh Dai with 178 households to distribute on agriculture land use transformations. An Object-Based Image Analysis (OBIA) and multi-temporal image analysis approach was developed to detect how LULC changes during 2010-2020 in the coastal Ben Tre province using Landsat TM and OLI data. The MODIS (MOD09 8-day reflectance) data was processed into monthly NDVI maps with the Time Series Product Tool software package and then used to classify regionally common rice crops LULC types using unsupervised classification by ISODATA algorithm. Based on primary data collection, evaluating adaptation measures was assessed the compilation of modification options based on a detailed description and criteria including human, society, infrastructure and natural conditions by standardized a weight ranges of adaptive indicators in the agriculture land use changes. The results detected five agriculture land use transformation including rice-shrimp crop rotation to aquaculture, single rice crop to aquaculture, double rice crop to perennial plant/orchards, double rice crop to rice-shrimp crop rotation, and triple rice crop to double rice crop. The adaptability of these transformations conducted the shrimp-rice crop rotation to aquaculture in Binh Dai of strongly high adaptability. Next is followed by double rice crops to orchards and double rice crops to rice-shrimp crop rotation with high adaptability while the rice-shrimp crop rotation to aquaculture is only moderate in Thanh Phu. The low adaptability levels were identified on single rice crop to aquaculture and triple rice crop to double rice crop transformations due to tolerant condition of saltwater for rice crop cultivation. The studies results can further contribute to support adaptation planning in these sectors by using, developing and streamlining this framework to additional and different socio-ecological contexts.

Laboratory and Numerical Study of Saltwater Upconing in Fractured Coastal Aquifers

This study investigated the saltwater upconing mechanism in fractured coastal aquifers. Head-induced saline intrusion was initiated into three narrow sandbox aquifers containing individual horizontal discontinuities placed on different positions. Subsequently, using a peristaltic pump, freshwater was abstracted from the aquifers’ center, triggering saltwater upconing. Progressively larger pumping rates were applied until critical conditions, resulting in the wells’ salinization, were achieved. Advanced image analysis algorithms were utilized to recreate the saltwater concentration fields and quantify the extent of the saline wedges with a high accuracy. A numerical model was successfully employed to simulate the laboratory results and conduct a comprehensive sensitivity analysis, further expanding the findings of this investigation. The impact of the fractures’ length, permeability and position on the upconing mechanism was identified. It was established that the presence of high permeability discontinuities significantly affected aquifer hydrodynamics. The conclusions of this study could constitute a contribution towards the successful management of real-world fractured coastal aquifers.

The saline Interface of a Shallow Unconfined Aquifer, Rangitikei Delta

<p>The coastal communities of Tangimoana and Scott's Ferry have a long history of using shallow groundwater bores. The cumulative effect of pumping over decades could influence the saline interface given the close proximity of the communities to the seashore and river estuary. It is important to quantify the effects of pumping on both the shallow groundwater system and the dynamics of the saline interface. This is necessary to protect the groundwater system against saline intrusion especially given the increasing number of high volume groundwater consents to support dairying. Resistivity soundings and traverses, coupled with chemical analyses of groundwater samples, were found to be an effective method for defining the saline interface of the shallow groundwater aquifer under the Rangitikei delta. The saline interface extends from the salt marsh to beneath the farmland north of Tangimoana. The interface is a zone of diffusion with freshwater and brackish water mixing from the estuary. The interface is currently located on the outskirts of Tangimoana, and it is likely to extend beneath the township. The infiltration of brackish surface waters into sediments of the salt marsh form a surficial mixing zone that decreases with distance from the salt marsh. There is no indication of salinity in the area to the north of the Rangitikei delta. This area is most at risk of contamination from saline intrusion because of high volume groundwater abstractions, even though these abstractions are from deeper aquifers. The shallow groundwater beneath Tangimoana showed high concentrations of Ca and HCO3 ions. This may be a result of carbonate dissolution, which can occur when saline and freshwater mix. This creates groundwater that is under-saturated with calcium. The mixing water dissolves carbonates and increases the concentrations of Ca and HCO3. The major source of sodium and chloride was likely rainwater with evaporated solutes from seawater. The saline interface near Tangimoana appears to be relatively static, but the estuary and salt marsh are areas of low relief. There are preferential flows paths across the salt marsh to the farmland. These factors make the shallow groundwater in the Rangitikei delta vulnerable to saline intrusion.</p>

The saline Interface of a Shallow Unconfined Aquifer, Rangitikei Delta

<p>The coastal communities of Tangimoana and Scott's Ferry have a long history of using shallow groundwater bores. The cumulative effect of pumping over decades could influence the saline interface given the close proximity of the communities to the seashore and river estuary. It is important to quantify the effects of pumping on both the shallow groundwater system and the dynamics of the saline interface. This is necessary to protect the groundwater system against saline intrusion especially given the increasing number of high volume groundwater consents to support dairying. Resistivity soundings and traverses, coupled with chemical analyses of groundwater samples, were found to be an effective method for defining the saline interface of the shallow groundwater aquifer under the Rangitikei delta. The saline interface extends from the salt marsh to beneath the farmland north of Tangimoana. The interface is a zone of diffusion with freshwater and brackish water mixing from the estuary. The interface is currently located on the outskirts of Tangimoana, and it is likely to extend beneath the township. The infiltration of brackish surface waters into sediments of the salt marsh form a surficial mixing zone that decreases with distance from the salt marsh. There is no indication of salinity in the area to the north of the Rangitikei delta. This area is most at risk of contamination from saline intrusion because of high volume groundwater abstractions, even though these abstractions are from deeper aquifers. The shallow groundwater beneath Tangimoana showed high concentrations of Ca and HCO3 ions. This may be a result of carbonate dissolution, which can occur when saline and freshwater mix. This creates groundwater that is under-saturated with calcium. The mixing water dissolves carbonates and increases the concentrations of Ca and HCO3. The major source of sodium and chloride was likely rainwater with evaporated solutes from seawater. The saline interface near Tangimoana appears to be relatively static, but the estuary and salt marsh are areas of low relief. There are preferential flows paths across the salt marsh to the farmland. These factors make the shallow groundwater in the Rangitikei delta vulnerable to saline intrusion.</p>

Integrated statistical and hydro-geochemical approach to identify the origin and process of saline contamination of Remila plain groundwater (Khenchela, Algeria)

ABSTRACT Groundwater is widely used in the semi-arid region of Remila plain (Khenchela, Algeria) for urban and agricultural supplies. An integrated statistical and hydro-geochemical approach was performed with 70 water samples in order to identify the main processes and the origin of water salinisation. The results have suggested the dominance of three chemical facies: Sulphato cloruro calcic (SO4–Cl–Ca) in the northeastern part, Sulphato cloruro calci magnisian (SO–4Cl–Ca–Mg) in most of the waters andalkali-earth bicarbonate (HCO3–Ca–Mg) in the southeastern part. Although based on principal component analysis and hierarchical clustering analysis, the statistical approach identified three water groups: (1) saline water (17 %; total dissolved solids >1000 mg l−1 with the dominance of Sulphate (SO42−)); (2) moderately saline water (17 %) with a dominance of bicarbonate (HCO3−); and (3) moderately saline water (66 %) with mixed facies. The binary diagrams confirmed the predominance of three processes: evaporite dissolution and/or precipitation, combined by ionic exchange. In the northeastern part of the area, however, another process was detected – the saline intrusion of Sabkha water, favoured by extensive groundwater use.

Assessing impact of saline intrusion on rice cultivating area in Ke Sach district, Soc Trang province, Vietnam

This study was carried out to evaluate the effects of saline intrusion on agricultural activities, thereby proposing adaptation and mitigation measures for local people. Salinity was measured at 15 locations on the main and tributary rivers in Ke Sach district, Soc Trang province, Vietnam from January to September 2020. The method of direct interview with farmers was used to evaluate the knowledge and effects of saline intrusion on agricultural production. Salinity measurement results showed that salinity intrusion oc-curred and lasted from February to the end of May during the dry season (the Winter-Spring rice crop). During the rainy season (June-September), due to the large amount of water, salinity was only be-tween 0.01 and 0.1‰. However, the research has found significant effects in the Summer-Autumn rice crop due to the accumulation of salinity in the soil from the Winter-Spring rice crop, which reduces the rice yield by 10-30%. The interview results revealed that more than 80% of the farmers were aware of the effects of saline water intrusion. Local authorities also regularly organize seminars to disseminate basic knowledge to the community to minimize the risks and impacts of saltwater intrusion. The proposed temporary solutions include rainwater storage, maintenance of saline prevention sluices, construction of more water regulation canals, financial support, and strengthening of salinity monitoring stations. In order to adapt to the long-term salinity conditions, local authorities need to focus on researching changing cropping patterns, crop structure, using new rice varieties that are able to adapt to drought and salty conditions. Besides, there will be technical assistance, capital for people to adapt well to the saline intrusion situation.