Seal of Dane County County of Dane
Dane County Land & Water Resources Department

Yahara/Mendota Phosphorus Mass Balance

A watershed-level phosphorus mass balance from 1992 to 2017 was developed for the Lake Mendota Watershed and Yahara River Watershed. Phosphorus accumulation rates declined substantially in both watersheds over the time period. While declines in agricultural fertilizer P imports were the largest drivers of accumulation rates declining, increases in exports of livestock and manure digester products were also important in the Lake Mendota Watershed and increases in net crop export and exports of livestock products were also important in the Yahara River Watershed.

This analysis will be updated every five years as new data become available, and will be used as an indicator of progress toward improving water quality in these watersheds.