The flow of water through the upweller is different for each of the three buckets pictured above. You can tell by the amount of sediment on the clams. The clams in the bucket on the left are pretty clean, the ones in the bucket on the right are covered with silt and other organic matter, and the ones in the middle are, well, in the middle.
The silt is not a good thing in itself. But silt indicates that water is flowing. When there is no flow, there is no silt. And “No Flow” is a problem. If no water is “upwelling” in the bucket, the clams are not immersed in the flow of nutrients, and the whole point of placing them in an upweller is lost.
The picture on the left shows what the problem is: the end of the plastic valve is barely in the water, which means that the water just sits in the bucket rather than flowing up and out. If water is not flowing out the top, no new, nutrient-rich water is flowing up through the screen at the bottom of the bucket.
Why is the water level below the height of the valve? If you look carefully at the picture at the top of the post, you will notice that the valve in the rightmost bucket DOES reach into the water. So, the problem is that when we drilled the holes for the valves in the big gray pipe that runs down the middle of the upweller, some of the holes were just a tiny bit higher or lower than the others. Because we were making holes on a round surface, just being a degree or so off along that circumference will make a difference in the valve’s angle. Water is remarkably good at finding and flowing to the lowest location. It is the lowest valves that set the water level.
So, what did we do? This week, Mike and Noah identified the buckets where the flow was fastest by putting confetti-sized bits of paper on the surface of the water in the buckets. Then they gently closed down the ball valves on those buckets, then put in more bits of paper and watched again. Working carefully and patiently, they were able to bring the water level up about a quarter of an inch so that all the valves are now in the water and all the buckets are getting flow.
We will continue to monitor the situation and will report more when we know more.
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