Water Resources: Surface and Ground Water

• Water is a crucial resource that is essential for life and various human activities
• This chapter discusses surface water, groundwater, associated hazards, and water management techniques

Surface Water

• Surface water includes bodies of water that collect on the Earth's surface such as seas, oceans, streams, lakes, canals, and swamps
• Seas and oceans are considered salt water because of their high salt content
• Streams, lakes, and canals are considered fresh water because of their low salt content
• Fresh water is vital for sustaining life on land

Global Water Distribution

• Oceans account for 97% of the earth's water
• Ice accounts for 2.2% of the earth's water
• Groundwater accounts for 0.7% of the earth's water
• Fresh water accounts for less than 0.1% of the earth's water

Water Cycle and Runoff

• When rain or snow falls, a portion of the water flows into the seas of the earth, while a portion falls on the ground
• Plants absorb some of the water, while some evaporates, and some seeps into the soil
• Runoff describes the excess water that is not absorbed by the surrounding area
• Runoff flows across the surface into streams, canals, ponds or swamps

Groundwater

• Groundwater is the water that sits underneath the surface of the ground in the zone of saturation
• The zone of saturation is where the space between soil particles is filled with water
• The zone of aeration sits above the saturation zone, and is where spaces between soil particles are filled with both air and water
• The water table is the boundary between the zone of saturation and the zone of aeration
• The water table level changes over time in response to changes in the water cycle, precipitation, stream flow, geological changes, and human activities

Groundwater Sources and Characteristics

• Groundwater originates from rain and snow seeping into the soil and moving downward until it reaches the impermeable layer
• Groundwater is stored underneath the impermeable layer
• Soil helps filter and clean the water so groundwater is often considered clean

Groundwater and Surface Water Interaction

• Groundwater and surface water are interconnected and can exchange places
• Groundwater can move through the ground and enter lakes or streams
• Surface water can seep into the ground and become groundwater
• Groundwater is often pumped out to meet water demands during dry periods
• Groundwater is replenished naturally during abundant rainfall
• Leaky underground tanks storing gasoline, landfills, and excessive use of fertilizers/pesticides can contaminate groundwater

Water Usage

• Fresh water and groundwater are consumed for survival
• Water is used for irrigation, washing, cleaning, generating electricity, and cooling equipment/machines

Water Conservation and Management

• Conserving surface water and groundwater lowers water bills, reduces water pollution, lowers costs for treating water, and reduces overall environmental impact
• Techniques for Water Conservation:
• Washing vegetables in basins instead of running water
• Washing only full loads of clothes in washing machines
• Taking short showers instead of soaking in tubs
• Repairing dripping taps
• Collecting rainwater to water plants/wash car porches
• Using a bucket instead of a hose to wash the car
• Broader water management strategies:
• Collecting rainwater in reservoirs and catchment areas to protect against flooding
• Collecting and treating wastewater for industrial use
• Using desalination plants to remove salt from seawater to address water insecurity (this process is expensive)

Hazards Related to Water

• Surface water and groundwater can pose hazards:
• Surface water flooding
• Soil erosion
• Landslides
• Sinkholes
• Land subsidence
• These hazards can cause extensive damage to life and property

Surface Water Flooding

• Surface water flooding occurs when runoff cannot soak into the ground or drain through urban drainage systems, leading to large puddles, flowing water, or stagnant water
• Heavy rainfall, prolonged wet weather, and saturated soil are major causes
• Urban areas are more susceptible to flooding due to paved surfaces that reduce water infiltration

Factors Influencing Flooding

• The amount and intensity of rainfall
• Vegetation cover
• Steepness of terrain
• Soil type
• Drainage system effectiveness

Negative Impacts of Flooding

• Destruction of homes, factories, and farms
• Damage to communication cables, bridges, and vehicles
• Displacement of people and disruption of normal life

Positive Impacts of Flooding

• Deposition of sediments and organic minerals can enhance soil fertility in new areas
• Replenishment of surface water and groundwater supplies can improve crop yields

Soil Erosion

• Moving water like rainwater and streams is the main cause of soil erosion
• Raindrops can break up the soil and displace soil particles
• Runoff removes the topsoil, which contains the most nutrients and organic matter
• The formation of tiny, fast-flowing channels, further erodes and deepens

Ways to Reduce Soil Erosion

• Increase vegetation to stabilize and hold the soil
• Reduce soil surface disturbance
• Build contour drains to break the slope length

Landslides

• A landslide is the movement of rock and soil down a slope
• Triggered by a slope receiving too much water, especially in monsoon season
• Too much water weakens soil bonding and adds extra weight

Factors Contributing to Landslides

• Erosion
• Earthquakes
• Volcanic eruptions
• Human activities

Damages Caused by Landslides

• Property damage
• Personal injury and/or death
• Damage to infrastructures (roads, railways, and buildings)

Sinkholes

• A sinkhole is a hole formed when the soil below collapses
• Happens when underlying rock is dissolved by water or when sinkholes sit on limestone and rock salt (soluble rocks)
• Groundwater erodes the rock until it is too weak to support the surface

Causes of Sinkholes

• Extraction of groundwater
• Mining activities
• Construction projects
• Broken water or drain pipes
• Improper soil compaction after excavation
• Heavy traffic

Land Subsidence

• Land subsidence is the gradual sinking of the ground
• Primarily caused by the removal of groundwater, oil, and natural minerals

Main Cause of Land Subsidence

• The massive extraction of groundwater

Factors that influence land subsidence

• Groundwater extraction exceeds natural replenishment rates reducing the water table level
• The reduced water table impacts the soil's ability to support the weight of the soil above

Problems caused by Land Subsidence

• Changes in elevation
• Damage to infrastructure (storm drains, sanitary sewers, roads, railroads, canals, bridges)
• Structural damage to public and private buildings
• Damage to wells
• Increased risk of flooding