TERENO - Holtemme - Germany

The Holtemme River is a third-order river that originates in the Harz National Park in Germany, at an elevation of 862 meters above sea level. It flows for 47 kilometers before merging with the Bode River. The catchment area covers 282 square kilometers and is primarily composed of Mesozoic rocks, which are overlain by Tertiary and Quaternary sediments. Land use in the catchment demonstrates a typical progression from previously forested headwaters to agricultural and urban areas downstream. Consequently, the river's hydromorphology is almost natural in the upstream reach, while it becomes highly altered downstream due to channelization, riparian clear-cutting, and incision in urban and agricultural areas. In addition to potential diffuse sources of chemicals from agriculture, the river receives significant nutrient inputs and a wide range of pollutants from point sources. This includes two wastewater treatment plants (WWTP), each serving a population equivalent of more than 60,000, as well as tributaries draining agricultural areas. With this increasing human impact, the Holtemme River serves as a typical example of a multiple-stressed ecosystem. Thus, it provides a valuable model site for studying the effects of various human stressors on ecosystem structure and function. Since 2017, the upstream catchment has experienced substantial forest dieback due to bark beetle infestations, resulting in over 80% of the previously forested catchment area becoming unforested.