Table 4.6: Spatial and time scales within which pollution occurs and can be remediated

Major Cause / Issues Major Related Issues1 Scale2 Time to pollute3 Time to Remediate4 Major Controlling Factors
Local Region Global < 1 1 to 10 10 to 100 < 1 1 to 10 10 to => 100 Byophysical Human
The nutrional status of most regions of the world has improved in all developing regions. Sub-Saharan Africa and South Asia have also improved their nutrional level, b ut they lag behind and are host to the majority of the undernourished people in the world.
1 Relevant primarity to * surface water, ** groundwater
2 Local < 10000 km2, region ->104 to 106 km2, global ->106 to 108 km2
3 Lag between cause and effect.
4 Longest time scale if for groundwater, followed by lakes, and shortest for rivers and streams.
Category Shading
Scale - the colour intensity increases as impact dimension becomes greater.
Time to pollute and Time to remediate are highlighted in red for most critical, orange for moderately critical, and yellow for the least critical situations. Green is shown for the situation where remedial actions could be less than one year (pathogens).
Source: Modified from Peters and Meybeck, 2000.
Population Pathogens                     Density & Treatment
Eutrophication(*)               Treatment
Micro-pollutants         Various
Water Management4 Eutrophication(*)                   Hydrodynamics Flow
Salinization           Water Balance
Parasites       >100 Hydrology
Land Management Pesticides                     Agrochemicals
Nutrients             Fertilizer
Suspended solids             Construction / clearing
Physical Changes         >100 Cultivation, Mining, Construction, Clearing
Atmospheric Transport Acidification (*)                     Cities, melting and fossil fuel emissions
Micro-pollutants         Cities
Radionuclides           >100 Industry
  Mega Cities Pathogens                     Population & Treatment
Mines Salinization                     Types of Mines
Nuclear-Radionuclides                 >100    
Global Climate Change Salinization                   Temperature & Precipitacion Fossil fue emissions & Greenhouse gases
Natural Ecology Parasites (*)       Permanent     Permanent Climate, Hydrology  
Natural Geochemistry Salts       Permanent     Permanent Climate, Lithology  
Fluoride (**)      
Arsenic, Metals (**)     Lithology

Source: UNESCO  The United Nations World Water Development Report 2
Section 2: Changing Natural Systems,
Chapter 4, Part 2. Nature, Variability and Availability, p.142

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Other Figures & Tables on this publication:

Table 4.1: Precipitation distribution into surface water and groundwater components (by climate region)

Table 4.2: Selected large aquifer systems with non-renewables groundwater resources

Table 4.3: Water availability information by country (AQUASTAT, FAO 2005)

Table 4.4: Major principal sources and impacts of sedimentation

Table 4.5: Freshwater pollution sources, effects and constituents of concern

Table 4.6: Spatial and time scales within which pollution occurs and can be remediated

Table 4.7: Potential applications for reclaimed water

Figure 4.1: Global distribution of the world’s water

Figure 4.2: Schematic of the hydrologic cycle components in present-day setting

Figure 4.3: Oxygen-18 content of stream water along the main stem of large rivers

Figure 4.4: Variations in continental river runoff through most of the twentieth century (deviations from average values)

Figure 4.5: Typical hydrographs in accordance with climatic settings

Figure 4.6: Acid rain and its deposition processes

Figure 4.7: Five-year mean of the pH level in rainfall in the eastern regions of Canada and the US

Figure 4.8: Primary sources of groundwater pollution

Map 4.1

Map 4.2

Map 4.3: Groundwater abstraction rate as a percentage of mean recharge

Aral Sea