Housing's Hydrological Impacts

Matt Yglesias and others who argue that there are too many restrictions on housing construction make some valid points.  (See Matt’s Slow Boring post “Farms Aren’t Nature” of July 15, 2026).  But they often ignore something big - the hydrological impacts of housing.

People use water and create wastewater. Dwellings bring along impervious surfaces such as roofs, parking areas, and roads. In the Northeast and many other populated areas, the tradeoff is usually not between large productive farms and small "cutesy" farms. Instead, it's between suburban sprawl and non-irrigated hayfields, orchards, and pastures.

When land is converted to housing, water that people need has to come from somewhere and the resulting wastewater has to go somewhere. If the houses have sewer service but the water is coming from wells, water is transported downstream or even out of the watershed. Stream flow can suffer and groundwater levels can decline. This is happening in parts of New Jersey, for example. If the houses don't have sewer service and are too close together, the groundwater will get polluted because even properly functioning septic systems discharge nitrates. Septic systems have to be far enough apart so that naturally occurring groundwater recharge will be enough to avoid pushing groundwater nitrate concentrations to unhealthy levels.  Impervious surfaces, even if they cover as little as 10% of the land, harm the biology of streams which impacts wildlife and degrades water quality. Too much impervious cover also makes streams “flashy” – prone to both flooding and drying up in periods of low rainfall. 

Orchards, hayfields, and pastures are closer to natural land cover than sprawling housing. If land preservation can drive housing construction to places that are already built up it can benefit the long-term health of the environment and society.