Underwater bathymetry of the Quarry Pond
Alan Lee and Neil Fitzharris
Bathymetry is used to estimate the volume of a lake or pond. This is important in stocking fish because we don't want the habitat to become overcrowded. Also, food chain lengths are limited by ecosystem size, which can be established through bathymetry.
We established transects across the Quarry Pond to cover every part. We used a GPS unit to keep track of latitude and longitude. We first attempted to do measurements with a raft, but encountered many difficulties. The raft had a hole in it. The sonar flashlight was unreliable for estimating depth. We drifted so much that we were sometimes outside of the range of error for the GPS. Next we got out and dragged the boat across the pond. This heavily disturbed the bottom of the pond, leaving a long cloud of black sediment. We tied Neil's lanyard to a fishing weight and a tape measure to measure depth.
The surface area of the Quarry Pond is 68,537 square meters. The volume of the Quarry Pond is 69,887 cubic meters. The maximum depth is 2 meters and the average depth is 0.87 meters.
We don't think that this project should be repeated. We did a very meticulous and detailed job. The only improvements would be going out to take a few more points in areas that have large spaces. However, we decided against taking points that were extremely close together because the water level in the pond doesn't vary much. Furthermore, we kicked up lots of black silt while wading through the pond. The silt stayed suspended in the water column, which lasted for so long that we actually used this to identify where we had walked. This, plus our trampling over aquatic plants and almost trampling fish nests, has potentially adverse effects on the ecosystem.