Global Water Supplies
Global Water Supply Overview
A pie chart illustrates sources of water (note: due to rounding, the figures sum to 99.9%).
Freshwater Proportion:
Only 2.5% of Earth's water is freshwater.
Freshwater Distribution:
68.7% stored in glaciers and ice sheets.
30% is groundwater.
1.3% in rivers, soil moisture, lakes, and atmosphere.
Uneven distribution; Canada has more lakes than the rest of the world combined.
Water Supply Sources
Main Water Supply Sources:
Three primary sources:
Lakes and Rivers
Aquifers
Reservoirs
Other Sources:
Desalination: Process of removing salt from seawater for various uses.
Rainwater Harvesting: Collecting precipitation for use.
Groundwater and Aquifers:
Groundwater is water stored underground, filtered through soil and rocks. Obtained via:
Drilling boreholes
Digging wells
An aquifer is saturated rock that stores water.
Springs can also provide groundwater to the surface.
Groundwater Issues:
Overuse/Over-abstraction: Aquifers do not recharge if water is overdrawn.
Pollution: Industrial, agricultural, and domestic waste can contaminate groundwater.
Surface Water Storage:
Water stored in lakes, reservoirs, and rivers faces issues like:
Pollution from runoff: Industrial and agricultural runoff contaminates surface water.
Dams: Used for reservoir storage, but construction has slowed due to site suitability and environmental concerns.
Desalination and Global Water Use
Desalination Overview:
Involves the removal of salt from seawater for human use (domestic, agricultural, industrial).
Desalination Issues:
High initial costs and operational expenses.
Significant energy consumption.
Global Water Use by Sector:
70% for agriculture (irrigation and livestock).
20% for industry (manufacturing and energy).
10% for domestic purposes (toilets, cooking, cleaning).
Usage patterns vary between MEDCs (More Economically Developed Countries) and LEDCs (Less Economically Developed Countries).
Increasing Global Water Demand:
Water demand rose from 1 trillion m³ in 1934 to 4 trillion m³ in 2014.
Water Demand in MEDCs and LEDCs
Water Use in MEDCs:
11% Domestic
30% Agriculture
59% Industry
Reasons for higher water demand:
Improved living standards and appliances.
Increased recreational and leisure water use.
Urbanization which intensifies demand.
Increased industrial activity requiring water.
Greater agricultural demands for livestock.
Water Use in LEDCs:
Dominantly agricultural use due to widespread reliance on farming.
Low industrial demand for water due to less industrial activity.
Many inhabitants lack access to piped water, promoting cautious water usage.
Water Shortages and Management
Water Shortages (Deficit):
Patterns often correlate with LEDCs and MEDCs positioning, typically concentrated near the equator.
Major factors contributing to water deficit:
Low Supply Reasons:
Insufficient precipitation
High evaporation rates
Inefficient water management
Drought conditions
Pollution effects
High Demand Reasons:
Population growth
Industrial expansion
Agricultural demand
A combination of both low supply and high demand often exacerbates the crisis.
Regions with Major Water Deficits:
Australia, parts of North, East and South Africa, the Middle East, southwest USA, and eastern Brazil including parts of Argentina and Chile, as well as India.
Levels of Water Shortage:
Water Stress: Less than 1700 m³ per person per year.
Water Scarcity: Less than 1000 m³ per person per year.
Types of water scarcity:
Physical Water Scarcity: Limited physical access to water resources.
Economic Water Scarcity: Lack of financial means to access available water resources.
UN Millennium Development Goals (MDG):
Goal: Halve the proportion of people without sustainable access to safe drinking water and basic sanitation by 2015.
While unmet, access to clean water has improved, with 74% of the global population granted access by 2020.
Challenges in Access:
2.2 billion people lack access to potable water, 4.2 billion without safely managed sanitation.
Continued water scarcity is impacted by:
Pop growth
Development-induced demand
Climate change effects (increased droughts and changes in aridity)
Pollution concerns.
Transboundary Water Issues:
Rivers crossing borders raise jurisdictional conflicts; upstream withdrawals undermine downstream access.
Activities such as dam construction can alter river flow and degrade water quality downstream.
Meteorological Effects:
Increased temperatures prompt higher evaporation rates, decreasing available water.
Impacts of Water Shortage
Consequences of Water Shortage:
Increased mortality and illness from waterborne diseases (e.g. cholera, dysentery).
Potential inter-country conflicts over shared water sources.
Educational disruptions for children allocated to water collection tasks.
Negative impacts on food production:
Reduced irrigation capacity leads to lower agricultural yields.
Livestock mortality due to insufficient water access.
Damaged ecosystems, loss of species habitats.
Slow economic growth due to industrial water shortages.
Managing Water Supply
Ways to Manage Water Supply:
More feasible in MEDCs due to financial resources for implementation.
Awareness and action needed on water recycling and efficient usage.
Technologies and Strategies:
Recycling water
Drip irrigation: significantly lowers water evaporation and waste.
Installation of water-efficient appliances.
Rainwater collection systems.
Using recycled 'grey water' for non-potable purposes.
Low-flush toilets and energy-saving showerheads.
Infrastructure improvements by water utility companies to reduce leaks.
Challenges in LEDCs
Management Challenges:
Lack of funding hinders effective water management in LEDCs.
NGOs like Water Aid often contribute to funding initiatives.
Adoption of appropriate technologies, including:
Wells
Gravity-fed systems supplying clean water
Boreholes with manual pumps
Rainwater collection methods
Drip irrigation technology
Cultivation of drought-resistant crops.
Case Study: Spain's Water Management
Tagus-Segura Project:
Average precipitation in Southeast Spain: 365 mm annually with most occurring in winter.
Dominant water use for agriculture (80% of total availability) across 147,000 hectares of arable land requiring irrigation due to recurring droughts.
Direct correlation: tourism exacerbates water issues.
Tourist water consumption: 450-800 liters/day vs. 127 liters/day for residents.
Project specifics (completed 1978):
Transports over 60% of water flow from Tagus to Southeast regions.
Construction of a 286 km pipeline linking four river basins: Tagus, Jucar, Segura, and Guadiana.
Aims to alleviate water deficit for regions like Alicante, Murcia, and Cartagena.
Challenges with Tagus-Segura Project:
Majority usage of transferred water goes to tourism and leisure, neglecting small-scale agricultural needs.
Increased consumption due to supply enhancement leading to resource strain.
Estimates indicate 15% of transferred water is illegally utilized for leisure activities (e.g., golf courses).
Ebro Project Proposal:
Considered in 2001, aiming to transfer water from River Ebro; ultimately abandoned due to:
Fails stemming from the Tagus-Segura initiative.
Concerns over high costs and potential ecological impacts on the Ebro Delta.
Transition to desalination plants as a water supply strategy to meet demand.
Summary
Water management is a critical issue with complex interdependencies between supply, demand, and environmental factors. Sustainable practices and innovative technologies are essential to balancing these demands, especially in regions facing acute shortages.