1998-BOARD OF SELECTMEN - Laserfiche WebLink

Home Browse Search

utilized as a simply-collected and accurate measure of flow from the pond. This will involve the use of a flow meter under various conditions to accurately measure flow, then comparing these measured rates with those predicted through calculations. Using this process, the calculated figures can be calibrated to actual conditions. While calibrating this system, also develop the relationship between flow at the spillway and the flow through the fish ladder at the pond adjacent to Route 130. This will allow a measurement at the spillway to be predictive of flow through the fish ladder. Long—term Management Issues 1. Establish the "design" elevation(s) for the pond under various conditions, and clearly assign responsibility for maintaining elevations of the pond. The Town of Mashpee must determine whether it intends to manage the elevation of the pond and, if so, what elevation, or elevations, it will attempt to maintain. If, as suspected, the sill of the spillway is at an elevation of 53.30 feet NGVD, it should be possible to maintain a pond elevation between 55.0 and 56.0 feet, which would allow a considerable margin for drought condition—we recommend a target elevation of 55.50. It appears to be possible to lower the water level somewhat for the winter months if ice damage is a concern, and raising the elevation once any significant ice is out to provide sufficient water for fish passage. The Town should establish a maximum pond elevation at which it will begin to release water for the protection of property around the pond--we recommend 56 feet--as well as a minimum flow necessary to allow ingress and egress of fish through the spillway and the fish ladder at Route 130. Pond elevations in future months may be roughly predicted by a review of monthly groundwater and precipitation trends and how they relate to the "average annual curves" (see Figures 4 and 2 respectively)--the review of these two trends will let the Town know in the spring whether groundwater reserves are low and suggest whether pond reserves should be built up by increasing the height of the boards in the spillway. The use of a combination of 2" x 6" boards and 2" x 4" boards will allow for finer adjustments than the current situation. 2. The most critical portion of the Mashpee River for maintaining flow through manipulation of the spillway at Mashpee-Wakeby Pond is the area between the spillway and the millpond just north of Route 130. A particular need is to ensure sufficient flow to keep the bed of the stream between the spillway and the millpond by Route 130 saturated in order to allow it to hold water if an additional release is needed. The period between Horsley & Witten, Inc. Mashpee-Wakeby Pond Management Plan Page 29