way. Renaturalisation projects raise more awareness for the environment, however, rapidly growing and urbanizing population needs to be supplied with enough water resources and hydropower energy, which calls for more sustainable solutions. River pollution Water pollution occurs when water bodies, such as rivers, lakes and oceans are contaminated with harmful substances. These substances degrade the water quality and are toxic to humans as consumers and to the environment. The contamination in a river can come from a point source or non-point source pollution. The most common types of surface water pollution are agriculture, sewage and waste water (including stormwater runoff), oil pollution and radioactive substances. The agricultural sector consumes a lot of fresh water and is the leading source for water degradation. Timeline Most settlements in human history were placed along rivers, developing into riverine cities and traceable by their considerable environmental footprint. The human influence on rivers can be divided into six chronological stages: Consequences While river engineering can improve the behaviour of the river or hold it back to adapt to our infrastructure, and therefore be rated as positive or negative impact, pollution undoubtedly has a negative impact on our environment. The consequences are very complex and difficult to measure and classify, as often benefits for humankind imply drawbacks for the environment and the other way around. Indicators Indicators that make the human impact measurable and quantitatively assessable are: artificial water surface ratio, artificial water surface density ratio, disruption of longitudinal connectivity ratio, artificial river ratio, sinuosity of artificial cutoff, channelization ratio, artificial levee ratio, road along river ratio, artificial sediment transport ratio and the integrated river structure impact index. Material and sediment flux Through anthropogenic impact the material flux of rivers has changed, which enters the sea and has a strong effect on coastal and shelf environments. Runoff Alternate land use, deforestation, afforestation and different types of river engineering have also led to changes in hydrologic processes, such as runoff. Mushrooming illegal mining activity can, for example, change the soil structure, the pressure-gradient between stream flow and groundwater and the vegetation cover and therefore lead to increased or decreased runoff. In southern Ghana in the Lower Pra River Basin, the percentage of runoff change, which is linked to human activity is approximately up to 66 %. Human presence and infrastructure has benefited from river management, by changing and straightening rivers to make the valuable land around them