Water quality under threat: land use shifts drive 69% increase in water extraction

A recent study by researchers at the University of Massachusetts Amherst, published in the journal PLOS Water, explores the relationship between hydrological changes (such as floods, droughts and runoff) and evolved land use patterns. The study specifically examines the Sudbury-Esbett and Concord watersheds in eastern Massachusetts.

Impact of human activities on hydrological

The researchers stress the importance of understanding the impact of human activities on the hydrological cycle. They highlight how the conversion of forests to roads, parking lots and residential areas has changed the landscape, reducing its hydrological resilience and causing water to flow faster downstream.

The study reveals an intriguing paradox seen in many parts of Massachusetts: Spring floods are often followed by summer droughts. Researchers question why the region continues to face water scarcity issues, despite excessive rainfall causing street flooding, indicating that the excessive water is not effectively recharging groundwater or depleting stream and lake levels are not maintained.

Disrupts environment's natural

We all live within a watershed, according to Timothy Randhir, professor of environmental conservation at the University of Massachusetts Amherst and lead author of the study. The constant modification of our landscape, such as converting forests to roads, parking lots and other development, disrupts the environment's natural hydrological resilience.

Research by the University of Massachusetts Amherst team sheds light on this important connection between land use change and the hydrological cycle.

However, understanding the complex links between these factors can prove challenging. An intriguing phenomenon observed in Massachusetts is the occurrence of summer droughts following spring floods. This paradox begs the question: If excess water from flooding floods streets across the state, shouldn't there be enough groundwater left over for drinking, irrigating gardens, and maintaining stream and lake levels?

To make the relationship between land use and hydrological impacts more visible, the researchers focused on the Sudbury-Esbett and Concord watersheds. Using historical data and modelling techniques, they projected future trends for 2035, 2065 and 2100.

The study's findings paint a troubling picture. By the end of the century, forested area is forecast to decrease by 51%, while impervious areas such as roads and parking lots will increase by 75%. These transformations will result in a 3% increase in annual flow and a staggering 69% increase in runoff.

The enhanced runoff will result in a 54% increase in sediment and other solids in the water, accompanied by elevated concentrations of phosphorus (12% increase) and nitrogen (13% increase).

Increasing vulnerability to drought

Randhir said that the raindrops have two possible paths: they can run off the ground into streams or infiltrate the ground, gradually replenishing the water table. However, extensive paving of the land, removal of wetlands, and channelling of rivers have prevented rainwater from penetrating the soil, increasing vulnerability to drought. Also, runoff from these changes flows directly into rivers.

He emphasizes that planning for the future must be done at the scale of river basins. This involves implementing urban planning strategies that prioritize site-specific and sustainable land use measures. Some examples of these measures include creating rain gardens, using pervious paving in large parking lots, and implementing vegetated ditches to curb runoff.

According to Randhir, the watershed serves as a crucial indicator of the overall health of the landscape. The quality of life within a particular landscape depends on how well the watershed is working. Therefore, it is essential to prioritize the sustainable management of watersheds to ensure the well-being of both natural ecosystems and human communities.

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