Impact of seawater intrusion control on the environment, land use and household incomes in a coastal area

Abstract

Agricultural production in the coastal wetlands of Asia is often hindered by salinity intrusion caused by tidal fluctuation. This paper reports changes in environmental and socio-economic conditions that followed the phased construction and operation of sluices for controlling seawater intrusion from 1994 -2000 in a coastal area of the Mekong River Delta, Vietnam. Canal water salinity decreased rapidly upstream of sluices, allowing rice cropping intensification and increased rice production in the eastern part of the study area. However, the livelihoods of farmers in the western part were adversely affected due to cessation of supply of brackish water that was needed for brackish-water shrimp farming, while the acid sulphate soils present there posed problems for rice cultivation. The poor farmers and landless people suffered more because the fishery resource that they depended on declined sharply due to reduced salinity and increased acidity in the canal water. The findings confirmed that the environment and resource use in the coastal lands are very sensitive to external intervention. A clear understanding of the socio-economic and environmental impacts of salinity control measures in coastal areas can help planning to enhance farmers' incomes while minimizing negative environmental impacts. Land-use policy formulation, planning and management should adopt a more holistic approach, taking into account the interests of all resource users, especially the poor, instead of focusing on any particular sector.

Large Scale Electrical Resistivity Tomography Survey Correlated to Hydrogeological Data for Mapping Groundwater Salinization: A Case Study from a Multilayered Coastal Aquifer in Rhodope, Northeastern Greece

“…The overexploitation of groundwater resources in coastal aquifers, along with the subsequent saltwater intrusion, result to the degradation of the natural ecosystems (Ranjan et al, 2006), with severe socioeconomic effects on local communities, through the decline in freshwater availability and the reduction of agricultural productivity (Beltran, 1999;Tuong et al, 2003;Pisinaras et al, 2010). Therefore, the need for a thorough aquifer system description and continuous quality monitoring is crucial in every coastal zone, in order to construct a sustainable groundwater management scheme and to implement appropriate regulatory policies.…”

Regional Consequences of Seawater Intrusion on Rice Productivity and Land Use in Coastal Area of the Mekong River Delta

“…While indicators such as duration of salinity exceeding a threshold value or maximum salinity during the period have been widely used for evaluating the intensity of seawater intrusion 14,18 , the former may have an instantaneous abnormal value potentially, and the latter requires a threshold of salinity optionally and the available data to evaluate was only 6 months. On the other hand, the average salt concentration is the simplest index among them but is strongly correlated with these indices (Figs.…”

“…Since the early 1990s, in response to intensive demand for rice by government policy, the government started to build a series of sluices that could be closed at high tide to protect the paddy area from seawater intrusion and an improved canal network to increase the supply of freshwater from rivers 18 . Such improvements in the hydrological infrastructure made it possible to produce two or three rice crops per year using high-yielding varieties with short growth durations.…”

“…Seawater intrusion caused by tidal fluctuations and low river-water levels is considered to be a major constraint to agricultural production in coastal areas 18 . This is particularly the case in delta regions with large lowland plains facing the sea.…”

Evolutionary social and biogeophysical changes in the Amazon, Ganges–Brahmaputra–Meghna and Mekong deltas

“…Rice cropping systems in the Mekong delta have shown signs of stress in response to an increasing number of severe floods, droughts, storms and tropical cyclones, followed by growing population demand for food production (Lusterio 2009;Nguyen 2011;Berg and Tam 2012;Huysveld et al 2013;Son et al 2013;Ahmed et al 2014). Food production systems are rapidly expanding into the flood and salinity-intrusion areas (Tuong et al 2003;Kotera et al 2014), as a result of engineering works aimed at protecting populations and infrastructure from storms, rice cropping systems and shrimp farms from saltwater intrusion (Berg et al 2012;Nguyen et al 2014). The construction of several large-scale dams, and major channel-bed mining activities (Piman et al 2013), have now been reported as the cause of an imbalance between flow and sediment entrainment conditions (Xue et al 2011), affecting human livelihoods and the ecological equilibrium in the delta.…”