There is no universally accepted meaning of the term "small dam". A is frequently considered as being more than 20 metres high. The International Commission on Large Dams defines large dams as being more than 15 metres high or in some cases between 10m and 15m high. In fact, there is no need for any precise demarcation between small and large dams. A 20m-high dam will be the largest of the small dams category for some, while others see it as the smallest large dam! We would suggest, to provide a general guide, calling dams less than 15 metres  high small dams  and those 15-25m high, medium-sized dams. This is not intended as a universal definition and has no legal significance.