A Profile on St Kitt's Freshwater Resource & Is It Managed Sustainably?

Is Our Island’s Water Resources Being Managed In A Sustainable Manner? – Is There A Plan For Climate Change Response?

Anyone living in Saint Kitts realizes that we have a water issue? Where the question arises from many is its origin? Is our water insecurity due to climate change, poor resource management, or a combination of both? The answers offered are often too reductive, failing to provide a comprehensive overview about the situation on the island. How do we ensure that our island is being managed sustainably and are we ready to face the threat of climate change head on?

With an area of 68 square miles and a population of around 40,000 persons, St. Kitts tropical climate receives an average of about 54 inches of rainfall per year; about 4.5 inches per month.  However, this rainfall is neither seasonally nor geographically uniform.  There is a Dry Season generally for the first half of the year (January to June) during which the monthly rainfall is about 2 to 3 inches per month; and then the Rainy Season during the latter half of the year (July to December) during which the average rainfall is about 6 inches per month.  This gives about a 35%:65% split of the rainfall over the year.

Rainfall distribution is further determined by the natural topography of the island. Mount Liamigua, the highest peak on the island reaches 3,792 feet above sea level.  Rainfall in this interior central forest peak can get as high as 115 inches per year compared to a mere 30 inches at the coastline. Apart from rain fall there are other hydrometeorological factors which impacts the Water Cycle such as atmospheric temperature, humidity, wind and cloud cover.  Average temperature is about 27oC and does not vary significantly during the year; average humidity is about 76% and does not vary much likewise; winds are typically about 12 miles per hour but can reach over 150 miles per hour during hurricanes; and cloud cover varies significantly, but averages about 40%.

These together compose of the hydro-meteorological factors (rainfall, atmospheric temperature, humidity, wind and cloud cover), that determine the availability of freshwater on the island. When we discuss the availability of the resource however, there are two other major factors that come to play: our Evapotranspiration and our Geology.  Evapotranspiration is the water (moisture) that is lost back to the atmosphere through evaporation from plants, the ground and water bodies.  In St. Kitts, our evapotranspiration rate is significant; estimated at about 80 percent of rainfall.  This demonstrates the importance of vegetation cover; less vegetation means less evapotranspiration and less rainfall.

All of our potential potable freshwater, therefore, comes from only about 20% of our rainfall (remember 80% of rainfall is re-evaporated).  Of this 20% of our rainfall that is not re-evaporated, about 2% runs off in our ghauts. Most ghauts only flow to the sea for a few hours a few times per year during high-intensity rainfall events.  The balance 18% of our rainfall infiltrates deep into the ground (below plants roots) and becomes Groundwater Flow.  Groundwater (in Aquifers), like surface water (in rivers) is not static but is flowing through the pores and cracks of rocks and soil, albeit at a slower rate.  Water in a river might be flowing at about 2 feet per second, while groundwater in an unconfined coastal aquifer such as on St. Kitts might be flowing as slowly as 2 feet per day.

This is where our geology (rocks and soil formation) is important; St. Kitts can be described as a giant “sponge.”  Even though the types of rocks and soils vary from area to area on the island, generally, we are able to drill into these rocks/soils to depths ranging from about 80 feet to several hundred feet and abstract this groundwater in a pristine state through wells.  Our wells range from about 30,000 gallons per day to 1 million gallons per day.

Once a well is drilled, tests are performed to determine what is the maximum rate at which it can be pumped to deliver a SUSTAINABLE yield.  This means that this well could be pumped 24-hours per day/365 days per year at this rate without any adverse impact on the aquifer.  Pumping of a well on St. Kitts above its safe-yield (over-pumping) would result in saline-intrusion.  Beneath the fresh groundwater ‘reservoir’ described above which is replenished by rainfall, lies seawater; over-pumping of a well would cause depletion of the fresh groundwater in that area and as a result, the seawater interface would be drawn up and into the well.  This must be avoided at all cost, as once it happens, that aquifer (well) would not be able to produce freshwater again for decades, if ever. 

With over pumping creating such an adverse risk to our water supply it is important to ensure that water is being extracted sustainably from our aquifer. Unfortunately, due to rising population, industry and development and limited aquifer resource, we have put a greater strain on water extracted from wells for decades. So, have we been overpumping our wells?

From the earliest days of settlement on St. Kitts persons exploited the water that is available from the streams running in the ghauts.  These range in size from less than 10,000 gallons per day to the largest which is the Wingfield River of about 800,000 gallons per day.  It is important to remember that these streams which emanate from the forest, are replenished by rainfall; and that they represent about 2% of average rainfall.  On the other hand, from about the 1960’s, St. Kitts began to exploit the other 18% of our rainfall (Groundwater) through the digging of wells.

Although the population of St. Kitts has not increased substantially over the past sixty years, as the standard of living multiplied so did the demand for water.  Ensuring the sustainability of our island’s freshwater supplies depends on striking a balance between the demand for water and the supply capacity of our water sources.  On the supply side this means the government must continue to make the necessary and timely investments in the drilling of new wells and the construction of desalination plants in areas where the groundwater reserves might be limited.  On the demand side, this means each user of water on the island must take responsibility for being economical and conservative in his/her usage of water.

One aspect of our water resources that I have not mentioned is that which falls on our roofs.  Just as there is a growing recognition that we can and should utilize more solar energy, perhaps it is time that individuals recognize that each of us can catch water from our roofs to augment the supply from the government.  This will put less strain on the wells and surface sources and make them more sustainable.  It would also decrease the need for significant capital investment to construct desalination plants and recurrent expenditure to operate them.

Now that we are crystal clear on exactly where our water comes from; the question is: what will be the impact of Climate Change on our freshwater resources and are we taking steps to mitigate and/or adapt to ensure their sustainability?  There are projections that show a significant reduction in rainfall due to climate change.  In fact, we have already seen an 18% reduction in rainfall in St. Kitts over the past decade.  If this trend continues, we would become increasingly dependent on desalination in the future, which is a very energy-intensive an expensive endeavor.

Public Awareness and Education on the limitations of our water supplies should be given utmost prominence.  All forms of media must be engaged to spread the message that the future sustainability of our island’s water supplies is not just up to the government, but to each consumer.