In areas where surface water is not readily available (located far away from areas where it is needed), groundwater is the primary water source. This graphic shows the chloride concentration and the potassium concentration, in milligrams per litre, in the city of Hat Yai's canals. It also shows the degree to which the polluted canal water has mixed with the groundwater. Finally, the graphic explains how the city's groundwater has been polluted by...

The agricultural sector is by far the biggest user of freshwater, primarily for irrigation of arable land. This graphic shows the relative percentages of water use by the agricultural, industrial and domestic sectors in the countries of the world in 2000.

The world's surface water is affected by different levels of precipitation, evaporation and runoff in different regions. This graphic illustrates the different rates at which these processes affect the major regions of the world, and the resulting uneven distribution of freshwater. It shows the amount of precipitation in cubic kilometres for each region, and the percentage of that amount which evaporates or becomes runoff. The text below the grap...

According to Population Action International, based upon the UN medium population projections of 1998, more than 2.8 billion people in 48 countries will face water stress or water scarcity conditions by 2025. An area is experiencing water stress when annual water supplies drop below 1700 m3 per person. Water scarcity means that the annual water supply is below 1000 m3 per person. This graphic shows which African nations are expected to be experie...

This graphic shows the amount of water withdrawal as a percentage of the total available supply, at the national level in 1995 and in 2025 (projected amounts). Overall, the percentages are expected to rise substantially by 2025. This resource also includes a graphic showing the number of people suffering from water stress and water scarcity worldwide in 1995, compared to projected rates for the year 2050. As the population continues to rise, the ...

Three-quarters of fish stocks are currently exploited to the maximum extent, if not excessively. The Northeast Atlantic Ocean continues to exhibit declining catches, as well as a shift towards fish at lower levels in the food chain. This graphic illustrates the decline in the catch ratios of predatory and plankton-feeding fish in the Northeast Atlantic Ocean from 1950 to 1995.

Freshwater represents a crucial sort for human development, for nature and for ecosystem services. This graphic compares freshwater supplies in cubic metres per capita, per river basin in 1995 with a projection of freshwater supplies for the same areas in 2025. The graphic shows which areas were experiencing water stress, which were experiencing water scarcity and which had sufficient quantities of freshwater in 1995, and shows projections for th...

Although freshwater ecosystems such as rivers, lakes and wetlands occupy less than 2% of the Earth's total land surface, they provide a wide range of habitats for a significant proportion of the world's plant and animal species. This graphic explains which areas of the world have high and low populations of fish species and of endemic fish.

This graphic illustrates groundwater flow, two types of aquifers (confined and unconfined) and three types of wells (artesian; flowing artesian and a water table well in an unconfined aquifer). It shows how groundwater is circulated through the aquifers and how it is recharged. Groundwater represents one of the most important resources for drinking water for human consumption.

The graphic shows the amount of water supply versus sanitation coverage between the world and developing nations in percentage. It shows statistics from 1990 and 2000, as well as comparing rural to urban.

This graphic shows the availability of freshwater through average river flows and groundwater recharge, in cubic metres per capita per year, at the national level in the year 2000. The graphic highlights the countries with the least freshwater resources (Egypt and the United Arab Emirates) and those with the most (Suriname and Iceland).

A comparison of the major watersheds between the two decades showed that Northern Europe and North America had lower phosphate concentrations, while the Ganges and Brahmaputra watersheds in South Central Asia had higher concentrations. Nutrient control programmes in municipal and agricultural activities may be key factors in the observed reductions in phosphate concentrations.

This resource includes four graphics that explain sea level change, an expected consequence of climate change. The first graphic, 'Relative Sea Level Over the Past 300 Years', shows the changes in sea level rise, in metres, that have occurred between 1700 and 2000 at three different locations: Amsterdam, Brest and Swinoujscie (in Poland). The second graphic, 'Causes of Sea Level Change: Simulated Global Mean Sea Level Changes 1900-2100' and the t...

The Marine Species Population Index provides an assessment of the average change over time in the populations of 217 species of marine mammals, birds, reptiles, and fish. The index represents the average value of six regional ocean indices. More pronounced declines are seen in the southern oceans, which is attributed to the fact that major losses and degradation of marine ecosystems in the industrialised world took place prior to 1970. Marine sp...

The water cycle consists of precipitation, evaporation, evapotranspiration and runoff. This graphic explains the global water cycle, showing how nearly 577 000 km3 of water circulates through the cycle each year. A table of estimated residence times of the world's water shows the estimated times that water resources exist as biospheric water; atmospheric water; river channels; swamps; lakes and reservoirs; soil moisture; ice caps and glaciers; oc...

This map shows the locations of 13 major river basins in Africa: the Senegal, Volta, Niger, Lake Chad, Nile, Lake Turkana, Juba Shibeli, Ogooue, Congo, Zambezi, Okavango, Limpopo and Orange river basins.

This graphic illustrates that there is a strong correlation between the world's industrial areas and the areas in which seasonally oxygen-depleted waters occur. The accompanying text explains some of the effects of land-based activities on the marine environment.

This graphic shows the average bicarbonate concentrations, in milligrams per litre, at major river mouths for the time periods 1976 to 1990 and 1991 to 2000. The graphic also shows the changes in average bicarbonate levels between these two time periods. Bicarbonate is an indication of the alkalinity in the rivers which reflects the geology (rock, minerals, sand) and increases the buffering capacity, but can also increase the risk of eutrophicati...

Alkalinity (as CaCO3) was analysed for all sampling stations available at the continental level. Concentrations remained reasonably steady between the two decades for Africa, Asia, South America and Australasia. Significant increases in alkalinity concentrations were noted for European and North American rivers, which may indicate a shift towards reduced acidic impacts at the continental scale.

The Mesopotamian marshlands in the Tigris and Euphrates river basins were devastated by damming and river channelisation during the late 1980s. This graphic illustrates the decline in the area's marshlands by comparing the locations of its marshlands and lakes in 1973 and in 2000. The graphic shows the locations of permanent and seasonal marshes; permanent, shallow and seasonal lakes and mud flats or temporary marshes. The graphic for the year 20...