Status and trends of water quality in the Mid-Atlantic Inventory and Monitoring Network, water years 2011?2023

Abstract

The Mid-Atlantic Inventory and Monitoring Network (MIDN) monitors water quality due to the ecological, management, and policy significance of aquatic resources in MIDN parks. Specifically, water quality is monitored due to the direct effect it has on aquatic communities, the National Park Service?s responsibilities for the protection and improvement of water quality, and the clear connection to state-based regulatory programs. Here we provide a summary report on the status and trends in ?core? water quality parameters as defined by the National Park Service (i.e., pH, dissolved oxygen, water temperature, and specific conductivity). We include data from discrete monthly or quarterly observations for water years 2011 to 2023 at 47 sites distributed across eight MIDN parks. Overall, the status of water quality at most sites met state standards for the parameters monitored. Where water quality observations deviated from state standards, this was often due to natural conditions in the associated watershed such as underlying acidic soils or beaver activity. Out of 141 site-parameter combinations, only 10 showed more than 10% of observations outside state standards. And, of these 10, only three are believed to be associated with anthropogenic activity. In those few locations, upstream agricultural use or development is negatively impacting water quality. In terms of trend, significant trends in water quality parameters were rare across the network, and when present, were relatively small. Even though current monitoring suggests relatively good water quality across the MIDN, these conclusions are based on discrete monthly or quarterly samples, and it is possible that field observations during other times of the day would reveal additional water quality issues given large diel changes in water quality in some streams. Although state water quality standards were generally met for the observed ?core? parameters, it is important to note that these parameters represent a small portion of the many factors necessary for healthy stream ecosystems. Traits such as quality substrate, habitat complexity, good riparian condition, and other water quality criteria (e.g., nutrients and heavy metals) are also important. A more complete understanding of stream ecosystem health must include other components such as biological and physical habitat assessments.