Examining spatiotemporal salinity dynamics in the Mekong River Delta using Landsat time series imagery and a spatial regression approach
Journal
Science of the Total Environment
Journal Volume
687
Pages
1087-1097
Date Issued
2019
Author(s)
Abstract
Most coastal areas globally face water shortages in the dry season due to salinization and drought. The Mekong River Delta (MRD) is recognized as the “Rice Bowl” in Vietnam but the negative effects of salinization and drought have damaged rice production in recent decades. However, regional assessment of the perturbation has been lacking. A Landsat-based satellite salinity index, the Enhanced Salinity Index (ESI), was developed in this study to explore patterns of annual salinity variations in agricultural land and their relationship to drought in the MRD from 1989 to 2018. The performance of the index was superior to that of other previously published remotely sensed indices, based on correlations with field measurements of electrical conductivity (i.e. groundwater and soil EC), which can be used as a proxy for salinity. The time-series ESI was then utilized to explore the spatiotemporal dynamics of salinity in the study area using the Theil-Send median trend (TS) and Mann-Kendall significance tests (MK). In addition, temporal relationships with the Normalized Difference Water Index (NDWI) were used to investigate the relationship between drought and saline intrusion. Our results showed that freshwater and brackish areas increased inland, whereas those developed for shrimp farming may increase soil and groundwater salinity. A negative correlation between drought and salinity was also observed in surface water where fish and shrimp farming activities took place, while a positive relationship was discovered in rice and annual cropland areas. This study highlights the use of ESI as an effective parameter for modelling vegetation salinity and its relationship with cropland change. We also demonstrate the feasibility of integrating satellite imagery with spatiotemporal analyses to monitor and assess regional salinization dynamics. © 2019 Elsevier B.V.
Other Subjects
Dynamics; Groundwater; Saline water; Satellite imagery; Shellfish; Surface waters; Time series; Electrical conductivity; LANDSAT; Normalized difference water index; Remotely sensed indices; Salinity indices; Spatio-temporal dynamics; Spatiotemporal analysis; Viet Nam; Drought; brackish water; fresh water; ground water; surface water; drought; Landsat; regression analysis; salinity; satellite imagery; spatiotemporal analysis; time series analysis; agriculture; Article; controlled study; correlation analysis; cropland; drought; electric conductivity; Enhanced Salinity Index; environmental monitoring; environmental parameters; fish; intermethod comparison; Mann Kendall analysis; mathematical analysis; nonhuman; Normalized Difference Water Index; performance; priority journal; rating scale; rice; river; salinity; satellite imagery; seasonal variation; shrimp; soil; spatial regression; spatiotemporal analysis; Theil Send analysis; time series analysis; trend study; vegetation; Viet Nam; Mekong Delta; Viet Nam; Decapoda (Crustacea)
Type
journal article