Diversion Tactics

Thirty years ago the waters of Harding Lake, near Fairbanks, lapped at grassy banks below the summer cottages surrounding the shore. Now, the lake level has lowered leaving not-so-lovely mudflats between the houses and the water.

In the grand scheme of things, small lakes--all lakes, in fact--are but temporary objects that eventually get drained or overgrown. The question for those around the lake is whether steps should be taken to try to keep Harding Lake at a desirable level or to let Nature take its course.

This is not a simple question to answer. For one thing, it may be hard to define the best level to hold the lake at. As the lake shore has retreated in recent years, houses have been built farther out from the old shoreline. Does one sacrifice some property to give better shorelines to other properties?

Also there is the question about long-term trends. Is the lake steadily lowering, or is its surface oscillating up and down with a 40 year cycle, as some evidence suggests?

Harding Lake has no outlet. Aside from the four square miles of its own area, the lake is fed by runoff from an area of about five square miles. A diversion ditch could be dug to bring in runoff from an additional ten square miles east of the lake.

Should the diversion be attempted? Years ago, the approach might have been trial by fire to see what would happen. Now, people are more inclined to ponder the possible consequences of such an action. In particular, the lack of an outlet gives real possibility to unwanted flooding if too much water gets into the lake. The University of Alaska's Institute of Water Resources has determined that the level of Harding Lake probably would have stabilized at a level about 8 feet (2.5 meters) above the current low level had the diversion been done in 1970.

Even with this encouraging result, people may be inclined to proceed with caution. Uncertainties exist about rainfall, evaporation rates, climatic cycle effects and groundwater flow in and out of the lake. Then there is the nasty question of who is responsible if an action is taken and things go badly.