Thursday: 23 August 2007
First, the weather. The peak temperatures out here exceeded the 107.0 degree high experienced August 11 by nearly half a degree - 107.4 degF. In town the trusted measurement was 104.4, so it won’t break the daily record of 106, which places the event in the category of being both satisfying and dissatisfying. Then a completely unpredicted thunderstorm occurred late evening, while I was at work, of course, unable to appreciate the rare event, bringing our August rainfall up to 0.20 inches, 1/20th normal.
Second, the issue of the dammed lake I described yesterday took on much more of a life than I had expected, driven by the actions of two Goulding Creek neighbors and of Glenn.
After some thought and conversation with Pat, who fronts Goulding Creek a mile downstream from us, I realized my conclusions that the dammed lake has little effect on the status of the water table was not quite correct. According to the memory of elderly neighbor Lee, who has lived on Goulding Creek all his life and has made it a major passion, there were springs driving Goulding Creek way before the dam was built and the lake covered them in the early 1970s. Thus the lake is probably nourished by the aquifer, as well as by inflow from Goulding Creek upstream (when it’s not dry). This means that the dam has for decades reduced the nourishment of Goulding Creek downstream and has actively, persistently imposed a reduction of the water table downstream. (This also helps to explain how the lake has remained full even though the inflow has dried up in the last few weeks.) Even without the alleged springs, I had to conclude that the minimization of outflow of the water from the lake over many years has exacerbated the emergency we’re now facing.
I also did some calculations (as had a third neighbor, and our results and recommendations converged almost exactly). These numbers will probably not be on the exam later.
The lake holds 160 million gallons of water and has a surface area of 74 acres and an average depth of 7.5 feet. I figured that for a downstream flow of water 3 inches deep and 10 feet wide moving at a mile an hour, a daily outflow from the dam of about 100,000 gallons a day would be required. This would lower the lake by 1.3 inches a day, disregarding any compensating input from other sources. My choice of this downstream flow was my own gut feeling of what it would take to keep the water table up, and keep the creek minimally nourished.
This changes the situation considerably, since it suggests an experiment that could not possibly harm the residents of the lake. And since the board of the lake association was having a meeting last night, Glenn, Pat, and Lee (none of us members of the association, of course), attended and discussed this with the board. Vague proposals were discussed but generally revolved around opening the outflow as soon as possible to create this volume of output and leave it that way for a week, then re-evaluate after observing the effects. Since we live about halfway down Goulding Creek, at 0.8 miles, and the other two neighbors live a mile farther downstream, we’re in an excellent position to make those observations.
Half the board was supportive, half was negative to one degree or another, but they were reasonably polite. They certainly must be credited with the courtesy of allowing the three outsiders to speak and argue. They left after the discussion, but before the board concluded its business so we don’t know what their conclusion was.
At any rate, the issue is not going to die. We need to come up with a specific proposal now and transmit them to the board members for consideration.
Third, there’s this terrible photo of a visitor from yesterday. I didn’t have my eyes in so had to use the automatic focus. I’ve kept the photo small so as to reduce the pain of having to view it:
With the yellow antennae, the long abdomen, the lack of the three long threadlike ovipositors, and the yellow highlights, this is probably a male Giant Ichneumon, Megarhyssa atrata. A female is shown in the linked bugguide page. My first encounter with one, if so, and a friendly wasp indeed. These are parasitic wasps, stingless, I think. With those long long ovipositors the female probes into crannies and burrows in tree bark and then deposits her eggs when she senses those of various bark beetles and bugs. Quite a nice adaptation and contribution to disease-causing tree pests.
Second, the issue of the dammed lake I described yesterday took on much more of a life than I had expected, driven by the actions of two Goulding Creek neighbors and of Glenn.
After some thought and conversation with Pat, who fronts Goulding Creek a mile downstream from us, I realized my conclusions that the dammed lake has little effect on the status of the water table was not quite correct. According to the memory of elderly neighbor Lee, who has lived on Goulding Creek all his life and has made it a major passion, there were springs driving Goulding Creek way before the dam was built and the lake covered them in the early 1970s. Thus the lake is probably nourished by the aquifer, as well as by inflow from Goulding Creek upstream (when it’s not dry). This means that the dam has for decades reduced the nourishment of Goulding Creek downstream and has actively, persistently imposed a reduction of the water table downstream. (This also helps to explain how the lake has remained full even though the inflow has dried up in the last few weeks.) Even without the alleged springs, I had to conclude that the minimization of outflow of the water from the lake over many years has exacerbated the emergency we’re now facing.
I also did some calculations (as had a third neighbor, and our results and recommendations converged almost exactly). These numbers will probably not be on the exam later.
The lake holds 160 million gallons of water and has a surface area of 74 acres and an average depth of 7.5 feet. I figured that for a downstream flow of water 3 inches deep and 10 feet wide moving at a mile an hour, a daily outflow from the dam of about 100,000 gallons a day would be required. This would lower the lake by 1.3 inches a day, disregarding any compensating input from other sources. My choice of this downstream flow was my own gut feeling of what it would take to keep the water table up, and keep the creek minimally nourished.
This changes the situation considerably, since it suggests an experiment that could not possibly harm the residents of the lake. And since the board of the lake association was having a meeting last night, Glenn, Pat, and Lee (none of us members of the association, of course), attended and discussed this with the board. Vague proposals were discussed but generally revolved around opening the outflow as soon as possible to create this volume of output and leave it that way for a week, then re-evaluate after observing the effects. Since we live about halfway down Goulding Creek, at 0.8 miles, and the other two neighbors live a mile farther downstream, we’re in an excellent position to make those observations.
Half the board was supportive, half was negative to one degree or another, but they were reasonably polite. They certainly must be credited with the courtesy of allowing the three outsiders to speak and argue. They left after the discussion, but before the board concluded its business so we don’t know what their conclusion was.
At any rate, the issue is not going to die. We need to come up with a specific proposal now and transmit them to the board members for consideration.
Third, there’s this terrible photo of a visitor from yesterday. I didn’t have my eyes in so had to use the automatic focus. I’ve kept the photo small so as to reduce the pain of having to view it:
With the yellow antennae, the long abdomen, the lack of the three long threadlike ovipositors, and the yellow highlights, this is probably a male Giant Ichneumon, Megarhyssa atrata. A female is shown in the linked bugguide page. My first encounter with one, if so, and a friendly wasp indeed. These are parasitic wasps, stingless, I think. With those long long ovipositors the female probes into crannies and burrows in tree bark and then deposits her eggs when she senses those of various bark beetles and bugs. Quite a nice adaptation and contribution to disease-causing tree pests.
