Human impacts on hydrological cycle

• Deforestation causes less vegetation that is able to intercept water, hence less evaporation
• Fewer trees mean less water is returned to the atmosphere by transpiration
• Agriculture means soils are compacted by heavy machines and livestock this means no water can infiltrate the soil this increases the surface runoff
• Rapid surface runoff can create flooding
• Urban development creates more impermeable surfaces where surface runoff can occur
• Global increase in temperatures effects rates of evaporation, transpiration and precipitation among other rates
• Water abstraction refers to process of taking or extracting water from natural resources for various human uses
• Water abstraction reduces volume of water in surface stores
• Water abstraction increases during dry seasons
• Human abstraction from aquifers as an output to meet water demand is larger that the input of water, this leads to goobal decline of water in stores
• Water abstraction can be bad if water sources are not returned, it affects downstream flow
• Rivers of Tibet, provide water to 1500 million people, growing demand has led to conflict and shortages in some areas
• Habitat change can cause damage as flooding the reservoirs destroys prior habitats, however this creates new valuable, uncommon wetlands
• Wildlife barriers include dams and reservoirs, they prevent migratory species being able to migrate. This prevents recolonisation
• River regime downstream of dams can be regulated by using reservoirs to regulate riverfront during shortages
• Sedimentation: sediments carried to the resovoir will sit when they should flow downstream to fertilise the floodplains
• Microclimates can be established due to the presence of large bodies of water, greater evaporation may increase humidity hence effecting precipitation
• Construction of a dam and resouvoir creates habitat change: flooding the reservoir destroys previous habitats, but creates unique wetland that are more valuable
• construction of dam and reservoir creates wildlife barriers: the dam prevents migration along a river, this prevent recolonisation
• construction of a dam and reservoir causes: regulation of river flow, in times of surplus and shortage. This reduced risk of flooding. changes in flow change river erosion and sedimentation affecting development of meanders
• construction of dam and reservoir causes: sediment to settle
• construction of a dam and reservoir causes microclimates: high heat capacity of water helps to reduce temperature fluctuations
• water across reservoirs provide less friction so wind speeds will be higher