Monitoring saline intrusion in the Ayeyarwady Delta, Myanmar, using data from the Sentinel-2 satellite mission

Abstract

Summer rice cannot be grown near the coast of the Ayeyarwady Delta, Myanmar, because of the high salinity in river water during the dry season. This means that saline intrusion should be monitored to manage the irrigated rice-growing area. The aim of this study therefore is to develop a model to estimate the salinity of river water using satellite imagery. The imagery of Sentinel-2 was suitable for monitoring saline intrusion because of their high spatial (10-m) and temporal (10-day) resolutions. We found that the reflectance of the visible bands was correlated with electrical conductivity, which was influenced by the concentration and composition of dissolved salts. When the river water mixed with the salt water from the sea, suspended particles tended to flocculate and settle, as a result, less turbid water was more saline. The best-fitting model was obtained with the green band (coefficient of determination R2 of 0.776, root mean square error of 4.896 dSm−1, and mean absolute error of 3.340 dS m−1). The saline intrusion showed considerable spatial and temporal variability during the dry season. The salinity intrusion extended approximately 80 km inland at the end of the dry season in March in the Pathein River. The 1 ppt salt concentration line in March marked the boundary between cultivated and non-cultivated areas of paddy field, which indicates that cultivable areas were strongly affected by saline intrusion. The results show that more frequent and higher resolution monitoring than before of the Sentinel-2 can support effective water resource management.

Decadal changes in the rice-cropping system in the Ayeyarwady Delta using a large archive of satellite imagery from 1981 to 2020

“…During the monsoon season, crop cultivation was possible even in the coastal area, as the salinity of soil and river water remained low due to the heavy rainfall (~ 3000 mm). However, there was almost no rain during the summer season, and thus seawater traveled many tens of km inland (Driel and Nauta 2014;Sakai et al 2021). River water contaminated with seawater was not suitable for irrigation.…”

Downstream Morphological and Sedimentary Transformations in Modern Continental-Scale Rivers

“…We have also compiled data on the upstream penetration of tidal signals and saltwater penetration in river channels from a variety of sources (e.g. Abam & Fubara, 2022;Abam & Omuso, 2000;Eisma, 1998;Giosan et al, 2006;Hedley et al, 2010;Kravtsova et al, 2008;Matsoukis et al, 2023;Obowu & Abam, 2014;Parsa & Shahidi, 2010;Sakai et al, 2021;Soileau et al, 1990;Syvitski et al, 2014;Taft & Evers, 2016;Velden, 2015;Wang et al, 2019). The presence of tidal signals defines the tidal river for each system, and in the 5 systems we studied, the tidal river and the estimated backwater length are essentially the same only in the macrotidal Irrawaddy River (~300 RK).…”

Toward the development of a weather index insurance for rice farmers in the coastal region of Myanmar

“…However, if cyclones land during the post-monsoon season, then the paddy field soil is expected to accumulate salt. Sakai et al (2021a) developed a method of monitoring saltwater intrusion to rivers in the Ayeyarwady delta using highresolution satellite data. The saline level in the river water was estimated using the relation between the river water reflection and electrical conductance.…”