Assessment of Spatial and Temporal Trend of Groundwater Salinity in Jaffna Peninsula and Its Link to Paddy Land Abandonment

Abstract

Salinization is an explicit global threat faced by coastal low lands. The increased seawater ingression into groundwater due to various climatic and anthropogenic factors affects functioning of ecosystems, biodiversity and the sustainability of coastal agriculture. This study was undertaken to investigate the changes in groundwater salinity in Jaffna Peninsula over a 20-year period and its relationship with paddy land abandonment. Permanently abandoned paddy areas were mapped using historical Landsat images, while groundwater salinity changes in 63 agricultural wells for the period 1999 to 2019 were analysed. The trend in salinity, including proximity to the coast, was examined. The results showed that approximately 8178 ha (43% of total paddy land) of paddy lands had been permanently abandoned while the groundwater salinity had increased by 1.6-fold over the last two decades. An increasing salinity trend with decreasing distance from the coast was observed. Presently, nearly 59% of the wells showed salinity levels that were unsuitable for crop irrigation. The results underline the need for urgent and effective management of groundwater resources in order to maintain the sustainability of the existing paddy lands and ensure availability of potable water for consumption along the coastal low land areas of Jaffna Peninsula.

Modeling and Mapping of Soil Salinity and its Impact on Paddy Lands in Jaffna Peninsula, Sri Lanka

“…In this context, having 46% of paddy lands affected by soil salinity is an alarming threat to the sustainability of paddy cultivation in Jaffna Peninsula. This agrees with our previous study [27] and field investigations in that the increasing salinization could be the cause of paddy land abandonment in the south-east and south-west regions of Jaffna Peninsula. However, an investigation into long-term soil salinity changes is required to further validate this concept.…”

“…In poor drainage conditions, when the groundwater table rises, the saline groundwater reaches the top soil layers [48]. This is in agreement with the previous studies of Gopalakrishnan, Kumar and Mikunthan [27] and Gunaalan, Ranagalage, Gunarathna, Kumari, Vithanage, Srivaratharasan, Saravanan and Warnasuriya [26], where the groundwater salinization in the dry seasons was reported in the north-east, south-east and south-west regions of Jaffna-areas where highly saline soils were distributed.…”

“…This increasing population along the coastal fringes of Jaffna Peninsula will further increase the vulnerability of the paddy lands in the coastal lowlands to salinization [55]. The subsequent construction of more new wells and the over-extraction of groundwater is likely to increase seawater intrusion into coastal aquifers [27].…”

“…Previous studies have reported that a significant number of wells and hundreds of acres of land have been abandoned due to salinity [24][25][26]. In a study by Gopalakrishnan, et al [27], it was established that during the last three decades, 8178 ha of paddy lands were permanently abandoned and groundwater salinity increased 1.6-fold.…”

Floral Distribution, Diversity, and Ecology of Mangrove Forests in Mandaitivu and Arali, Sri Lanka

“…Ranawana, 2017). It belongs to the dry zone with uniformly high temperature all year around (range 26 o C -33 o C) and an annual precipitation that rang between 696mm to 1125mm (Gopalakrishnan, Kumar, & Mikunthan, 2020). The highest elevation is 15.3 meters above sea level (masl), with a median being 2.72m and the average tidal amplitude is between 0.115 and 0.17 m.Of the several mangrove patches two of them Mandaitivu and Arali were selected for this study purpose (Figure 1).…”