Gwen, Sophia and Willow are measuring dimensions of our ladder in order to calculate the volume of water flowing through its length
The rainy and cool spring has increased the water levels spilling over the dam and we wondered, could alewives swim up the current in the ladder? We found we make some measurements and calculations and compare the flow rate to that of published research about alewife swimming speeds.
Contributed by Lydia Myers, Gwen Miller, Mya Simmons
On Friday May 31st at 11:28 am our eighth grade class went down to the marsh to calculate the water velocity in our newly placed fish ladder. It was important for us to do this to determine whether or not our alewives could make it from the many pools up into the marsh through the strong current in the ladder.
The first thing we did as always, was sneak up onto the culvert to check for returning alewives. When it was determined that none were spotted, we continued on to the ladder to calculate the velocity.
The first thing we did was to take a yardstick and measure the depth of the ladder, then the width, and finally the length. The few that gathered the data then reported it to those that were recording. The final measurement needed was the speed of the flow, or how fast the water was traveling in the ladder. To gather this information we used a tennis ball and cut a small slit into it. We then filled the ball with water approximately halfway so that we would get an accurate measurement. Our next step was to send the ball down the ladder, starting farther into the marsh so that it was accurate, and time until it reached the end.
Using this data and a sheet provided to us we calculated that the water velocity of our fish ladder is 26.52 centimeters per second. Using a published study we discovered that greater than 92% of alewives can swim through this current we have created for the length we have assessed (five feet).
Our “calculators”, Lydia and Maggie