The Chesapeake Bay Model is the basis for the Watershed Implementation Plans. It is really tricky to actually measure the progress. The best real world data comes from the U.S. Geological Survey (USGS). Relatively unnoticed, the USGS issued their report on the monitoring results for the Chesapeake Bay for the 2014 water year last week. The USGS obtains the data from the Chesapeake Bay Non-tidal Water-Quality Monitoring Network is a partnership among the States in the Chesapeake Bay watershed, the U.S. Environmental Protection Agency, the USGS, and the Susquehanna River Basin Commission. This group has created a network of monitoring stations to measure nutrient and sediment pollutant loads and changes in pollutant loads over time.
The initial network formed in 1985 had nine river monitoring stations. In 2004, the Chesapeake Bay Program formalized the network, and a period of expansion followed at the EPA’s Chesapeake Bay Program was developing the mandated . In 2010 and 2011, the network was further expanded to address the needs of the EPA mandated TMDL. The network currently has 117 sites designed to measure changes in nitrogen, phosphorus, and suspended sediment in the Chesapeake Bay watershed. Nitrogen, phosphorus, and suspended-sediment loads and trends are determined based on continuous streamflow monitoring, extensive water-quality sampling, and statistical analysis. The USGS computes the loads and trends and makes the data available on the Web.
Because there is a relationship between rainfall and nitrogen, phosphorus and sediment pollution the USGS attempts to normalized the flow data before they look at the tends in the data. They use an algorithm to estimate the trend in “flow-normalized load,” trying to minimizes the confounding effect of any concurrent trend in discharge. In addition, this year there was a change in data used.
Historically, the USGS did not compute trends for water monitoring stations having recorded data for less than 10 years. However, in 2014 a large number of newer stations had records that reached 9 years. Because of the needs of the Chesapeake Bay Program for the most comprehensive analyses available ahead of the “Mid-Point Assessment” for the bay total maximum daily load set for 2017, the USGS elected to compute and include trends for stations having only 9 years of data (2006-2014) in the 2014 water year results. This data dominates the short term trend analysis performed by the USGS.
Overall, the short term analysis showed trends in nitrogen, phosphorus and suspended-sediment loads for the Chesapeake Bay monitoring stations that were more often degrading than improving. You can dress this up and put a ribbon and bow on it and point out that since 1985 the trends in nutrient and sediment pollution had been predominantly improving in nitrogen pollution, and evenly divided in phosphorus pollution and more often improving for suspended-sediment load, but still it is puzzling why the recent trends have been in the wrong direction.
|Nitrogen Load from USGS|
|Phosphorus Loads from USGS|
|Sediment loads from USGS|
Maybe, the problem is the flow normalization methods and heavy rain and run-off impacts, or maybe we have not yet begun to see the results of the steps taken under the Watershed Implementation Plans. Next year EPA will measure the results of the Watershed Implementation Plans progress, it will be interesting to understand how the progress will be judged.
The EPA has call “resilience” an indication of the state of the ecosystem. Nick DiPasquale, the director of the Chesapeake Bay Program, said “Over the years, in any number of ways, we’ve seen evidence that when we make the right decisions and take the right actions, the ecosystem is resilient enough to come back. We’ve restored rockfish populations, improved crab management and numbers and, more recently, have seen restored grass beds survive and new ones emerge despite heavy rains and sediment-laden runoff. These signs of resilience are indicators that we are on the right track. They mean our collective work to restore, protect and engage people in Bay issues can have an impact.”
The Chesapeake Bay is a complex, sensitive and dynamic ecosystem and it is impossible to define the current state of the Chesapeake Bay in short, simple terms. To understand the health of the Bay watershed, we must consider all of these indicators and their long-term trends and the trends are not looking good.