Biological Projects

US Fish and Wildlife Service

Water levels in many Kenai Peninsula ponds and lakes have fallen in recent years. The reasons for this are not entirely clear, but they probably relate to climate warming and increased evapotranspiration, and in some cases to post-1964 earthquake changes. Regardless of the causes, the effects of lower water tables can be quite striking, e.g., a boat dock no longer reaches the water in a lake or a household well runs dry.

The goal of this survey is to document water level changes around the Peninsula to assess the pattern of change, both spatially and through time. From these observed patterns we hope to determine the causes of change, and make predictions about water levels in coming years and decades. Pond and lake levels and water tables can affect drinking water supplies, septic systems, shoreline property values, fish and wildlife abundance, and fire frequency; hence this survey has practical as well as scientific interest. The survey is part of the permanent Water Quality Program of the Kenai National Wildlife Refuge.

We have an illusion of abundant water on the Kenai, but our modest 19" of total precipitation per year could look quite arid if annual temperature was to rise 5 or 10^oF, as the global climate models predict during the next 50-100 years. We have already experienced a 3^oF rise in Kenai and a 4^oF rise in Homer in mean annual temperature since the cool late 1940's.

Water table: The water table is the top of the water-saturated zone. When the water table is below ground, we can measure its depth in an open well. With a lake or a stream, the water table is above ground, and the shoreline is the place where the water table goes underground. Our study focuses on shorelines to look for evidence of long-term lowering (or raising) of water tables over a period of several to many years.

Lakes vs. Ponds: In this survey we consider ponds to be small lakes, and will use the term "lake" to include both ponds and lakes. For our purposes, ponds are just as valuable as larger lakes for indicating the water table. Indeed, we first became interested in falling water tables when we noticed that many ponds on the 1950's maps and aerial photos have dried up completely and are now grassy pans with invading trees and shrubs.

Lake levels can change for a variety of reasons: beavers, erosion or damming of the outfall, earthquake effects (tectonic uplift or subsidence), long-term changes in annual precipitation, long-term changes in temperature and solar irradiance (sunshine), vegetation changes in the watershed (due to fire, logging, beetle kill, growth of trees and shrubs), and human activities (road building, ditching, water use).

Open-basin vs. closed-basin lakes: An open-basin lake has a stream outfall, i.e., a stream flowing out of the lake. A closed-basin lake has no outfall, so all of its water is lost through evaporation or underground flow. For studying climate effects, closed-basin lakes are the most interesting because the water level change is mostly controlled by measurable climate features, i.e., annual precipitation, temperature, relative humidity, and wind patterns. Open-basin lakes, on the other hand, can maintain a constant level as long as water is flowing out through the outfall, like an overflowing bathtub. In this case, a recording device at the outfall to measure the lake discharge (rate of outflow) would be best, but this would be very expensive. In this survey we will gather data on open-basin lakes, as well as closed-basin lakes, primarily for future reference. The rate of water table decline is severe enough in some areas that open-basin lakes are being converted to closed-basin lakes, e.g., the water level in Upper Jean Lake is now 2' below its old (inactive) outfall. For climate change purposes, however, our primary interest is in closed-basin lakes.

Open-basin lake levels can fall if the outfall stream is eroding and cutting a deeper channel, but this is unusual with our heavily vegetated lake perimeters. A more likely case is a rising lake level due to a beaver dam, and perhaps a periodic fall of the lake level when the beaver dam is breached and rebuilt.

Springs: a spring is simply a place where ground water comes out of the ground with a noticeable flow. Most lakes in this area are fed by groundwater, as well as by surface runoff, and therefore are in some sense "spring fed," although one might reserve the term "spring fed" for lakes where one can see an active bubbling up of water at the lake edge or in shallow water.

Beach apron: Lakes with low water levels often show a gently sloping sand or gravel apron from the old shoreline down to the water line. The age of the new vegetation on this apron can be used to date how long the water level has been down. For example, if there are only small annual plants (with fine roots) growing on the apron, the water may have been down for only a year or two. If woody seedlings or saplings have established, we can count their terminal bud scars or tree-rings to determine their age. Hardwood seedlings can be quite profuse on beach aprons, e.g., cottonwood, alder, birch, and willow.

Flooding: Lake levels often rise in the spring with snow melt and can flood the plants growing on a beach apron and lake perimeter. This spring flooding doesn't usually kill the plants. If, however, the water level stays up all summer, it would kill the woody plants.

Fluctuating lake levels: Apart from spring snowmelt flooding, most closed-basin Kenai Peninsula lakes that we have examined appear to be getting lower and lower each year. That is, lake level lowering on the Kenai seems to be a "unidirectional" process that doesn't reverse direction. If the process reversed itself, and beach aprons and lake shores were flooded for an entire season, we would see dead (water-killed) vegetation. When the lake level is up, we might see dead stems sticking out of shallow water, or if the lake level had gone up and then come down, we might see dead stems along the beach apron. Since we have not so far seen any indications of this kind of reversal of the trend, we are especially interested that such signs of reversal (i.e., summer-long flooding) be reported on the Data Sheet. Contradictory evidence is the most interesting kind of evidence!

Dead trees in a lake: Dead trees in standing water are an excellent indication that lake level has risen. Beaver ponds often show flood-killed dead trees. We can determine the death dates of such trees by comparing their ring-width patterns with those of live trees on the shore. If the death dates are the same in a group of flooded trees, that date is probably the year that the water level first rose. (Whether or not the water level has since remained high would have to be determined from other evidence.)

Timing of the survey: Lake levels should be surveyed well after snow melt and spring runoff have occurred, so as to avoid any temporary spring rise of water level. Summer 1999 should be a particularly good year to survey lake levels because of the heavy snowfall last winter. If lake levels are still down after a big pulse of snowmelt, this will be good evidence that we are in long-term drying trend that is independent of year-to-year variation in precipitation.

Heavy snowfall last winter: As of April 2, the Moose Pens (Swan Lake Road) snow depth measured 35" with a water content of 9.6". This is 4x above the 1961-90 average of 9" snow depth with a water content of 2.5". Jean Lake was 2x above the 1961-90 average, with 23" snow depth and 6.2" water content, as opposed to the average of 12" snow depth and 3.1" water depth. This very high snowpack should start off the summer with high lake levels. (NRCS Alaska Basin Outlook Report, April 1, 1999)

Photographs: One photo is worth a thousand words. A good photograph should show a profile of the bank and waterline if possible, taken by standing on the beach apron or in shallow water. Flooded trees, if any, should be photographed.

Local knowledge: We especially need observations from people who have viewed or used a lake for a number of years. These could be shoreline property owners, people who fish the lake, trappers, birdwatchers, and boaters. This survey is a good opportunity to record their observations about a variety of other features besides lake levels, such as fishing conditions, birds and wildlife, human usage, and vegetation. The key thing to emphasize is any change in these things, e.g., fewer loons or swans, more aquatic vegetation, more boating, introduced fish, etc. If possible, provide names of sources, in case we need to follow up their comments for more information.

Pond and Lake Level Data Sheet (Page 1)
Pond and Lake Level Data Sheet (Page 2)