Urbanisation –
Water
• Impermeable surfaces reduce infiltration.
• Urban drainage systems remove surface water rapidly.
• River water levels rise rapidly due to fast transfer of surface water.
• Developments on floodplains reduce storage capacity and increase flood risk.
Carbon
• Reduced surface vegetation
• Emissions from industry, transport and cement manufacture.
Forestry –
Water
• Natural forest increase interception.
• Increased evapotranspiration from leaves.
• Run-off and river discharge reduced, long lag-time.
Carbon
• Increased carbon stores through sequestration in biomass.
• Only an active carbon sink for the first 100yrs.
Farming –
Water
• Irrigation diverts water to cultivated land (some released by transpiration).
• Interception, evaporation and transpiration reduced in agroecosystems.
• Ploughing increases soil moisture loss and drainage channels leads to soil erosion.
• Underground drainage increases transfer to rivers.
• Heavy machinery compacts soil
Carbon
• Forest clearance reduces stores.
• Ploughing reduces soil store and exposes organic matter to oxidation.
• Rice paddies and livestock generate methane.
• Tractor carbon dioxide emissions.
Water extraction –
• For industry, agriculture or domestic use.
• Hydrogeology used to monitor safe levels of water extraction to prevent river drying
and sinking water tables (if extraction exceeds recharge).
• Salt water degrades groundwater.
Volcanic Activity –
• Release sulfur dioxide into upper-atmosphere, reducing incoming solar radiation.
• Often counterbalanced by the absorption of outgoing terrestrial radiation by
greenhouse gases emitted.
• Resulting climate change uncertain.
Aquifers =
Water-bearing rocks. Groundwater extracted by wells and boreholes. Border between
saturated and dry rock is the water table which fluctuates with seasons and abstraction.
Artesian Basins =
Sedimentary rocks may form a basin shape (syncline). An aquifer trapped between
impermeable rock layers is under artesian pressure. Wells allow water to flow to the surface
under its own pressure (artesian aquifer).
1/3 of the Earth’s largest groundwater basins are rapidly depleted by human consumption.
21/37 exceeded sustainability tipping points + are being depleted. 13 are significantly
distressed, threatening regional water security + resilience. Most overburdened aquifers in
driest areas, where populations draw heavily on underground water (climate change and
population growth intensify problem). → (NASA 2015 study of GRACE satellites)
E.g = Water extraction from the River Kennet Catchment, Southern England.
Water table reduced by 10-14%. Temporary wetland areas. Supports several urban areas
including Swindon (population over 200,000).