Chesapeake Bay - Overview:
It's not the rain, it's what the rain carries
Although it was a quiet year for extreme events like hurricanes, July 2013 was one of the hottest on record, and annual rainfall was above average. Nutrients and sediments carried by stormwater are important factors in Chesapeake Bay Health.
Overall, Chesapeake Bay scored a 45%, a C, which is almost the exact same score as last year even though there was a lot more rain. Water clarity in the Bay is declining; the amount of chlorophyll in the water was also higher, which added to the murkier water conditions.
The indicator with the most improvement was aquatic grasses, largely due to increases of wigeon grass or Ruppia. The expansion of Ruppia, while welcome, is often a boom and bust phenomenon, so we should be cautiously optimistic and see if it is sustained over several years.
Reducing nutrients improves Bay health
While the overall Chesapeake Bay grade did not change, there are some important differences within reporting regions. There is continuing degradation of the Eastern Shore tributaries which are dominated by agricultural land use. The Upper Eastern Shore, which includes tributaries between the Chesapeake-Delaware Canal and the Choptank River, such as the Elk, Sassafras, Chester, and Miles Rivers, received a poor grade, a D. This region has a negative trajectory, so it is getting worse, not better. The Choptank River and the Lower Eastern Shore regions also had low grades, in part due to rainfall in excess of 50 inches on the Delmarva peninsula, which washed fertilizer and chicken manure from fields into the Bay.
The western shore tributaries generally improved last year, due in part to the success of the sewage treatment upgrades removing nitrogen and phosphorus, and the decline in atmospheric nitrogen deposition noted in the recently released New Insights report (see back page). Of particular note is the James River which has a positive trajectory and whose grade dramatically improved in 2012, despite high rainfall.
Major changes to report card last year
In 2013, there were two major changes that applied to the annual report card.
1) We added 3 new fisheries indicators, although they do not calculate into the report card grades since they are only available at the Baywide scale. These fisheries indicators are a) Blue crabs (adult females), b) Bay anchovy, which is the most abundant fish in Chesapeake Bay (annual mean), and c) Striped bass, using an index of adult fish. Blue crabs were below the target level of 215 million adult females, but Maryland and Virginia have taken steps to adjust the harvest levels accordingly. Bay anchovy levels have been increasing since 2008. Striped bass is based on the three year average of the abundance index to account for long lifespan. The three year average striped bass value was up for 2011-2013, although the single year abundance in 2013 was down.
2) Current work is occurring to develop a Climate Change Resilience Index for the Chesapeake Bay. Protection and restoration of the Chesapeake Bay must account for climate change impacts that we are experiencing now. These impacts include sea level rise, increasing water temperatures and rainfall, increasing storm frequency and intensity, changes in salinity, and ocean acidification (pH). We are currently developing a suite of indicators that will measure resilience of Chesapeake Bay to climate change. These indicators are coastal wetlands, submerged aquatic vegetation, fish, shellfish, and pathogens.
We are creating the Climate Change Resilience Index using a 5-step process:
Conceptualize: illustrate the ways that climate change may affect resources from sea level rise, increased temperature, precipitation, and storm frequency and intensity, and ocean acidification.
Choose Indicators: choose indicators that reflect the processes from the conceptualization.
Define Thresholds: determine the desired condition for each one of the indicators.
Calculate Scores: compare data to the desired conditions, and combine into an index for climate resilience.
Communicate Results: the index will be incorporated into the Chesapeake Bay Report Card, and will be highlighted in newsletters and other reports.
As an example, Conceptualization shows that coastal wetlands are likely to be affected by their ability to migrate landward or grow upwards as sea levels rise, and will be protected by underwater grasses and oyster habitat, which reduce wave action and erosion during storms. Indicators that can be used to measure wetland resilience include migration pathways that will allow the wetlands to migrate landward, and sediment supply, which allows wetlands to grow upward as sea levels rise.
We can improve water clarity, which helps aquatic grasses grow, promotes the right balance of phytoplankton (algae) in the water column, and influences benthic communities (clams and worms living in the sediment) in the following ways:
Stop sediment and nutrients from running off
your property into storm drains. Divert rainwater
into rain barrels, rain gardens, and natural areas.
Reduce fertilizer use and re-use materials by
Support local initiatives that convert hard
surfaces like parking lots into green space like
rain gardens. Report turbid water running off
from public sites, such as construction areas,
to your local government.
Use public and alternative transportation
where possible to decrease the particulates
from exhaust that enter waterways. Support
state and federal initiatives for low-impact and
environmentally friendly development.
Health Index Map
This map shows the Bay Health Index for all reporting regions. You can also access individual reporting region summary pages by clicking on them, or mousing over for quick summaries.
2013 Bay health remains steady at moderate health
Overall Bay health remained steady from 2012 to 2013, decreasing from a score of 47% to 45%, which is rated as a C. Four out of the fifteen reporting regions had a significantly improving trend - indicating that the health of these regions has improved over time. The four regions with significantly improving trends were the Upper Western Shore, Upper Bay, James River, and Elizabeth River. York River, which scored a D, showed a slightly improving trend, although it was not significant. The Patapsco and Back Rivers region was the lowest-ranked region, which scored a F, with very poor ecosystem health. The Mid Bay region, which scored a C, shows a significantly decreasing trend - indicating that the overall Mid Bay health is declining over time.
This table shows the overall Bay Health Index for all reporting regions, which is derived from the following indicators: Chlorophyll a, Aquatic Grasses, Dissolved Oxygen, Benthic Index, Water Clarity, Total Nitrogen, and Total Phosphorus. Mouseover the index values to see the values of the component indicators/indices. You can also access individual reporting region summary pages by clicking on their name, or indicator details by clicking on their icons.
|Bay Health Index||61||50||47||45||45||42||40||40||40||37||37||35||26||25||23||19|
Listed in order of Bay Health Index from best to worst. You can access more detailed information on each reporting region by click on the region names.
Moderately good ecosystem health. Continues to be the highest scoring region, especially for total nitrogen and total phosphorus. Aquatic grasses and dissolved oxygen also improved.
Moderate ecosystem health. Second highest ranked with highest scores in dissolved oxygen, aquatic grasses, and chlorophyll. Over time this region is showing a significantly improving trend.
|Lower Eastern Shore (Tangier)|
Moderate ecosystem health. There were improvements in the total nitrogen and aquatic grasses scores. All other indicators declined.
Moderate ecosystem health. This area remained steady in 2013 with small improvements in some indicators and small declines in others. Over time this region is showing a significantly improving trend.
|Moderate ecosystem health. Overall, Chesapeake Bay scored a 45%, a C, which is almost the exact same score as last year even though there was a lot more rain. Water clarity in the Bay is declining; the amount of chlorophyll in the water was also higher, which added to the murkier water conditions. The indicator with the most improvement was aquatic grasses, largely due to increases of wigeon grass or Ruppia.|
|Upper Western Shore|
Moderately poor ecosystem health. Improved the most in overall score and scored the best dissolved oxygen score. Over time this region is showing a significantly improving trend.
Moderately poor ecosystem health. One of the only areas where water clarity improved, but is still failing. Other indicators showed small improvements.
Moderately poor ecosystem health. Continued decreases in total phosphorus and chlorophyll were offset by small improvements in other indicators. Benthic community continues to be one of the highest scoring indicators.
Moderately poor ecosystem health. Continued improvement from a low score in 2011. This region remains in the middle ranks of all regions with average indicator scores.
Poor ecosystem health. There were improvements in all indicators. There is no benthic community score for 2013. Over time this region is showing a significantly improving trend.
Poor ecosystem health. Most indicator scores decreased, with dissolved oxygen scoring the poorest of all regions. Over time this region is showing a significantly declining trend.
Poor ecosystem health. Continued improvements in total nitrogen, total phosphorus, dissolved oxygen, and aquatic grasses has led to an increase in the overall score.
Poor ecosystem health. This region remains steady in poor health. While some indicators improved, other declined. This region had one of the lowest dissolved oxygen scores.
|Upper Eastern Shore|
Poor ecosystem health. Most indicators showed a decline in scores with only marginal improvements in benthic community. Over time this region is showing a significantly declining trend.
|Lower Western Shore (MD)|
Poor ecosystem health. Failing scores for four out of seven indicators are leading to continued poor health. Slight improvements in benthic community were offset by declines in total phosphorus.
|Patapsco and Back Rivers|
Very poor ecosystem health. Although overall health improved, this continues to be the lowest ranked region. Four out of the seven indicators had failing scores. Over time this region is showing a slightly improving trend.
Comparison of Bay Health Index scores for 2013 () compared to ()
|0 20 40 60 80 100|
|Lower Eastern Shore (Tangier)|
|Upper Western Shore|
|Upper Eastern Shore|
|Lower Western Shore (MD)|
|Patapsco and Back Rivers|
Overall Bay Trends Graph*Note that for the Bay Health Index indicator (purple line), all annual scores are calculated using the historical method of six indicators (three water quality, three biotic) averaged into two sub-indices (Water Quality Index and Biotic Index) and then averaged into the Bay Health Index EXCEPT the 2012 and 2013 scores, which are calculated using the current method of seven indicators averaged into the Bay Health Index.
This graph is dynamic, you can: a) show and hide items by clicking them in the legend, b) select year range (click and drag), and c) export as an image.
The report card aims to inform citizens on the progress Chesapeake Bay is making toward becoming a healthy ecosystem. This year's report card shows that the health of the Bay improved slightly in 2007 when compared to 2006. While the overall health of the Bay and most regions of the Bay improved, the health of some regions of the Bay declined. This newsletter also explores some of the long-term changes in report card scores, making a connection between the scores and influencing factors such as land use and nutrient loads.
Getting to the source of the problem
It is well understood that excessive nitrogen, phosphorus, and sediments are major causes of Chesapeake Bay's poor health condition. To help reduce the amount of these pollutants entering the Bay, it is important to determine their sources, so that restoration efforts can be targeted for maximum effect. One of the tools used to estimate pollutant sources and loads and the effectiveness of best management practices (BMPs) is the Chesapeake Bay Watershed Model. This model estimates loads for a variety of land use types, based on factors such as BMP assumptions, average hydrology, vegetation cover, and point source nutrient loads. A simple assessment of the modeled nitrogen load estimates illustrates that the largest contributors are the Susquehanna, Potomac, and James Rivers, mainly due to the fact that these rivers have the largest watersheds. The main sources of nitrogen within each of the regions vary significantly. Agriculture is estimated to be the main source of nitrogen in the Eastern Shore regions, while point sources (wastewater) are the main factors in the James River and Patapsco and Back Rivers regions. The different primary nitrogen sources and the Bay health scores highlight the need for targeted implementation of best management practices. While the figure below provides a modeled estimate of nitrogen into each of the report card regions, it does not account for mixing or transport of nutrients from one region (e.g., the mainstem Bay) to another (e.g., a tributary such as the Patuxent River).
Estimated total nitrogen loads for 13 watersheds/regions in the Chesapeake Bay Watershed and the 2007 Bay Health Index for the 15 reporting regions.
Data: The Chesapeake Bay Watershed Model, Phase 4.3, 2007 Progress Run was used to estimate total nitrogen and phosphorus loads to Chesapeake Bay. Estimates for wastewater based on measured discharges; other categories based on average hydrology and current BMP efficiency assumptions. Does not include contributions from direct atmospheric deposition to tidal waters, tidal shoreline erosion, or the ocean.
Linking land use to Bay health
The Bay Health Index (BHI) provides a broad-level approach to assess the connection between land use and Bay condition. Land use within each of the watersheds is compared with the health of the adjacent waterway. In general, the higher the proportion of agricultural and developed land relative to forested land, the lower the BHI. This approach does not account for pollutants from other sources, such as coastal erosion or transport from adjacent waterways, but the strong correlation suggests that watershed activities in each region highly influence the BHI of the corresponding waterway. This relationship provides a useful framework from which the effects of land use change and best management practice (BMP) implementation can be viewed. Theoretically, if land use (% development and agriculture) stays the same, and the implementation of urban and agricultural best management practices is increased, then the health of the Bay will improve. Conversely, if BMPs were to decrease, then we can expect the health of the Bay to deteriorate. Additionally, if BMPs stay the same and land use (area % development and agriculture) changes, then the health of the Bay will also respond. This is an oversimplification of these relationships, but still serves as a good conceptual framework. An example of this oversimplification can be seen when looking at the effects of land use change from agriculture to developed land. Developed land (including urban run-off and partial treatment of human waste) within the Chesapeake watershed generates on average a total of 14.8 pounds of nitrogen per acre compared with the average agricultural rate of 11.71. Based on these numbers, a shift toward developed land at the expense of agricultural land will lead to increased nutrient loads unless urban BMPs can keep up with land use change — a factor not captured by the relationship shown.
The average Bay Health Index decreases with increasing conversion of forested lands to agriculture and urban development.
Estimated total nitrogen loads for 13 watersheds/regions in the Chesapeake Bay Watershed.
Data: Chesapeake Bay Watershed Model, Phase 4.3.
Best Management Practices
There are literally hundreds of Best Management Practices (BMPs) that target reduction of nutrient and sediment loads to Chesapeake Bay. These may be as simple as individuals fertilizing their lawn during the recommended time of the year (fall), to large and expensive engineering exercises such as upgrading municipal wastewater treatment plants. Here are some of the most important and some of the new BMPs being undertaken in agriculture and urban areas.
A. Cover crops - Non-harvested cereal cover crop specifically planted in fall for nutrient removal. Cereal cover crops reduce erosion and the leaching of nutrients to groundwater by maintaining a vegetative cover on cropland and holding nutrients within the root zone during the non-growing cash crop season (winter).
B. Riparian buffers - Up to 100-foot-wide buffer of grass, non-woody, or woody (forest) vegetation between crop and waterway. A 100-foot-wide strip of grass buffer can reduce sediment significantly. Fencing to exclude farm animals, although not a riparian buffer, can help slow the erosion of streamside soil.
C. Animal manure management - Animal farming uses directed flows to better contain waste products from animal houses. Lagoons, ponds, steel or concrete tanks, and storage sheds are used for the treatment and/or storage of wastes.
D. Septic upgrades - Septic denitrification represents the replacement of traditional septic systems with more advanced systems that have additional nitrogen removal capabilities. Septic connections/hookups represent the replacement of traditional septic systems with connection to and treatment at wastewater treatment plants.
E. Stormwater management control - Includes rain gardens (which direct flow from impervious surfaces to a vegetated area before the water reaches the storm drain), green roofs (which use the rainwater hitting the roof to feed plants), and riparian buffers. Filtering practices capture and temporarily store the water quality volume and pass it through a filter of sand, organic matter, and vegetation, promoting pollutant treatment and recharge.
F. Enhanced nutrient removal - Wastewater treatment plants are being upgraded to enhanced nutrient removal, which uses the most efficient removal process available, before the water is discharged into local waterways.