Vineyard views
Cliff Ohmart
If you have not seen the acronym “TMDL” in print, or heard someone talk about TMDLs at a workshop you recently attended, or saw attended, or saw it in some newsletter, there is a good chance that sometime during the next year you will hear about it. Because it is a measure of water quality, it is directly related to sustainable viticultural practices. Furthermore, it is an issue that could have a significant impact not only on they way we grow winegrapes, but on all other farming in California as well.
What is a TMDL?
TMDL is short for total maximum daily load. It was a concept/measurement that was created by the Federal Clean Water Act of 1972. Basically, it specifies the maximum amount of a specific type of pollution that a specific body of water can assimilate in a day and still meet its water quality standard(s). In other words, the body of water needs to be clean enough to be safe for its intended use. The Clean Water Act requires that each state establish water quality standards. In California, for example, two of the basic water quality standards for lakes, streams and rivers are that they are swim-able and fish-able. It is important to note that a TMDL is specific to a body of water, such as a river, or a segment of this body of water, as well as to a specific pollutant causing or threatening to cause the impairment. Therefore, there can be multiple TMDLs for one body of water.
A TMDL can be required for anything that impairs a body of water from meeting its quality standards. The first things that come to mind are chemicals, such as fertilizers and pesticides. However, things such as trash can be pollutants and subject to a TMDL if they impair the body of water. Other examples that can be subject to TMDLs are water temperature and dissolved oxygen.
Why haven’t we heard much about this issue if it has been around since 1972? It is mainly due to the fact that no one paid much attention to it until now. Sometimes Congress passes a law which contains some components that do not get noticed or come into play until many years after it is signed into law. TMDLs are a great example.
After the Clean Water Act went into effect, much of the attention to pollution focused on point source pollution. This type of pollution is literally what comes out of pipes into bodies of water, such as sewer lines, storm-water outlets, and industrial dumping. There has been great progress in addressing and cleaning up these problems. Years ago many of you probably read about rivers catching on fire as a result of industrial contamination. This was the result of point source pollution and, fortunately, it has really been significantly reduced.
However, once major progress was made with point source pollution, people realized there was another significant source of pollution, and that is non-point source pollution. When this issue comes into play, agriculture enters the spotlight. Non-point source pollution is any pollution that cannot be traced back to a ‘point’. Pesticides and nitrates in ground and surface water are two good examples of non-point source pollution.
How does the TMDL process work?
The Clean Water Act requires the state to identify bodies of water, or segments of bodies of water, which are “impaired”. In other words, they do not meet one or more of the standards for water quality established by the state, such as the swimable/fish-able standards mentioned above. Once a body of water is declared impaired, the Act requires the state to establish a TMDL (or TMDLs) for the pollutant or pollutants causing the impairment. After a TMDL is set for a particular pollutant, the total allowable loading is then allocated among the various sources of this pollutant in the watershed. Section 303(d) of the Clean Water Act requires the state to generate a list of impaired bodies of water and this list is called the ‘303(d) list’. This list can be viewed at the state of California’s Web page at www.wsrcb.ca.gov/html/news.html.
It seems that most people, both stakeholders and regulators, are unsure of the full meaning of the TMDL requirements and that the issue is evolving. In California at the moment, lawsuits have pretty much determined where and when TMDLs have been or are being set. To make matters worse, there are no statewide policies or regulations guiding TMDL development. Most involved parties readily admit that the state of California lacks sufficient data to determine which bodies of water are clean and which need TMDLs. Furthermore, interested groups disagree on how to define polluted bodies of water.
Nevertheless, one can begin to imagine how the TMDL process could affect winegrape growing. For example, if the river flowing through your watershed is declared impaired due to an excessive level of nitrates, then a TMDL would be set for nitrates. If this level was exceeded in the river, then all sources of nitrates, such as fertilization of crops, would be regulated. Another example would be, if the river running through your watershed had increased in temperature to the point that it was deleterious to fish, then a TMDL would be established so that steps would need to be taken to bring the water temperature back to an unimpaired level. These steps would most likely be things such as reducing sedimentation and establishing plants along the waterway that would shade the water and result in a lower temperature.
What can the winegrape industry do about TMDLs?
It is obvious from talking with people involved in the TMDL process and/or reading about TMDLs that no one really knows where this is all leading to and what impacts it will have on non-point source polluters, such as agriculture. One thing does seem clear, however–most winegrape growing regions will be affected by the process at some point in the future. It is hard to prepare for something that is not well-defined yet. One message that is coming out of the process is that regulators look very favorably on groups that are being pro-active about reducing non-point source pollution. How does one achieve a reduction in non-point source pollution in vineyards? The answer is reduction of vineyard inputs. So now you can see that we are back to discussing sustainable viticulture, which emphasizes input reductions.
Even though the TMDL process is focusing on specific pollutants, programs designed to address TMDLs will most likely be ones that involve whole farm management planning. By looking at your vineyard management as a whole system, you will be better able to decide where you can achieve input reductions. Two grower self-assessments have been developed by winegrape growers to aid in assessing the level of adoption of sustainable viticultural practices; one is the Positive Point System authored by the Central Coast Vineyard Team and the other is the Lodi Winegrower’s Workbook written by the Lodi-Woodbridge Winegrape Commission.
Grower self-assessment programs seem to meet the multiple challenges presented by issues such as TMDLs. They provide growers with: * a tool to assess their level of adoption of sustainable practices; * stimulation to implement more of these practices; * a way to measure improvement over time; and * a framework for a certification system that would be necessary to develop an “eco-label” for winegrapes, to add value to the product in the marketplace.
Furthermore, the Lodi Winegrowers Workbook contains educational material that provides education information to aid growers in implementing specific sustainable practices, and encourages growers to develop action plans for their implementation programs.
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