Figure 4.5: Typical hydrographs in accordance with climatic settings

Source: Note: For tropical climates close to the equator (Af), perennial rivers flow all year. Towards the north and south the tropical climates have a distinct rainy season and a dry season (Am and Aw). In dry climates (B) rivers are often ephemeral and only flow periodically after a storm. In the temperate Cf climate, there is no distinct dry or wet season, whereas the ‘Mediterranean climate’ (Cs) has a pronounced seasonal water deficit in the summer and a rainy winter reflected in the hydrograph. The cold climates (D) have a distinct snowmelt runoff peak and the Df climate has an additional peak in the autumn caused by rain. Source: Stahl and Hisdal 2004.

Source: UNESCO  The United Nations World Water Development Report 2
Section 2: Changing Natural Systems,
Chapter 4, Part 1. Global Hydrology and Water Resources, p.127

Water Resources

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