Cities can grow without harming lakes: Lake Washington has become less eutrophic despite rapid population growth

As cities grow, lakes are often assumed to suffer from increasing nonpoint pollution. Many waterbodies have become more eutrophic in recent decades, as expected, but many others have become less eutrophic, especially in urban/suburban areas. What policies, practices, and ecosystem processes have helped some lakes stay stable or become less eutrophic even in a growing city? Identifying and understanding success stories is important to continue protecting these lakes and improving other urban/suburban lakes. We found one such success story when we examined water-quality trends over the past 25 years (1998–2022) in Lake Washington, a well-studied large lake in the Seattle metro area. The watershed population grew rapidly during that time (34% from 2000–2020), yet Lake Washington became substantially less eutrophic, and indicators of development impacts stabilized or decreased. Chlorophyll concentrations during the main spring bloom decreased sharply ( 25%/decade), and water clarity and nea..., , # Data from: Cities can grow without harming lakes: Lake Washington has become less eutrophic despite rapid population growth

Dataset DOI: [10.5061/dryad.dfn2z35fj](10.5061/dryad.dfn2z35fj)

## Description of the data and file structure

This contains the water-quality data associated with the following manuscript:

Nidzgorski, Daniel A. and DeGasperi, Curtis L. (2025). Cities can grow without harming lakes: Lake Washington has become less eutrophic despite rapid population growth. Ecosphere.

For questions or requests, please contact Daniel Nidzgorski at [[e-mail],](mailto:[e-mail]) and we would appreciate it if you cited.

### Files and variables

#### File: LakeWashingtonWaterQuality1998-2022.csv

**Description:** These water-quality data were collected from Lake Washington (Seattle area, USA; 47.6° N, 122.3° W) by King County's long-term monitoring program. This dataset includes data from 1998-2022 from the Madison Park 0852 monitoring location at one of the dee...,