• Agricultural practices influence water flow: The ways in which farming is conducted can result in decreased infiltration and increased overland flow. Various factors determine this, including the scale of farming, field size, use of machinery, and implemented soil conservation methods.

Easy-peasy example: Think of water seeping into a sponge (infiltration) versus water gliding across a tiled floor (overland flow). Heavy-duty farming practices can turn the soil from a sponge-like structure into a hard floor, resulting in water skimming across the surface rather than seeping into the ground.

• Major factors leading to less infiltration and more overland flow:
  • Intensified agriculture
  • Heavier and stronger machinery
  • Soil compaction by machines or animals, especially near waterholes
  • Cultivation on steeper slopes
  • Field enlargement resulting in higher wind speeds
  • Hedgerow removal, leading to faster winds
  • Winter cereals planting leaves soil exposed for months.

Fun Fact: The phrase "Make hay while the sun shines" takes on a new meaning here. The timing of planting crops, like winter cereals, could leave the soil bare and exposed to wind and water erosion for months!

• Deforestation changes water cycles: The way deforestation occurs (clear felling vs selective removal) will have different impacts. Generally, deforestation increases river flood levels, but these levels can return to normal once the forest regenerates. However, this could take decades.

Global Example: Ever heard of the Amazon rainforest? Known as the 'lungs of the earth', its destruction could drastically increase flood levels in the Amazon River.

• Reasons behind these changes:
  • Mature forests have high interception rates (they catch more rainfall!)
  • Overland runoff decreases beneath a mature forest
  • Infiltration rates are higher under forests
  • Soils are deeper under tree covers.
• Post-deforestation measures: To reduce soil erosion after deforestation, the use of shade trees and cover crops is helpful. But beware, grazing increases overland runoff due to surface compaction and vegetation removal.
• Negative effects of deforestation: Deforestation can lead to an increase in sediment and chemical loads in streams. The scale depends on forest management. Quick replanting and partial deforestation can lessen these effects.

Dramatic Real-World Example: In Northeast USA, extreme deforestation led to sediment loads increasing fifteen-fold and nitrate loads shooting up by almost fifty times! Yikes!