Abstract
Sri Lanka contains a large number of natural and man-made water bodies, which play an essential role in irrigation and domestic use. The island has recently been identified as a global hotspot of climate change extremes. However, the extent, spatial distribution, and the impact of climate and anthropogenic activities on these water bodies have remained unknown. We investigated the distribution, spatial and temporal changes, and the impacts of climatic and anthropogenic drivers on water dynamics in Dry, Intermediate, and Wet zones of the island. We used Landsat 5 and Landsat 8 images to generate per-pixel seasonal and annual water occurrence frequency maps for the period of 1988–2019. The results of the study demonstrated high inter- and intra-annual variations in water with a rapid increase. Further, results showed strong zonal differences in water dynamics, with most dramatic variations in the Dry zone. Our results revealed that 1607.73 km2 of the land area of the island is covered by water bodies, among this 882.01 km2 (54.86%) is permanent and 725.72 km2 (45.14%) is seasonal water area. Total inland seasonal water increased with a dramatic annual growth rate of 7.06 ± 1.97 km2 compared to that of permanent water (4.47 ± 2.08 km2/year). Sri Lanka has the highest permanent water area during December–February (1045.97 km2), and drops to the lowest in May–September (761.92 km2) when the seasonal water (846.46 km2) is higher than permanent water. The surface water area was positively related to both precipitation and Gross Domestic Product, while negatively related to the temperature. Findings of our study provide important insights into possible spatiotemporal changes in surface water availability in Sri Lanka under certain climate change and anthropogenic activities.
Highlights
The surface water area of Earth is continuously varying with time [1]
The accuracy of the water extraction was assessed in terms of omission and commission errors for both Thematic Mapper (TM) and Operational Land Imager (OLI) Learning vector quantization (LVQ) models separately
Results indicated that overall accuracy of water was high for both TM and OLI data (99.90% and 99.93%, respectively)
Summary
The surface water area of Earth is continuously varying with time [1] These variations are mostly related to climate change processes as well as anthropogenic reasons [2]. Vast spatial and temporal variability of water and low storage capacity resulted in competing demands over limited water bodies [4,5,6], despite receiving annual average precipitation from 900 to 5000 mm [7]. It continuously witnesses the challenges of climate change with frequent and more intense precipitation extremes, regular floods, and droughts [8,9]. Climate Risk Index list for 2019 ranked the island as the global second [10]
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