大井川には支流も含めて多くのダムがある。この笹間川ダムもその一つで、他のダムと同様に取り込まれた水は発電に使われた後、下流に送られ、次は農業・工業用水として再び取水される。そのため大井川の本流を流れる水は極端に減ってしまい、かつての大井川の姿はもう見ることができない。

The Oi River has many dams, including on its tributaries. The Sasama River Dam is one of them, and like other dams, the water taken in is used for power generation before being sent downstream and then used again for agricultural and industrial purposes. As a result, the amount of water flowing in the main stream of the Oi River has drastically decreased, and the river can no longer be seen in its former glory.