Economist Focused on the Benefits of Clean Water Joins YSE Faculty

David Keiser has spent his career focused on a question that affects everyone's life: What are the social costs of water pollution?

He has built new data sets, hydrology tools, and national models to investigate the benefits and tradeoffs of water policy. His work has reshaped how policymakers understand the economic stakes of clean rivers, lakes, and drinking water systems. Keiser, who earned his doctorate at the Yale School of the Environment in 2014, will join the faculty July 1 as professor of water policy and management.

Keiser became interested in environmental economics while working for a Washington, D.C.-based environmental litigation consulting firm that focuses on pollution and human health. He later went on to earn a master’s degree in agricultural and applied economics at the University of Georgia. Keiser said he chose to pursue a doctorate in environmental economics at YSE because of its strong reputation in environmental policy. Here, he studied with Robert Mendelsohn, the Edwin Weyerhaeuser Davis Professor Emeritus of Forest Policy, and James Saiers, the Clifton R. Musser Professor of Hydrology.

“YSE is a unique place where you get this phenomenal education in an interdisciplinary setting. It offers a mixture of great economics training, along with a deep understanding and appreciation of the environmental issues,” he said.

Keiser’s work on the 1972 Clean Water Act and 1974 Safe Drinking Water Act has provided some of the clearest evidence to date on how federal policy has shaped water quality over the past half‑century. His widely cited research shows that U.S. surface water quality has improved substantially since the 1970s, and that federal grants to upgrade wastewater treatment plants have produced measurable downstream benefits. Yet, the measured costs of those grants exceeded the benefits, such as clean water’s role in helping to sustain a robust housing market, raising difficult questions about regulatory design and spending priorities.

“The findings emphasize a critical social question: Does U.S. water quality regulation have costs that exceed benefits, or is current research failing to measure a large share of the benefits? Are there categories we are missing out on that we haven’t measured or measured well?” he said.

His research extends across a wide range of water quality and policy issues.

Keiser, who is currently a professor in the Department of Resource Economics at UMass Amherst, is a co‑inventor on a provisional patent for a machine‑learning tool that predicts which waters fall under federal jurisdiction — a critical question as the definition of “Waters of the United States” has narrowed due to recent Supreme Court decisions.

One of his most significant ongoing projects is a National Integrated Assessment Model that, for the first time, quantifies the economic damages of nutrient pollution across nearly 2.5 million river and lake segments in the United States. There is little regulation of nutrient runoff, Keiser noted.

“It’s a really tough issue because these pollutants are degrading bodies of water that provide drinking water to communities and places where we recreate, swim and fish,” he said. “But there’s been a strong aversion to placing strict regulations to reduce nutrients and sediments from getting into our waterways, especially in agriculture.”

By combining economic models with hydrologic models, the assessment model allows researchers to calculate the social cost of emitting nitrogen or phosphorus into U.S. waterways at any specific location. Preliminary findings put annual damages from nutrient pollution at between $50 billion and $100 billion. With 20% of watersheds accounting for roughly 80% of the harm, these findings have direct implications for how federal conservation programs should target their resources, Keiser noted.

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"Think of it this way, if you go to a store and buy a Snickers bar, you see a price for that. But if you dump phosphorus on your lawn and it flows into a waterway, you're not seeing what the price of that phosphorus is in terms of its cost to society. That's what this work is trying to measure,” he said.

To connect his research to policymaking, Keiser co-founded the Social Cost of Water Pollution Workshop, an annual convening of academics and EPA officials that has served as a model for translating academic findings into policy-relevant guidance.

While much of Keiser’s work focuses on the U.S., he is expanding his research internationally. In India, he is working with doctoral students to study the effectiveness of investments in municipal wastewater treatment — mirroring his U.S. work on infrastructure and sanitation. In Brazil, he is collaborating with researchers to understand how communities adapt to drought and how deforestation policies affect water resources.

Saiers said Keiser brings an innovative approach to research and his teaching will strengthen YSE’s water science and management specialization.

“Dave’s scholarly contributions will establish YSE as a leader in advancing understanding of the costs and benefits of regulatory actions that are intended to safeguard the quality of surface and drinking waters of the United States,” he said.

Keiser will teach courses on U.S. clean water policy, water sanitation and hygiene in developing countries, and a seminar on floods, droughts, and markets.

“My goal is to give students a clear understanding of how environmental economists evaluate the design and tradeoffs of water resource policies — and how those tools can help solve some of the world’s most pressing water challenges,” he said.