About 80-90% of the ponds in the Upper Harz Water Regale were created in the 16th and 17th centuries, whilst the system of dam ditches was further expanded in the 19th century. These structures contributed significantly to the Harz becoming the largest industrial region of Germany in the early modern period. The invention of the steam engine and the discovery of electrical energy did not immediately change the use of hydropower. These other forms of energy were introduced relatively gradually in the Upper Harz. Of course, with the introduction of the steam engine, the difficulties of acquiring coal in sufficient quantities was also a factor until the construction of the Innerste Valley Railway.