Analysis of Water Sources
Summary of Water Testing
In an effort to create a plan for post-disaster water source options, a series of water source analyses were conducted on the western side of Île à Vache. The goals were to gather information about current water quality and elevation and to explore water source collection methods. Thirty-nine sources were measured consisting of a mixture of pumps, wells, and rainwater cisterns. A majority of the water sources tested were cisterns, either from rainwater catchment or pumps. Wells on the island are predominantly used as drinking sources and for domestic purposes, such as bathing and washing dishes. The following are characteristics of the measured water sources.
Most rainwater cisterns are free flowing systems that collect water through PVC pipes connected to the roof that then drains into cement or large plastic cisterns. Many systems, specifically the larger sources of water owned by the hotels, are ‘closed systems.’ The majority of the rainwater cisterns are considered to be ‘open systems’ due to the collection method. It was noted that six water sources dried out during the summer season, around June and July. This included both wells and rainwater cisterns. Two wells were said to have a salty flavor.
One of the key issues with cistern storage is the sealing method. The cement cisterns on the island for personal use typically have a square hole on top of the cistern. Frequently these access points are ill maintained and often covered by a piece of sheet tin or a wood covering. Water tests produced better results for the cisterns with a more adequately covered access point. The plastic rainwater cisterns for personal use typically have access points at the bottom. These are not well maintained and often use homemade plugs made of corncobs or other organic material. Better sealing methods would allow less organic material to enter the cisterns, resulting in cleaner water.
Water Test Results
The total coliform samples only showed one sample (Rain Cistern 4) that did not have a presence of total coliform. There are many factors contributing to the lack of total coliform in this particular cistern, including sampling error. The E. coli samples showed seven samples that did not have a presence of E. coli in the water. These sources are important because the processes being used to harvest the water are more successful in collecting clean water. The areas without E. coli included a few rainwater catchment areas and the Madame Bernard water system.
The pH levels varied between 4.5 and 7. Generally, the acidity/pH level is affected by the amount of organic material present in the water. Nitrates varied depending on where the water source was located. Wells that were close to the ground or collected ground water often had a higher level of nitrates. Most rainwater catchment systems had acceptable amounts of nitrates.
Salinity in the water sources ranged from 1000-1005 ppm with 1000 ppm signifying no salt in the water. Specific gravity ranged from 1.0 to 5.0 depending on the source of the water.
When investigating the effect of environmental factors on water sources a 30-meter radius surrounding each water source was examined. Approximately half of the sources were within the minimum distance of human or animal fecal matter. Seven animal pens were found within the 30-meter radius of water sources. Yet, within each area there were many free-range animals. If animals could be contained outside of the 30-meter buffer then water would be less contaminated.
Within the 30-meter radius there were a few cases of wastewater disposal, including used dish washing water and bathing water. Solid waste, such as burnt garbage, motor oil, and used charcoal, was present in multiple areas. Additionally, there is often standing water near the water sources. This is a problem because viruses and bacteria are easily transferred from one water source to another. There was standing water near eight sources and the ocean was within 30 meters of five sources. Agricultural activity was present near ten different sources. The fertilizer affects the soil composition that in turn impacts the nitrate levels.
It is important to note that when these environmental factors are at a greater distance from the water sources it is less likely that various materials will contaminate the water post-disaster.
Data collected on water sources is available in Appendix A.