There has been a lot of discussion at the annual NALMS symposium over the last 5 years about the value of watershed management. Much of this discussion was a reaction to federal and state directives to focus on watershed management to solve lake problems, as we know from many years of experience that some problems cannot be solved with watershed management (e.g., internal phosphorus loading, excessive plant density) and watershed management has proven very difficult over large areas under multiple jurisdictions. In articles in LakeLine and presentations at NALMS meetings a few people have made statements that have been interpreted as opposing watershed management, but these statement are being misinterpreted in the context of protection vs. restoration.
First of all, there is very little lake restoration going on. We often rehabilitate lakes, altering them to meet use goals, but that is not the same thing as restoration. For lakes created by erecting a dam, true restoration would mean removing the dam and eliminating the lake; this is not usually what lake managers have in mind when they use the word “restoration”. But whether we call it restoration or rehabilitation, reducing nutrient levels, algae blooms and nuisance vascular plant growths is rarely achieved by watershed management once the lake gets to the point of supporting such growths. Once in a while we find the “smoking gun” and can implement a focused watershed management plan, but usually it is a slow, incremental process that very rarely moves the lake adequately in the right direction. Consequently, in-lake efforts are often needed to meet use goals, including phosphorus inactivation, dredging, herbicides, harvesting and other commonly applied methods.
Protection, however, is another matter. If a lake is in a desirable state, it is wrong to assume it will always be that way. Watershed influences can be gradual or catastrophic, but their presence is undeniable. If the watershed is large enough (>10:1 ratio with lake area is a commonly cited threshold), inputs over many years will eventually change the character of the lake, and water quality issues become more probable when the watershed is >50 times the area of the lake, even with no human activities in the lake. However, human activities greatly accelerate loading of sediment, nutrients and a variety of other contaminants. Thresholds as low as 6% development in the watershed have been cited as resulting in measurable changes in water quality, and at development levels on the order of 25-30% it is rare not to see deterioration of water quality. Watershed management is therefore essential to protecting lakes, but the potential to adequately protect the lake declines as the percentage of development or agriculture increases.
Watershed management is a logical component of any lake management plan. It is wrong to hold an invasive plant control project hostage until the applicant produces a watershed management plan, but it is entirely reasonable to expect holistic lake management programs to incorporate watershed management. If protection of desirable features is the goal, watershed management is a must. If rehabilitation of degraded conditions is needed, watershed management is not likely to be the whole answer. Keep protection and restoration elements of any plan separate when discussing lake management to avoid controversy over the role of watershed management.