Locations of the surveyed surface wells in the bay of Palu

Central Sulawesi Reconnaissance: Surface Well Water Quality

Dr. Ella Meilianda collecting water sample from wells in affected areas
Dr. Ella Meilianda collecting water sample from surface wells in tsunami inundated areas

On November 18, 2018 (day 2 of the field survey), Dr. Ella Meilianda proceeded to investigate the water quality of the surface wells at various locations of the neighbourhood affected by earthquake and tsunami. The investigation aimed to explore any changes of water quality including discolouration and salinization from salt-water intrusions from the sea. Salization was likely since the surface wells take water from shallow ground, only about 7 to 9 meters deep. In addition, heavy ground shaking during the earthquakes and infiltration of the saltwater from the tsunami inundation might as well have affected well water quality.

Dr. Ella collected well water samples along the earthquake-affected areas of Lere Village, particularly in the neighbourhoods that survived the earthquake but were significantly affected by the tsunami. However, she found that only a small number of households in the neighbourhoods still rely on surface wells. Most of the households have turned to deep wells for better water quality. The neighbourhoods had also been served by the local drinking water state company (PDAM), whose supply lines have been badly damaged by the recent disaster.

The appearance of water samples from the 5 surveyed wells
The appearance of water samples from the 5 surveyed wells

Samples 1 and 2, each approximately 250 ml, were collected at Lere Village at the coastal area near the center of Palu bay. They are located in the tsunami-inundated area. Well 1 is located about 12 m away from well 2. From the interviews with the owner, it was found that well no. 1 had had remarkably poor water quality since after the event. Previously the water was not saline and odourless. The well had been used for a long time for household water supply. After the disaster event, the water became saline, with odour and yellowish color.

Well number 2 was an interesting case. The owner said that before the event, the water quality of the well was poor. It contained heavy metal contamination and was saline. The base of the well was clayey. However, after the event, the water sample taken from the well was found to be of good quality. It appeared clean as purified water and was odourless and not saline (see also Fig 2). The owner added later that the base of the well was now currently layered with fine white sandy substrate.

Later on the day, Dr. Ella took another sample at another well (well no. 3) located closer to the coastline. If was found that the water condition remains the same as in the pre-event, where the quality is rather poor; yellowish, slightly saline, although odourless.

On the morning of day 5, Dr. Ella took another two samples in wells no. 4 and 5 in the coastal neighbourhood, which was not affected by the tsunami. Both wells experienced poorer water quality than before the event, but only during the early couple of weeks after the event. Currently, the water quality is at similar state as it was before the event.