KINGSTON, R.I. – November 16, 2021 – A University of Rhode Island hydrogeologist is conducting an assessment of the availability of freshwater on Block Island out of concern that the growing number of visitors, combined with the effects of climate change, may force the community to reduce the number of tourists that visit the island and reduce future residential development.
Thomas Boving, URI professor of geosciences, is leading an effort to evaluate how much water is being pumped from the six wells owned by the Block Island Water Company, which provides half of the island’s water needs. He is also assessing how much water is available in area wells, how quickly they are recharged, and how likely salt water is to intrude into the drinking water supply.
“Almost all of the freshwater on Block Island comes from rain, but if the islanders pump more water than can be recharged by precipitation, they’re going to drain the bathtub. And that’s what’s happening now,” said Boving, who has studied aquifers and drinking water supplies in a dozen countries around the world.
Demand for water on the island is increasing year after year, according to Boving, due to the large number of tourists that visit. On average, tourists who stay overnight on Block Island use four to five times as much water as the typical resident. During July and August, the water company can barely meet demand.
“During high demand days, they’re on the verge of pumping salt water,” he said. “In the aquifer, the available freshwater is floating on a layer of salt water, and if they drill too deep, they’ll be pumping salt water.”
One of the big unknowns about the Block Island water supply is the effect of climate change. Boving said that the increasing frequency of strong storms could deliver more rainwater to the island and recharge the aquifer, but it’s also possible that much of that precipitation runs off the surface and into the ocean before it can make its way into the aquifer. Warming temperatures could also result in more evaporation, which could further deplete the island’s water resources.
So Boving and his graduate student, Jibban Panthi, are installing electronic devices in several wells to measure how quickly the wells are recharged, how much water is pumped, how much water is lost to evaporation, and other factors. They are also conducting a geo-electrical resistivity survey of the island’s coastline to track how far inland the ocean water intrudes beneath the surface.
The assessment is a follow-up to a similar study conducted 20 years ago by URI Professor Anne Veeger, which concluded that water was available to meet the island’s needs at that time. However, water demand, tourist visitation, housing density and standard of living have all increased significantly since then.
“If the people pump too much water and they start getting salt water, then those wells will have to be shut down,” Boving said. “We’re trying to see if there have been changes over time and what that will mean for the wells and the island in general.”
One surprising factor affecting water availability on Block Island is visiting boaters who fill their tanks with freshwater from the island.
“Much of the water used on the island ends up returning to the aquifer via the sewage system, but boaters take water away and it never returns,” said Boving. “That’s a factor we need to consider as well.”
Boving’s study is funded by the Rhode Island Water Resources Center, a division of the U.S. Geological Survey. He will prepare a report of his findings next summer that will help the community make future plans.
“Whatever we find will give us an idea of what the island’s future is,” he said. “It will tell us whether we need to ring the alarm about limiting the number of people visiting and living on the island. The residents are very aware of the issue, and it’s something they’re going to have to come to terms with.”