A coalition of environmental groups have announced that they have filed a motion in federal court to oppose the efforts of the American Farm Bureau Federation and their group. The environmental coalition includes the Chesapeake Bay Foundation (CBF), Citizens for Pennsylvania's Future, Defenders of Wildlife, the Jefferson County Public Service District, the Midshore Riverkeeper Conservancy, and the National Wildlife Federation. These groups are seeking to intervene in a lawsuit filed earlier this year by the American Farm Bureau and other agricultural groups. Intervening is a legal tactic that, if successful, would make the environmentalists a party in the case.
American Farm Bureau Federation and the Pennsylvania Farm Bureau went to federal court in Pennsylvania have since been joined the Fertilizer Institute, the National Pork Producers Council, the National Corn Growers Association, the National Chicken Council, the U.S. Poultry and Egg Association, and the National Turkey Federation. The American Farm Bureau and their groups argues that the EPA’s “allocation” of pollutant loads among sources in a TMDL exceeds EPA’s authority under the Clean Water Act; the assigned TMDLs are based on erroneous information that was input into computer models that are unsuitable for determining such loads even if accurate information had been used. Finally, the Farm Bureau contends that during the comment period the public did not have access to the information it needed to comment effectively on the modeling results and the assumptions in the Final TMDL.
The Chesapeake Bay Model is really made up of several models that are added together to create the whole: the Watershed Model, the Estuary Model, the Scenario Builder, the Airshed Model, the Land Change Model and the Land Use Models. The Watershed Model incorporates information about land use, fertilizer applications, wastewater plant discharges, septic systems, air pollution, farm animal populations, weather and other variables to estimate the amount of nutrients and sediment reaching the Chesapeake Bay and which of the major land uses produce these pollutants. This is the most robust and calibrated portion of the model sequence because it is calibrated and validated on the major tributary basin levels where there is decades of measured water quality data available. The Watershed Model divides the 64,000-square-mile Chesapeake Bay watershed into more than 2,000 segments. According to the 2010 versions of the EPA models that were used to derive the TMDLs, cropland accounts for 25% of sediment in the bay, 32% of the nitrogen and 27.5% of the phosphorus while accounting for only 10% of the Chesapeake Bay watershed acreage.
The waste load allocations in the TMDL are based to a large extent on land use data, and the amount that is impervious area. The EPA used satellite photographs to derive the amount of impervious surface. An analysis of Geographic Information System (GIS) land use data sampled in the Hampton Roads area of Virginia showed that the satellite imagery used by EPA for its land use inputs to the watershed model had underestimated the amount of paved surfaces in the region by an average of 48% compared to their GIS information. Neither EPA nor Hampton Roads provided an explanation of why these numbers are so different. Mike Rolband of Wetland Studies and Solutions, Inc. reported that his organization found that 2010 version of the model had used approximately 675,917 acres for the impervious surface area and 1,885,915 acres for the pervious surface area in the Virginia segments of the model. His organization reviewed the EPA’s own data from another sources and found that there were 1,569,377 impervious acres and 3,442,346 pervious acres in the urban areas in the Virginia segments of the model. This aligns with the Hampton Roads data.
Pollutions loads for nitrogen, phosphorus and sediment in the urban areas are calculated using a constant pounds/acre/year for impervious acres as a fixed input, and the pervious load is based on total fertilizer sales data. Pollutions loads for nitrogen, phosphorus and sediment in the urban areas are calculated using a constant pounds/acre/year for impervious acres as a fixed input, and the pervious load is based on total fertilizer sales data. Thus, if the EPA used their own data instead of the satellite data, the total current load for the urban areas would increase by 2,238,449 pounds of nitrogen per year, 636,097 pounds of phosphorus/year and 137,680 pounds of sediment/per year in Virginia. However, the total watershed loads for the overall model would remain the same since they were based on sampling results. So if the urban area loads increase, other area loads will have to decrease to keep the model’s output consistent with sampling data. The waste water treatment plants numbers are based on constant sampling necessary for their permits so their overall total contaminant load will not change. The forest lands number is also believed to be a “good” number, so that leaves the agricultural sector
In the regulatory world the model is reality. If the EPA chooses to not fully correct this error, and instead stays with the under reported amount of impervious surfaces the result would be MS4 permits that would be calculated based on a fraction of the total paved areas, and will have to reduce their urban runoff loads based on modeling data which assumes less impervious area than they actually have. In other words, the urban land area that will have to be treated in order to attain their mandated waste limits would be almost twice the land area assumed in the TMDL. In addition, the model would require a more extensive implementation of Agricultural BMPs to meet the required reduction in nitrogen, phosphorus and sediment than if the urban/suburban segment had correctly reflected the amount of pavement. This will unnecessarily increase the cost to the states of compliance with the TMDL. The Chesapeake Bay Phase 5.3.2 Model is due from the EPA on July 1, 2011.
The Farm Bureau claims that their lawsuit challenges a specific, unlawful EPA regulatory action. It is about federal government overreaching into state rights to self govern across seven jurisdictions. The States within the watershed have estimated that implementation will cost billions of dollars making this a very high stakes argument for the States, cities and farmers. At their news conference the Chesapeake Bay Foundation described the Farm Bureau and their coalition as "big ag" and described their lawsuit as an attempt to derail the latest bay cleanup program for profit. Earning a profit is not necessarily evil.
The EPA model’s allocation of pollution origination is one of sources for the current “green community” anti agriculture stance. The agricultural sector is being viewed as an excessive polluter, though farm management practices have improved over the years as output has increased to feed the ever growing population. The farmers (both family and corporate) feel they have not been given full credit for that improvement. The Chesapeake Bay Watershed Model is a good tool in understanding how nitrogen, sediment, and phosphorus loads from different sources are delivered to the Bay. On a major tributary basis, real world data has been used to calibrate and validate the watershed portion of the model. Thus, it can provide predictive results of implementing best management practices, a useful tool to help make decisions about tradeoffs to control the loads of nutrients and sediment in the Chesapeake Bay Watershed. Implementing and maintaining best management practices and conservation plans on farms is difficult, because it involves changing often long established practices and the way that farmers manage their land and operations and requires a management plan for each operation no matter the size, but it is still probably the most cost effective method of meeting the TMDL. Instead of paying for lawyers maybe both of these groups should consider funding agricultural wells for animal operations so that water way exclusion fencing (which has available cost share dollars) can be built.
Showing posts with label Mike Rolband. Show all posts
Showing posts with label Mike Rolband. Show all posts
Thursday, June 9, 2011
Monday, January 31, 2011
In the EPA’s TMDL Pollution Diet The Biggest Looser is Northern Virginia
The most recent meeting of the Potomac Watershed Roundtable was in Warrenton, VA at Lord Fairfax Community College and had a series of speakers on the Chesapeake Bay strict pollution diet, the Total Maximum Daily Load (TMDL) mandated by the EPA to the six Chesapeake Bay Watershed states and the District of the Columbia. The TMDLs were assigned by the EPA to each segment of the Chesapeake Bay Watershed. For the TMDL, the Chesapeake Bay’s tidal waters have been divided into 92 tidal water segments. There are 35 segments controlled by Virginia and another five Maryland owned segments that include Virginia drainage areas. The different water segments are determined by their varying degrees of salinity, recalling that the Chesapeake Bay Watershed is an estuary. Finally, the TMDLs address only pollution from excess nitrogen, phosphorus and sediment. No action has been taken on other pollutants that might be present in the Chesapeake Bay and its tributaries.
On November 29th 2010 Virginia, submitted the final version of the Virginia Chesapeake Bay Watershed Implementation Plan (WIP) to the U.S. Environmental Protection Agency and December 29th the EPA accepted the revised version of Virginia’s WIP and issued the “final” TMDL, but with “enhanced oversight.” (Doesn’t that sound like fun.) The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution. It is possible that they have been spending a wee bit too much time looking at computer output and missed the big picture.
Mike Rolband, President of Wetland Studies and Solutions, Inc. had an interesting presentation pointing out poor model behavior, mistakes and injustices of the current TMDL, what EPA has called the strict pollution diet, but really is an excess nutrient diet. When Mike showed the group his slides, several aspects of the Chesapeake Bay Watershed, the EPA’s models, the mandated TMDLs became very clear for me. First of all, the level of excess nutrients in each of the major tributaries to the Chesapeake Bay is fairly well known and well predicted and calibrated by the models. Second, this is indeed a diet, the Chesapeake Bay is overwhelmed with excess nutrients and sediment, and like an obese person, less nutrients will improve the situation. Thirdly, land use and population density matter, but generally the higher the population the more total nutrients are released. Waste water treatment plants and urban runoff and septic contribute a larger load of nitrogen than the agricultural sector. Finally, the EPA mandated TMDL and the approved WIPs to implement them require a percentage reduction in nutrient load from each sector.
This turns out to be vastly inequitable. Eliminating the agricultural sector, Northern Virginia with 46% of the watershed population is required to obtain a total nitrogen load for the waste water treatment plants, urban and septic of 2.52 pounds of nitrogen/person/year while the James River Basin is only required to obtain 6.38 pounds of nitrogen/person/year and the state target average is 4.43 pounds of nitrogen/person/year. This is the equivalent of mandating a diet for everyone in Virginia to lose 1/3 of their body weight. This might be just fine and actually beneficial for the 300 pound people who will be forced to lose 100 pounds, but it is lethal for the 150 pound Potomac Watershed that will have to loose 50 pounds each. We in northern Virginia are trapped in some Kafka version of a diet where slow death by starvation (stopping population growth and potentially reducing population) may be the unintended consequences of the EPA mandated pollution diet.
On November 29th 2010 Virginia, submitted the final version of the Virginia Chesapeake Bay Watershed Implementation Plan (WIP) to the U.S. Environmental Protection Agency and December 29th the EPA accepted the revised version of Virginia’s WIP and issued the “final” TMDL, but with “enhanced oversight.” (Doesn’t that sound like fun.) The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution. It is possible that they have been spending a wee bit too much time looking at computer output and missed the big picture.
Mike Rolband, President of Wetland Studies and Solutions, Inc. had an interesting presentation pointing out poor model behavior, mistakes and injustices of the current TMDL, what EPA has called the strict pollution diet, but really is an excess nutrient diet. When Mike showed the group his slides, several aspects of the Chesapeake Bay Watershed, the EPA’s models, the mandated TMDLs became very clear for me. First of all, the level of excess nutrients in each of the major tributaries to the Chesapeake Bay is fairly well known and well predicted and calibrated by the models. Second, this is indeed a diet, the Chesapeake Bay is overwhelmed with excess nutrients and sediment, and like an obese person, less nutrients will improve the situation. Thirdly, land use and population density matter, but generally the higher the population the more total nutrients are released. Waste water treatment plants and urban runoff and septic contribute a larger load of nitrogen than the agricultural sector. Finally, the EPA mandated TMDL and the approved WIPs to implement them require a percentage reduction in nutrient load from each sector.
This turns out to be vastly inequitable. Eliminating the agricultural sector, Northern Virginia with 46% of the watershed population is required to obtain a total nitrogen load for the waste water treatment plants, urban and septic of 2.52 pounds of nitrogen/person/year while the James River Basin is only required to obtain 6.38 pounds of nitrogen/person/year and the state target average is 4.43 pounds of nitrogen/person/year. This is the equivalent of mandating a diet for everyone in Virginia to lose 1/3 of their body weight. This might be just fine and actually beneficial for the 300 pound people who will be forced to lose 100 pounds, but it is lethal for the 150 pound Potomac Watershed that will have to loose 50 pounds each. We in northern Virginia are trapped in some Kafka version of a diet where slow death by starvation (stopping population growth and potentially reducing population) may be the unintended consequences of the EPA mandated pollution diet.
Monday, January 24, 2011
The Error in the Allocation to Agriculture Under the Virginia TMDL
The most recent meeting of the Potomac Watershed Roundtable was in Warrenton, VA at Lord Fairfax Community College and had a series of speakers on the Chesapeake Bay strict pollution diet, the Total Maximum Daily Load (TMDL) mandated by the EPA to the six Chesapeake Bay Watershed states and the District of the Columbia. The TMDL addresses only pollution from excess nitrogen, phosphorus and sediment. No action has been taken or at this time is intended on other pollutants that might be present in the Chesapeake Bay and its tributaries. Part of the meeting was devoted to educating the audience on the Chesapeake Bay Model.
The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution.
Mike Rolband of Wetland Studies and Solutions, Inc. had some fun with what is apparently one of the large mistakes in the model that is expected to have a correction released in the near future. His professional interest is in managing impervious and pervious surface run off. His consulting firm looked at the underlying data used to create the Land Use estimates. Land Use model estimates the types and amounts of pollution that run off a particular land use are based on comprehensive reviews of the latest scientific literature there is limited measurement here for many of the land uses, but the responsible land use is assigned a numeric blame. Using EPA published data Wetland Studies and Solutions was participant in pointing out to the EPA that they had massively underestimated the impervious and pervious surface areas in the Urban Areas in Virginia (and I assume other areas).
It seems that the most recent version of the model had used approximately 675,917 acres for the impervious surface data and 1,885,915 acres for the pervious surface data. A review of the EPA’s own data found that there were 1,569,377 impervious acres and 3,442,346 pervious acres in the urban areas in the Virginia segments of the model. These include all the paved and landscaped areas of suburbia. Between the 1990 census and the 2010 census the population of Virginia grew from 6.2 million people to 8.0 million people. The bulk of that growth took place in the urban and suburban centers of the Chesapeake Bay watershed.
Now here is where it gets interesting. Pollutions loads for nitrogen, phosphorus and sediment in the urban areas are calculated using a constant pounds/acre/year for impervious acres as a fixed input, and the pervious load is based on total fertilizer sales data. The bottom line is that the EPA has confirmed that they will not change the loading rate because they have high confidence in the loading rate for the impervious surfaces and the total fertilizer sales are reported and tracked data and is a hard number. Thus the total current oad for the urban areas will increase by 2,238,449 pounds of nitrogen per year, 636,097 pounds of phosphorus/year and 137,680 pounds of sediment/per year. However, the total watershed loads for the overall model will remain the same. So, while the urban area loads will increase, other area(s) loads will have to decrease.
Mike Rolband has pointed out that the agricultural sector will probably have their load reduced. The waste water treatment plants numbers are based on constant sampling necessary for their permits so their overall total contaminant load will not change. The forest lands number is also believed to be a “good” number, so that leaves the agricultural sector and in the case of total nitrogen, also septic. Over 2.2 million pounds a year is a lot of nitrogen it represents of the total load attributed to agriculture. The farm segment has been protesting loudly that they are not being given proper credit for implementation of best management practices and that surface waters are already degraded when they reach their farms.
It seems that the American Farm Bureau Federation who have recently filed suit against the EPA claiming the models are flawed is right. The smug assumption that farmers are the bad guys by the new generation of environmentalists is to an extent wrong. Man is the animal contributing the most nitrogen to the Chesapeake Bay in the form of wastewater treatment plant permitted waste, septic and urban/ suburban runoff. The Chesapeake Bay Foundation owes the American Farm Bureau Federation an apology for their recent quote in the Washington Post.
The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution.
Mike Rolband of Wetland Studies and Solutions, Inc. had some fun with what is apparently one of the large mistakes in the model that is expected to have a correction released in the near future. His professional interest is in managing impervious and pervious surface run off. His consulting firm looked at the underlying data used to create the Land Use estimates. Land Use model estimates the types and amounts of pollution that run off a particular land use are based on comprehensive reviews of the latest scientific literature there is limited measurement here for many of the land uses, but the responsible land use is assigned a numeric blame. Using EPA published data Wetland Studies and Solutions was participant in pointing out to the EPA that they had massively underestimated the impervious and pervious surface areas in the Urban Areas in Virginia (and I assume other areas).
It seems that the most recent version of the model had used approximately 675,917 acres for the impervious surface data and 1,885,915 acres for the pervious surface data. A review of the EPA’s own data found that there were 1,569,377 impervious acres and 3,442,346 pervious acres in the urban areas in the Virginia segments of the model. These include all the paved and landscaped areas of suburbia. Between the 1990 census and the 2010 census the population of Virginia grew from 6.2 million people to 8.0 million people. The bulk of that growth took place in the urban and suburban centers of the Chesapeake Bay watershed.
Now here is where it gets interesting. Pollutions loads for nitrogen, phosphorus and sediment in the urban areas are calculated using a constant pounds/acre/year for impervious acres as a fixed input, and the pervious load is based on total fertilizer sales data. The bottom line is that the EPA has confirmed that they will not change the loading rate because they have high confidence in the loading rate for the impervious surfaces and the total fertilizer sales are reported and tracked data and is a hard number. Thus the total current oad for the urban areas will increase by 2,238,449 pounds of nitrogen per year, 636,097 pounds of phosphorus/year and 137,680 pounds of sediment/per year. However, the total watershed loads for the overall model will remain the same. So, while the urban area loads will increase, other area(s) loads will have to decrease.
Mike Rolband has pointed out that the agricultural sector will probably have their load reduced. The waste water treatment plants numbers are based on constant sampling necessary for their permits so their overall total contaminant load will not change. The forest lands number is also believed to be a “good” number, so that leaves the agricultural sector and in the case of total nitrogen, also septic. Over 2.2 million pounds a year is a lot of nitrogen it represents of the total load attributed to agriculture. The farm segment has been protesting loudly that they are not being given proper credit for implementation of best management practices and that surface waters are already degraded when they reach their farms.
It seems that the American Farm Bureau Federation who have recently filed suit against the EPA claiming the models are flawed is right. The smug assumption that farmers are the bad guys by the new generation of environmentalists is to an extent wrong. Man is the animal contributing the most nitrogen to the Chesapeake Bay in the form of wastewater treatment plant permitted waste, septic and urban/ suburban runoff. The Chesapeake Bay Foundation owes the American Farm Bureau Federation an apology for their recent quote in the Washington Post.
Monday, January 17, 2011
The Chesapeake Bay Model
The most recent meeting of the Potomac Watershed Roundtable was in Warrenton, VA at Lord Fairfax Community College and had a series of speakers on the Chesapeake Bay strict pollution diet, the Total Maximum Daily Load (TMDL) mandated by the EPA to the six Chesapeake Bay Watershed states and the District of the Columbia. The TMDL addresses only pollution from excess nitrogen, phosphorus and sediment. No action has been taken or at this time is intended on other pollutants that might be present in the Chesapeake Bay and its tributaries. Two of the speakers, walked the Roundtable audience through some of the issues and uncertainties will impact implementing a plan to achieve the TMDLs on the local level.
Clifton Bell of Malcolm Pirnie, Inc. and Mike Rolband of Wetland Studies and Solutions, Inc. walked the group through some of the issues with the EPA “final” TMDL loading levels and how they were obtained. The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution. Mr. Bell lifted the curtain to point out some aspects of the models.
Although model simulations are an important part of the Chesapeake Bay regulatory mandate, they are not considered by the EPA to be perfect forecasts. Rather, model simulations are the current best estimates. The Chesapeake Bay Model is really made up of several models that are added together to create the whole: the Watershed Model, the Estuary Model, the Scenario Builder, the Airshed Model, the Land Change Model and the Land Use Models.
The Watershed Model incorporates information about land use, fertilizer applications, wastewater plant discharges, septic systems, air pollution, farm animal populations, weather and other variables to estimate the amount of nutrients and sediment reaching the Chesapeake Bay and which of the major land uses produce these pollutants. This is the most robust and calibrated portion of the model sequence because it is calibrated and validated on the major tributary basin levels where there is decades of measured water quality data available. The Watershed Model divides the 64,000-square-mile Chesapeake Bay watershed into more than 2,000 segments.
The Estuary Model examines the effects that pollution loads generated by the Watershed Model have on water quality. In the Estuary Model, the Chesapeake Bay is further divided into more than 57,000 computational cells and is built on two sub-models: The hydrodynamic sub-model and the water quality sub-model. The water quality sub-model is well calibrated for dissolved oxygen.. However, it is unclear that dividing up the world in ever smaller pieces gives you better resolution when there are not enough hard data points in the cells. Zooming in on a picture without adequate pixels does not increase the resolution.
The Scenario Builder can generate simulations of the past, present or future state of the Chesapeake Bay watershed to explore potential impacts of regulation and management actions and evaluate alternatives. This model creates the assumptions in the regulated community much like Sims game.
The Airshed Model uses information about nitrogen emissions from power plants, vehicles and other sources to estimate the amount of and location where these pollutants are deposited on the Chesapeake Bay and its watershed using information from vehicle registrations and DOT and weather.
The Land Change Model analyzes and forecasts the effects of urban land use and population on sewer and septic systems in the Chesapeake Bay watershed based on: population trends and forecasts, migration, satellite imagery, and waste water treatment plant service area and data. Finally, the Land Use model estimates the types and amounts of pollution that run off a particular land use are based on comprehensive reviews of the latest scientific literature.
Since most of the models were built and calibrated on the data that has been collected over the years they are well calibrated on the major tributaries and basins where most of the sampling and research has been done. The models are designed conservatively; all waste water treatment plants are assumed to discharge their maximum load simultaneously. The best management practices, BMPs, used to manage stormwater and runoff are assumed to be effective only at the low end of their effectiveness range.
In addition, according to Mr. Bell, the model was never designed to be accurate on the local level and this was confirmed in 2008 when the Scientific and Technical Advisory Committee, STAC, Peer Review recommended that the model not be used for local TMDLs. Nonetheless, that is exactly what the EPA did. The models reportedly produce some non-intuitive trends, poorly calibrated results and poor model behavior raising the question of whether the regulatory scheme relies too heavily on the model and will distort desired behavior. They have created a situation where base assumptions are based on the model’s presentation of reality and management practices are not selected for the cost and measured improvement on water quality or ease to maintain, but rather the impact these steps have on model results.
Clifton Bell of Malcolm Pirnie, Inc. and Mike Rolband of Wetland Studies and Solutions, Inc. walked the group through some of the issues with the EPA “final” TMDL loading levels and how they were obtained. The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution. Mr. Bell lifted the curtain to point out some aspects of the models.
Although model simulations are an important part of the Chesapeake Bay regulatory mandate, they are not considered by the EPA to be perfect forecasts. Rather, model simulations are the current best estimates. The Chesapeake Bay Model is really made up of several models that are added together to create the whole: the Watershed Model, the Estuary Model, the Scenario Builder, the Airshed Model, the Land Change Model and the Land Use Models.
The Watershed Model incorporates information about land use, fertilizer applications, wastewater plant discharges, septic systems, air pollution, farm animal populations, weather and other variables to estimate the amount of nutrients and sediment reaching the Chesapeake Bay and which of the major land uses produce these pollutants. This is the most robust and calibrated portion of the model sequence because it is calibrated and validated on the major tributary basin levels where there is decades of measured water quality data available. The Watershed Model divides the 64,000-square-mile Chesapeake Bay watershed into more than 2,000 segments.
The Estuary Model examines the effects that pollution loads generated by the Watershed Model have on water quality. In the Estuary Model, the Chesapeake Bay is further divided into more than 57,000 computational cells and is built on two sub-models: The hydrodynamic sub-model and the water quality sub-model. The water quality sub-model is well calibrated for dissolved oxygen.. However, it is unclear that dividing up the world in ever smaller pieces gives you better resolution when there are not enough hard data points in the cells. Zooming in on a picture without adequate pixels does not increase the resolution.
The Scenario Builder can generate simulations of the past, present or future state of the Chesapeake Bay watershed to explore potential impacts of regulation and management actions and evaluate alternatives. This model creates the assumptions in the regulated community much like Sims game.
The Airshed Model uses information about nitrogen emissions from power plants, vehicles and other sources to estimate the amount of and location where these pollutants are deposited on the Chesapeake Bay and its watershed using information from vehicle registrations and DOT and weather.
The Land Change Model analyzes and forecasts the effects of urban land use and population on sewer and septic systems in the Chesapeake Bay watershed based on: population trends and forecasts, migration, satellite imagery, and waste water treatment plant service area and data. Finally, the Land Use model estimates the types and amounts of pollution that run off a particular land use are based on comprehensive reviews of the latest scientific literature.
Since most of the models were built and calibrated on the data that has been collected over the years they are well calibrated on the major tributaries and basins where most of the sampling and research has been done. The models are designed conservatively; all waste water treatment plants are assumed to discharge their maximum load simultaneously. The best management practices, BMPs, used to manage stormwater and runoff are assumed to be effective only at the low end of their effectiveness range.
In addition, according to Mr. Bell, the model was never designed to be accurate on the local level and this was confirmed in 2008 when the Scientific and Technical Advisory Committee, STAC, Peer Review recommended that the model not be used for local TMDLs. Nonetheless, that is exactly what the EPA did. The models reportedly produce some non-intuitive trends, poorly calibrated results and poor model behavior raising the question of whether the regulatory scheme relies too heavily on the model and will distort desired behavior. They have created a situation where base assumptions are based on the model’s presentation of reality and management practices are not selected for the cost and measured improvement on water quality or ease to maintain, but rather the impact these steps have on model results.
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